sci.electronics.repair
http://groups.google.com/group/sci.electronics.repair?hl=en

sci.electronics.repair@googlegroups.com

Today's topics:

* Phase Linear 400 output transistors - 5 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/d0cb28fa4ada674c?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? - 11
messages, 7 authors
http://groups.google.com/group/sci.electronics.repair/t/4272d6a61f9f8866?hl=en
* ATX power supply capacitor identification. - 7 messages, 5 authors
http://groups.google.com/group/sci.electronics.repair/t/fb67dd39f9c3abcc?hl=en

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

== 1 of 5 ==
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









== 2 of 5 ==
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.




== 3 of 5 ==
Date: Sat, Feb 15 2014 6:16 pm
From: "Phil Allison"



<jurb6006@gmail.com>

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

** It does if you mix up devices.


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.

** The relay contacts will arc and burn soon as they open under a DC fault.





.... Phil






== 4 of 5 ==
Date: Sat, Feb 15 2014 10:16 pm
From: jurb6006@gmail.com


>"** It does if you mix up devices. "

Not much. In each bank you got the bases all connnected directly together and the emitters are only separated by 0.33 resistors. However you are right that it will matter because if you tray to push these things and the current isn't shared it will fry fast and the outputs will probably read zero all the way arond.

>"** The relay contacts will arc and burn soon as they open under a DC fault. "

Well now I got a solution to that believe it or not and I am surprised that noone does it. (or maybe they do)


take a nice 47 uF or so bipolar cap across the contacts. Period. think aabout it no before to go saying anything.

First of all the cap is not in the circuit during normal operation. The relay only kicks "out" by the application of high DC, which of course WOULD produce an arc due to the inductance, but a capacitor will take care of that. We are not concerned with AC here, just DC blowing your fucking $3,000 Tannoy. Plus when amps put out full DC, they are not puttin gout any AC except for maybe some power supply ripple.

You know, that was a damn goo danswer about why they put those magnets around the speaker realys in amps that make the Ampzilla look like Kermit the frog, but my question is why didn't they just put a fucking capacitor across the terminals ?

You tell me. I am not being sarcastic. I can't tnink of a single reason why they couldn't just put a 10/300 bipolar across there and be done with it anstead of fucking with magnets. that solution probably cost directly in manhours to implement, a cap could simply be on the board.

What's more, from a fidelity standpoint, if the realy had any inductance the cap would improve its performance there. Maybe even better the slew rate.

I wonder why these highly paid enjunears cunt figger dat out.

I see no downside to the caps. they are probably even cheaper than magnets. they are certainly cheaper to install.




== 5 of 5 ==
Date: Sat, Feb 15 2014 11:26 pm
From: "Phil Allison"



<jurb6006@gmail.com>

>"** It does if you mix up devices. "

Not much. In each bank you got the bases all connnected directly together
and the emitters are only separated by 0.33 resistors.

** If you have 3 of one kind on one side, then 10 ohms drops to 7 and the
pre bias is skewed.


>"** The relay contacts will arc and burn soon as they open under a DC
>fault. "

Well now I got a solution to that believe it or not and I am surprised that
noone does it. (or maybe they do)
take a nice 47 uF or so bipolar cap across the contacts. Period. think
aabout it no before to go saying anything.

** Far cheaper to use a triac, DC crowbar to protect speakers.

OR a changeover relay wired to open the output link PLUS short the speakers
to ground under DC fault conditions.

Must have installed 50 of those in PL400s and PL700s years ago.



... Phil










==============================================================================
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 11 ==
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 11 ==
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 11 ==
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 11 ==
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 11 ==
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




== 6 of 11 ==
Date: Sat, Feb 15 2014 3:59 pm
From: Bert


In news:ldoso5$jm8$1@speranza.aioe.org Judy Miller <jmiller@not.gmail.com>
wrote:

> I assumed that the code I received is ONLY for my phone.

It is.

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




== 7 of 11 ==
Date: Sat, Feb 15 2014 7:21 pm
From: tlvp


On Sat, 15 Feb 2014 23:20:38 +0000 (UTC), Judy Miller wrote:

> 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?

You are quite right: the unlock code is specific to the one handset in the
world with the IMEI that your phone bears. Moreover, the procedure the
email describes -- the "instructions for unlocking your LG device" -- are
specific to your particular model of LG phone. Motorolas, Nokias, etc.,
have unlock codes of different lengths, and unlock instructions of
different character.

Finally, as a general rule, unlock codes -- and unlock instructions -- are
good until used -- and beyond (one Motorola phone I had gotten unlock
instructions for -- and successfully unlocked -- mysteriously got itself
re-locked again when I put in a new carrier's SIM card -- fortunately, I
still had access to the old unlock instructions, applied them, and Presto!
the phone was unlocked once again :-) .

So don't lose that unlock instruction email :-) ! HTH. Cheers, -- tlvp
--
Avant de repondre, jeter la poubelle, SVP.




== 8 of 11 ==
Date: Sat, Feb 15 2014 10:19 pm
From: "Geoffrey S. Mendelson"


Bert wrote:
>
> 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?
>
They are actually specific not only to the phone, but to the service
provider. So if you bought the phone from T-Mobile, it would have a different
code than the same phone bought from AT&T.

Some phones can be unlocked by buying the code from various vendors in
Eastern Europe. I have unlocked several Motorola phones that way.

Some phones require the code come from the service provider, who will only
provide them to current customers and may have other restrictions.

iPhones really need to be unlocked by Apple, who will only do it if the
service provider who bought it from them asks them to do it. Then a
magical unlock code is sent via iTunes to the registered owner of the phone.

There are many unlock hacks for iPhones, most of them don't work, or stop
working if you reboot the phone.

Geoff.



--
Geoffrey S. Mendelson, N3OWJ/4X1GM/KBUH7245/KBUW5379





== 9 of 11 ==
Date: Sun, Feb 16 2014 12:27 am
From: tlvp


On Sun, 16 Feb 2014 06:19:21 +0000 (UTC), Geoffrey S. Mendelson commented
on:

>> 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?
>>
> They are actually specific not only to the phone, but to the service
> provider. So if you bought the phone from T-Mobile, it would have a different
> code than the same phone bought from AT&T.

More particularly, an unlock code is specific to a given handset's IMEI.
The manufacturers leave it, in part, to the service providers to determine
to whom and under what circumstances to reveal the unlock code and
directions for its use. But "service provider" is not used so restrictively
as to mean cellular operators only, for, as you say,

> Some phones can be unlocked by buying the code from various vendors in
> Eastern Europe. I have unlocked several Motorola phones that way.

Mainly, it means Nokia or Motorola won't divulge unlock codes to you or me.
Or anyway, that's the impression I've always been under :-) .

Cheers, -- tlvp
--
Avant de repondre, jeter la poubelle, SVP.




== 10 of 11 ==
Date: Sun, Feb 16 2014 12:48 am
From: Machiel de Wit


Anthony R. Gold schreef op 16-02-2014
in <gotvf9d5gstbi1nb32v49t7koofqo96tdb@4ax.com>:
> 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.

The unlock code alone not indeed, but the IMEI code is a unique
identifier.
But who take care these days for personal securyty? One gives
everything away for a free lunch [1]. Apparently Judy is not aware of
the transparency of usenet.

[1] "There ain't no such thing as a free lunch"


--
MdW.




== 11 of 11 ==
Date: Sun, Feb 16 2014 5:05 am
From: Olaf Schmitt


Am 15.02.2014 23:04, schrieb 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.
>

Look at this:
http://www.youtube.com/watch?v=4mndv4gmYEI








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

== 1 of 7 ==
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






== 2 of 7 ==
Date: Sat, Feb 15 2014 4:20 pm
From: Ian Malcolm


"David Farber" <farberbear.unspam@aol.com> wrote in
news:ldoue5$o9d$1@dont-email.me:

> 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

> 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.
>

Its *NOT* a cap, its a varistor and is supposed to clip any spikes on the
AC in. Replace it with one rated for continuous operation at your local
supply voltage or the next time there's a surge the PSU will puke its
guts and is quite likely to take out the motherboard and/or hard drive.
There may be one across the other big cap as well and if so they should
be replaced as a pair. Its essential to replace the heatshrink (and make
sure its non-flamable) or the next failure will deposit a conductive
coating over the rest of the PSU.


--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & >32K emails --> NUL




== 3 of 7 ==
Date: Sat, Feb 15 2014 4:39 pm
From: "David Farber"


Ian Malcolm wrote:
> "David Farber" <farberbear.unspam@aol.com> wrote in
> news:ldoue5$o9d$1@dont-email.me:
>
>> 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
>
>> 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.
>>
>
> Its *NOT* a cap, its a varistor and is supposed to clip any spikes on
> the AC in. Replace it with one rated for continuous operation at your
> local supply voltage or the next time there's a surge the PSU will
> puke its guts and is quite likely to take out the motherboard and/or
> hard drive. There may be one across the other big cap as well and if
> so they should be replaced as a pair. Its essential to replace the
> heatshrink (and make sure its non-flamable) or the next failure will
> deposit a conductive coating over the rest of the PSU.

Thanks for that info. I'll remove it from the pc until I get the correct
parts. You are correct, there is another one of these across the other big
cap.

--
David Farber
Los Osos, CA






== 4 of 7 ==
Date: Sat, Feb 15 2014 8:44 pm
From: "Phil Allison"



"Ian Malcolm"
>
>
> Its *NOT* a cap, its a varistor and is supposed to clip any spikes on the
> AC in.

** Nonsense.

Large electros kill spikes just like sledgehammers kill flies.

A bridge rectifier followed by a filter electro is the best spike suppressor
you will ever see.


> Replace it with one rated for continuous operation at your local
> supply voltage or the next time there's a surge the PSU will puke its
> guts and is quite likely to take out the motherboard and/or hard drive.
> There may be one across the other big cap as well and if so they should
> be replaced as a pair.

** All they do is make the fuse blow if the electros are overvoltaged by
connection to a too high AC supply.


.... Phil









== 5 of 7 ==
Date: Sat, Feb 15 2014 10:01 pm
From: jurb6006@gmail.com


Our buddy Phill composed, in an unusually non-berating way today thusly :

>"Large electros kill spikes just like sledgehammers kill flies. "

And they got better aim. As long as you have full wave rectification, and the rectifiers can handle alot of peak current, they are quite effective. However they are not effective so much against having simple overvoltage applied.

You are not in the US, if the power there is like the UK or whatever it is different. While you have 240 coming in referenced to neutral, in the US it is half that. The line is balanced with two 120 volt legs out of phase. Almost all smaller appliiances run from one leg to neutral. If the neutral loses continuity it can apply as much as double the effective, peak to peak, RMS and whatever other way you want to measure it - voltage to your appliance.

This cannot happen in the good countries but I am not here to bitch. At the moment...

At any rate, I have seen a bunch of equipment saved by these MOVs over the years and in fact at one time I did install them as an option on repair jobs. When I worked where they sold service contracts, I should have installed them as a matter of standard operating procedure.

Of course this does not necessarily apply in other countries.

I have also noticed a few tings that actually switch themself. What most of them do is to simply rectify without doubling and then kick it up with a chopper circuit, the usual boost thing. When the incoming is well above the 160 rectified the booster simply shuts down and passes the juice.

A long time ago I worked on a bunch of little TVs for a limo service that actually ran on 24 volts but had an upconvertor for use on 12 volts. The upside to these little Sonys (who else ?) was that they could be simply connected into 24 volt systems (tractor trailers/lorries) with zero modifications. You could fuse it a little lower but that wasn't all that bad.

I think as soon as Edison's body was cold they should have made it 240, yes center tapped like it is, but made all the outlets and appliances 240 all the time. they also should have changed the frequency to 400 Hz. (CPS LOL) Or better yet, maybe 360 or something to make it easier to make electric clocks. Synchronous motors would be a little more complex but think of all the speeds you could have.

Enough, I am not drunk enough to write more right now... lol.




== 6 of 7 ==
Date: Sat, Feb 15 2014 11:45 pm
From: "Phil Allison"



<jurb6006@gmail.com>
Our buddy Phill composed, in an unusually non-berating way today thusly :

>"Large electros kill spikes just like sledgehammers kill flies. "

And they got better aim. As long as you have full wave rectification, and
the rectifiers can handle alot of peak current, they are quite effective.
However they are not effective so much against having simple overvoltage
applied.

You are not in the US, if the power there is like the UK or whatever it is
different. While you have 240 coming in referenced to neutral, in the US it
is half that. The line is balanced with two 120 volt legs out of phase.
Almost all smaller appliiances run from one leg to neutral. If the neutral
loses continuity it can apply as much as double the effective, peak to peak,
RMS and whatever other way you want to measure it - voltage to your
appliance.


** The 120V leg with the greater load will drop voltage when the neutral is
lost - so the other leg goes up until something goes bang.

This cannot happen in the good countries but I am not here to bitch.

** It happens now and then in live entertainment venues when 3 phase power
is used.

Same reason, no neutral exists or loss of the of neutral conductor.


.... Phil






== 7 of 7 ==
Date: Sun, Feb 16 2014 1:03 am
From: "Michael A. Terrell"



jurb6006@gmail.com wrote:
>
> I think as soon as Edison's body was cold they should have made it 240, yes center tapped like it is, but made all the outlets and appliances 240 all the time. they also should have changed the frequency to 400 Hz. (CPS LOL) Or better yet, maybe 360 or something to make it easier to make electric clocks. Synchronous motors would be a little more complex but think of all the speeds you could have.


You are already too drunk to make sense. There were a lot of 25 Hz
power plants for rialroads, mines and other places that required low
speeds and very high starting torque. Also, 400 hz would reduce the size
of a power grid segments, before the losses become excessive. This would
require a lot more HV AC to DC and DC to AC conversion for distribution
between grid segments. That also lowers the overall grid efficiency,
which will raise your electric bill. This is why no one asked your
opinion of our power distribution systems.

<http://en.wikipedia.org/wiki/Amtrak%27s_25_Hz_traction_power_system>


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




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