A portable Beta VCR (Toshiba V-X340) from 1985 works perfectly except
there is no color:

1. Pre-recorded color tapes play back in B&W
2. Tapes recorded on this VCR play back in B&W on this VCR
3. Tapes recorded on this VCR play back in B&W on other known good VCRs


Therefore, the VCR can neither record nor playback color signals.

The machine has no switch for B&W/Color and the 3.58 MHz oscillator is
not out of adjustment. I have checked out all of the Chroma circuitry
and all measurements are within the range stated in the Service Manual.


Could it be the video heads even if the B&W picture is flawless?
If not, what else can be tried?

"VCR Gymnast" wrote in news:1155522224.368675.165020
@p79g2000cwp.googlegroups.com:

A portable Beta VCR (Toshiba V-X340) from 1985 works perfectly except
there is no color:

1. Pre-recorded color tapes play back in B&W
2. Tapes recorded on this VCR play back in B&W on this VCR
3. Tapes recorded on this VCR play back in B&W on other known good VCRs


Therefore, the VCR can neither record nor playback color signals.

The machine has no switch for B&W/Color and the 3.58 MHz oscillator is
not out of adjustment. I have checked out all of the Chroma circuitry
and all measurements are within the range stated in the Service Manual.


Could it be the video heads even if the B&W picture is flawless?
If not, what else can be tried?



Have you cleaned the video heads?

I had a VHS VCR that lost color until I cleaned the video heads. It
didn't come back all the way, but most of the way. It was really on its
last legs, though.

Puckdropper
--
Wise is the man who attempts to answer his question before asking it.

To email me directly, send a message to puckdropper (at) fastmail.fm

Have you cleaned the video heads?


Of course, it was the very first thing I tried. Made no difference
whatsoever.

VCR Gymnast wrote:

A portable Beta VCR (Toshiba V-X340) from 1985 works perfectly except
there is no color:

1. Pre-recorded color tapes play back in B&W
2. Tapes recorded on this VCR play back in B&W on this VCR
3. Tapes recorded on this VCR play back in B&W on other known good VCRs

Therefore, the VCR can neither record nor playback color signals.

The machine has no switch for B&W/Color and the 3.58 MHz oscillator is
not out of adjustment. I have checked out all of the Chroma circuitry
and all measurements are within the range stated in the Service Manual.

Could it be the video heads even if the B&W picture is flawless?
If not, what else can be tried?

Just a shot in the dark, but have you tried playing the VCR on a different
TV? I'm thinking that if you've only played it on one TV it might be a
problem with that TV and not a problem with the VCR.

Mikey wrote:

Just a shot in the dark, but have you tried playing the VCR on a different
TV? I'm thinking that if you've only played it on one TV it might be a
problem with that TV and not a problem with the VCR.


Yes, the problem is the VCR because it occurs on any TV or monitor.

VCR Gymnast wrote:
: A portable Beta VCR (Toshiba V-X340) from 1985 works perfectly except
: there is no color:

: 1. Pre-recorded color tapes play back in B&W
: 2. Tapes recorded on this VCR play back in B&W on this VCR
: 3. Tapes recorded on this VCR play back in B&W on other known good VCRs


: Therefore, the VCR can neither record nor playback color signals.

: The machine has no switch for B&W/Color and the 3.58 MHz oscillator is
: not out of adjustment. I have checked out all of the Chroma circuitry
: and all measurements are within the range stated in the Service Manual.


Well, just an opinion here but I'd go back and check the measurements again,
you are overlooking something.

Althought I've seen beta's go black and white because of the heads, I only
remember it effecting the playback. Tapes recorded on that machine might
look like crap played on another, but you wouldn't get a "really good" b&w
only picture.

With a machine that old (21 years?) I'm pretty sure there is some kind of
simple color shutdown circuit, a gate from one of the large scale IC's or
even a simple comparator using a transistor or two. Keep in mind back then
those machines were somewhat dependent on the broadcasters cutting the color
pilot off during B&W telecasts so you wouldn't get that blue snow in the
pix.

I hate to say it myself repeatedly but unless that thing has some
sentimental value like was the machine you used record your honeymoon night
with the wife, I can't really see why you are bothering with it.

Even if it says Toshiba on the front, in 1985 it would still be a re-badged
Sony model and if I remember history correctly, those things were a
nightmare to work on, the portables. You didn't give a history of it but I'd
guess it was either dropped or more likely disassembled by someone who
didn't know what they were doing and didn't stuff the guts back in
correctly.

My guess is you are dealing with a hairline crack, probably on one of the
boards that uses the side-sled to hold it in. With the amount of wiring
those machines had, the boards were pretty tightly packed and it didn't take
much to flex them into that graveyard in the sky.

If you insist on repairing it, two suggestions, put the machine on the side
and study the service manual, ignoring their troubleshooting guide, those
were worthless for the most part. Study the schematic, especially around the
chroma circuit. There has to be a measurement point listed that shows a
"color only" or "b/w only" reading. That is going to be the gate. It might
be like 6-8v color and 1v b/w, or the other way around but the point is,
it's a fairly measurable swing between the two modes that any cheap meter
should be able to read.

I can almost guarantee this point is dead as a duck and by mearly tying it
high or low will bring the color back. Chances are it's going to go back to
one of Sony's nearly propritary LSIC's which were as nearly as impossible to
get 15 years ago, so I'd just leave it in color mode.

If you really want to bang your head against the wall with it, pick up one
of those (if memory serves) B&K 1472 ntsc generators, or any ntsc generator
that has a simple bw/color on-off switch. Get that meter or scope out and
start taking measurements cycling back and forth on the generator. Something
is going to stick out like a sore thumb and work backwards from there.

Of course there are as many other likely problems as there are total parts
in the machine, dried caps, defective delay lines, cat ****. My bet is still
on a hairline crack or interconnects, remember chasing those in the
portables more than anything else.

Good luck with it but beta portables are in my top 5 list of stuff that just
should be pitched. Depending where you live you'll be far better off
scrounging around yard sales and surplus places for another one. Not that it
would be in mint shape after all these years but simpler to repair. Alot of
those were packed away in the basement because the batteries were too
expensive to replace or the owner went to vhs after the war between the two
was over.

-bruce

Bruce...thanks for taking the time to write such a great post. My
responses follow within your text below:


Bruce Esquibel wrote:
Well, just an opinion here but I'd go back and check the measurements again,
you are overlooking something.

I totally agree with you on this point.


Althought I've seen beta's go black and white because of the heads, I only
remember it effecting the playback. Tapes recorded on that machine might
look like crap played on another, but you wouldn't get a "really good" b&w
only picture.

You are correct here too, because I actually put in known good heads
and the B&W problem remains.


With a machine that old (21 years?) I'm pretty sure there is some kind of
simple color shutdown circuit, a gate from one of the large scale IC's or
even a simple comparator using a transistor or two. Keep in mind back then
those machines were somewhat dependent on the broadcasters cutting the color
pilot off during B&W telecasts so you wouldn't get that blue snow in the
pix.

I hate to say it myself repeatedly but unless that thing has some
sentimental value like was the machine you used record your honeymoon night
with the wife, I can't really see why you are bothering with it.

I'm sure that no one would argue with this point. The reasons I am
"bothering' at all are 1) this was a unique model unlike even Sony
portables like the SL-2000, 2) the thing is mechanically otherwise
perfect, 3) I like the challenge and 4) it keeps me off the steets when
my OCD starts to act up (lol)


Even if it says Toshiba on the front, in 1985 it would still be a re-badged
Sony model and if I remember history correctly, those things were a
nightmare to work on, the portables. You didn't give a history of it but I'd
guess it was either dropped or more likely disassembled by someone who
didn't know what they were doing and didn't stuff the guts back in
correctly.

I don't know much about the history, although there is fairly good
evidence that I am the first to take it apart (e.g., all the original
tape and stickers are in place on inner wiring, the "glue" on
adjustment screws is undisturbed, etc). Of course, it could have been
dropped, but there is no evidence of any significant trauma. According
to the service manual, all the parts are present.


My guess is you are dealing with a hairline crack, probably on one of the
boards that uses the side-sled to hold it in. With the amount of wiring
those machines had, the boards were pretty tightly packed and it didn't take
much to flex them into that graveyard in the sky.

This is a very good thought. As you no doubt know, this machine really
is a "one-piece" made up of modules and then a board that folds up in
the front and back. I can e-mail you the service manual if you like.


If you insist on repairing it, two suggestions, put the machine on the side
and study the service manual, ignoring their troubleshooting guide, those
were worthless for the most part.

Agree!


Study the schematic, especially around the
chroma circuit. There has to be a measurement point listed that shows a
"color only" or "b/w only" reading. That is going to be the gate. It might
be like 6-8v color and 1v b/w, or the other way around but the point is,
it's a fairly measurable swing between the two modes that any cheap meter
should be able to read.

I can almost guarantee this point is dead as a duck and by mearly tying it
high or low will bring the color back. Chances are it's going to go back to
one of Sony's nearly propritary LSIC's which were as nearly as impossible to
get 15 years ago, so I'd just leave it in color mode.

This will be the very next thing I try!!


Good luck with it but beta portables are in my top 5 list of stuff that just
should be pitched. Depending where you live you'll be far better off
scrounging around yard sales and surplus places for another one. Not that it
would be in mint shape after all these years but simpler to repair. Alot of
those were packed away in the basement because the batteries were too
expensive to replace or the owner went to vhs after the war between the two
was over.


I'd love to hear what rounds out the rest of the top 5! Regarding
finding another one, I am on the look-out (for the fun of swapping
boards, etc), but they are fairly rare. This ultraportable model was
quite expensive ($1200) in 1985, and show up on eBay only 2-3 times per
year. Thanks again!!