No sound on right sound channel (ADPCM fixed)

Duo_R · 09/03/2009, 03:49 AM

Ok, if you haven't been following along, I got a US TurboDuo that has had every cap replaced, sound has been restored but the overall volume has been reduced about 30%, but it is static free and no fade in and out. The main problem I am having however is there is no ADPCM sound. Let me clarify since I want to make sure I am describing the problem correctly.

The best example of what is wrong is when you play YS III, at the beginning of the game you follow Dogi to his house and a girl comes out (I think her name is Maria). She walks up to you but you hear nothing. That is ADPCM voice sample correct? Any idea what could be the source of the problem? So far I have replaced:

* EVERY cap on the TurboDuo except for the 3.3uf cap
* OKI5205
* OKIM41464-10 x2
* M51131

I haven't replaced the 4558 Op amps and today I was thinking that this might be my issue. Remember when I said the sound was reduced by 30%? That happened after I dishwashed the system, and maybe the OP AMPS were damaged somehow. Obviously the total sound was reduced in volume, but maybe the one related to ADPCM was damaged?

This is my original US Turbo Duo and honestly I just keep working on it because it has some sentimental value to me. Now the sound works fine, the games play great....should I just forget all the hassle and just enjoy games on my Duo-R??? Or do you think we can solve this bitch?

esteban · 09/03/2009, 08:57 AM

Quote from: Duo_R on 09/03/2009, 03:49 AMThe best example of what is wrong is when you play YS III, at the beginning of the game you follow Dogi to his house and a girl comes out (I think her name is Maria). She walks up to you but you hear nothing.

Ahhh, did you equip a nut from the Roda tree? It turns out that amino acids in the Roda nut can cure this character of her muteness. She then thanks you and provides you with a extremely useful piece of information.

Years later, a large pharmaceutical conglomerate form Esteria begins marketing these amino acids, under the brand name "Rodanol" to cure Pharyngitis.

override · 09/03/2009, 09:50 AM

Duo_R

I'm sorry to hear that those two chips I sent you didn't fix your system the way you were hoping...When you replaced the M5205 OKI and the M51131L did you replace them with new or used known working chips? Just curious....Also you mentioned replacing op amps, to be honest I believe that would be the next best route to go with! They are enexpensive to replace, usually less than a dollar a piece....If it were me I would start with the three I have circled in this picture, those are tied in from the M5205 OKI straight to the CD Pins.

I have a PCE Duo that has done this same thing to me and I have never gotten it back out to try and fix it, ofcourse at the moment it has two chips pull from it but other than that it still had this same sound issue.

If those dont work I have 2 other chips you could try replacing, I believe I can get them for you aswell!

Duo_R · 09/03/2009, 10:02 AM

Estaban - thanks for the laugh =).

yeah override, I appreciate u sending those chips, we are just doing the process of elimination. I will send u the IC's that I extracted since most likely they were fine. Yes the other ICks came from a system with no ADPCM issues. So next are the OP AMP. I could use some help finding a direct replacement since I want to make sure they will be drop in that fit.

Also any tips removing the old 4558's? I almost took one off but I literaly had to lift one leg at a time and it was a little tedius.

Erik

Sent from my Blackberry Tour

override · 09/03/2009, 10:12 AM

Quote from: Duo_R on 09/03/2009, 10:02 AMyeah override, I appreciate u sending those chips, we are just doing the process of elimination. I will send u the IC's that I extracted since most likely they were fine. Yes the other ICks came from a system with no ADPCM issues. So next are the OP AMP. I could use some help finding a direct replacement since I want to make sure they will be drop in that fit.

Also any tips removing the old 4558's? I almost took one off but I literaly had to lift one leg at a time and it was a little tedius.

Erik

The Tip I would give to you on removing then would be either using a heat gun like I told you that I do, or use desolder braid, get as much up as possible and lift each leg at a time, if you could get your hands on a hot air rework station that would be even more convenient! Hell if you know anyone with some soldertweez thats the best route! On the Op-amps, I believe any general purpose SMD 4558 will work! They should be the same size.

Charlie · 09/04/2009, 09:52 AM

If I may:
"* EVERY cap on the TurboDuo except for the 3.3uf cap
* OKI5205
* OKIM41464-10 x2
* M51131
I haven't replaced the 4558 Op amps ..."

Assuming we're talking about the same unit that I have in my notes:

1. Good that you've done the typical legacy cap replace; we all know about that.
2. Why the M51131? It's not part of the ADCPM audio.
3. Doubtfull the memory is the problem, it would show up elsewhere also
4. Good on the 5205, it IS the ADCPM, after all.
5. I think U503 is a 4558 (among others), that's also ADCPM. But all the other 4558's are not ADCPM, so if you have any audio at all (CD, music, game sounds), don't waste your time replacing them.

Specifically, if you all other audio except ADCPM, the only significant active components are U502(the 5205) and U503 (again, I THINK it is a 4558). Of course, the data that drives the ADCPM comes from the MCU and CPU, but if they were bad, you'd have a lot worse problems than just bad audio. The passive components are C652,C623,C653,C621,C622.

Finally, if, again, you do have all audio expect ADCPM, and given what you have already replaced, I'd look at U504 (usually a 4053), the audio switch. This is the only component that is common the the ADCPM and the other audio; it actually switches the amplifier/speaker circuit from ADCPM to {other audios}. You could check and see if U504 is even being TOLD to switch at the appropriate time on pin 9.

Of course, if you have a different system than I think you do..??

Good luck.
Charlie

kattare · 09/27/2009, 11:18 PM

I have a unit here with a similar issue. Had only the blips and beeps type audio, no redbook and no adcpm. Replaced all the leaky caps, and that brought back the redbook 100% and the adcpm to about 20% volume. With no more caps to replace, I flipped the board over and found a ton of leakage on the other side of the board right in and around U503. So replacing U503... you think that would bring the adcpm to 100%?

kattare · 09/27/2009, 11:23 PM

Hmmm... I should have played with it more before posting. I lifted 4 of the pins on the 4558 (IC503) and was going to start working on the other 4 when I realized that it was horribly gunky underneath the thing. So I just bent it up, cleaned out underneath it, bent it back down and resoldered the 4 pins. adcpm seems to work pretty good now, around 80%. Not sure where I'm losing the 20%, but I think I'm about just about gtg with this repair.

Gotta hand it to you guys... I wouldn't have known to look at IC503 without this thread... It woulda been ages before I would have thought to look at the back of the board for leakage that had seeped through.

Charlie · 09/29/2009, 05:56 PM

Glad to be of help, but I can't help wondering about this statement:
"I wouldn't have known to look at IC503 without this thread"

U503 was clearly mentioned in the thread:
https://www.pcengine-fx.com/forums/index.php?topic=960.msg113601#msg113601

Or maybe the explanation was not clear enough?

Charlie

kattare · 09/29/2009, 11:25 PM

Charlie, LOL, your explanation there is awesome. Appreciate the link!

To be clearer, I have a pile of Duo's here, and this particular one would have made it's way to the bottom of the pile to be looked at "ages from now" if this thread hadn't piqued my interest. ;-)

Charlie · 09/30/2009, 07:48 AM

" have a pile of Duo's here"
Cool. Let's tackle them all!

Charlie

Duo_R · 09/30/2009, 12:41 PM

Ok update to the ADPCM saga, IC503 replaced last night. No change. Now IC504? I feel like I am running out of things to replace..... Any sources for this part or will I have to swap from another Duo? So much has been replaced already (see my post earlier).

Duo_R · 09/30/2009, 12:43 PM

Oh and Override I still owe u those chips. Please PM ur address again. Thanks!

Charlie · 09/30/2009, 07:03 PM

"No change. Now IC504?"
Maybe, maybe not. I'd do some more testing, if you can (I don't know what equipment you have).

More detail on ADPCM (why didn't anyone tell me I was spelling it incorrectly!???) audio:
1. Out U502, pin 10
2. Through C652, a .1uf (you DID replace this, yes?)
3. Through R657/C623/R688 (replace C623, yes?)
4. Into pin 6, U503
5. Outof pin 7, U503
6. Through C653, a 10uf (replaced?)
7. Through R654/C621/R656 (C621?)
8. Into pin 2, U503
9. Filtered by C622 (replaced?)
10. Outof pin 1, U503
==> any of the above caps, if leaking, would affect the audio

Pin 1 of U503 feeds into pin 4 of U504, an audio switch. When switched on (via pin 9), the audio comes out pin 5. At this point, it is mono. It then splits, via R627 & R629, and is amplified by the left and right channel circuits. If you seem to have good audio out of both channels when using other, non-ADPCM, audio, this is probably ok.

So, you might want to A) check more closely into those components mentioned above, and/or B) temporarily jump
U504, pins 4 & 5 together. If there is no change, U504 is probably already turned fully on via pin 9, and is ok. If there is a big change, either U504 is turned fully on (again pin 9), but is NOT ok...or it is not being turned on at all.

Overall, if you have sufficient equipment, I'd use a 'scope and view the ADPCM audio at the in's and out's of the various amplifier stages, to make sure that each stage actually is amplifying. If you have a good unit to compare to, so much the better.

Kind of hard to do this via "remote control"

Charlie

Duo_R · 09/30/2009, 07:55 PM

as far as equipment I only have a multimeter. I can certainly try to jump pins 4 and 5 (you have done this before correct?).

I will check those caps, but as stated all the caps on the topside of this US Duo have been replaced. Again here is my problem:

* Overall sound reduced about 30% after a dishwash method clean (but the scratchiness was fixed)
* All sound works but there is NO ADPCM sound

Duo_R · 10/01/2009, 04:25 AM

Charlie,

I jumped pins 4 and 5 on the IC504 and still did not hear ADPCM. I haven't replaced the tiny components you mentioned, can those go bad? I did reflash the solder on them but that didn't fix anything. All the large caps on this board was replaced, but all those tiny parts are still stock. Do you know the values of all those parts? Would it be bad to just temporarily jump them?

Charlie · 10/01/2009, 07:45 AM

Well, if you're not hearing it AT ALL, it has to be within that group of components mentioned. That brings up a new bunch of questions, like:
1. Is ADPCM even being generated? That is, are you SURE you are operating in a mode whereby ADPCM should even be there? Can you check against a good unit?
2. Given the 5202 is the analog source (and you've replaced it - are you sure it, and any other new stuff, is actually any good?), you could check to see if it actually has any power on it, and also check to see if the digital data is actually coming into it.
3. A quick trick, but I don't know if this will work: many times, if an amplifier or ampliflying circuit is strong enough, you can inject a signal of your own using just the tip of a screwdriver (carefully) at the source, and hear a hum or some kind of noise at the output. If you have a working unit to compare to, this makes the test easy, as you can compare the loudness of the two; it may help to use headphones. The idea is to determine if the "screwdriver sound" is equally loud, or even close, in both units. However, this trick only works if the amplifier can amplify the signal strongly enough; some amp circuits do only a minimum of amplification.

To answer your question, the "tiny components" are much less likely to go bad, but of course they are not 100% guaranteed. It is possible two other things are the issue:
1. Within that entire amplifier circuit chain of components, there is enough leakage/corrosion on the board to kill the amplifing function,

or

2. The smaller (value-wise) caps, which typically don't actually leak, can short or open. Either will kill the signal.

After-thought edit: Are you sure the amp chips are getting power?

I would NOT recommend you jump them, at least not yet. I will get more data on the specific parts and/or part-values.

Charlie

Duo_R · 10/01/2009, 03:25 PM

I am not fully understanding the screwdriver test. I am positive that it is not outputting adpcm, I have a good unit for cross compare.
Which pins should I test for power? I am stumped and not sure what to do next. Maybe swap IC504 next then small parts?

Charlie · 10/01/2009, 05:28 PM

U502 should have 5V on pins 1,3,18.
U503 should have power on pin 8.
>Edit: U503 should have 4 volts (I think - check against good unit) on pin 8, and 2.5 volts on pin 3 and pin 5<

I assume you can find the Ground connection for yourself, maybe on the power plug?

Clarify this statement:
"I am positive that it is not outputting adpcm". Do you mean you have determined positively that U502 itself is not GENERATING audio, or do you mean the final output of the whole amplifier chain has no audio?

Assuming you mean the whole amplifier chain has no audio (that is, you feel U502 is ok):
To do the screwdrive quick test, plug in the headphones. With the unit on, carefully touch the screwdriver (actually, any reasonably stiff piece of metal that you can handle safely) to U502 pin 10. Make sure that you are touching the metal of the screwdriver; that way, your body becomes part of the circuit, which is what we want. Perform this test on the good unit first. Also, of course, the volume should be full up. You should hear something in the headphones, either static, a hum or buzz, or at least a kind-of-click when you actually make contact. We need to get this to work first, so do whatever is normal to enable ADPCM audio (it obviously won't work anyway if you have the good unit in a configuration where the ADPCM audio is turned off!)
Once you have the good unit working, and have a kind of "feel" for how the circuit responds/sounds, repeat the test on the bad unit. If you hear the same sound, the amplifier chain is good, and U502 is not generating any sound.

If you don't hear any sound, move to U503 pin 6; if no sound, move to U503 pin 2. Remember to check on the good unit first, so as to "train your ear" for what the correct sound is.

Finally, if you still don't hear any sound, move to pin6 of U506 (this is right channel audio only). THIS MUST WORK, as U506 is part of the generally amplifier chain, and you have indicated that other, non-ADPCM sound works. If at this point, you don't hear any sound, then either you are performing the test incorrectly, or the other non-ADCPM sound actually are NOT working.

Assuming you meant that U502 is not generating at all(or, of course, you discover that via the screwdriver test):
check for the voltages as listed above. The digital data comes into U502 from the CPU on pins 4,5,6,7,14,15,16.

Let me know where you do, and do not, hear the static/hum/buzz/click.

Good luck,
Charlie

cosmos99 · 12/12/2009, 03:22 AM

Thanks Charlie for the info about ADPCM sound , i did change c653 on my japanese DUO and i get loud ADPCM sound now,it was weak before,as redbook audio ,i did change the 6 usual caps with success.

Duo_R · 11/15/2010, 12:30 AM

ok so update here - I swapped out IC503 as previously mentioned with no success. This morning I did a trace and discovered that pin 4 of the 4558 was not grounded. I had a bad trace and I proceeded to jump pin 4 to ground. I grounded to the closest ground (about an inch away) with a small wire. Booted up the Duo and to my surprise the ADPCM now works! that is great news, a step forward after a long time of no progress.

However, final issue remains, my sound volume is now about 20% of normal capacity. Somehow jumping this 4558 has caused my already low volume to decrease even more. Since this is now the issue, think I should start swapping out the 4558's on the top of the board? Here is a summary of the work done:

* EVERY cap on the TurboDuo except for the 3.3uf cap
* OKI5205
* OKIM41464-10 x2
* M51131
* I503 IC (4558 Op Amp)

Duo_R · 11/15/2010, 02:51 AM

ok I am almost there. I discovered a bad connection in a cap in the pre-amp circuit (did the pencil eraser test). After reflowing solder I got 100% sound volume in the left channel, and about 20% in the right channel. I am suspecting another bad connection. It is no surprise with how many times I have been tinkering with this board, just a matter of identifying the right cap now. I swapped out the 4558 near the audio circuit but didn't do anything different. Does anyone know which caps are a part of the the right sound channel here (post and pre):

Also this is the pinout of the 4558 I have been swapping. It is useful to know the pinouts for tracing, etc:

Charlie · 11/15/2010, 06:26 PM

Does this help?

https://www.pcengine-fx.com/forums/index.php?topic=960.msg113601#msg113601

If it's not clear, C604 is Right, c610 is Left.

Charlie

Duo_R · 11/15/2010, 06:30 PM

That should, forgot that you posted that. Do you have an idea on how I can test the circuit (perhaps earlier on) to figure out when the right channel quits? Like could I jump this to a small speaker somehow? I would need to know the left and right channel circuits when doing this.

Duo_R · 11/15/2010, 06:42 PM

Also I could use a headset to test, just match up the + and - to the caps that are associated with the right sound channel correct?

Charlie · 11/16/2010, 06:52 PM

At this point, the L & R circuits going forward are pretty much identical. So, in theory, you can just connect identical points between L and R and see what happens. One common sense things to be aware of: If there is a serious problem in one channel, jumping it "in parallel" to the good channel could very well blow the good channel.

There are a couple of ways to reduce the chances of an error:
1. Use a meter/scope to compare identical points on each channel. If the DC voltage is very close (< .5v or so) , those two points are probably ok; if there is a more serious voltage difference, don't just connect via a jumper wire. Of course, if it IS a serious difference, you have a hint of where the problem is already!

2. If you don't have a meter, or you do and it shows non-compatible voltages, get a non-polarized cap. (Or, make one out of two polarized caps...connect them in series, either + to + OR - to -). Use a low value cap (1uf, maybe 4.7uf), and make the jump via the two open connections on the cap pair. This will protect the good channel from any bad voltages on the bad channel.

In either case, you want to try to determine whether the problem is further "ahead" in the circuit, or further "back" in the circuit. Using the jumper technique, common sense will tell you which way to go. If connecting C604 and C610 together gives good output on both channels, then obviously the "ahead" circuity is ok...the problem is that the audio is not getting to it. Keep working the jumper cap forward in the circuit, until you find the point at which something drastically changes. And, of course, vice-versa.

Also, is the problem in the headphone jack...maybe the internal switch?

Finally, remember that there is an anti-thump circuit, but only on the headphone out...and you can check audio on the L & R of the AV out.

If you have a question on this part of the circuit, especially in reference to L vs R, please ask...but try to be specific.
Charlie

Duo_R · 11/16/2010, 07:03 PM

I only have a ohmeter/multimeter, but if I am measuring voltages then that won't be a problem. So I will do voltage test and start at one end and move forward / back. I really like your idea of using the non-polarized cap, that makes perfect sense. So jumping the pairs live and see if I get sound or don't get sound. Great idea! I know where the pairs travel near the 4558 opamp circuit, but further behind there I am not so sure (like once it gets to I believe IC505). I know based on what you stated what IC is in the series, but not sure on the pins. But I will start checking that out.

Yes the right channel is not working via AV connector or the headphone jack. And it isn't 20%, it is 0%. I though it was 20% but realized it was my TV using the mono sound and putting sound in both speakers. Hooked up to my headphones / speakers the right channel is dead.

Thanks a ton Charlie, your insight has been extremely helpful! Again where did you get such insight into the Duo circuits?

Charlie · 11/16/2010, 07:16 PM

Well, I don't have a lot of insight into the internals of a DUO, but I do know electronics.
Ok, rather than go back through all this stuff, let's just hit the high points:
1. Right channel NG, left channel ok? I assume so, for the following (If I'm backwards, then, of course, reverse the L & R stuff)
2. Are we really talking ADPCM? As comes from the U502? To check this, have left channel working, then temporarily connect U503 pin6 to ground. If the sound continues, it's NOT ADPCM from U502.

Check this first. Does the sound continue, or disappear?

Charlie

Charlie · 11/16/2010, 07:26 PM

Next, if the sound disappears, then yes it is from U502. This is good, as at this point it is monoaural, so if either one channel works, all the monoaural must be working. This audio goes into u504, pin 4 (still good as monoaural). It should be coming out pin 5, still monoaural. This, finally, is the point at which it separates.

Make sure we're correct to this point, as the next stuff gets complicated.

(If the sound does NOT disappear when you do the temp jump, we're already going the wrong way.)

Charlie

Duo_R · 11/16/2010, 09:23 PM

just to clarify ADPCM works (well in the left channel at least). So the issue now is just no sound in the Right sound channel.

BlueBMW · 11/16/2010, 09:47 PM

Quote from: Duo_R on 11/16/2010, 09:23 PMjust to clarify ADPCM works (well in the left channel at least). So the issue now is just no sound in the Right sound channel.

This is on both the headphones port and through the A/V out?

I chased around a right channel audio problem for a LONG time on my Duo... turns out the right channel connector on my TV was wonky...

Duo_R · 11/16/2010, 09:52 PM

correct, the ADPCM problem fixed, now just right sound channel (lol). I am positive it is an issue since headphone jack and AV port both don't output it.

Charlie · 11/17/2010, 05:52 PM

(Well, I was hoping for a more definitive answer, like "Yes, the audio does definitely disappear when I short...", etc...but I will assume that the answer was YES, THE AUDIO DISAPPEARED in both cases. I want to make sure we are not confusing the ADPCM audio source with Game Audio, External Device Audio, or DAC Audio, etc)

As I said, U504 pin 5 is where the monoaural audio becomes "stereo"; it is actually only two-channel monoaural audio. This pin connects to a common point on R629/R627. (Right channel first component, left channel second component). These two resistors feed the two identical R & L circuits. Audio now into U506-6/U506-2. Out U506-7/U506-1 to C604/C610. Through R608/R610 to AudioJack JK601-5/JK601-1.

We can stop here for now, as any sound not at the AudioJack pins will certainly not make it any further anyway, although we still have to check to see if the problem is actually further down.

As I have previously mentioned, there are various mute and anti-pop circuits in here also. It so happens that there is one such circuit in this area also...so it may be that the right channel "turn off" circuits are malfunctioning and killing the audio, even if the actual amplifier circuits are ok. We'll check that after you give the a definite answer on the above path from U504-5 through the rest of the points to eventually reach the AudioJack.

I assume you can unsolder a few parts if we need to...and replace them undamaged?

Ever think of getting an o'scope?

Charlie

Duo_R · 11/19/2010, 01:25 AM

Charlie thanks a ton again for your help. I have been away on business a couple days but will give this a shot this weekend. I don't have an o'scope, but I think I do want to eventually get one. Any ideas which would be an affordable but good one to use?

As far as SMD parts, yes that won't be a problem to replace parts. I am confident I could remove a HU6260 without breaking a pin.

Charlie · 11/19/2010, 04:36 PM

OK, fine. I'm going on vacation myself for the week of Thanksgiving, so I won't be back until next Friday.

If you still can't get audio out the AudioJack, remove C671 (right, C70 is left). This will disconnect the circuitry further down the amplifier chain; if the problem is down there, it will be unable to affect the AudioJack audio, so if you get the missing audio back, you know the problem is after C671/C670... if you don't get audio back at the AudioJack, you will have narrowed the problem area to about 1/2.

I don't think you will get it back, however, because the circuitry further down, even if flawed, only has a small effect on the AudioJack.

Next, try removing transistor 603 (right, 604 left). This is the "turnoff" circuit. By removing it, you will have disabled the turnoff, which obviously means it should turnon!

Good luck, see you in a week.
Charlie

Duo_R · 11/20/2010, 09:56 PM

Ok Charlie, I am definitely getting somewhere with the no audio on the right channel. I did some measurements and here are the results:

C18 - 3.19V
C17 - 3.2V

C614 - 3.87V
C613 - 3.31

C610 - 5.23V
C604 - 1.398 V

so obviously an issue with C604. The voltage was significantly different. So I then did a jumper using a 1uf non-polarized cap between C610 and C604. The result, I had sound in both sound channels. Doing the same L/R jumping between C614 and C613 did not change anything (still no sound in right sound channel).

This concludes the problem is between C610/604 and C614/613

So next I did a measurement on IC506.

Pins
1 - 5.27V (OUT)
2 - 3.88V (IN)
3 - 3.88V
4 - N/A
5 - 3.88V
6 - 3.32V (IN)
7 - 1.38V (OUT)
8 - 7.75V

So here you can see that the 4558 opamp is not outputting a signal at the same consistent voltage level as what is coming in for input 1 & 2. Going in, the signals are pretty close, but going out the voltage measurement shows there is a significant difference for the right channel.

Now I swapped in this 4558, so I doubt that it is a bad part. I could swap another one in, unless you think there is something in the circuit that is causing the 4558 to output a low signal for pin 7?

I haven't tried removing the parts you suggested yet, not sure if where I am getting the signal to work would make the assumption that removing that would do anything. Let me know what you think.

Duo_R · 11/21/2010, 06:12 AM

another update - removed the cap C671 and didn't have any changes.

Duo_R · 11/22/2010, 10:33 PM

another update, removed transistor 603, no change. I have looked over the board with a magnifying glass, nothing looks bad. time to test the resistors and other small parts in that area of the circuit?

Charlie · 11/24/2010, 03:04 PM

Well, since you believe that the circuit around C604 is the problem, first check R692. It connects between U506-7 and U506-6. (R691 for Left channel). It may be cracked, etc....actually, any problem in the path from U506-7 back to R692 and on through it to U506-6 could cause this.

Second, check R629, same as above. It connects between U506-6 and the audio source at U504-5.

Third, check your soldering on U506 pins; make sure removing the old IC didn't break this path, even while NOT breaking the path into C604. Also make sure there is no flux residue, etc, that could be providing a high-impedance path.

It is also possible that the incorrect voltage is cause by one of the other circuits feeding that IC. Remove R613, R616, R630, R690 and C604 (all of them as a group...keep track of which is which!). This should leave on the IC itself, R692 and R629. Does the voltage become correct? (It almost HAS TO, there's nothing else there to cause the problem!). Either way, you're down to only three parts and their associated circuitry, to work on.

When you are eventually able to get the correct voltage, re-install C604 first. This will let the (hopefully repaired) audio finally get to the Audiojack and the headphones.

Then go back and reinstall R613, R616, R630 and R690, in that order. Check after each one to see which cause the correct voltage to go bad (and presumably, the audio to go away).

[by the way, you said:
C18 - 3.19V
C17 - 3.2V
did you mean C618 and C617?]

Charlie

Edit: Hey, why did you check the voltages on those first four caps...they are not part of the ADPCM!?!?

Duo_R · 11/24/2010, 09:24 PM

Thanks for the reply I will try that. Yes I meant c617 and c618.

[by the way, you said: C18 - 3.19V C17 - 3.2V did you mean C618 and C617?]

Duo_R · 11/24/2010, 09:36 PM

Well they are a part of the L/R circuit correct? My adpcm is apparently working now.

QuoteEdit: Hey, why did you check the voltages on those first four caps...they are not part of the ADPCM!?!?

Duo_R · 11/25/2010, 12:14 AM

it's fixed!!!! It's fixed!!!! Hallelujah!!!!!

Pin 5 on the 4558 wasn't properly soldered back on when I did the swap. I cannot believe it!!!! Full stereo sound and ADPCM fixed!!!! Damn Charlie you are the man!!!!!!!!!!

Charlie · 11/25/2010, 10:01 AM

==>Well they are a part of the L/R circuit correct? <==
They are part of a DIFFERENT audio source.

Someday I should probably make the schematic of this circuit....it generally appears that the audio seems to be a pretty common problem.

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Here's a side thought, which may actually qualify for a different thread....
What do you think of making a TG16/TGExpress/Duo full development station? I mean the hardware that will give you full control over the CPU, address breakpoints, single stepping, data display, etc. You could certainly make/change programming really fast when writing that "killer game"! It would mean cutting into a working unit, although you could certainly restore it. I just wonder how much interest there would be in this vs how much usefullness, given the availability of things like Medafen, etc.

I'm also considering making a TG-based prom emulator (cheap!) that can be loaded from the parallel port of a typical home computer and look like an HUCard....but how many of them come with parallel ports these days? This would be easier/faster than programming a prom chip in an external programmer, then plugging it into some kind of HUCard equivalent, etc. I know there are similar things out there (USB based), but they are somewhat expensive.

Any other thoughts, hardware speaking?

Charlie

OldMan · 11/25/2010, 12:06 PM

I don't think a full-blown development station is worth the time/effort. It's fairly easy to check the code in one of the emulators, and I can usually manage to figure out what's going wrong without single-stepping the code.

However, I would -love- to have a prom emulator. That would allow us to hunt down / fix bugs that the emulators just don't reproduce (like video snow, due to VRAM writes....) I would suggest that it be 2 boards, though; one 'master' board that does the prom emulation, and a second board to handle the I/O to/from the pc. That way, if your pc has a parallel port, you can purchase that version of the i/o board. And, if you lack a parallel port, you can purchase the USB version.

The only real problem I foresee is that some people are going to treat this as a flash cart, and trash talk it since it only holds one game :-)

Duo_R · 11/25/2010, 01:43 PM

Audio schematic would rock and be a great sticky thread.

Charlie · 11/26/2010, 01:46 PM

(Edit: update to add text notes, fix a few typos. Also, I made the pictures bigger, so that they could be copied, zoomed, and viewed easier...but I may have overdone it! If they're objectionable, let me know...I'll reduce them a bit!!!)

Finally! Resolved my errors....oops, I mean questions (yeah! That's it---"questions") on the actual DUO audio circuitry.

Abbreviated schematic of DUO audio circuitry, part 1:

Abbreviated schematic of DUO audio circuitry, part 2:

Charlie