sci.electronics.repair
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Today's topics:

* 75 ohm Termination Question - 7 messages, 5 authors
http://groups.google.com/group/sci.electronics.repair/t/be000fe11979bff2?hl=en
* Phase Linear 400 output transistors - 9 messages, 7 authors
http://groups.google.com/group/sci.electronics.repair/t/d0cb28fa4ada674c?hl=en
* Loss of preset settings on LCD monitor - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/a04d8e22e7d8fc34?hl=en
* Magnastat soldering iron bits users in the UK , here? - 3 messages, 2
authors
http://groups.google.com/group/sci.electronics.repair/t/f2ca2d42217d01e2?hl=en
* Does this T-Mobile/LG smartphone carrier unlock code ever expire? - 5
messages, 4 authors
http://groups.google.com/group/sci.electronics.repair/t/4272d6a61f9f8866?hl=en
* ATX power supply capacitor identification. - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/fb67dd39f9c3abcc?hl=en

==============================================================================
TOPIC: 75 ohm Termination Question
http://groups.google.com/group/sci.electronics.repair/t/be000fe11979bff2?hl=en
==============================================================================

== 1 of 7 ==
Date: Thurs, Feb 13 2014 7:32 pm
From: Michael Black


On Thu, 13 Feb 2014, Jeff Liebermann wrote:

> On Thu, 13 Feb 2014 17:41:28 -0800, Bennett <bjprice@cal.berkeley.edu>
> wrote:
>
>> On 2/13/2014 5:17 PM, Jeff Liebermann wrote:
>>> On Thu, 13 Feb 2014 10:40:26 -0800, Bennett <bjprice@cal.berkeley.edu>
>>> wrote:
>>>
>>>> A friend replaced her Comcast TV box with an over-the-air antenna but
>>>> continues to use Comcast Internet service. This leaves her
>>>> Comcast-supplied splitter with an unterminated socket - does it matter?
>>>
>>> Yes, it matters.
>>>
>>>> Should I bother to terminate it?
>>>
>>> Yes, you should terminate it.
>>>
>>>> (A barrel connector isn't a good replacement for the splitter as the
>>>> splitter provides a grounding point.)
>>>
>>> Sorta. Apparently she has a 2 way splitter installed with one port
>>> left unterminated. A barrel connector is a very good replacement.
>>> However, you're correct that you'll need to do something about the
>>> grounding point. If this is indoors, just remove the grounding wire,
>>> wrap it around the barrel connector, and hold it in place with a small
>>> hose clamp. For outdoors, use a proper grounding clamp:
>>> <http://www.solidsignal.com/pview.asp?p=pvgb1&d=perfect-vision-pvgb1-single-grounding-blocks-%28pvgb1%29>
>>> <https://www.google.com/search?tbm=isch&q=cable+tv+grounding+block>
>>> For outdoors, also don't forget to recreate the coax drip loop so that
>>> water doesn't run into the connector block, or into the house.
>>> <http://activerain.com/blogsview/3168531/drip-loop-really-do-you-need-it-wenatchee-and-leavenworth-home-inspection>
>>> <http://images.meredith.com/diy/images/2009/03/p_SCW_240_02.jpg>
>
>> Thanks for all your replies. It's an indoor splitter. Since I had a 68
>> ohm resistor and appropriate connector (but no hose clamp), I just built
>> a terminator. Factory-builts are cheap - if you want 10, 25 or 100 but
>> I only needed one.
>
> Not good enough. If you just crammed a 68 ohm resistor into the
> F-connector jack, you probably have a fairly good approximation of an
> antenna. It's going to radiate junk, and pickup more junk (ingres).
> If you insist on doing it like that, wrap the resistor with some
> insulating tape, and then cover it with aluminum foil.
>
One time I was looking into switches that couldn't be accidentally
toggled, and I thought of type F connectors.

I'm sure I took a bit of wire for the center conductor, then a bit of thin
copper sheet. PUt the wire into the centre of the copper sheet, soldered
it, then soldered the copper sheet to the outer part of the connector.
So switching was by screwing in the connector or unscrewing it.

I'm blank about soldering the copper sheet to the outer part of the
conenctor though, but I can picture the finished connector.


> Yeah, you're right that nobody sells them in small quantities. The
> best I can do on eBay is 10 pcs for $3.85 including shipping.
> <http://www.ebay.com/itm/261230167868>
>
That's why I tend to keep junk. Terminators may seem like the most
mundane thing found in a pile of junk on the sidewalk, but if you need
one, you actually save money and effort, while the 60gig iPod that I found
somewhere else needs a battery in order to be useful.

Michael






== 2 of 7 ==
Date: Thurs, Feb 13 2014 7:48 pm
From: Jeff Liebermann


On Thu, 13 Feb 2014 22:32:15 -0500, Michael Black <et472@ncf.ca>
wrote:

>One time I was looking into switches that couldn't be accidentally
>toggled, and I thought of type F connectors.

No need to build your own. Most switch manufacturers make "locking
lever" type of switches. I've used them in various devices where I
didn't want any accidentally toggling. They're also common in
aerospace and military equipment:
<http://infinityaerospace.com/LL_Toggle_Sw_for_Preoiler.jpg>
<http://www.chiefaircraft.com/edm-7103k2zqe.html>
<http://www.ebay.com/bhp/locking-toggle-switch>

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558




== 3 of 7 ==
Date: Fri, Feb 14 2014 6:38 am
From: dave


On 02/13/2014 06:07 PM, Jeff Liebermann wrote:
> On Thu, 13 Feb 2014 17:41:28 -0800, Bennett <bjprice@cal.berkeley.edu>

>
> Not good enough. If you just crammed a 68 ohm resistor into the
> F-connector jack, you probably have a fairly good approximation of an
> antenna. It's going to radiate junk, and pickup more junk (ingres).
> If you insist on doing it like that, wrap the resistor with some
> insulating tape, and then cover it with aluminum foil.
>

Do you have any idea what the wavelength is at 600MHz? It's half a meter
(Meters times megaHertz equals 300). That makes the length of a quarter
wave is 1/8 meter or about 5". A tiny resistor is not going to radiate
efficiently enough. If the "splitter" is a hybrid the unterminated port
will cause higher attenuation through the splitter. Maybe a single dB.
Not important when receiving.

You'd be better off getting a DC block. The splitter loses at least 3 dB.





== 4 of 7 ==
Date: Fri, Feb 14 2014 7:24 am
From: "Michael A. Terrell"



dave wrote:
>
> On 02/13/2014 06:07 PM, Jeff Liebermann wrote:
> > On Thu, 13 Feb 2014 17:41:28 -0800, Bennett <bjprice@cal.berkeley.edu>
>
> >
> > Not good enough. If you just crammed a 68 ohm resistor into the
> > F-connector jack, you probably have a fairly good approximation of an
> > antenna. It's going to radiate junk, and pickup more junk (ingres).
> > If you insist on doing it like that, wrap the resistor with some
> > insulating tape, and then cover it with aluminum foil.
> >
>
> Do you have any idea what the wavelength is at 600MHz? It's half a meter
> (Meters times megaHertz equals 300). That makes the length of a quarter
> wave is 1/8 meter or about 5". A tiny resistor is not going to radiate
> efficiently enough. If the "splitter" is a hybrid the unterminated port
> will cause higher attenuation through the splitter. Maybe a single dB.
> Not important when receiving.
>
> You'd be better off getting a DC block. The splitter loses at least 3 dB.


A DC Block is nothing more than a capacitor between two connectors.
Some use more than one capacitor to extend the usable frequencies. I've
used up to five to have a flat response from <100 KHz to >1400 MHz at 50
Ohms for a production test line. The insertion loss was about .1 dB at
each end of the usable range.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.




== 5 of 7 ==
Date: Fri, Feb 14 2014 9:03 am
From: Jeff Liebermann


On Fri, 14 Feb 2014 06:38:54 -0800, dave <ricketzz@earthlink.net>
wrote:

>On 02/13/2014 06:07 PM, Jeff Liebermann wrote:
>> On Thu, 13 Feb 2014 17:41:28 -0800, Bennett <bjprice@cal.berkeley.edu>
>
>>
>> Not good enough. If you just crammed a 68 ohm resistor into the
>> F-connector jack, you probably have a fairly good approximation of an
>> antenna. It's going to radiate junk, and pickup more junk (ingres).
>> If you insist on doing it like that, wrap the resistor with some
>> insulating tape, and then cover it with aluminum foil.

>Do you have any idea what the wavelength is at 600MHz? It's half a meter
>(Meters times megaHertz equals 300). That makes the length of a quarter
>wave is 1/8 meter or about 5". A tiny resistor is not going to radiate
>efficiently enough.

Whether it radiates efficiently or inefficiently, it still radiates.
Assuming a 1/2 watt resistor, with one lead wrapped around the
grounding screw, and the other shoved into the F-connector center
wire, there will be about 1/4" of exposed wire between the center pin
and the 60 ohm resistor. That's not much, can probably be tolerated,
and will be sufficient to slightly increase base line noise level in
the area. I would hate to think what might happen if EVERYONE decided
to use leaky terminators.[1]

I like to play ham radio (VHF/UHF) in my vehicle when driving. I
constantly hear the digital hash as I drive repeatedly by specific
locations. At first, I assumed that these were leaks from the
overhead cable plant. Nope. When I started banging on doors, I found
some really creative wiring and connector crimping. Most were caused
by distribution amps with unterminated cables, where the coax cable
becomes somewhat of an antenna. I also found either a defective drop
or tap on the pole (Comcast didn't tell me what they found, but they
did fix it).

Obviously, a leaky cable is a much longer length of wire than 1/4" of
exposed center conductor. Yet, after the gross leaks were fixed, I
still could still hear the test tones on the borrowed Trilithic
something leakage detector. I had to install terminators on literally
everything to reduce it to zero. Admittedly, I was working well below
the FCC Part 76.605 leakage limits:
<http://transition.fcc.gov/mb/engineering/605.html>
<http://www.cablefax.com/tech/sections/columns/broadband/Broadband-Signal-Leakage-in-an-All-Digital-Network_33882.html>
<http://www.cablefax.com/tech/deployment/bestpractices/A-Leak-Is-A-Leak&hellip%20Or-Is-It_52272.html>
but I needed to get the radiated junk down to a level where I could
use my radios in the neighborhood. Overkill yes, but necessary.

It's also a problem in the other direction, which is called ingress.
Nearby transmitters, such as mine, can easily get into the cable
system, and interfere with reception. Once it gets in, there's no
easy way to get rid of the signal. The best approach is proper
shielding. It isn't just my transmitters, but broadcast stations,
intermod with cordless phones, RF remotes, wireless security cameras,
and other RF devices. Mostly, they cause problems with cable modems,
which use the higher RF frequencies, but in extreme cases, can affect
TV reception. It's also difficult to see with a spectrum analyzer:
<http://www.jdsu.com/ProductLiterature/DSAM-D3-Spectrum-Analyzer-App-Note.pdf>
Can you see it? Spoiler:
<http://blogs.jdsu.com/hfc/Lists/Photos/dd6cc9ceb7e6a11e1006e1ad654edd7f.jpg>

More:
"Characterizing Signal Leakage from an All-Digital Cable Network"
<http://www.incospec.com/resources/webinars/files/Characterizing%20Signal%20Leakage%20from%20an%20All-Digital%20Cable%20NetworkMS.pdf>

>If the "splitter" is a hybrid the unterminated port
>will cause higher attenuation through the splitter. Maybe a single dB.
>Not important when receiving.

Without a termination, the splitter begins to resonate with the coax
cable which can be made to radiate. I'm not sure of the unterminated
losses, but I suspect it's more than 1dB. I'll try it on the bench
when I have time (mostly to clean off the accumulated junk from the
bench).
<http://802.11junk.com/jeffl/pics/home/slides/test-equip-mess.html>

>You'd be better off getting a DC block. The splitter loses at least 3 dB.

A DC block won't do anything useful except block DC. I think you
might have meant a straight through barrel connector.



[1] Incidentally, you might be amused to look at my study of monopole
antenna gains versus length.
<http://802.11junk.com/jeffl/antennas/Monopole/index.html>
The title includes the wavelength. For example, 0_750 is 3/4
wavelength long and 5_250 is 5.25 wavelengths long. If you look at
the antenna gains, you'll notice that the gain doesn't really drop
very much for shortened antennas. From the antenna patterns:
Wavelength Gain dBi
0.250 5.19
0.125 4.85
0.050 4.75
That's a 0.45dB gain loss in an antenna that's 1/5th the length of a
1/4 wave radiator. That might explain why I'm concerned about even
small amounts of exposed center conductor.


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558




== 6 of 7 ==
Date: Fri, Feb 14 2014 11:16 am
From: dplatt@coop.radagast.org (David Platt)


In article <f7fsf99rlb7drdsn9h8b6v9b5gv1n74lg1@4ax.com>,
Jeff Liebermann <jeffl@cruzio.com> wrote:

>It's also a problem in the other direction, which is called ingress.
>Nearby transmitters, such as mine, can easily get into the cable
>system, and interfere with reception.

Heh. I remember a discussion hereabouts, some years ago... it might
even have been you posting, Jeff?... in which the poster reported
having detected cable-leakage problems in his town, reported them to
the cable company, and was being ignored. He found that even the
cables system's central facility (where the downlinks and primary
head-end amplifiers were) was leaking like a sieve.

He visited the office, asked to speak to the lead engineer, and
explained what he'd found. The engineer poo-pooh'ed and said "No, our
system is tight, we're very careful about that." The OP took out his
2-meter radio, keyed down... and the signal monitors in the next room
went crazy, as the 2-meter signal leaked into the system and saturated
the first-stage amplifiers. Picture quality went to hell all over
town and the phones started ringing...








== 7 of 7 ==
Date: Fri, Feb 14 2014 11:52 am
From: Jeff Liebermann


On Fri, 14 Feb 2014 11:16:43 -0800, dplatt@coop.radagast.org (David
Platt) wrote:

>In article <f7fsf99rlb7drdsn9h8b6v9b5gv1n74lg1@4ax.com>,
>Jeff Liebermann <jeffl@cruzio.com> wrote:
>
>>It's also a problem in the other direction, which is called ingress.
>>Nearby transmitters, such as mine, can easily get into the cable
>>system, and interfere with reception.
>
>Heh. I remember a discussion hereabouts, some years ago... it might
>even have been you posting, Jeff?... in which the poster reported
>having detected cable-leakage problems in his town, reported them to
>the cable company, and was being ignored. He found that even the
>cables system's central facility (where the downlinks and primary
>head-end amplifiers were) was leaking like a sieve.

Not me. I've reported specific leaks, with photos of my test
equipment and attached reports to Comcast. However, that's when I had
a friend employed by Comcast to expedite the process. Even so, it
would usually take a month for any kind of response. I no longer have
an inside track into Comcast, so I don't know what will happen if I
tried that today.

>He visited the office, asked to speak to the lead engineer, and
>explained what he'd found. The engineer poo-pooh'ed and said "No, our
>system is tight, we're very careful about that." The OP took out his
>2-meter radio, keyed down... and the signal monitors in the next room
>went crazy, as the 2-meter signal leaked into the system and saturated
>the first-stage amplifiers. Picture quality went to hell all over
>town and the phones started ringing...

That definitely wasn't me. I would never do that. The most sensitive
point of the cable system is at the head end. That's where all the
gain is buried, where all the numerous RF sources come together, and
where there's a high probability of nearby RF sources creating
problems. I also doubt the story. I'm quite familiar with the
Comcast head-end in Scotts Valley. Nobody gets anywhere near the
equipment unless they have a very good reason for being there. A
leakage complaint doesn't qualify. Also, there's no "lead engineer".
All the Comcast engineers are either in Denver, or outside
contractors.

If you sit in the parking lot at the Scotts Valley office, you'll hear
some RFI coming from the building on VHF and UHF. I've walked around
2 sides of the building with a portable spectrum analyzer and didn't
see anything really disgusting. However, I will admit that everything
above 700 MHz was problematic due to the proximity of a nearby cell
site. That was also many years ago, so things may have changed (or
deteriorated).

So far, what I've seen of the local Comcast plant, it's quite well
done. There's some junk cable Comcast inherited years ago north of
Boulder Creek that should have been ripped out and replaced, but
otherwise, it's quite well done and shielded. Unfortunately, Comcast
is using more and more outside contractors, with minimal oversight,
resulting in some rather lousy installations.
<http://802.11junk.com/jeffl/pics/Comcast/slides/Comcast-cabling.html>
I have more photos that are worse, but I think you can see the
problem.

Also, there are problems with the roadside amplifier and pull boxes.
These are targets for vandals, copper thieves, and sloppy installers.
I've found them broken open and reported them to Comcast. I usually
get an instant reaction, not because of the potential loss of customer
service, but because there's high voltage on the big cable (to run the
amplifiers) which could easily kill some idiot trying to steal the
copper.

Incidentally, if you run into the test frequency that Comcast is using
for leakage testing, I'm interested. It changed a few months ago when
they went all digital and I haven't been able to pry it out of anyone.


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558





==============================================================================
TOPIC: Phase Linear 400 output transistors
http://groups.google.com/group/sci.electronics.repair/t/d0cb28fa4ada674c?hl=en
==============================================================================

== 1 of 9 ==
Date: Fri, Feb 14 2014 2:23 am
From: georgesantel@gmail.com


On Sunday, June 1, 1997 3:00:00 AM UTC-4, John Whitmore wrote:
> I've recently acquired a Phase Linear 400. This was
> an historically important audio amp, as it was the first of the
> wave of high-powered amplifiers that came out of the 1970's.
>
> This unit, though, has been through some tough times.
> I've found lots of shorted and fried components, but the
> main difficulty is in the output transistors.
>
> There are four different types plugged in to the
> sixteen TO-3 sockets. The outputs are four composite-Darlington
> transistors, each having a single driver feeding three
> paralleled output transistors. Someone in the past
> replaced some of the paralleled outputs with various types.
> So, I don't trust the types of transistors I see there.
> Also, I don't know what the original drivers were.
>
> Driver types: GE-37, DTS-701, RCA410
> The first two are 700V, 1A; the third is 300V, 5A rated.
>
> Output types: GE-37, PL-909
> The first is clearly inappropriate in this application,
> and the second is (apparently) a Fairchild special part
> number for Phase Linear. I assume it's intended to be
> a high current type, and possibly similar to 2N5264
> (a Fairchild power transistor of the right era).
>
> From the emitter degeneration resistance (0.22 ohms)
> I suspect the output transistors should be roughly 5A rated.
> Does anyone know? Should I just jam in MJ15003's?
> Or maybe MJ410's (very similar to the RCA410)?
>
> And as for the drivers; should they all be the same
> type as the outputs? What were the original drivers?
>
> Thanks for any info; this can't interest many folk,
> so e-mail is preferred.
>
> John Whitmore
> whit@hipress.phys.washington.edu


If interested I have some XPL909 for sale
georgesantel@gmail.com




== 2 of 9 ==
Date: Fri, Feb 14 2014 8:22 am
From: Smarty


On 2/14/2014 5:23 AM, georgesantel@gmail.com wrote:
> On Sunday, June 1, 1997 3:00:00 AM UTC-4, John Whitmore wrote:
>> I've recently acquired a Phase Linear 400. This was
>> an historically important audio amp, as it was the first of the
>> wave of high-powered amplifiers that came out of the 1970's.
>>
>> This unit, though, has been through some tough times.
>> I've found lots of shorted and fried components, but the
>> main difficulty is in the output transistors.
>>
>> There are four different types plugged in to the
>> sixteen TO-3 sockets. The outputs are four composite-Darlington
>> transistors, each having a single driver feeding three
>> paralleled output transistors. Someone in the past
>> replaced some of the paralleled outputs with various types.
>> So, I don't trust the types of transistors I see there.
>> Also, I don't know what the original drivers were.
>>
>> Driver types: GE-37, DTS-701, RCA410
>> The first two are 700V, 1A; the third is 300V, 5A rated.
>>
>> Output types: GE-37, PL-909
>> The first is clearly inappropriate in this application,
>> and the second is (apparently) a Fairchild special part
>> number for Phase Linear. I assume it's intended to be
>> a high current type, and possibly similar to 2N5264
>> (a Fairchild power transistor of the right era).
>>
>> From the emitter degeneration resistance (0.22 ohms)
>> I suspect the output transistors should be roughly 5A rated.
>> Does anyone know? Should I just jam in MJ15003's?
>> Or maybe MJ410's (very similar to the RCA410)?
>>
>> And as for the drivers; should they all be the same
>> type as the outputs? What were the original drivers?
>>
>> Thanks for any info; this can't interest many folk,
>> so e-mail is preferred.
>>
>> John Whitmore
>> whit@hipress.phys.washington.edu
>
> If interested I have some XPL909 for sale
> georgesantel@gmail.com


Service manuals for Phase Linear 400s, 700s, etc. with schematics, PCB
layouts, instructions, are available at numerous places for free. A
Google search turned this one up, among others:

http://www.vintageshifi.com/repertoire-pdf/Phase-Linear.php










== 3 of 9 ==
Date: Fri, Feb 14 2014 8:52 am
From: jurb6006@gmail.com


There is a website for these.

http://thecarversite.com/

THAT is where you get information on these. I bought one with a fried right channel a couple years ago and due to improper servicing it had blown it all the way back to the current limiters. Surprisingly it did not blow the drivers, but it did blow one predriver. I forgot what I used for those but I DID look at spec sheets etc. because you don't just go to NTE and get transistors for something like this. If you need anything other than the outputs I will find you the correct transistors, don't trust anyone on this. A couple of them are germanium.

The current correct output transistor type is MJ15024 available from Digikey for reasonable, about five bucks each. Replace them ALL in one bank, no exceptions. Each in a bank of three has to equally share the current, and rated down to four ohms with 85 volts rails that pretty much stay put, you don't need any current hogs. That's what happened to mine, it blew the emitter resistor on the one in a bank used for current detection. This is why it blew the predrivrs but not the drivers.

Remove the transistors for checking, all the resistances are too low in the whole thig to do it in circuit. Check ALL emitter resistors. After all is said and done, you can run it on the bench without a load connected with all of the outputs removed and it should look right on a scope, with possible SLIGHT early clipping on one side of the waveform.

There are two types of these, most use all NPN outputs and drivers, the other uses complemmentary. As far as I know only some of the Series Two amps were complementary. If it has the LED meters you don't know, those were built around 1979 and 1980 right after Pioneer bought the company. These have an IC on the board rather than the usual diff pair at the input.

The older ones with the analog meters as fas as I know all used all NPN outputs and drivers.

After I got the right channel fixed I was jamming it and the damn left channel fried. The reason was that where the heavy wires act as a bus and connects all the collectors together in one of the banks of outputs had come loose, it broke the solder over the years. Check ALL connections to ALL outputs because even one of them off can fry the whole channel.

Really, if you are not used to working on high power amps like this, you could waste alot of silicon.

The price break on the MJ15024s comes at ten pieces, so just get twelve and replace them all. With any luck they will all be from the same batch so matching will not be a big problem. There is a matching procedure required after replacing the outputs to assure they are properly matched. If not they could fail prematurely when pushed hard, and you buy this amp to push it hard.

A short at the output terminals should not fry this amp, but connecting it to certain low impedance loads can. The book says never go below four ohms, but many four ohm systems do just that. Bob Carver knew this and set the current limiting to handle probably down to about three ohms because of those gnarly woofers and infinite baffle systems of the day, but any lower and it is vulnerable.

Aso note these amps have abslutely no speaker protection whatsoever, no relay no nothing. They recommend you use speaker fuses calculated to your particular speaker handling capabilities, the formula is in the book.

If you buy the manual you have been scammed, it is available for free not only from carversite, but a few other places. I think you can get it at bama as well, but the best one with the addendums etc. is at carversite. There is a note about certain Infinity speakers that use some ungodly high value cap in their crossover that affects the power down of these amps and can result in a transient if turned back on too quickly. If you got this, you got the right manual. Also note that you do have to sift through that manual as more than one version is covered.

When you get it working you probably won't want to sell it. Even at flat response it sounds better due to an extraordinarily high damping factor. This is one of the few amps that can really benefit from heavy guage (and short) speaker wires. The cones of the speakers act like servomotors actually. Mine is not for sale except under extreme duress, and I mean for alot more than it's worth. You can't buy an amp like this for less than twice what you could sell it for.

So fix it right.

There is a guy on eBay who claims to fix these right for about $350 no matter what is wrong with them. Of course two way shipping is probably extra. The point is, there is a reason people don't fix these things for a hundred bucks.

Get the ohmmeter out before even plugging the thing in and keep us posted.




== 4 of 9 ==
Date: Fri, Feb 14 2014 11:06 am
From: dplatt@coop.radagast.org (David Platt)


>> If interested I have some XPL909 for sale
>> georgesantel@gmail.com

>Service manuals for Phase Linear 400s, 700s, etc. with schematics, PCB
>layouts, instructions, are available at numerous places for free. A
>Google search turned this one up, among others:

But, as the original posting and inquiry has a 1997 date on it, the
issue is probably moot (from the OP's point of view)/






== 5 of 9 ==
Date: Fri, Feb 14 2014 11:33 am
From: jurb6006@gmail.com


Dammit ! Why are people regurgitating old posts now ? This is not hte first time this has happened. It has happened a few times lately.

Oh well, if anyone need advice on those thins I guess there it is.




== 6 of 9 ==
Date: Fri, Feb 14 2014 12:45 pm
From: Jon Elson


jurb6006@gmail.com wrote:

> Dammit ! Why are people regurgitating old posts now ? This is not hte
> first time this has happened. It has happened a few times lately.
>
> Oh well, if anyone need advice on those thins I guess there it is.
It seems to be a problem with some news server that does this, then the
messages propagate to other servers which have long since forgotten
they ever had this message, so it shows as new. Yup, seen a LOT of these
relics from the VERY distant past!

Jon




== 7 of 9 ==
Date: Fri, Feb 14 2014 2:23 pm
From: Leif Neland


Følgende er skrevet af Jon Elson:
> jurb6006@gmail.com wrote:
>
>> Dammit ! Why are people regurgitating old posts now ? This is not hte
>> first time this has happened. It has happened a few times lately.
>>
>> Oh well, if anyone need advice on those thins I guess there it is.
> It seems to be a problem with some news server that does this, then the
> messages propagate to other servers which have long since forgotten
> they ever had this message, so it shows as new. Yup, seen a LOT of these
> relics from the VERY distant past!
>
These ghosts of christmas pasts almost always comes from somebody
replying to a message on google groups.

I wish Google would add a test: "You are replying to an old message. Do
you really want this?"

Leif

--
Husk kørelys bagpå, hvis din bilfabrikant har taget den idiotiske
beslutning at undlade det.






== 8 of 9 ==
Date: Fri, Feb 14 2014 8:16 pm
From: "Phil Allison"



<georgesantel@gmail.com>

> If interested I have some XPL909 for sale


** They the ones with inbuilt B-E resistor or is that the XPL910 ?

A DMM will show about 68 ohms B-E with either polarity at the probes.

BTW:

Phase 400s had in *interesting* design flaw that would cause both channels
to go DC when one channel suffered an output device failure, due to using
common DC fusing for both channels. It worked like this:

1. A single output device fails short in channel A sending that output full
rail DC.

2. The same channel tries to pull the output back to zero by driving the 3
output devices on the other side hard - so one or more of them fails short
immediately due to SOA being grossly exceeded.

3. Channel A's output stage is now shorted rail to rail.

3. One of the two DC rail fuses instantly opens removing the short on the
PSU.

4. Both channels now have their DC supplies connected to a single rail of
either + or - 85V.

5. One of the "flyback" diodes wired from DC rail to speaker output become
forward biased in channel B.

6. The speakers connected to both channels now start smoking .....

FYI:

One can normally remove either DC rail fuse on a PL400 with no ill effect.

The PL700 has 4 DC rail fuses, which eliminates the problem.

Many stereo power amps have NO rail fuses, which also eliminates the
problem by forcing the AC supply fuse to blow.


.... Phil









== 9 of 9 ==
Date: Sat, Feb 15 2014 11:09 am
From: jurb6006@gmail.com


The B-E resistor really makes no difference since the amp has a 10 ohm across it anyway.

Yes, I am not really happy with the fusing arraingement in these, they should be separate for each channel. I can't seem to find 8 amp fuses easily, right now mine has 5s. It works you just can't crank it up too much. I'll p[robably put 19s in it eventualy. It would probably not be a good idea to eliminate them though because in the case of a short the thing can put out significant current. Hell, you can probably get over 10 out of it under normal conditions, 85 volts... and it WILL run into 4 ohms.

One little thing I was thinking of doing is to build a little protection circuit for such amps. At these power levels a I could use the NC contacts of a relay, use a couple resistors and a cap to filter out DC and rectify it to operate the relay and possibly save the woofers. If not at least prevent a fire.

A guy contaced me about a GAS, so for the hell of it I looked up the Ampzilla. It also has no relay, but it does at least have speaker fuses. I bet those things smoke pretty good because they have the outputs in series rather than parallel. I think the power out is close, and the Ampzilla uses only four outputs instead of six but is cooled by forced air.

Anyway, the diodes and the fuse situation is why I told the guy to take the outputs out to test.





==============================================================================
TOPIC: Loss of preset settings on LCD monitor
http://groups.google.com/group/sci.electronics.repair/t/a04d8e22e7d8fc34?hl=en
==============================================================================

== 1 of 1 ==
Date: Fri, Feb 14 2014 3:55 am
From: Ken


Thanks for the replies, I shall look closer at the caps should I open up
the monitor again.





==============================================================================
TOPIC: Magnastat soldering iron bits users in the UK , here?
http://groups.google.com/group/sci.electronics.repair/t/f2ca2d42217d01e2?hl=en
==============================================================================

== 1 of 3 ==
Date: Sat, Feb 15 2014 5:29 am
From: Chris Jones


On 13/02/2014 06:21, N_Cook wrote:
> I cannot find any major suppliers of these bits anymore in the UK,
> despite the likes of RS selling magnastat irons.
> I have a few hundred NOS , plated copper long cone bits, not Weller or
> Cooper AFAIK, that take about 10 minutes to convert to magnastat ,
> assuming you have the curie temp magnastat end caps from old bits
> hanging around, easily removed when you know how.
> If any interest I'll post more details, I'll not be around long enough
> to have used up a few hundred
http://uk.farnell.com/jsp/search/productdetail.jsp?sku=416435
http://uk.farnell.com/jsp/search/productdetail.jsp?sku=416691





== 2 of 3 ==
Date: Sat, Feb 15 2014 6:36 am
From: N_Cook


On 15/02/2014 13:29, Chris Jones wrote:
> On 13/02/2014 06:21, N_Cook wrote:
>> I cannot find any major suppliers of these bits anymore in the UK,
>> despite the likes of RS selling magnastat irons.
>> I have a few hundred NOS , plated copper long cone bits, not Weller or
>> Cooper AFAIK, that take about 10 minutes to convert to magnastat ,
>> assuming you have the curie temp magnastat end caps from old bits
>> hanging around, easily removed when you know how.
>> If any interest I'll post more details, I'll not be around long enough
>> to have used up a few hundred
> http://uk.farnell.com/jsp/search/productdetail.jsp?sku=416435
> http://uk.farnell.com/jsp/search/productdetail.jsp?sku=416691
>

I've never seen a "Frenchman" style before but the tip diameter and
general conicity? looks much the same as the popular long conical type




== 3 of 3 ==
Date: Sat, Feb 15 2014 8:07 am
From: Chris Jones


On 16/02/2014 01:36, N_Cook wrote:
> On 15/02/2014 13:29, Chris Jones wrote:
>> On 13/02/2014 06:21, N_Cook wrote:
>>> I cannot find any major suppliers of these bits anymore in the UK,
>>> despite the likes of RS selling magnastat irons.
>>> I have a few hundred NOS , plated copper long cone bits, not Weller or
>>> Cooper AFAIK, that take about 10 minutes to convert to magnastat ,
>>> assuming you have the curie temp magnastat end caps from old bits
>>> hanging around, easily removed when you know how.
>>> If any interest I'll post more details, I'll not be around long enough
>>> to have used up a few hundred
>> http://uk.farnell.com/jsp/search/productdetail.jsp?sku=416435
>> http://uk.farnell.com/jsp/search/productdetail.jsp?sku=416691
>>
>
> I've never seen a "Frenchman" style before but the tip diameter and
> general conicity? looks much the same as the popular long conical type

As usual at least one of the pictures on the Farnell site is wrong, but
if you get the manufacture's part number and look it up elsewhere you
can see what shape it is. Those are the two kinds of Weller tips I use
regularly, one of them is fine and conical and the other is a big fat
one for large terminals. I do all my really fine soldering with a Metcal
these days.

Chris





==============================================================================
TOPIC: Does this T-Mobile/LG smartphone carrier unlock code ever expire?
http://groups.google.com/group/sci.electronics.repair/t/4272d6a61f9f8866?hl=en
==============================================================================

== 1 of 5 ==
Date: Sat, Feb 15 2014 2:04 pm
From: Judy Miller


Do carrier unlock codes expire?

I received the message below from T-Mobile containing
the procedure to unlock my kid's cellphone.

I can email that procedure to the kid, who is away for a
few months, but the kid sometimes messes things up, and it
says that you can destroy the phone if you do it wrong.

If I wait, the kid will be back in a few months.

Do you know if these carrier unlock instructions expire?

------------------------------------------------------
FROM: AR Notification <DoNotReply@T-Mobile.com>
SUBJECT: T-Mobile Sim Unlock Notification 2125688898
T-Mobile Sim Unlock Request
Sim Unlock Reference: 6493322
IMEI: 023447039850033

Unlock Code: 5398328494192082

Thank you for taking the time to contact T-Mobile.
Below you will see the Instructions for unlocking your LG device.

NOTE: If you receive an error message while performing the instructions
below, stop. Please be aware that if an excessive amount of incorrect
attempts are made, the phone will be permanently locked.

1. Insert T-Mobile or Non T-Mobile SIM card in to the device.
2. Tap the Dialer
3. Enter 2945#*659#
4. Selct Network Lock
5. Enter in the unlock code
7. Click done
8. Click unlock

The phone should display "Network Unlock"
Thank You,
Customer Service
T-Mobile USA, Inc.




== 2 of 5 ==
Date: Sat, Feb 15 2014 2:42 pm
From: Machiel de Wit


Judy Miller schreef op 15-02-2014
in <ldoo9l$870$1@speranza.aioe.org>:
> Do carrier unlock codes expire?
>
> I received the message below from T-Mobile containing
> the procedure to unlock my kid's cellphone.
>
> I can email that procedure to the kid, who is away for a
> few months, but the kid sometimes messes things up, and it
> says that you can destroy the phone if you do it wrong.
>
> If I wait, the kid will be back in a few months.
>
> Do you know if these carrier unlock instructions expire?
>
> ------------------------------------------------------
> FROM: AR Notification <DoNotReply@T-Mobile.com>
> SUBJECT: T-Mobile Sim Unlock Notification 2125688898
> T-Mobile Sim Unlock Request
> Sim Unlock Reference: xxxxxxxx
> IMEI: xxxxxxxxxxxxx
>
> Unlock Code: xxxxxxxxxxxxxxx
>
> Thank you for taking the time to contact T-Mobile.
> Below you will see the Instructions for unlocking your LG device.
>
> NOTE: If you receive an error message while performing the
> instructions below, stop. Please be aware that if an excessive
> amount of incorrect attempts are made, the phone will be
> permanently locked.
>
> 1. Insert T-Mobile or Non T-Mobile SIM card in to the device.
> 2. Tap the Dialer
> 3. Enter 2945#*659#
> 4. Selct Network Lock
> 5. Enter in the unlock code
> 7. Click done
> 8. Click unlock
>
> The phone should display "Network Unlock"
> Thank You,
> Customer Service
> T-Mobile USA, Inc.

Are you serious? Then you better cancel your message.
Not only never expires de unlock code, you make it posible to kidnap
it, due sending all the codes free into the whole world.


--
MdW.




== 3 of 5 ==
Date: Sat, Feb 15 2014 3:20 pm
From: Judy Miller


On Sat, 15 Feb 2014 23:42:59 +0100, Machiel de Wit wrote:

> Are you serious? Then you better cancel your message.
> Not only never expires de unlock code, you make it posible to kidnap
> it, due sending all the codes free into the whole world

I do not understand.
I assumed that the code I received is ONLY for my phone.
So, what good would that unlock code be for someone with a different phone?




== 4 of 5 ==
Date: Sat, Feb 15 2014 3:27 pm
From: "Anthony R. Gold"


On Sat, 15 Feb 2014 23:42:59 +0100, Machiel de Wit
<reply-to-ng.machiel.dewit@xs4all.nl> wrote:

> Judy Miller schreef op 15-02-2014
> in <ldoo9l$870$1@speranza.aioe.org>:
>> Do carrier unlock codes expire?
>>
>> I received the message below from T-Mobile containing
>> the procedure to unlock my kid's cellphone.
>>
>> I can email that procedure to the kid, who is away for a
>> few months, but the kid sometimes messes things up, and it
>> says that you can destroy the phone if you do it wrong.
>>
>> If I wait, the kid will be back in a few months.
>>
>> Do you know if these carrier unlock instructions expire?
>>
>> ------------------------------------------------------
>> FROM: AR Notification <DoNotReply@T-Mobile.com>
>> SUBJECT: T-Mobile Sim Unlock Notification 2125688898
>> T-Mobile Sim Unlock Request
>> Sim Unlock Reference: xxxxxxxx
>> IMEI: xxxxxxxxxxxxx
>>
>> Unlock Code: xxxxxxxxxxxxxxx
>>
>> Thank you for taking the time to contact T-Mobile.
>> Below you will see the Instructions for unlocking your LG device.
>>
>> NOTE: If you receive an error message while performing the
>> instructions below, stop. Please be aware that if an excessive
>> amount of incorrect attempts are made, the phone will be
>> permanently locked.
>>
>> 1. Insert T-Mobile or Non T-Mobile SIM card in to the device.
>> 2. Tap the Dialer
>> 3. Enter 2945#*659#
>> 4. Selct Network Lock
>> 5. Enter in the unlock code
>> 7. Click done
>> 8. Click unlock
>>
>> The phone should display "Network Unlock"
>> Thank You,
>> Customer Service
>> T-Mobile USA, Inc.
>
> Are you serious? Then you better cancel your message.
> Not only never expires de unlock code, you make it posible to kidnap
> it, due sending all the codes free into the whole world.

Judy, relax. Yes, the unlock code will not expire but also it can not be
used or abused to kidnap anyone or anything.




== 5 of 5 ==
Date: Sat, Feb 15 2014 3:58 pm
From: Bert


In news:52ffed79$0$2835$e4fe514c@news2.news.xs4all.nl Machiel de Wit
<reply-to-ng.machiel.dewit@xs4all.nl> wrote:

> Not only never expires de unlock code, you make it posible to kidnap
> it, due sending all the codes free into the whole world.

Unlock codes are specific to the phone. If one worked for all phones, do
you think people would go to such trouble to get one?

--
bert@iphouse.com St. Paul, MN





==============================================================================
TOPIC: ATX power supply capacitor identification.
http://groups.google.com/group/sci.electronics.repair/t/fb67dd39f9c3abcc?hl=en
==============================================================================

== 1 of 1 ==
Date: Sat, Feb 15 2014 3:48 pm
From: "David Farber"


There was a power surge at the customer's house. PG&E said their neutral
line failed. The computer now has an ATX power supply that smells quite
crispy. The 6.3 amp fuse was blown. I replaced it, then shorted pins 13 and
14 together on the main connector to test it outside of the box. I brought
the voltage up slowly with a variac and 100W bulb in series. The fan came on
but the bulb was a bit bright. I removed the bulb and tried it with just the
variac. The fan came on, then smoke came pouring out of one component which
was shorted. It's located between the largest two capacitors on the board
which are 470uF @ 200V. I was able to peel off the heat shrink and it
appears to be a ceramic disk capacitor. The part number starts with 241k. I
cannot read the other numbers that follow. I'm guessing it's 240pF but at
what voltage? It's wired in parallel to the previously mentioned largest
capacitor on the board. Any idea what the voltage rating should be on this
cap? Is it even necessary to replace it? The power supply works fine now
that the short has been removed.

Thanks for your reply.
--
David Farber
Los Osos, CA






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