sci.electronics.repair - 25 new messages in 13 topics - digest

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

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Today's topics:

==============================================================================
TOPIC: C Audio Pulse 2x 1100 watt amp
http://groups.google.com/group/sci.electronics.repair/t/c3528d48b1472472?hl=en
==============================================================================

== 1 of 1 ==
Date: Wed, Jul 28 2010 12:13 am
From: "N_Cook"

Jim <ifixaudio@gmail.com> wrote in message
news:74a484e6-688f-434d-944b-859bdfc3bc09@d37g2000yqm.googlegroups.com...
Have you repaired the amp yet?
I sent you a couple of off list messages but they bounced.
I have repaired a few of this type of amplifier and may be able to
help troubleshoot it.
Contact me off list at IFixAudio at GMail.com.

Jim

No valid emails used on usenet
The one with leaky TO92 repaired and waiting for owner to return from
holiday.
Second one initially looked at , problems again in a TO02 device in a
different area of one amp, gone B-C-E shorted so more obvious a problem.
Waiting for owner to return before progressing on that one. Third one not
looked at other than also goes into protect and no obvious problems with the
TO3s , perhaps so well protected that rarely do the YO3s get a chance to
fail.

I will use a valid email account to contact you

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==============================================================================

== 1 of 1 ==
Date: Wed, Jul 28 2010 2:16 am
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==============================================================================
TOPIC: Site
http://groups.google.com/group/sci.electronics.repair/t/2ea26dc4623e6d0d?hl=en
==============================================================================

== 1 of 4 ==
Date: Wed, Jul 28 2010 3:18 am
From: dhananjay

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== 2 of 4 ==
Date: Wed, Jul 28 2010 6:00 am
From: "William Sommerwerck"

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== 3 of 4 ==
Date: Wed, Jul 28 2010 9:10 am
From: Adrian C

On 28/07/2010 11:18, dhananjay wrote:
> A new site is lunched for largest softwares,technology,mobile
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== 4 of 4 ==
Date: Wed, Jul 28 2010 2:19 pm
From: "Michael A. Terrell"

William Sommerwerck wrote:
>
> > A new site is lunched...
>
> That's what your computer is likely to be after you visit the site.
>
> Why don't these idiots get someone to write their spam in good English? It
> would be much more prepossessing.

Have you seen the new SPAM, made with Hormell bacon? :)

==============================================================================
TOPIC: Midiverb ii issues?
http://groups.google.com/group/sci.electronics.repair/t/aaedd7aef36420d1?hl=en
==============================================================================

== 1 of 3 ==
Date: Wed, Jul 28 2010 3:35 am
From: JW

On Tue, 27 Jul 2010 12:52:09 +0000 (UTC) Meat Plow <mhywatt@yahoo.com>
wrote in Message id: <pan.2010.07.27.12.52.02@hahahahahahahah.nutz>:

>On Mon, 26 Jul 2010 13:35:24 -0700, El Grillo wrote:
>
>> Thank you everyone for your help!
>>
>> I will try to work out some of the issues tomorrow at the shop.
>>
>> Also, if a filter cap tests good using a ESR meter, could it still be
>> bad??
>
>If there is a doubt, sub it. As far as I'm concerned if it passed the ESR
>test it's good (for the time being)

Well, it could be shorted. Somewhat rare for electrolytics IME, though.

== 2 of 3 ==
Date: Wed, Jul 28 2010 6:22 am
From: "Arfa Daily"

"JW" <none@dev.null> wrote in message
news:ht1056l7egepmdrn9epm4ddkabbr3iquel@4ax.com...
> On Tue, 27 Jul 2010 12:52:09 +0000 (UTC) Meat Plow <mhywatt@yahoo.com>
> wrote in Message id: <pan.2010.07.27.12.52.02@hahahahahahahah.nutz>:
>
>>On Mon, 26 Jul 2010 13:35:24 -0700, El Grillo wrote:
>>
>>> Thank you everyone for your help!
>>>
>>> I will try to work out some of the issues tomorrow at the shop.
>>>
>>> Also, if a filter cap tests good using a ESR meter, could it still be
>>> bad??
>>
>>If there is a doubt, sub it. As far as I'm concerned if it passed the ESR
>>test it's good (for the time being)
>
> Well, it could be shorted. Somewhat rare for electrolytics IME, though.

In the past, I have seen many electrolytics that were serving as rail
decouplers, that have gone short. The little purple 10uF's that Panasonic
used to litter everything that they built with, were favourites for failing
short. As you say, doesn't seem to be as common an occurrence these days as
it once was, though. Interestingly, I had a s/c electrolytic just today (see
my post regarding some Restek speakers). It was one of those brown plastic
'Siemens' types that you used to see a lot of in Grundigs and B&O's.

Arfa

== 3 of 3 ==
Date: Wed, Jul 28 2010 2:18 pm
From: "Michael A. Terrell"

Arfa Daily wrote:
>
> "JW" <none@dev.null> wrote in message
> news:ht1056l7egepmdrn9epm4ddkabbr3iquel@4ax.com...
> > On Tue, 27 Jul 2010 12:52:09 +0000 (UTC) Meat Plow <mhywatt@yahoo.com>
> > wrote in Message id: <pan.2010.07.27.12.52.02@hahahahahahahah.nutz>:
> >
> >>On Mon, 26 Jul 2010 13:35:24 -0700, El Grillo wrote:
> >>
> >>> Thank you everyone for your help!
> >>>
> >>> I will try to work out some of the issues tomorrow at the shop.
> >>>
> >>> Also, if a filter cap tests good using a ESR meter, could it still be
> >>> bad??
> >>
> >>If there is a doubt, sub it. As far as I'm concerned if it passed the ESR
> >>test it's good (for the time being)
> >
> > Well, it could be shorted. Somewhat rare for electrolytics IME, though.
>
> In the past, I have seen many electrolytics that were serving as rail
> decouplers, that have gone short. The little purple 10uF's that Panasonic
> used to litter everything that they built with, were favourites for failing
> short. As you say, doesn't seem to be as common an occurrence these days as
> it once was, though. Interestingly, I had a s/c electrolytic just today (see
> my post regarding some Restek speakers). It was one of those brown plastic
> 'Siemens' types that you used to see a lot of in Grundigs and B&O's.

It was very rare with American built electronics. Most failures were
open filter capacitors, or damaged 160 mF, 250 V 'Low Power Factor'
electrolytics used in the voltage doubler power supplies. BTW, 'Low
Power Factor' were rated in the ripple current they could handle.
Today, they would be a Low ESR rating.

The only shorted electrolytics I remember in American built
electronics was the low voltage caps used in the cathode circuits of
audio amps.

==============================================================================
TOPIC: Simple Hack To Get $2000 Watch Video.
http://groups.google.com/group/sci.electronics.repair/t/cf5a9cc1a5f683dd?hl=en
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TOPIC: JVC DR MH20SEK HDD DVD recorder
http://groups.google.com/group/sci.electronics.repair/t/0b41d7f44dc58003?hl=en
==============================================================================

== 1 of 2 ==
Date: Wed, Jul 28 2010 4:49 am
From: "N_Cook"

Ticking smps , caused by failing hot side electro on the supply V for the
switching ic driver. Uprated and smps is stable putting out right sorts of
higher DC , according to the schematics.
But the LV 3.3V etc regulators seem to be waiting for a control signal.
No display, no fan , no button function and flow chart on e-service is in
Russian but I suspect like the error code page needs the display up and
running . Is there something very basic to do or mantra to say?

== 2 of 2 ==
Date: Wed, Jul 28 2010 6:25 am
From: "N_Cook"

Broken land number 23 on the main ribbon meant 17V supply was going nowhere,
not me honest, I always wrap proper cloth tape around these ribbon ends , to
beef them up, before inserting them. Someone else had tried repairing this
one. All functions seem to be returned as far as not connected up to a
screen is concerned so far.

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TOPIC: Restek powered studio monitors
http://groups.google.com/group/sci.electronics.repair/t/3d5bac222a0b8837?hl=en
==============================================================================

== 1 of 7 ==
Date: Wed, Jul 28 2010 6:11 am
From: "Arfa Daily"

Owner of local high-end hifi store that I do some service work for, bought
these in with the surrounds rotted away on the bass drivers. Apparently,
these things were 8 grand apiece 12 years ago when new. He managed to get
some new cones / surrounds from the States somewhere for a reasonable price,
and fitted them. One of the amps also needed a new level pot, so he put one
of those in, too. When he repowered them, one worked perfectly, but the one
that he had put the pot in, buzzed so loudly that it nearly destroyed his
new cone work. He couldn't see anything that he had done wrong, so he sent
them both to me. One double hernia later, I had them both up on the bench.
They are signal-sensing for main power turn on, so first I had to work out
which was the relay for this, and bridge it such that the amp could be
powered via a variac. At about 40v input, the amps started working (separate
amps for bass and mid / top drive) but the bass amp started motorboating
violently. I spent a very long time checking caps in the power supply and
bass amp. Interestingly, I found one with very poor ESR on the driver board,
but replacement made no improvement, and then a 470uF that read very good
ESR - in fact so good, that it rang alarm bells, so I whipped it out and put
a good old analogue ohm meter across it. It was short circuit (near enough).
Remember we were talking about just this a couple of days back in the thread
about SMPS cap testing, where someone asked if an ESR meter showed a cap as
good, could it still be bad, and someone else then commented that a straight
ohms test should be carried out "for sanity" I think was the phrase. Well
here we are with a good real life example. Anyway, that turned out to be a
red herring too. I don't know what that cap did as I have no schematics, but
a replacement had no effect on the instability problem.

At this point, having already spent too long on the job, I phoned the store
owner to tell him where we were at with the problem. He then went through
what he had done again, and then casually tossed in that the voice coils on
the bass units that he had re-coned, were unusual in that there were two of
them per driver ...

Now some real alarm bells started to sound in my head. I asked him if he
meant that the drivers had four wires going to each of them, and he said
yes. I hadn't actually seen the backs of the drivers, as they come out from
the fronts of the cabs, and the backs are packed with damping material. I
rang off, and pulled one out, and indeed, there were four terminals, two of
which had a fairly heavy piece of twin connected to them, and the other two,
had a piece of thin screened wire connected to them. Looking at the
soldering, he had definitely had these wires off, so I removed the screened
wire, and reversed it. That cured all the problems, so I have to conclude
that the second 'voice coil' is in fact some kind of feedback winding, and
when the cone went say forward, this winding, being reverse connected, was
telling the amp that it had moved backwards, playing havoc with the
stability.

In many many years of servicing all sorts of hifi and audio amplification
equipment, I don't ever recall having come across a bass driver with a
feedback coil like this. Has anyone else on here, or anyone have any
knowledge of the system, and what the advantages are claimed to be ?

Arfa

== 2 of 7 ==
Date: Wed, Jul 28 2010 6:29 am
From: Ron

On 28/07/2010 14:11, Arfa Daily wrote:
> Owner of local high-end hifi store that I do some service work for,
> bought these in with the surrounds rotted away on the bass drivers.
> Apparently, these things were 8 grand apiece 12 years ago when new. He
> managed to get some new cones / surrounds from the States somewhere for
> a reasonable price, and fitted them. One of the amps also needed a new
> level pot, so he put one of those in, too. When he repowered them, one
> worked perfectly, but the one that he had put the pot in, buzzed so
> loudly that it nearly destroyed his new cone work. He couldn't see
> anything that he had done wrong, so he sent them both to me. One double
> hernia later, I had them both up on the bench. They are signal-sensing
> for main power turn on, so first I had to work out which was the relay
> for this, and bridge it such that the amp could be powered via a variac.
> At about 40v input, the amps started working (separate amps for bass and
> mid / top drive) but the bass amp started motorboating violently. I
> spent a very long time checking caps in the power supply and bass amp.
> Interestingly, I found one with very poor ESR on the driver board, but
> replacement made no improvement, and then a 470uF that read very good
> ESR - in fact so good, that it rang alarm bells, so I whipped it out and
> put a good old analogue ohm meter across it. It was short circuit (near
> enough). Remember we were talking about just this a couple of days back
> in the thread about SMPS cap testing, where someone asked if an ESR
> meter showed a cap as good, could it still be bad, and someone else then
> commented that a straight ohms test should be carried out "for sanity" I
> think was the phrase. Well here we are with a good real life example.
> Anyway, that turned out to be a red herring too. I don't know what that
> cap did as I have no schematics, but a replacement had no effect on the
> instability problem.
>
> At this point, having already spent too long on the job, I phoned the
> store owner to tell him where we were at with the problem. He then went
> through what he had done again, and then casually tossed in that the
> voice coils on the bass units that he had re-coned, were unusual in that
> there were two of them per driver ...
>
> Now some real alarm bells started to sound in my head. I asked him if he
> meant that the drivers had four wires going to each of them, and he said
> yes. I hadn't actually seen the backs of the drivers, as they come out
> from the fronts of the cabs, and the backs are packed with damping
> material. I rang off, and pulled one out, and indeed, there were four
> terminals, two of which had a fairly heavy piece of twin connected to
> them, and the other two, had a piece of thin screened wire connected to
> them. Looking at the soldering, he had definitely had these wires off,
> so I removed the screened wire, and reversed it. That cured all the
> problems, so I have to conclude that the second 'voice coil' is in fact
> some kind of feedback winding, and when the cone went say forward, this
> winding, being reverse connected, was telling the amp that it had moved
> backwards, playing havoc with the stability.
>
> In many many years of servicing all sorts of hifi and audio
> amplification equipment, I don't ever recall having come across a bass
> driver with a feedback coil like this. Has anyone else on here, or
> anyone have any knowledge of the system, and what the advantages are
> claimed to be ?
>
> Arfa

Didn't Phillips do something like this back in the 70's? Motion feedback
or some such daft name?

Ron

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== 3 of 7 ==
Date: Wed, Jul 28 2010 8:37 am
From: whit3rd

On Jul 28, 6:29 am, Ron <r...@lunevalleyaudio.com> wrote:
> On 28/07/2010 14:11, Arfa Daily wrote:
>
>
>
>
>
> > Owner of local high-end hifi store that I do some service work for,
> > bought these in with the surrounds rotted away on the bass drivers.
> > Apparently, these things were 8 grand apiece 12 years ago when new. He
> > managed to get some new cones / surrounds from the States somewhere for
> > a reasonable price, and fitted them. One of the amps also needed a new
> > level pot, so he put one of those in, too. When he repowered them, one
> > worked perfectly, but the one that he had put the pot in, buzzed so
> > loudly that it nearly destroyed his new cone work. He couldn't see
> > anything that he had done wrong, so he sent them both to me. One double
> > hernia later, I had them both up on the bench. They are signal-sensing
> > for main power turn on, so first I had to work out which was the relay
> > for this, and bridge it such that the amp could be powered via a variac.
> > At about 40v input, the amps started working (separate amps for bass and
> > mid / top drive) but the bass amp started motorboating violently. I
> > spent a very long time checking caps in the power supply and bass amp.
> > Interestingly, I found one with very poor ESR on the driver board, but
> > replacement made no improvement, and then a 470uF that read very good
> > ESR - in fact so good, that it rang alarm bells, so I whipped it out and
> > put a good old analogue ohm meter across it. It was short circuit (near
> > enough). Remember we were talking about just this a couple of days back
> > in the thread about SMPS cap testing, where someone asked if an ESR
> > meter showed a cap as good, could it still be bad, and someone else then
> > commented that a straight ohms test should be carried out "for sanity" I
> > think was the phrase. Well here we are with a good real life example.
> > Anyway, that turned out to be a red herring too. I don't know what that
> > cap did as I have no schematics, but a replacement had no effect on the
> > instability problem.
>
> > At this point, having already spent too long on the job, I phoned the
> > store owner to tell him where we were at with the problem. He then went
> > through what he had done again, and then casually tossed in that the
> > voice coils on the bass units that he had re-coned, were unusual in that
> > there were two of them per driver ...
>
> > Now some real alarm bells started to sound in my head. I asked him if he
> > meant that the drivers had four wires going to each of them, and he said
> > yes. I hadn't actually seen the backs of the drivers, as they come out
> > from the fronts of the cabs, and the backs are packed with damping
> > material. I rang off, and pulled one out, and indeed, there were four
> > terminals, two of which had a fairly heavy piece of twin connected to
> > them, and the other two, had a piece of thin screened wire connected to
> > them. Looking at the soldering, he had definitely had these wires off,
> > so I removed the screened wire, and reversed it. That cured all the
> > problems, so I have to conclude that the second 'voice coil' is in fact
> > some kind of feedback winding, and when the cone went say forward, this
> > winding, being reverse connected, was telling the amp that it had moved
> > backwards, playing havoc with the stability.
>
> > In many many years of servicing all sorts of hifi and audio
> > amplification equipment, I don't ever recall having come across a bass
> > driver with a feedback coil like this.

> Didn't Phillips do something like this back in the 70's? Motion feedback
> or some such daft name?

I think they called it 'David', it was a motion feedback woofer in a
powered-speaker
form factor. This kind of system can control the low frequency
behavior
of the cone very accurately. Mossbauer apparatus uses the same
hardware for motion control with < .01% distortion, but that's a
linear-motion
measurement, no idea what the air movement effectiveness is.

== 4 of 7 ==
Date: Wed, Jul 28 2010 9:50 am
From: "Arfa Daily"

>
>> Didn't Phillips do something like this back in the 70's? Motion feedback
>> or some such daft name?
>
> I think they called it 'David', it was a motion feedback woofer in a
> powered-speaker
> form factor. This kind of system can control the low frequency
> behavior
> of the cone very accurately. Mossbauer apparatus uses the same
> hardware for motion control with < .01% distortion, but that's a
> linear-motion
> measurement, no idea what the air movement effectiveness is.
>

OK, both. Don't remember the Philips system, but then the company that I was
working for back then, didn't do much with Philips. Still, that sounds like
the sort of system. Those specs for the Mossbauer are impressive. I guess
that's the sort of thing that it's going to be, given the claimed value of
these things. I've just been listening to a CD through them. They sound
nice, and very smooth with a very flat and stiff sounding bass. Quite easy
on the old lug-holes, but I'm not sure that I would rate them as 16 grand
more easy than my home-built EMI 13 x 8 cabs from the 70's ... :-)

Arfa

== 5 of 7 ==
Date: Wed, Jul 28 2010 12:10 pm
From: Ron

On 28/07/2010 17:50, Arfa Daily wrote:
>
>
>>
>>> Didn't Phillips do something like this back in the 70's? Motion feedback
>>> or some such daft name?
>>
>> I think they called it 'David', it was a motion feedback woofer in a
>> powered-speaker
>> form factor. This kind of system can control the low frequency
>> behavior
>> of the cone very accurately. Mossbauer apparatus uses the same
>> hardware for motion control with < .01% distortion, but that's a
>> linear-motion
>> measurement, no idea what the air movement effectiveness is.
>>
>
> OK, both. Don't remember the Philips system, but then the company that I
> was working for back then, didn't do much with Philips. Still, that
> sounds like the sort of system. Those specs for the Mossbauer are
> impressive. I guess that's the sort of thing that it's going to be,
> given the claimed value of these things. I've just been listening to a
> CD through them. They sound nice, and very smooth with a very flat and
> stiff sounding bass. Quite easy on the old lug-holes, but I'm not sure
> that I would rate them as 16 grand more easy than my home-built EMI 13 x
> 8 cabs from the 70's ... :-)
>
>
> Arfa

Ahh 13 x 8's did they have the whizzer cone in the centre?

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== 6 of 7 ==
Date: Wed, Jul 28 2010 1:16 pm
From: David Nebenzahl

On 7/28/2010 12:10 PM Ron spake thus:

> On 28/07/2010 17:50, Arfa Daily wrote:
>
>> I've just been listening to a CD through them. They sound nice, and
>> very smooth with a very flat and stiff sounding bass. Quite easy on
>> the old lug-holes, but I'm not sure that I would rate them as 16
>> grand more easy than my home-built EMI 13 x 8 cabs from the 70's
>> ... :-)
>
> Ahh 13 x 8's did they have the whizzer cone in the centre?

Whizzer cones? Are you pulling our legs?

I always associated whizzer cones with the know-nothing, 6x9 oval weird
expensive speakers to throw in the back of your car market, not anything
near audiophool quality. Am I wrong?

--
The fashion in killing has an insouciant, flirty style this spring,
with the flaunting of well-defined muscle, wrapped in flags.

- Comment from an article on Antiwar.com (http://antiwar.com)

== 7 of 7 ==
Date: Wed, Jul 28 2010 1:23 pm
From: "William Sommerwerck"

> I always associated whizzer cones with the know-nothing,
> 6x9 oval weird expensive speakers to throw in the back of
> your car market, not anything near audiophool quality.
> Am I wrong?

Yes, and no.

The whizzer was a kind of tweeter. But it also served the purpose (though I
don't understand the mechanics) of decoupling the central section of the
driver, allowing it to do a better job with the mids and highs.

My understanding is that there /were/ some "good" drivers with whizzers, but
I don't remember the manufacturers or models.

Please do not equate "audiophile" with "audiophool". If nothing else, it's a
rude insult to the people who have gotten high-quality sound reproduction to
the point where it is.

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TOPIC: Parrot Clip Test Probes
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== 1 of 1 ==
Date: Wed, Jul 28 2010 10:19 am
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== 1 of 1 ==
Date: Wed, Jul 28 2010 12:50 pm
From: b

On Jul 28, 3:10 am, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:
> "b" <reverend_rog...@yahoo.com> wrote in message
>
> news:7d34ed60-55eb-4174-bf68-80ec0af85389@f15g2000vbq.googlegroups.com...
>
>
>
> > Picked this up a few months back and just hauled it out. The units
> > power up, and lights come on but the cassette deck stubbornly remains
> > dead.
>
> > This is a 'pseudo-separates' affair, where each box is connected by
> > means of a flat ribbon cable. The main trafo. is in the amp which then
> > feeds a 'sound processor'/input selector box, from whence the dvd and
> > cassette decks are fed. The dvd, which is downstream from the
> > cassette, powers up fine. I'm assuming they use the same power rail,
> > so will concentrate on the cassette unit first.
> > Going to take some measurements on the cassette pcb, but I'd like the
> > service data to speed things up, as this is quite a complex unit and
> > it would save me the hassle of having to unscrew and open all the
> > boxes to trace the basic voltage lines.
>
> > Anyone suggest a source for a schematic? Tried eserviceinfo to no
> > avail....
> > cheers,
> > B
>
> I've sent you a set of schematics direct off-group. Let me know that you get
> them ok
>
> Arfa

Quick update.
Took a few measurements - all 3 entry safety resistors in the cassette
main pcb 'psu' are fine with the correct voltages present.
Checked Q604, which drops the 10v to 5v and that has 5v on its
emittter. This 5v is also present on pin 5 of main pcb connector 901
which goes to the LED/button panel.
Checked Q602 the 9.6v regulator. Voltage present and correct there
too.
hmmm...
could this be something amiss on the button /LED panel? Will do this
next.
As an aside, whilst I had the thing on, I noticed there is a sub pcb
in the amp module with 3x B1548 power transistors mounted on a small
heatsink - getting red hot, not a good sign. may or may not be
related.
-B

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