Most common cause of no ADPCM on the Duo?

ApolloBoy · 04/27/2012, 08:31 PM

I'm in the process of fixing/modding a PCE Duo for a customer and when I tested it, it worked fine except that the PCM audio was totally dead. I'm not sure where to start, so I'm wondering what the most common cause of this problem is.

Duo_R · 04/27/2012, 08:45 PM

Did this unit have a full cap replacement? I tried a jumper method thanks to TheSteve that helped me narrow the problem to the source.

grahf · 04/27/2012, 08:59 PM

I guess it goes without saying to consider the capacitors? I also seem to remember someone having to replace the ADPCM memory, but i'm not positive.

thesteve · 04/28/2012, 01:17 AM

adpcm probs could be mixer or data
see if the chip outputs sound

ApolloBoy · 04/28/2012, 01:25 AM

Quote from: Duo_R on 04/27/2012, 08:45 PMDid this unit have a full cap replacement? I tried a jumper method thanks to TheSteve that helped me narrow the problem to the source.

I recently did a total recap of this Duo and both Redbook and HuC6280 audio work perfectly. What's the possibility of a bad op-amp being the cause?

Keith Courage · 04/28/2012, 01:53 AM

Sometimes a bad trace can be the issue. I have followed the trace off of pin 10 on the 5205 chip and found that a few of the small resistors there were either not working or a trace was not going from one to the other. Check to see if there is any sound coming from the chip at all by running pin 10 all the way to one of the audio out pins on the AV port. This way you can at least determine if the chip is working or not.

Duo_R · 04/28/2012, 01:57 AM

mine was a bad trace

ApolloBoy · 05/26/2012, 01:01 AM

Just did the pin 10 jumper wire and the PCM chip is not putting out any audio whatsoever.

How much do M5205s usually go for?

thesteve · 05/26/2012, 01:23 AM

slow down, NLA but likely not failed.
use a logic probe to check it for data, clock, power ect.
best bet is still a bad trace/via

ApolloBoy · 05/26/2012, 01:42 AM

Quote from: thesteve on 05/26/2012, 01:23 AMuse a logic probe to check it for data, clock, power ect.
best bet is still a bad trace/via

Double checked and I didn't see any bad traces or vias. Luckily I found a logic probe so I can check out the chip in further detail. What pins should I test for and what should their states be?

thesteve · 05/26/2012, 02:11 AM

IDK i dont have a pinout for it.
i know someone else had a data issue, that was a bad trace

Snow Crash · 05/26/2012, 06:19 AM

Quote from: ApolloBoy on 05/26/2012, 01:42 AM
Quote from: thesteve on 05/26/2012, 01:23 AMuse a logic probe to check it for data, clock, power ect.
best bet is still a bad trace/via
Double checked and I didn't see any bad traces or vias. Luckily I found a logic probe so I can check out the chip in further detail. What pins should I test for and what should their states be?

http://www.jammarcade.net/oki-m5205-datasheet/

Duo_R · 05/26/2012, 12:25 PM

I had some members here send me parts from a bad duo, and if that wasn't the issue I sent the part back. Maybe you can have some luck there because some of the parts don't have easily obtainable replacements.

Steve is right though, my issue was just a bad trace.

thesteve · 05/26/2012, 02:31 PM

http://www.datasheetarchive.com/indexdl/Datasheet-027/DSA00482771.pdf

ApolloBoy · 05/27/2012, 02:10 PM

Triple checked the board this morning and still no signs of bad traces or vias. I'll whip out my logic probe in a bit and see what I get.

EDIT: Just checked the voltage pin on the M5205 and it's reading as 3.93V instead of 5, hm...

thesteve · 05/27/2012, 03:30 PM

unfortunately i havent been able to get a confirmed pinout for the 5205.
in stock http://store.americanmicrosemiconductor.com/msm5205rs.html

thesteve · 05/27/2012, 03:37 PM

http://www.datasheets.org.uk/indexdl/Scans-002/Scans-0053070.pdf
has somewhat better data (could be interchangeable)

ApolloBoy · 05/27/2012, 03:39 PM

So what could be causing the voltage problem I'm having? I'm beginning to think the chip is still alive, it's just being undervolted somehow and hence why it doesn't work.

ApolloBoy · 05/29/2012, 11:54 PM

No ideas?

thesteve · 05/30/2012, 12:18 AM

trace it back
should it be 5V or 8V?
8V regulator is a common issue.
the amps are 8V, so you can check at them

ApolloBoy · 05/31/2012, 01:49 AM

Both the op amps under the board and the one near the AV port checked OK and put out 8V as they should. The surface mount caps on the voltage line for the M5205 check out as well. I'm utterly confused as to why this isn't working...

Keith Courage · 05/31/2012, 02:21 AM

I say try changing the chip so you can at least rule that out. I have some spares that I mail ordered(sold out now). I'd be happy to sell you one for what I paid. Just PM me if you want one.

ApolloBoy · 06/26/2012, 12:34 AM

Managed to get a PCM chip from Keith and it turned out to be the culprit after all. Thanks to everyone for their suggestions!

thesteve · 06/26/2012, 12:57 AM

you found the easter bunny

ApolloBoy · 06/26/2012, 01:58 AM

Quote from: thesteve on 06/26/2012, 12:57 AMyou found the easter bunny

I did indeed. Now if I can just get the laser calibrated right...

turbokon · 08/05/2012, 04:13 PM

I got a duo here where I just replaced all the caps. I'm getting audio tracks from the cd where before I didn't but the voices and sound effects are low. Could this be the same thing?

thesteve · 08/05/2012, 04:28 PM

most sound effects are chiptunes (huCard sound)
the bonk voice in the 3 in 1 demo disk is ADPCM

turbokon · 08/05/2012, 04:55 PM

Was playing lords of thunder when I was noticing the low voices and sound effects. So I need to loock around the Adpcm chip?

thesteve · 08/05/2012, 05:01 PM

check around the mixer circuit

turbokon · 08/05/2012, 07:38 PM

Found a bad trace at C653. Thanks.