Toshiba TV29C90 problem; Image fades to black...

[Bill Jeffrey]

I've tried this (coupling to the phone line) a couple times, without
real good luck. The problem I experienced is that the outgoing audio is
MUCH louder than the incoming audio. Kinda makes sense, since the
outgoing audio will undergo line loss before it get to the other end,
whereas the incoming audio has already undergone that loss.

Question: has anyone else found this to be true? And if so, would it
make sense to take the tap at the earpiece in handset instead of across
the line? The incoming audio is present at the earpiece, of course -
and so is the outgoing audio, in the form of sidetone, which is
carefully set up to have the same apparent loudness.

BTW, if you have an old Bell phone (the hefty ones, like the 302), it is
easy to monitor it without making any connection. Simply place an audio
transformer on the case, and connect one of the windings to the mic
input of the recorder/sound card. The transformer picks up the audio
from the induction coil inside the phone. We used to do this in the old
old days, using the output transformer from any old radio. Of course it
won't work in modern lightweight phones, since they have no coil inside.

Bill
---------------

DaveM wrote:

The unit at http://www.omnicronelectronics.com/PC/LIC-1PC.htm is more
appropriate for the OP, according to his stated problem. However, if the OP
has the ability, there is a schematic of such a unit at
http://www.solorb.com/elect/phone/tap. Another one with some good details
at http://www.epanorama.net/documents/telecom/telerecord.html.
The problem with the cable he bought on Ebay is that since there is no
isolation, one side of the phone line is directly grounded to the computer
case, which will indeed kill the phone line. The phone line must stay
balanced and isolated from ground at all times, otherwise, the telco gets
mighty upset. In fact, if you leave the line in a shorted condition, they
will send a guy out to test your circuit, and if he finds the short exists
inside your house, most likely the service will be disconnected until you
remove the short. And they will charge you for the service incident.

 

[Travis Jordan]

Bill Jeffrey wrote:

I've tried this (coupling to the phone line) a couple times, without
real good luck. The problem I experienced is that the outgoing audio
is MUCH louder than the incoming audio. Kinda makes sense, since the
outgoing audio will undergo line loss before it get to the other end,
whereas the incoming audio has already undergone that loss.

True, but with good AGC you can compensate for this.

 

[Steve Muccione]

switch the colors first...

if it moves you can swap transistors to verify the cross was ok (yeah it's a
bitch to resolder but...)

"Keith Jewell" <implode@gmail.com> wrote in message
news:1116009183.034814.261050@g14g2000cwa.googlegroups.com...

I have a Wells Gardner K4600 in a cocktail style game. When I got it,
there was no blue, and it had very poor geometry. I did a cap kit,
which cleared the geometry up as well as made for an overall clearer
and much more stable picture. Also, replaced TR403 on the neck PCB,
which was shorted, with the NTE cross. The picture is overall pretty
good now but the risetime seems to be bad on the blue. In other words,
the blue has smeared edges on both the rising and falling. Switching
colors on the input changes nothing, so I'm sure it's in the monitor. I
figure this is one of the following, but can't be sure. Any ideas? I'm
thinking:

-One of the other two transistors (TR204 or TR207) is marginal but
still tests good
-A small cap that wasn't in the circuit is bad
-The NTE cross isn't a good cross in some way

It just occured to me writing this message that I can try switching
around the colors going to the neck board to further isolate the
problem, but has anyone seen a problem like this before? It's not so
bad, really quite usable now, but I'd love the blue to be as crisp and
clean as the red and green are. Thanks.

-Keith

 

[Robert Bullock]

Try adjusting the color drives and cutoffs. Also contrast and screen knob on
the flyback. If you can't get it low enough and still get red and green,
might be time for a rejuve or clean and balance on the tube.


"Keith Jewell" <implode@gmail.com> wrote in message
news:1116009183.034814.261050@g14g2000cwa.googlegroups.com...
In other words,

the blue has smeared edges on both the rising and falling. Switching
colors on the input changes nothing, so I'm sure it's in the monitor. I

 

[NSM]

<ZZactly@aol.com> wrote in message
news:1116031791.320802.255370@f14g2000cwb.googlegroups.com...

Has anyone ever seen a SMD transistor pop off the board without
"assistance"?

No, but it wouldn't amaze me. Probably a fault in the reflow soldering
process.
--
N

 

[Sam Goldwasser]

"NSM" <nowrite@to.me> writes:

ZZactly@aol.com> wrote in message
news:1116031791.320802.255370@f14g2000cwb.googlegroups.com...

Has anyone ever seen a SMD transistor pop off the board without
"assistance"?

No, but it wouldn't amaze me. Probably a fault in the reflow soldering
process.

You should be able to closely examine the solder pads to determine if
it was actually unsoldered, or poorly soldered in the first place. That
is, of course, if you haven't already replaced the part!

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.

Important: Anything sent to the email address in the message header above is
ignored unless my full name is included in the subject line. Or, you can
contact me via the Feedback Form in the FAQs.

 

[N Cook]

<ZZactly@aol.com> wrote in message
news:1116031791.320802.255370@f14g2000cwb.googlegroups.com...

Hi;

I just can't explain it. Sony XBR 1997 model. Symptom whited out
negative image. Under our warranty and no print. I'm glad it's not the
busy season.

Set uses a TA1226 IC for video enhancement. Good video in, bad video
out. Lucky I had a used one because it wasn't the problem, but it came
from a working set that we own for future sale. No change in symptom at
all. I literally put the sets side by side on the same input and
started flying by the seat of my pants. Armed only with the Tektronix
and a pinout of the IC I found it.

The tippy tops of the sandcastle input to pin 10 were missing.
Following traces etc. I got a bit of a mental map of it. Three diodes
going to that pin etc... On the working set the sync tips for the SCP
are derived from Q1353 IIRC. Turning to the device under test to check
on the status of Q1353 I discovered it missing.

This set was delivered not too long ago and I'm told they have no
reason to suspect sabotage, other than what I had just told them.

Has anyone ever seen a SMD transistor pop off the board without
"assistance" ? If we've been scammed it was by someone either
incredibly lucky or who knows what they're doing. This particular part
of the video circuit seems common only to XBRs. No debris or damage to
the foil and the solder was still there. Damn I wish a defective SMD
transistor would come out so easily. Are we wasting our time
desoldering these things ?

Now playing devil's advocate here, that transistor mounts with the
collector toward the front of the set. In that position flexing of the
PC in the direction caused by up and down movement would apply
compressional/tensional force on those short leads.

I find it hard to believe that all three connections were fine and not
intermittent and just gave up all at the same time. Any one of them
open and the whole device is effectively open. Conversely could the set
have had a highly intermittent problem that we (our shop) has never
seen, and then simply disassembling the set caused the last little bit
holding it to break away ? I'm not really even ready to take a guess on
that right now. Any takers ?

How about the possibility of the customer adamantly wanting the set
replaced having someone else sabotage the set. It wouldn't be the first
time. Back when I was in business an employee of mine did that for
someone and I fired him on the spot. That's not to say there aren't any
people out there who can and will do it.

I need a bit of input, do they sometimes just fall off ? The set is
getting delivered tomorrow, I don't work Saturdays now that I've "paid
my dues", but I might like to call the boss tomorrow and tell him to
warn the customer. Being very careful not to accuse, it should be
explained that if something happens again that looks like sabotage we
will be reluctant to cover it under warranty. Maybe he didn't do it,
maybe someone else did it to him. I'm told the PIP is almost always on
for a security camera, and this could be a factor here.

I'm kinda looking for a figure here where we can tell the customer "my
guy says it's a XX% chance of sabotage. Should I say 90, or more like
75 ? IMO right now it's over 50. I have never seen an SMD just pop off,
even with a bad connection a two terminal device doesn't fall off. This
is a three terminal device, and I think that makes it pretty unlikely.
The problem is you have to tread lightly here when what you say can be
construed as an accusation of fraud.

A penny for your thoughts. Hell we're giving them away, I just found
out I'm not making quite a dollar a day. Today's dollar has about a
nickel's worth of purchasing power, $200 in an eight hour day comes out
to $25 an hour, I fall just a bit short. Perhaps I'm underpaid ? (I
mean more underpaid than others) Even if I am I don't want to see the
company get screwed.

Thanks in advance, for ANYTHING that can shed some light on this.

JURB

The only sabotaged for refund I've ever come across was a fuse replaced with
a much higher amperage rating but blown fuse. Deliberately desoldering an
SMD seems highly unlikely.
I would suggest the SMD was only held on by the glue spot and was never
soldered in the first place, if
light loading, then would function until the glue fails due to minimal
flexing from temperature or vibration.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

 

[Asimov]

"Bill Jeffrey" bravely wrote to "All" (13 May 05 10:29:49)
--- on the heady topic of "Re: Phoneline to Soundcard - NEED HELP"

BJ> From: Bill Jeffrey <wjeffreyAT@alum.DOTmit.edu>
BJ> Xref: aeinews sci.electronics.repair:48060

BJ> I've tried this (coupling to the phone line) a couple times, without
BJ> real good luck. The problem I experienced is that the outgoing audio
BJ> is MUCH louder than the incoming audio. Kinda makes sense, since the
BJ> outgoing audio will undergo line loss before it get to the other end,
BJ> whereas the incoming audio has already undergone that loss.

BJ> Question: has anyone else found this to be true? And if so, would it
BJ> make sense to take the tap at the earpiece in handset instead of
BJ> across the line? The incoming audio is present at the earpiece, of
BJ> course - and so is the outgoing audio, in the form of sidetone, which
BJ> is carefully set up to have the same apparent loudness.

BJ> BTW, if you have an old Bell phone (the hefty ones, like the 302), it
BJ> is easy to monitor it without making any connection. Simply place an
BJ> audio transformer on the case, and connect one of the windings to the
BJ> mic input of the recorder/sound card. The transformer picks up the
BJ> audio from the induction coil inside the phone. We used to do this in
BJ> the old old days, using the output transformer from any old radio. Of
BJ> course it won't work in modern lightweight phones, since they have no
BJ> coil inside.


What you need is a hybrid phone network. Basically it balances the
voice so that it has the same volume as the speaker. Older phones used
a transformer to balance the levels. New phones use an IC instead.
Another trick is to clip onto the speaker of a speaker-phone.

A*s*i*m*o*v

.... I worked hard to attach the electrodes to it.

 

[Mark D. Zacharias]

michael.w.appenzeller@lmco.com wrote:

ZZactly@aol.com wrote:
This would make the repair too expensive, since >these (and the bias
transistor) blew while bench testing after fixing >the original
fault.


This would worry me. Even if you could get the parts for a dime a
dozen, don't waste silicon. I bet you did not fix the original fault.

(quoted text cut)
JURB

Thanks, guys,

I'm going to take JURB's advice and do some more testing before I
order those transistors. The reason I was concerned about the
counterfeits was that I only wanted to make one more parts order
for this unit. Having to meet a minimum order and pay $8 shipping
each time starts to add up, so some scope testing with the outputs
removed makes sense.

This Pioneer VSX-454 is a Pro-Logic receiver with a 4 channel amp.
My father-in-law gave it to me to repair, but it looks like he got
it from a flea market or yard sale. ("$7.00 as-is" written in black
marker on the top cover.) So I had no history of what was wrong with
it. The only symptom was that it smoked when it was turned on.

The power amp in this unit is a "module" of sorts: It's like a box,
made of two circuit boards (L/R and C/S amps) and two heatsinks
(all NPN outputs from both boards on one sink, all PNPs on the other
sink). The heatsink fins point inwards and there is a fan at one end
that blows thru the box. The heatsinks are "live" - they are at the
+/- rail voltages, and no insulators are used on the transistors.
This makes testing the amp outside the receiver very risky, as it
can't touch anything, not even the chassis, and the multiple ribbon
cables connecting it to the main board aren't long enough to get the
amp completely out of the receiver.

3 of the 4 channels had already been repaired before: The Right
channel has an off-brand 2SA1302, the Center channel outputs were
subbed with Matsushita transistors, and the Surround outputs were
subbed with physically smaller Toshiba transistors. A few of the
flameproof resistors on the L/R amp board had been replaced by cutting
the old ones off and soldering new ones to the "stubs". (In order to
get to the bottoms of the boards to do any soldering, all the outputs
& drivers & bias transistors have to be removed from the heatsinks to
free the board up.)

Anyway, what I found was a few 1/8 W resistors on the L/R amp board
burnt to a crisp, and a browned area on the board around them, which
covered a few unburned resistors. This is what smoked when powered
up. The amp circuits looked pretty simple, and I got the burnt
resistor's values from the other amp channels, so I decided not to
order a schematic, and just test parts. Since I didn't know the
extent of the damage, or if more than one channel was faulty, I
checked everything on both boards. I found the damage was confined
to the Left channel, and the Outputs & Drivers were about the only
parts NOT blown. 3 of the 4 "tall TO92" transistors as well as the
little bias transistor
on the heat sink were shorted, 4 47 & 4.7 ohm flameproof resistors
connected to them were open, and 4 zener diodes were shorted.

I replaced all the bad parts, all the resistors in the "burned area"
even the ones that looked & measured OK, and all 4 of the "tall TO-92"
transistors. Powered it up with load resistors on L&R outputs and
speakers on center & surround outs, at 90V on a Variac. It seemed
to work OK, no DC on the outputs, and I was able to get sound form the
Center & surround from its FM tuner, so the rest of the receiver was
working, so I brought the line voltage to 120. I checked the voltages
across the .33 ohm emitter resistors, and it was only 1 mV on all 4
channels. The bias is not adjustable on this model, and all channels
read the same, so I assumed it was OK.

When I turned up the Volume to about 10:00, a flameproof resistor in
the left channel immediately lit up like a sparkler, then the line
fuse blew a few seconds later. I never got around to putting the
scope

on the outputs, but the air blowing thru the heatsinks was coming out
cool, so there probably wasn't any high-level oscillation taking place
(at least until I turned up the volume.)

So I tore the amp module down again, retested everything in the Left
channel, and the only bad parts were the resistor that lit up, and
both outputs and the little Bias transistor on the heatsink were
shorted. Since I replaced nearly everything else, and those parts were
still good, I figured replacing the outputs (and drivers for
insurance)

should take care of it. But there is a possibility that it took a
certain signal level to kick off an oscillation...

Mike
WB2MEP

I tried JURB's technique yesterday and 8 resistors burned up. Use caution.

Mark Z.

 

[Dave Plowman (News)]

In article <fu5he.10093$D91.3759@fed1read01>,
Bill Jeffrey <wjeffreyAT@alum.DOTmit.edu> wrote:

I've tried this (coupling to the phone line) a couple times, without
real good luck. The problem I experienced is that the outgoing audio is
MUCH louder than the incoming audio. Kinda makes sense, since the
outgoing audio will undergo line loss before it get to the other end,
whereas the incoming audio has already undergone that loss.

You need a TBU - telephone balance unit - to correct this properly.
They're used to connect a telephone line to a broadcast sound mixing desk
- etc. Basically, a hybrid transformer or electronic equivalent. This
convert the two wire telephone circuit to a four wire so you can adjust in
and out levels, IIRC.

--


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

 

[N Cook]

As an aside does anyone know if it possible to have a bubble form
in flow solder operation so failure to solder a small area ?
That is gas from outgassing from the board or just contamination forming a
bubble on the molten solder.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

 

[Rich Grise]

On Fri, 13 May 2005 22:01:35 -0700, simoung wrote:

"Travis Jordan" wrote
Jeroen wrote:
FW0128 is probably some production date code. The 'W' seems to
be the Motorola logo. So the full part number is FQP50N06.

$1.36 at Mouser.

Thanks for searching. And thanks for the correction, Jeroen, which
allowed me to replace it with a Motorolla N-Channel (MTW 14N50E 01,
attached to a larger heat-sink) I'd salvaged from a computer monitor. I
don't believe that salvaging a part from a computer monitor is
professional

You'd be surprised.

but it seems to solve the problem quiet fine.

Cheers!
Rich

 

[NSM]

<jerry@tr2.com> wrote in message
news:1116079419.070984.182380@z14g2000cwz.googlegroups.com...

The
out of tune ones were WAY out of tune, as if somebody had messed
with them.

I suggest you mark these internally as to how they were out (high or low).
If you find yourself readjusting them later replace them - they are jumping
frequency.
--
N

 

[Wild Bill]

I'd suspect that it's just a manufacturing defect. I suppose that there are
many millions (billions?) of components picked-and-placed each year.
When I look at a high-component board like a laptop main board, I'm amazed
that so many different components are present, and that all of them are
securely mounted.. then again, sometimes they aren't.

A close examination of the leads and the site might have revealed a
reasonable answer. The paste solders are generally applied/dispensed by
needles, or maybe even a faster method presently, and of all the potential
things that could go wrong, maybe the component leads might've had some
contamination on them at the time it was manufactured. There would be
numerous other possibilities.
It might've been hand rework on a small batch of boards, done with a hot air
iron.

I think you've probably been participating in the SER group long enough to
remember the thread "why can't manufacturers solder?", or something similar.

Good techniques, applied/done poorly, yield poor results. And then there's
the planned obsolesence and quality control factors.. it's only consumer
grade stuff.
Poor soldering has kept a lot of shops in business through the years.

I was completely surprised to find a desoldered HOT in a working 25" TV
years ago. It was one of several that I bought at an auction, and I was
checking their operation to see if any of 'em were working.
This particular one had apparently been worked on, and the HOT had been
desoldered and removed, then just put back with the leads thru the board
holes.

There have been several times that I've encountered contamination on
component mounting pads that resulted in oxidation and complete separation
of the solder. These appeared to be a result of unclean boards used at the
time of manufacture.

Cheers
WB
..................

<ZZactly@aol.com> wrote in message
news:1116031791.320802.255370@f14g2000cwb.googlegroups.com...

Hi;
snippages

I find it hard to believe that all three connections were fine and not
intermittent and just gave up all at the same time. Any one of them
open and the whole device is effectively open. Conversely could the set
have had a highly intermittent problem that we (our shop) has never
seen, and then simply disassembling the set caused the last little bit
holding it to break away ? I'm not really even ready to take a guess on
that right now. Any takers ?

Thanks in advance, for ANYTHING that can shed some light on this.

JURB

----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
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[Ken Weitzel]

cnctut wrote:

I'm trying to locate a DPDT rocker switch--12V 8amp--for a 3-way
electrical installation for my RV. Any suggestions? Auto parts stores
no help?

Thanks

Tut

Hi Tut...

Radio shack...

http://www.radioshack.com/product.asp?cookie%5Ftest=1&catalog_name=CTLG&category_name=CTLG_010_007_002_000&product_id=275-695

Take care.

Ken

 

[**THE-RFI-EMI-GUY**]

Are you wiring three way or four way? A three way uses two SPDT switches
back to back with two travelers. You only need a DPDT when adding a
third switch.

cnctut wrote:

I'm trying to locate a DPDT rocker switch--12V 8amp--for a 3-way
electrical installation for my RV. Any suggestions? Auto parts stores
no help?

Thanks

Tut

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"

The Lost Deep Thoughts By: Jack Handey
Before a mad scientist goes mad, there's probably a time
when he's only partially mad. And this is the time when he's
going to throw his best parties.

 

[NSM]

"cnctut" <cnctutwiler@wmconnect.com> wrote in message
news:1116093866.685461.117590@g43g2000cwa.googlegroups.com...

I'm trying to locate a DPDT rocker switch--12V 8amp--for a 3-way
electrical installation for my RV. Any suggestions? Auto parts stores
no help?

Sounds like you want a battery changeover switch. Try an RV seller - they'll
point you to places.
--
N

 

[Ken Weitzel]

cnctut wrote:

Thanks everyone--to answer each question--

1. It would be a 3-way switch setup--I have two SPDT switches currently
and would like to add a third.
2. Radio Shack was the first place I tried--the young'ns working there
aren't like days of old--they weren't familiar with the term DPDT--and
had none in stock in the switch area
3. Visited local RV dealer--best they could do was to offer two switchs
to gang together
4. Attempting to move the water pump switch to the kitchen where it
should have been in the first place.

Thanks again

Tut

Hi Tut...

They just don't make them younger folks like they used to

The RS part number is on the link I sent; ask 'em to
order in one or two for you.

Take care.

Ken

 

[Rick]

"Ken Weitzel" <kweitzel@shaw.ca> wrote in message news:Btthe.1351838$8l.872444@pd7tw1no...

cnctut wrote:

Thanks everyone--to answer each question--

1. It would be a 3-way switch setup--I have two SPDT switches currently
and would like to add a third.
2. Radio Shack was the first place I tried--the young'ns working there
aren't like days of old--they weren't familiar with the term DPDT--and
had none in stock in the switch area
3. Visited local RV dealer--best they could do was to offer two switchs
to gang together
4. Attempting to move the water pump switch to the kitchen where it
should have been in the first place.

Thanks again

Tut


Hi Tut...

They just don't make them younger folks like they used to

I'm not sure why RS even bothers any more. Most of their
stores are the size of shoeboxes and 99% of the time don't
have what you're looking for.

 

[Franc Zabkar]

On 13 May 2005 17:49:51 -0700, ZZactly@aol.com put finger to keyboard
and composed:

Has anyone ever seen a SMD transistor pop off the board without
"assistance" ?

Was this a power transistor or a signal transistor? It's a long shot,
but could it be that a fault in the transistor caused it to get so hot
that it desoldered itself? I've seen a bridge rectifier do that ...
after its fuse had been uprated.


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.