sci.electronics.repair@googlegroups.com

Today's topics:

* Orange Rocker 30, combo, 2006 - 5 messages, 4 authors
http://groups.google.com/group/sci.electronics.repair/t/fdf96ce609e107d9?hl=en
* Where to get schematic of Funai TV, Model FT1371? - 3 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/f75b6f935b5d3675?hl=en
* Danger of running hot receiver (Kyocera)? - 7 messages, 6 authors
http://groups.google.com/group/sci.electronics.repair/t/2eeb7d68559500c5?hl=en
* Teac AG-790 has me stumped... - 5 messages, 4 authors
http://groups.google.com/group/sci.electronics.repair/t/19f1f1c9d95691fb?hl=en
* continuous action solder sucker - 2 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/1447a02166d89d01?hl=en
* oops! coffee into the top of TV! - 2 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/927853c231d2a8d2?hl=en
* So, who's the king of finding data sheets ... ? - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/4e444c319ac55fa0?hl=en

==============================================================================
TOPIC: Orange Rocker 30, combo, 2006
http://groups.google.com/group/sci.electronics.repair/t/fdf96ce609e107d9?hl=en
==============================================================================

== 1 of 5 ==
Date: Tues, Jun 29 2010 12:24 pm
From: "Geoffrey S. Mendelson"

Arfa Daily wrote:
> Er, that would be a yes then ... Probably three or four a week, most every
> week, and have been doing them for around 40 years

If you are such an expert, please tell us how they got that volume
control to go to 11, while (whilst?) everyone knows they only go to 10?

:-)

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM
I do multitasking. If that bothers you, file a complaint and I will start
ignoring it immediately.

== 2 of 5 ==
Date: Tues, Jun 29 2010 5:43 pm
From: "Arfa Daily"

"Geoffrey S. Mendelson" <gsm@cable.mendelson.com> wrote in message
news:slrni2khtm.60r.gsm@cable.mendelson.com...
> Arfa Daily wrote:
>> Er, that would be a yes then ... Probably three or four a week, most
>> every
>> week, and have been doing them for around 40 years
>
> If you are such an expert, please tell us how they got that volume
> control to go to 11, while (whilst?) everyone knows they only go to 10?
>
> :-)
>
> Geoff.
>
> --
> Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM
> I do multitasking. If that bothers you, file a complaint and I will start
> ignoring it immediately.

If I told you that Geoff, I'd be destroying my niche market. Suffice to say
that they used triodes with more than three electrodes ... d;~}

Arfa

== 3 of 5 ==
Date: Tues, Jun 29 2010 5:59 pm
From: "Phil Allison"

"Arfa Daily"
>
>> ** What planet do you live on ???
>>
>
> Apparently, a very different one from you ...

** Where reality never intrudes on you rose tinted view.

> But then, of course, I was forgetting who I was trying to have a reasoned
> discussion with.

** Shame you have not seen or MISSED the common valve amp faults I
mentioned.

Maybe Marshall, Gibson, Fender, Peavey and others ship their bad batches to
Australia deliberately or maybe you have been leading a charmed existence.

> It had completely slipped my mind that anyone who looks at anything from a
> different point of view to you, must be wrong.

** Now you are completely off with the fairies.

What you have NOT see cannot be dismissed as non existent.

> I suppose you'll start in on the hysterical abuse hurling next.

** You are supplying plenty of smug, pommy provocations for that.

> Well, if that's what you need to do, go right ahead. I really don't care.

** You don't have a case or a clue - really.

> And I suppose you know Jim all the way from upside down land do you ?

** Jim Marshall visited Australia a number of years back, did interviews
with the trade press and gave a presentation to an audience of industry folk
in Sydney.

Before Jim accepted any questions, the MC gave a stern warning to the
assembled audience that Jim was not involved in the design or manufacture of
Marshall amps and that no questions about the notoriously poor design or
appalling reliability of the amps would be allowed.

Wise move.

.... Phil

== 4 of 5 ==
Date: Tues, Jun 29 2010 6:24 pm
From: dplatt@radagast.org (Dave Platt)

In article <VqwWn.84179$_F1.18386@hurricane>,
Arfa Daily <arfa.daily@ntlworld.com> wrote:

>> If you are such an expert, please tell us how they got that volume
>> control to go to 11, while (whilst?) everyone knows they only go to 10?
>>
>> :-)

>If I told you that Geoff, I'd be destroying my niche market. Suffice to say
>that they used triodes with more than three electrodes ... d;~}

Let me guess... instead of using thorium as a dopant in the filaments
to enhance electron emission, they used quadmium, right?

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

== 5 of 5 ==
Date: Tues, Jun 29 2010 9:59 pm
From: "Geoffrey S. Mendelson"

Arfa Daily wrote:

> If I told you that Geoff, I'd be destroying my niche market. Suffice to say
> that they used triodes with more than three electrodes ... d;~}

I figure you could get an extra 20 to 30 quid an amp if you offered to
upgrade them from a maximum of 10 to 11. :-)

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM
I do multitasking. If that bothers you, file a complaint and I will start
ignoring it immediately.

==============================================================================
TOPIC: Where to get schematic of Funai TV, Model FT1371?
http://groups.google.com/group/sci.electronics.repair/t/f75b6f935b5d3675?hl=en
==============================================================================

== 1 of 3 ==
Date: Tues, Jun 29 2010 12:30 pm
From: Robert Macy

Anybody got one lying around?

Or at least covering the PCB on the back of the CRT neck?

== 2 of 3 ==
Date: Tues, Jun 29 2010 4:17 pm
From: PeterD

On Tue, 29 Jun 2010 12:30:56 -0700 (PDT), Robert Macy
<macy@california.com> wrote:

>Anybody got one lying around?
>
>Or at least covering the PCB on the back of the CRT neck?

So you narrowed it down to that board?

== 3 of 3 ==
Date: Tues, Jun 29 2010 5:53 pm
From: Robert Macy

On Jun 29, 4:17 pm, PeterD <pet...@hipson.net> wrote:
> On Tue, 29 Jun 2010 12:30:56 -0700 (PDT), Robert Macy
>
> <m...@california.com> wrote:
> >Anybody got one lying around?
>
> >Or at least covering the PCB on the back of the CRT neck?
>
> So you narrowed it down to that board?

After starting the thread,
"oops! coffee into the top of TV!"
and not receiving any URL's for a schematic I started this one, trying
to be more specific.

The liquid ran onto the HV electrode and HV cable that physically laid
on top of a bare connection on that PCB.
Just seemed that's probably the area that got damaged.

==============================================================================
TOPIC: Danger of running hot receiver (Kyocera)?
http://groups.google.com/group/sci.electronics.repair/t/2eeb7d68559500c5?hl=en
==============================================================================

== 1 of 7 ==
Date: Tues, Jun 29 2010 12:54 pm
From: David Nebenzahl

Got someone with a Kyocera receiver (R-851, 85 w/chan.) that they say
"smells like something's burning". Don't have more specific information
than that; I'm assuming no magic smoke is visible. I'm advising them
that perhaps something (dust, etc.) is in the heat sink that's getting
heated and smelling. Apparently the output stages (MOSFET) of these
beasts tend to run on the hot side.

Question: does anyone know what kind of overcurrent or overtemperature
protection this unit has? User is concerned about "ruining" it if it is
in fact overheating (which I can't determine at this distance). They're
running it with 4-ohm speakers at not-very-high levels; I also suggested
trying it with 8-ohm speakers and seeing if the smell lessens.

Not much info to go on, I know, but I really would like to know more
about any protection circuitry in this piece of gear.

--
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)

== 2 of 7 ==
Date: Tues, Jun 29 2010 1:15 pm
From: "William R. Walsh"

Hi!

I'm guessing this is of a similar vintage to something like my Kyocera
DA-610 CD player (1985)?

If it is, I'd expect that you'll find it is Incredibly Overbuilt
inside. Kyocera absolutely was *not* cheap-skating on these things.

Even so, the DA-610 I found had some problems and needed some simple
R&R before it was at its best. Most of it was just age-related wear
and tear. The electronics themselves have never needed a thing, but
then again, they're not under the stress that an audio amplifier would
be.

I would at least clean the thing.

William

== 3 of 7 ==
Date: Tues, Jun 29 2010 1:20 pm
From: Meat Plow

On Tue, 29 Jun 2010 12:54:13 -0700, David Nebenzahl ǝʇoɹʍ:

> Got someone with a Kyocera receiver (R-851, 85 w/chan.) that they say
> "smells like something's burning". Don't have more specific information
> than that; I'm assuming no magic smoke is visible. I'm advising them
> that perhaps something (dust, etc.) is in the heat sink that's getting
> heated and smelling. Apparently the output stages (MOSFET) of these
> beasts tend to run on the hot side.
>
> Question: does anyone know what kind of overcurrent or overtemperature
> protection this unit has? User is concerned about "ruining" it if it is
> in fact overheating (which I can't determine at this distance). They're
> running it with 4-ohm speakers at not-very-high levels; I also suggested
> trying it with 8-ohm speakers and seeing if the smell lessens.
>
> Not much info to go on, I know, but I really would like to know more
> about any protection circuitry in this piece of gear.

If it smells of burning electronics I would strongly suggests the person
unplug the unit and get it somewhere to be looked at. Smoking the outputs
in a DC coupled amp can cascade back through driver and current control
stages in the blink of an eye and cause a catastrophic amount of damage.

== 4 of 7 ==
Date: Tues, Jun 29 2010 4:15 pm
From: Robert Macy

On Jun 29, 12:54 pm, David Nebenzahl <nob...@but.us.chickens> wrote:
> Got someone with a Kyocera receiver (R-851, 85 w/chan.) that they say
> "smells like something's burning". Don't have more specific information
> than that;  I'm assuming no magic smoke is visible. I'm advising them
> that perhaps something (dust, etc.) is in the heat sink that's getting
> heated and smelling. Apparently the output stages (MOSFET) of these
> beasts tend to run on the hot side.
>
> Question: does anyone know what kind of overcurrent or overtemperature
> protection this unit has? User is concerned about "ruining" it if it is
> in fact overheating (which I can't determine at this distance). They're
> running it with 4-ohm speakers at not-very-high levels; I also suggested
> trying it with 8-ohm speakers and seeing if the smell lessens.
>
> Not much info to go on, I know, but I really would like to know more
> about any protection circuitry in this piece of gear.
>
> --
> 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)

A bit of a reach... A 35 degree rise above ambient in a room at 68 F
feels warm to the touch, but when you run the same amp in a hot
location, room temp 90F that absolute temperature is now 125F and you
feel burnt touching it. Just like its summer here the room temp there
could be high, perhaps there is something overheating and outgassing,
for a while.

== 5 of 7 ==
Date: Tues, Jun 29 2010 4:39 pm
From: David Nebenzahl

On 6/29/2010 4:15 PM Robert Macy spake thus:

> On Jun 29, 12:54 pm, David Nebenzahl <nob...@but.us.chickens> wrote:
>
>> Got someone with a Kyocera receiver (R-851, 85 w/chan.) that they say
>> "smells like something's burning". Don't have more specific information
>> than that; I'm assuming no magic smoke is visible. I'm advising them
>> that perhaps something (dust, etc.) is in the heat sink that's getting
>> heated and smelling. Apparently the output stages (MOSFET) of these
>> beasts tend to run on the hot side.
>>
>> Question: does anyone know what kind of overcurrent or overtemperature
>> protection this unit has? User is concerned about "ruining" it if it is
>> in fact overheating (which I can't determine at this distance). They're
>> running it with 4-ohm speakers at not-very-high levels; I also suggested
>> trying it with 8-ohm speakers and seeing if the smell lessens.
>>
>> Not much info to go on, I know, but I really would like to know more
>> about any protection circuitry in this piece of gear.
>
> A bit of a reach... A 35 degree rise above ambient in a room at 68 F
> feels warm to the touch, but when you run the same amp in a hot
> location, room temp 90F that absolute temperature is now 125F and you
> feel burnt touching it. Just like its summer here the room temp there
> could be high, perhaps there is something overheating and outgassing,
> for a while.

That's along the lines of what I was thinking too.

I used to use this receiver, which ran fine for years with no noticeable
odors whatsoever. It *is* incredibly overbuilt, as someone else
mentioned here, so I'm not particularly worried about an impending
catastrophic failure.

Still would be nice to find out specifically what kinds of protection
circuits it has from someone who actually knows ...

--
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)

== 6 of 7 ==
Date: Tues, Jun 29 2010 4:36 pm
From: "William Sommerwerck"

My gut feeling is that the owner is simply smelling "burning dust". But he
should stop using it immediately, and have someone look it over. It might
need only a thorough vacuuming.

== 7 of 7 ==
Date: Tues, Jun 29 2010 5:52 pm
From: Cydrome Leader

David Nebenzahl <nobody@but.us.chickens> wrote:
> Got someone with a Kyocera receiver (R-851, 85 w/chan.) that they say
> "smells like something's burning". Don't have more specific information
> than that; I'm assuming no magic smoke is visible. I'm advising them
> that perhaps something (dust, etc.) is in the heat sink that's getting
> heated and smelling. Apparently the output stages (MOSFET) of these
> beasts tend to run on the hot side.

weird heatsink in that thing:

http://www.audiokarma.org/forums/showthread.php?t=246095

==============================================================================
TOPIC: Teac AG-790 has me stumped...
http://groups.google.com/group/sci.electronics.repair/t/19f1f1c9d95691fb?hl=en
==============================================================================

== 1 of 5 ==
Date: Tues, Jun 29 2010 1:01 pm
From: "William R. Walsh"

Hi!

> Twice I had asked what the function of the cap was, and
> twice you had not replied.

I am sorry about that. I must have missed seeing it.

> I assumed that as you had the service manual, and were engaged
> in fault finding to component level, that you would have sufficient
> understanding of circuit design to be able to just look at the cap on
> the schematic, and determine its function without a second
> thought.

You could say that. But I'm still *very* much in the learning phase. I
started with studying basic home appliances and household electricity
long ago. I started to study the workings of transistors,
semiconductors and other components after that. (This particular
process continues today.) Then, after much trial, I decided that I was
going to learn how to solder properly. And I finally did. My plan is
to know how to repair things even if nobody cares to. I don't plan to
do this sort of thing professionally. I'm getting there...I've built
simple electrical devices to solve problems or improve things in some
way, modified circuits, mended broken up circuit boards a few times
now and done "other stuff".

I haven't really looked into what that cap is doing...yet. I've been
very busy with many other things, including the repair of cars,
computer consulting work and "other jobs". I just haven't had the time
to sit down with the schematic and look at what's going on.

> You seem to have put this down to coincidence, and indeed, it
> may be, but from many long years of experience, it usually
> isn't.

No, I don't think it's a coincidence. I'm familiar with the concept of
more than one part being bad, and more faults surfacing as damaged
circuitry is repaired.

> Either something went wrong with the process of changing it
> - print damage, component damage, via damage, un-noticed
> solder splat, etc

Well, I'm pretty sure I didn't do any of those things. When I first
noticed the behavior change, I looked over my work very carefully. I
wanted to be sure that I had not induced this problem by my own doing.

> I don't know how much experience you have of component level
> faultfinding, but if it's not that much, don't be afraid to admit
> that.

It's probably on the lower end of intermediate, or just out of the
"total beginner" range. Of the things I've tried, though, I've had a
100% success rate...including the diagnosis of my linear tracking
turntable's front panel control failure.

> OK, no probs.

As it is, I've got enough stereo receivers, some of which I have
repaired. Maybe I have too many...at last count I'd repaired at least
four units in some way or another. One was a case of the previous
owner experiencing "operator error" so maybe it does not really count.

> It depends what they meant by "shotgunning".

This is a direct quote. Note the style as well, which has been left
intact.

"HI William.We only have what's in the manual too.Since you already
have the service manual,it shouldn't be too difficult to
troubleshot.Power supply rails o.k.?,D.C. offset?
Other than "shotgunning"parts,I don't know what else to recommend."

The power supply rails seem to be OK...they're all doing something
(don't recall the exact measurements). I wasn't sure where exactly
they wanted me looking for DC offset...I have some idea what it is,
and that's about it.

Maybe I'm reading more into it than I should be, but I take what was
written to mean "oh, we really don't repair those when one comes in
under the terms of the warranty". And maybe they don't?

I asked if there was any documentation for the error codes, or if
anyone there might know what they meant. I felt, perhaps incorrectly,
that knowing what an error code meant would help. (I do realize that
error codes are not always definitive and that they could send me
barking up the wrong tree.) I also asked if my manual was
complete...if maybe there was a piece I didn't have.

I never heard back.

I don't mind "shotgunning" parts of a circuit, but I have reservations
about doing the whole darn unit. I'd have to think whether it is worth
that to me...and I'm not convinced that it is.

> Of course, whoever was replying to you might just have
> been being facetious, and was actually suggesting that you
> stood it on a post at the end of the yard, and took a 12 gauge
> to it ....    :-))

Being as it was through e-mail, I can't reliably know the intention of
what was written. I like to see the best in people, so I assume it
probably was serious.

Compared to the other receivers I have worked on, I don't think this
one is as good of a design. I may not be qualified to say that, but
then again, I did fix the others.

William

== 2 of 5 ==
Date: Tues, Jun 29 2010 1:36 pm
From: Baron

Arfa Daily Inscribed thus:

> So usually, if a manufacturer recommends "shotgunning", it's for a
> good reason. Of course, whoever was replying to you might just have
> been being facetious, and was actually suggesting that you stood it on
> a post at the end of the yard, and took a 12 gauge to it .... :-))
>
> Arfa

Thats probably what they did mean... ;-)

--
Best Regards:
Baron.

== 3 of 5 ==
Date: Tues, Jun 29 2010 2:03 pm
From: "William R. Walsh"

Hi!

> 7C26 is in reverse series with 7C27 (i.e. non-polarised'
> configuration) and I guess may be short, open or leaky?
> Change it?

I had this feeling that I should change that cap, if for no other
reason than its immediate neighbor was bad. I'd even go so far as to
say that said feeling just had something about it, telling me that I
shouldn't ignore it.

No, I'm not superstitious or anything like that. But I know when I
have a gut feeling, and I *do*.

So I'm going to do that and see what happens.

> The burning of the resistors first mentioned is indicative of an
> overload prior to the final output transistors (7V19 to 7V22).

I don't know either. The only inkling I have is that someone played it
very, very hard. (The previous owner didn't want to talk about what
happened, but I don't think they were inside it. So it's another one
of these feelings.) One channel still played without issue when I got
it.

As best I can tell, the final transistors are good.

The only thing that's really driving me batty about this is the fact
that it's a pain to do any testing, since I have to put the board back
in. I really don't want to rearrange all the internal parts for
testing purposes, because I am afraid I will lose some of them.

William

== 4 of 5 ==
Date: Tues, Jun 29 2010 2:50 pm
From: b

On 29 jun, 18:26, "William R. Walsh" <wm_wa...@hotmail.com> wrote:
> Hi!
>
> > Is it a double-sided (or worse - multilayer) pcb?
>
> No, it appears to be a simple PCB with one layer on one side.
>
> I would not call this receiver the greatest design I have seen.
> Compared to the Sherwood and Sony receivers that I have been working
> on, it strikes me as being unnecessarily complex. The main PCB is
> littered with all sorts of components where the others are much
> cleaner and simpler.
>
> William

I'd retrace my steps a bti by desoldering that last cap and checking
it out.use junk speakers just in case.
-B

== 5 of 5 ==
Date: Tues, Jun 29 2010 6:18 pm
From: "Arfa Daily"

"William R. Walsh" <wm_walsh@hotmail.com> wrote in message
news:1de39763-9576-4ab5-99f0-6730bd9359b5@d37g2000yqm.googlegroups.com...
> Hi!
>
>> Twice I had asked what the function of the cap was, and
>> twice you had not replied.
>
> I am sorry about that. I must have missed seeing it.
>
>> I assumed that as you had the service manual, and were engaged
>> in fault finding to component level, that you would have sufficient
>> understanding of circuit design to be able to just look at the cap on
>> the schematic, and determine its function without a second
>> thought.
>
> You could say that. But I'm still *very* much in the learning phase.

OK, that's fair enough. At least we now have an idea of your capabilities.
When Teac asked you to check for DC offset, they were referring to a
standing DC component at the power amplifier midpoint. This is at the
junction of 7R43 / 45 for one channel, and 7R44 / 46 for the other channel.
The voltage with respect to chassis measured at this midpoint, should be
zero. Any positive or negative standing voltage at this point, is termed a
"DC offset". If large enough, it could be damaging to a loudspeaker, so for
this reason, there is circuitry to sense any offset, and if there is one,
block a relay from operating. This relay is normally in series with the
speaker feeds. As you are hearing some hum through one channel, this would
suggest that the relay is closing (can you hear it close after a short delay
from switching on ?) and if it is, that might suggest that there was no DC
offset . But, if the protection circuit was not working correctly, it might
just allow the relay to close with an offset present. As 7C27 is in inverse
series with 7C26, I would be inclined to replace them as a pair. Your first
move though, would be to check if an offset is present on either channel.

Arfa

==============================================================================
TOPIC: continuous action solder sucker
http://groups.google.com/group/sci.electronics.repair/t/1447a02166d89d01?hl=en
==============================================================================

== 1 of 2 ==
Date: Tues, Jun 29 2010 1:23 pm
From: zekfrivo@zekfrivolous.com (GregS)

In article <4014381d-7eea-4c0c-a2c3-72bbb46f7743@y4g2000yqy.googlegroups.com>, rush14 <rush14@columbus.rr.com> wrote:
>I'm attempting to fabricate a continuous action solder sucker along
>the lines of those used at work
>

My Weller's hose is surprisingly soft. Must be more flow than suction.
It needs frequent cleaning.

greg

== 2 of 2 ==
Date: Tues, Jun 29 2010 8:36 am
From: "Dave Plowman (News)"

In article
<4014381d-7eea-4c0c-a2c3-72bbb46f7743@y4g2000yqy.googlegroups.com>,
rush14 <rush14@columbus.rr.com> wrote:
> I'm also familiar with other desoldering tools including plunger and
> squeeze bulb solder suckers, solder wick and built in suckers on
> soldering irons. I've found them all lacking in one way or another
> compared to the gizmo I'm trying to imitate from the factory.

> Any ideas from you guys about the error of my ways will be greatly
> appreciated.

You want what's known as a desolder station. They've been somewhat
overtaken by hot air devices so older ones can be picked up cheaply on
Ebay. Basically, a soldering iron with a hole through the middle of the
tip which is connected via a filter to a vacuum pump. At one time they
were fiendishly expensive. There may well be cheaper ones new from the far
east now.

--
*Beauty is in the eye of the beer holder *

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

==============================================================================
TOPIC: oops! coffee into the top of TV!
http://groups.google.com/group/sci.electronics.repair/t/927853c231d2a8d2?hl=en
==============================================================================

== 1 of 2 ==
Date: Tues, Jun 29 2010 2:42 pm
From: b

On 28 jun, 00:12, Robert Macy <m...@california.com> wrote:

>
> QUESTIONS:
> 1) Any schematic for a Funai FT1371 ?
> 2) Anybody know what got zapped on the top tab of that PCB?
> 3) Assuming each video color channel is still capable, what adjustment
> to bring back color balance?

I would not advise you to make any colour balance adjustments. These
are not usually used unless to compensate for component drift with
age, or after replacement or other scenarios where recalibration is
needed; the problem here probably lies elsewhere.
Only tweak if you are sure liquid got at the pots, and even then, mark
the original position with correction fluid or a marker pen. The fact
that you have already seen the colour shift from red to green might
well mean that all is not yet dry.

Firstly try removing and reinserting the small pcb on the neck of the
tube, check to see if any liquid made it to the pins or the CRT
socket. Usually this pcb contains the RGB output IC or
transistors...how old is this TV?
-B

== 2 of 2 ==
Date: Tues, Jun 29 2010 3:36 pm
From: Robert Macy

On Jun 29, 2:42 pm, b <reverend_rog...@yahoo.com> wrote:
> On 28 jun, 00:12, Robert Macy <m...@california.com> wrote:
>
>
>
> > QUESTIONS:
> > 1) Any schematic for a Funai FT1371 ?
> > 2) Anybody know what got zapped on the top tab of that PCB?
> > 3) Assuming each video color channel is still capable, what adjustment
> > to bring back color balance?
>
> I would not advise you to make any colour balance adjustments. These
> are not usually used unless to compensate for component drift with
> age, or after replacement or other scenarios where recalibration is
> needed; the problem here probably lies elsewhere.
> Only tweak if you are sure liquid got at the pots, and even then, mark
> the original position with correction fluid or a marker pen.  The fact
> that you have already seen the colour shift from red to green might
> well mean that all is not yet dry.
>
> Firstly try removing and reinserting the small pcb on the neck of the
> tube, check to see if any liquid made it to the pins or the CRT
> socket. Usually this pcb contains the RGB output IC or
> transistors...how old is this TV?
> -B

Thank you for your reply.

Should be dry. It's been 48 hours with perhaps over 30 hours of
operation. This TV being old runs a bit toasty. At the timeof the
accident, I expected the residual heat, coupled with the constant
operation since then, to be able to thoroughly dry everything out.
Also, being in California, drying is fast.

Will try that remove insert. and generally mechanically manipulate
everything. I don't think the PCB itself was washed, rather the HV
electrode wire was washed, flooding down to the bare terminal on the
PCB where very likely grounded out the HV. That's why the image
shrunk ultimately going black as the HV died. There is high
probability that the short to gnd path 'injured' low voltage
components.

White is not white, but greenish, like underwater now. I can't tell if
a color is missing, or green is simply too strong. It appears that red
is there, blue is there, green is there, flesh tones are almost ok,
but not quite. It may be that 1/2 blue is now 1/8 blue, or such. Like
very distorted transfer function. like a leaky transistor that keeps
signal very low until finally it can get turned off. And leaky
transistor would make sense with a zap going into the PCB somewhere.
It would help to have a schematic yo find out just where that
discharge entry point was.

Age? label said manufactured January 1998
Funai Model FT1371

Robert

==============================================================================
TOPIC: So, who's the king of finding data sheets ... ?
http://groups.google.com/group/sci.electronics.repair/t/4e444c319ac55fa0?hl=en
==============================================================================

== 1 of 1 ==
Date: Tues, Jun 29 2010 7:45 pm
From: "Phil Allison"

"Arfa Daily"

> The unit has a switch mode power supply (why though?)

** Lower cost and much lower weight - that PSU has to deliver over 500
watts.

> I would have thought that if you were going to bother putting a switcher
> in a junky piece of hifi that was for worldwide use, you would have used a
> design with an efficient PFC front end, that makes it universal in terms
> of input voltage.

** That only increases the expense.

The PSU in that JVC is likely to be of the unregulated kind - ie a simple
square wave inverter.

These are far preferable for audio amplifiers and cheaper to make too.

> Heaven knows, there's enough cheap and cheerful examples out there, used
> by the million in LCD TV sets.

** Irrelevant what LCD TVs use.

> Anyway, that aside, the bridge was twatted, as were two diodes?? , one
> across each of the filter caps. These devices *look* like diodes, and the
> symbol on the board is for a diode, and they're called D34 and D35, but I
> can't recall having seen diodes in this position before. Voltage sharing
> resistors, maybe. The type number on them is R4KL,

** That type is an "avalanche " diode that is specified to zener breakdown
at a particular voltage - like 200 volts.

Does two jobs:

1. It sacrifices itself and goes short to protect the electo when some
idiot does what your customer did.

2. It prevents reverse polarity current from flowing into the electro ( via
the load) during the switch on surge period - this is only an issue for 120
volt use when the circuit is acting in voltage doubler mode. Any diode with
adequate voltage an current ratings is OK for this.

.... Phil

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