Toshiba TV29C90 problem; Image fades to black...

meow2222@care2.com wrote:

wrongaddress@att.net wrote:

only cost two dollars. So I put the radio in the freezer for 30 minutes
and took it out and it didn't work at all. Then I applied a hot
sodering iron to the body of the oscillator transistor and it very
quickly started working again. Seems the oscillator doesn't run at low
temperature.

Would you guess the solution is a silicon transistor? or just adjust
the bias on the existing germanium transistor?

-Bill

neither, increase the stage gain. That probably means higher collector
R or similar. You may then need to adj the bias a little.

Or with an old radio like that it might just be biased way wrong, where
gain is down. Meter it and see where Vce sits when not oscillating.

The collector appears to drive the oscillator coil and mixer coil in
series (no collector R other than maybe decoupling). There is a emitter
resistor of 2K with a drop of 0.35 volts. I figure the oscillator stage
is running at 0.35/2000 = 175 miroamps. I added a 3K resistor in
parallel with the 2K so the current is increased to 0.35/1200 = 292
microamps. This brings up the gain about 3dB, but the radio still fails
at low temperature in the refrigerator. At low temperature there is
only noise and no signal. I tried this with a more modern radio using
silicon transistors and it works well an 40 degrees or so. So, I'm
almost convinced the problem is the germanium transistors.

Will continue to investigate.

-Bill

 

[Homer J Simpson]

"David Nebenzahl" <nobody@but.us.chickens> wrote in message
news:455bdc82$0$5804$822641b3@news.adtechcomputers.com...

Which implies that, at least sometime in the past, there were those who
repaired those radios. Did they? I remember when those things appeared on
the market, and I always thought of them as disposable items. Did people
actually take them in to be fixed?

The first Sony shirt pocket (just) sized one cost me more than a week's
wages - at wholesale! I repaired them for a few years until I moved on to
other things.

 

[Homer J Simpson]

"Michael Black" <et472@FreeNet.Carleton.CA> wrote in message
news:ejgp2l$eh4$1@theodyn.ncf.ca...

Who knows. But early transistor radios, that would have used germanium
because there was no choice, were not cheap radios. They cost significant
amounts at the time. Even later, one could still get decent transistor
portables that would have cost a fair amount at the time. I once found
a Sony portable from the early sixties, and it has metal casing and is
quite heavy, complete with the large speaker. People would have been
having those repaired, there's no way they'd toss them if they stopped
working.

The cheap transistor portables came later. Likely they were less likely
to be repaired, but circuit wise they weren't that different from the
expensive portables.

We had a popular Philips model that had a transistor audio output stage
(OC71s and OC72s) but still had tubes for the convertor and IF. Later they
came out with the OC44 and OC45 and went fully solid state.

 

[William R. Walsh]

Hi!

Believe me, it is possible to push a ATA drive into the SATA slot and
have it lock (seemingly). That is what I did.

I'm sure it is. The drives themselves are of the same shape and size. But
what I still have trouble with is how the connector ever made any kind of
contact with the pins in the PATA drive. They are very different connectors.

Even if contact was made, I'd have to think that it must have been from the
smaller power cable--the data connector shouldn't have caused any damage to
the drive, even with signals in the wrong place.

Good luck with your board swap. I hope it works. If it should happen to
work, have plans in place to transplant your data quickly. The board may not
work as well when the drive reaches full operating temperature.

William

 

[Michael Black]

"Homer J Simpson" (nobody@nowhere.com) writes:

"Michael Black" <et472@FreeNet.Carleton.CA> wrote in message
news:ejgp2l$eh4$1@theodyn.ncf.ca...

Who knows. But early transistor radios, that would have used germanium
because there was no choice, were not cheap radios. They cost significant
amounts at the time. Even later, one could still get decent transistor
portables that would have cost a fair amount at the time. I once found
a Sony portable from the early sixties, and it has metal casing and is
quite heavy, complete with the large speaker. People would have been
having those repaired, there's no way they'd toss them if they stopped
working.

The cheap transistor portables came later. Likely they were less likely
to be repaired, but circuit wise they weren't that different from the
expensive portables.

We had a popular Philips model that had a transistor audio output stage
(OC71s and OC72s) but still had tubes for the convertor and IF. Later they
came out with the OC44 and OC45 and went fully solid state.

There was that whole period where transistors were available commercially,

but not very good. I can't say I've heard of hybrid portables before,
but of course car radios that used tubes but a transistor audio amplifier
were quite common.

And I seem to recall that some of the Motorola "lunchbox" style transceivers
used some transistors in the IF stages along with the subminiature tubes
that provided the active elements at higher frequencies.

Michael

 

Michael Black wrote:

There was that whole period where transistors were available commercially,
but not very good. I can't say I've heard of hybrid portables before,
but of course car radios that used tubes but a transistor audio amplifier
were quite common.

And I seem to recall that some of the Motorola "lunchbox" style transceivers
used some transistors in the IF stages along with the subminiature tubes
that provided the active elements at higher frequencies.

Michael

do you remember what years those hybrid car radios were produced?

NT

 

wrongaddress@att.net wrote:

James Sweet wrote:
meow2222@care2.com wrote:
wrongaddress@att.net wrote:

I have an old 8 gernamium transistor, protable AM radio that is noisy
on weak stations when cold. It works reasonably well when set it in the
sunshine and warms up. The problem seems to be the RF section since the
noise goes away when the volume is turned down. I'm suspecting the
germanium transistors may be the problem and wondering which one might
be replaced with a silicon variety to cure the temperature problems?

I'm not sure what all 8 transistors do. Two are in the output stage,
and another is used as a audio driver that drives the audio input
transformer.There are four RF coils, the usual oscillator (red) and
mixer (yellow) and white (1st IF) and (black (second IF). But that only
requires 6 transistors, and there are eight total. The detector is a
diode, so they didn't use a transistor for that. I haven't figured out
what the other 2 transistors do.

I'm thinking of replacing the oscillator transistor with a high gain
silicon variety to try and eliminate the temperature problems?

Any other ideas?

-Bill



Sounds like a perfect job for a can of freeze spray. Warm it up until
the problem goes away, then give suspect components a quick shot of cold.

Yes, good idea, but the can of freeze spray costs $10, and the radio
only cost two dollars.

where in the world does a can of lighter gas or camping gas cost 10
bucks?


NT

 

[Homer J Simpson]

<meow2222@care2.com> wrote in message
news:1163659650.790950.125690@m73g2000cwd.googlegroups.com...

Michael Black wrote:

There was that whole period where transistors were available
commercially,
but not very good. I can't say I've heard of hybrid portables before,
but of course car radios that used tubes but a transistor audio amplifier
were quite common.

And I seem to recall that some of the Motorola "lunchbox" style
transceivers
used some transistors in the IF stages along with the subminiature tubes
that provided the active elements at higher frequencies.

do you remember what years those hybrid car radios were produced?

Mid 60's? IIRC the tubes used ran OK with just 12 VDC on the plates.

I'm sure there was no vibrator then.

 

wrongaddress@att.net wrote:

meow2222@care2.com wrote:
wrongaddress@att.net wrote:

Would you guess the solution is a silicon transistor? or just adjust
the bias on the existing germanium transistor?

neither, increase the stage gain. That probably means higher collector
R or similar. You may then need to adj the bias a little.

Or with an old radio like that it might just be biased way wrong, where
gain is down. Meter it and see where Vce sits when not oscillating.

The collector appears to drive the oscillator coil and mixer coil in
series (no collector R other than maybe decoupling). There is a emitter
resistor of 2K with a drop of 0.35 volts. I figure the oscillator stage
is running at 0.35/2000 = 175 miroamps. I added a 3K resistor in
parallel with the 2K so the current is increased to 0.35/1200 = 292
microamps. This brings up the gain about 3dB, but the radio still fails
at low temperature in the refrigerator. At low temperature there is
only noise and no signal. I tried this with a more modern radio using
silicon transistors and it works well an 40 degrees or so. So, I'm
almost convinced the problem is the germanium transistors.

Will continue to investigate.

-Bill

This is just illogical. What is Vce when not oscillating, and whats psu
v? Posing the osc cct would give more opportunities for upping or
stabilising the gain.


NT

 

[Dave Plowman (News)]

In article <1163659650.790950.125690@m73g2000cwd.googlegroups.com>,
<meow2222@care2.com> wrote:

do you remember what years those hybrid car radios were produced?

First one I saw was early '60s.

--
*If PROGRESS is for advancement, what does that make CONGRESS mean?

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

 

[Morse]

"Sammy" <swatchit@eircom.net> wrote in message
news:Xt46h.15977$j7.333731@news.indigo.ie...

Correction to my last message. . . I should have said that
the faulty component (diac)
is marked Z2 07D431K. It is blue, with 2 leads. It measures
low resistance
in both directions.

So it's a MOV, not a diac, as Franc pointed out. It serves a passive role
until there's voltage spikes etc and then presents a very low impedance
across the mains and blows the fuse and usually itself.

You can leave it out really, there's no user safety issues I can think of,
though a bad mains spike could take out the triac without one fitted, then
you'd get an 'always on' lamp. It's not like it's a box of sensitive,
expensive electronics though so I wouldn't worry about it too much.

At the very least, leave it out, replace the fuse and test the light, it may
well work. Replace the MOV once you've cleared the fault, if indeed there is
one other than the MOV itself, if you really feel happier with one back in
circuit.

You're lucky you didn't put two back to back diodes or whatever in its
place, they would have exploded and possibly embedded their casing in your
flesh or eyes! What made you think it was a diac? Did you give the circuit
layout a look over before you came to that conclusion? Diacs are always in
line with the triac gate, never across the supply!

A friendly tip: Always be sure about components before naming them,
misunderstandings can be very dangerous when dealing with mains operated
equipment.

Morse

 

[Michael A. Terrell]

meow2222@care2.com wrote:

Michael Black wrote:

There was that whole period where transistors were available commercially,
but not very good. I can't say I've heard of hybrid portables before,
but of course car radios that used tubes but a transistor audio amplifier
were quite common.

And I seem to recall that some of the Motorola "lunchbox" style transceivers
used some transistors in the IF stages along with the subminiature tubes
that provided the active elements at higher frequencies.

Michael

do you remember what years those hybrid car radios were produced?

NT

Late '50s & early '60s. Most of the hybrid car radios used tubes
that operated with +12 VDC on the plates, as well. This eliminated the
problem of bad vibrators.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Michael A. Terrell]

Michael Black wrote:

David Nebenzahl (nobody@but.us.chickens) writes:

Which implies that, at least sometime in the past, there were those who
repaired those radios. Did they? I remember when those things appeared
on the market, and I always thought of them as disposable items. Did
people actually take them in to be fixed?

Who knows. But early transistor radios, that would have used germanium
because there was no choice, were not cheap radios. They cost significant
amounts at the time. Even later, one could still get decent transistor
portables that would have cost a fair amount at the time. I once found
a Sony portable from the early sixties, and it has metal casing and is
quite heavy, complete with the large speaker. People would have been
having those repaired, there's no way they'd toss them if they stopped
working.

The cheap transistor portables came later. Likely they were less likely
to be repaired, but circuit wise they weren't that different from the
expensive portables.

A lot of transistor radios were repaired in the '60s and & '70s. Sams
published 159 different TSM manuals, covering about 1000 models. B&K
made a piece of test equipment specifically to repair transistor radios,
as well. It had a power supply for the radio, a signal generator, signal
tracer, and voltmeter all in one package so you could quickly locate and
repair the faults. Most of the problems were bad transistors at that
time, followed by bad volume controls and variable capacitors.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Dave Plowman (News)]

In article <455C44DA.4634E436@earthlink.net>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:

Late '50s & early '60s. Most of the hybrid car radios used tubes
that operated with +12 VDC on the plates, as well. This eliminated the
problem of bad vibrators.

Yup - and just in time for 'Good Vibrations'...

--
*Sometimes I wake up grumpy; Other times I let him sleep.

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

 

[David Naylor]

Leonard Caillouet wrote:

dantecl@gmail.com> wrote in message
news:1163325374.398729.196190@b28g2000cwb.googlegroups.com...

Hello people,

I have a Sony KP-46S15 tv with some strange problem. The picture is
good, but it's black/white, doesn't matter if it's cable or video
input. But, the weird thing is that the OSD is colored, all the menu
items are normally colored.

This color problem was flickering some time ago, and now it's
permanently B/W...

Any tips?

Dante


Basic troubleshooting would be the tip. If you need tips at this point, you
need a tch to evaluate the set.

Leonard

--------------------------------------------------------------------------------
I am using the free version of SPAMfighter for private users.
It has removed 11876 spam emails to date.
Paying users do not have this message in their emails.
Try SPAMfighter for free now!
SYMPTOMS

Unit had no color.

Intermittently unit had streaks of red and blue across black and white
picture.

RESOLUTION

Had good chroma siganal to the Y/C jungle.
Found no 3.58 at pin 7 of jungle chip.
Replaced X302 restored normal operation.

>

 

[Flyguy]

Sam Goldwasser wrote:

"ian field" <dai.ode@ntlworld.com> writes:


"Flyguy" <Flyguy@bluesky.net> wrote in message
news:XU86h.2749$bj1.1163@trndny05...

Homer J Simpson wrote:

mwpmorris@gmail.com> wrote in message
news:1162839588.995972.108850@h48g2000cwc.googlegroups.com...



Could I have been exposed to anything when the glass shattered inside
the set or when I powered the thing on with the glass shattered?


No.

Do they still use mercury to flash the getter in the CRT gun assembly? I'd
be a little worried about that possbility.

Do you have any technical info sources that show mercury was ever used in
getters?


I doubt it. Mercury is not that reactive. He's probably just thinking
of the shiny getter coating and associating it with mercury.

I got my vacuum technology mixed up. Mercury is used in some kinds of
vacuum pumps. Barium is the most used material for a vacuum tube getter.

 

[ian field]

"Flyguy" <Flyguy@bluesky.net> wrote in message
news:1bl7h.5$gJ1.4@trndny09...

Sam Goldwasser wrote:
"ian field" <dai.ode@ntlworld.com> writes:


"Flyguy" <Flyguy@bluesky.net> wrote in message
news:XU86h.2749$bj1.1163@trndny05...

Homer J Simpson wrote:

mwpmorris@gmail.com> wrote in message
news:1162839588.995972.108850@h48g2000cwc.googlegroups.com...



Could I have been exposed to anything when the glass shattered inside
the set or when I powered the thing on with the glass shattered?


No.

Do they still use mercury to flash the getter in the CRT gun assembly?
I'd be a little worried about that possbility.

Do you have any technical info sources that show mercury was ever used in
getters?


I doubt it. Mercury is not that reactive. He's probably just thinking
of the shiny getter coating and associating it with mercury.


I got my vacuum technology mixed up. Mercury is used in some kinds of
vacuum pumps. Barium is the most used material for a vacuum tube getter.

You might be thinking of barium and/or strontium cathode emissive coatings.

 

Yes i have looked for DC, and there isnt any.
Also there are 4 different relays, Front-Rear L&R None of them are
kicking in.


The fact that none of the relays is dropping in, is neither here nor
there - except to indicate that the problem is likely *not* related
to any particular relay driver. To avoid unncessary duplication, the
fault monitoring and switch on delay circuitry, will be a single
entity, monitoring all channels simultaneously, and acting on all
relay drivers simultaneously. Thus, any fault ( DC offset, over
current, over temp etc ) detected on *any* channel, will cause *all*
relay drivers to be inhibited. So, I would suggest that your problem
lies either with the fault monitoring circuitry itself, or the fact
that it is genuinely detecting a problem on one or more channels.

Arfa

Good point Afra

I think I've seen a couple bad 1 ohm resistors in the power supply cause
this. They're at the rear corner of the machine.

Mark Z.

Thanks mark.. Anything more specific on this 1 ohm resistor? location # perhaps?

i saw a few other posts of people complaning of the same problem, with no reply's of course, in other fourms on the web.
Ive put my Voltmeter on the outputs at the relay, i get 0.01 volts DC not enough to trip any protection circuit's.
thats why im seeking answers more like what mark has posted.
Known problems that ocassionally rear thier head.

I dont have the sony database of tips anymore cause I no longer subscribe, (i just dont do repairs like i used to)
but perhaps there is a sony bulliten on this issue?

 

[Ken Weitzel]

Ancient_Hacker wrote:

The 1958 Fords had radios with 12 volt tubes and a 2-transistor power
amplifier. The transistors were 2N256's or thereabouts. If you looked
them up in the GE transistor manual, their high frequency cutoff was
like 4Kc ! Not Mhz or GHz, KHz!

Hi...

But for those of us who were able to order them with the incredibly
expensive optional radio, they sure sounded good to us

Take care.

Ken

 

Ken Weitzel wrote:

Ancient_Hacker wrote:

The 1958 Fords had radios with 12 volt tubes and a 2-transistor power
amplifier. The transistors were 2N256's or thereabouts. If you looked
them up in the GE transistor manual, their high frequency cutoff was
like 4Kc ! Not Mhz or GHz, KHz!

Hi...

But for those of us who were able to order them with the incredibly
expensive optional radio, they sure sounded good to us

Take care.

Ken

AM radio doesnt go that high anyway. There still would have been output
above 4kHz, and preemphasis is not so hard.

Worst Ge spec I ever saw was 2kHz ft. Not for audio.


NT