Hi all
I have an old-ish Toshiba DVD player which until now has done good service.
Recently it's developed a fault and I'm wondering if it's likely to be
repairable.

What happens is that at intervals, the output from the player becomes tinged
with a green, or green/magenta, hue, and simultaneously lots of macroblock
type interferences occurs on the video. The audio is (mostly) OK, although
there are occasional 'chirrups'. However the actual player part appears to
be working fine - no hunting or skipping AFAICT.

If the fault occurs as you power on the unit, then it looks like the
player's 'welcome' screen is affected in a similar way. This, together with
the lack of player skipping or hunting, makes me think it's likely to be a
fault in the decoder chain - either the decoder itself (Zoran), or the
associated memory.

I have opened up the unit and cleaned the main board of dust etc. to no
effect. I am also going to try using the other video outputs the unit has -
S-VHS instead of the (I assume) RGB my scart lead is currently using. If
that fails I was going to waft a heat gun around the general area of the
Decoder and memory on the mainboard. But is there anything more ... targeted
.... I might try, before giving up on the player?

Thanks for any suggestions.

J^n

"The Night Tripper" wrote in message
o.uk...
Hi all
I have an old-ish Toshiba DVD player which until now has done good
service.
Recently it's developed a fault and I'm wondering if it's likely to be
repairable.

What happens is that at intervals, the output from the player becomes
tinged
with a green, or green/magenta, hue, and simultaneously lots of macroblock
type interferences occurs on the video. The audio is (mostly) OK, although
there are occasional 'chirrups'. However the actual player part appears to
be working fine - no hunting or skipping AFAICT.

If the fault occurs as you power on the unit, then it looks like the
player's 'welcome' screen is affected in a similar way. This, together
with
the lack of player skipping or hunting, makes me think it's likely to be a
fault in the decoder chain - either the decoder itself (Zoran), or the
associated memory.

I have opened up the unit and cleaned the main board of dust etc. to no
effect. I am also going to try using the other video outputs the unit
has -
S-VHS instead of the (I assume) RGB my scart lead is currently using. If
that fails I was going to waft a heat gun around the general area of the
Decoder and memory on the mainboard. But is there anything more ...
targeted
... I might try, before giving up on the player?

Thanks for any suggestions.

J^n






Don't ignore the possibility of power supply related issues.Look to see if
any power supply capacitors - mostly on the secondary side of the SMPS
transformer - may have puffed up (vented) tops. This is pretty common the
past few years.

Mark Z.

Meat Plow wrote:

[...]

So you say this error manifests in the players own self generated
video also?

yes, exactly

J^n

Mark Zacharias wrote:



Don't ignore the possibility of power supply related issues.Look to see if
any power supply capacitors - mostly on the secondary side of the SMPS
transformer - may have puffed up (vented) tops. This is pretty common the
past few years.

Mark Z.

Hi Mark
good point - and I've encountered that problem on PC motherboards and
routers ... but I can see no evidence of cap. failure here.

I've also checked the composite output and that seems to be exhibiting the
same symptom.

J^n

The Night Tripper wrote:
Mark Zacharias wrote:


Don't ignore the possibility of power supply related issues.Look to see if
any power supply capacitors - mostly on the secondary side of the SMPS
transformer - may have puffed up (vented) tops. This is pretty common the
past few years.

Mark Z.

Hi Mark
good point - and I've encountered that problem on PC motherboards and
routers ... but I can see no evidence of cap. failure here.

Or just caps that were minimally specified reducing in capacity.

Sylvia.

Meat Plow wrote:

Ouch! I'd go for the SMPS like others might suggest. Don't know about
the scale of the Zoran chip set but others since at least 2005 have
employed a SoC stratagy or System On a Chip. Usually one large SMD
with maybe 200 pins. Hell it may even have been Zoran that I have seen
in some cheapy players. I doubt manys ability to dive into a SoC and
t-shoot it let alone find and replace.

Hi again
I've managed to get hold of the schematic and from a cursory examination
the PSU output seems OK. The same outputs from the Zoran chip are used for
RGB and for composite, so it looks like the problem is there, or upstream of
there. The Zoran chip is a ZR36732, and there's a 16M ROM and a 64M SDRAM
attached.

It wasn't a terribly expensive player and it's done good service - I just
don't want to chuck it if there's an 'easy' (heh) fix...

Cheers
J^n

"The Night Tripper" wrote in message
o.uk...
Meat Plow wrote:

Ouch! I'd go for the SMPS like others might suggest. Don't know about
the scale of the Zoran chip set but others since at least 2005 have
employed a SoC stratagy or System On a Chip. Usually one large SMD
with maybe 200 pins. Hell it may even have been Zoran that I have seen
in some cheapy players. I doubt manys ability to dive into a SoC and
t-shoot it let alone find and replace.

Hi again
I've managed to get hold of the schematic and from a cursory examination
the PSU output seems OK. The same outputs from the Zoran chip are used for
RGB and for composite, so it looks like the problem is there, or upstream
of
there. The Zoran chip is a ZR36732, and there's a 16M ROM and a 64M SDRAM
attached.

It wasn't a terribly expensive player and it's done good service - I just
don't want to chuck it if there's an 'easy' (heh) fix...

Cheers
J^n




Did you look at the PSU supply lines with a 'scope or just a DMM? A high ESR
can cause a large high frequency ripple on the DC line(s) which won't be
apparent using a voltmeter...

Mark Z.

The Night Tripper wrote:

It wasn't a terribly expensive player and it's done good service - I just
don't want to chuck it if there's an 'easy' (heh) fix...

You are sure it's not crosstalk from an insufficent screened SCART lead
connected to the TV with an active return tuner output?

--
Adrian C

Hi Again

Meat Plow wrote:

Well I hate to see you give up on it. If I had done that I might have
never learned. In order to inspect the PSU properly you are going to
have to do more than just eyeball it and some voltages on a DVM. You
need to check that the voltages are within the rated tolerance and are
producing cleanly withough ripple or spikes under load.

Yes, I appreciate this - my previous report was just 20mins spent in the
shed on a Sunday evening... I have a good 'scope and will have another look
later in the week.

Once you're
certain your getting clean power from the PSU it might be time to
chuck it unless you can get replacement boards and while at it replace
the optics sled. Probably end up with enough spent to buy something
new though unless you're hell-bent on the repair and learning
something.

Yeah, quite - getting the service manual cost ~$10 (I'm in the UK) and I'm
only in the market for a sub-$100 replacement at the moment. Which is
another reason for tinkering a bit more.

I might also try to have a look at the SDRAM signals, although my my test
equipment I doubt I'll see much unless it's pretty gross. And it's probably
worth having a look at the actual video output from the Zoran - that might
give men an indication of a fault elsewhere.

Thanks again
J^n

Meat Plow wrote:

Yeah ok nothing wrong with tinkering. The SDRAM is no doubt onboard
the Zoran SoC. Read up if you haven't already on MPEG2 compression and
you'll better understand what goes on, P,B,I frames. quantized
matrixes and codings. It's fascinating stuff.

FWIW the SDRAM is separate to the Zoran. I used to work on UK Digital Set-
top boxes so I'm pretty familiar with MPEG ;-)

Cheers
J^n

Hi All
FYI, I took the main board off and wafted a Heat Gun around the parts
which I regarded as suspect - mainly the Zoran chip, RAM and Flash. Put it
all back together and ... whaddya know? It's been working fine now, for a
week or so. Only had light use, and of course it might go wrong at any time,
but I'm pleased for now.

I dunno if I reflowed a dodgy solder joint, or dried off something, or blew
a spec of something away ... but I'm happy to mark this one down as a win.
Thanks for your previous thoughts on the matter.

Cheers
J^n