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Another system saved to play more Bonk.  Good job!
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Chit-Chat / Re: Mario Bros. Special video is up (PC-98 Paradise!)
« Last post by kazekiri on August 07, 2022, 06:07:00 PM »
It's about time I covered one of the Hudson/Nintendo games. Here's Mario Bros. Special!


https://youtu.be/oEqCD4muhrw
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Yes, the high voltage issue was affecting all three audio op-amps.

After much work looking over the board and adding patch wires and “cut capacitor legs through corroded vias” fixes, I finally fixed the audio on this Duo! CDs, Hucards, AV Port and headphone jack all work great now. The final fix was R323 and R324, specifically I removed both resistors, cleaned up under them and added a patch wire from R324 to ground.

I went back after and did a final voltage check and there wasn’t a big change, but still a bit. Audio op-amps show about 10v on input voltage and the 22uF caps are around 5v now. I won’t look a gift horse in the mouth though, the audio works again so I’m happy.

Also fixed the issue of “CD spindle spins immediately on power-on” but I did that before making this thread by reading old posts and finding a certain Keith Courage mentioning a corroded via by C149 causing the issue.  :D

In total, all the fixes to this board:

C149 (positive side, corroded via)
C135 (positive side, via was partially corroded but worked, fixed for future-proofing)
Big via near C149 (fixed CD spindle)
R321 replaced (cap leakage under it)
R322 replaced (cap leakage plus the corroded via connecting to IC503 ground)
R323 replaced (cap leakage under it)
R324 replaced (cap leakage plus the corroded via connecting to ground)
C616 (positive side connecting to IC505)
R639 to IC505 (corroded via)
C305 (both solder pads were corroded on component side of PCB)

IC503 replaced (pin 5 and pad were badly corroded, pad fell off board)
IC521 replaced (found cap leakage underneath and a leg fell off)
IC506 replaced (maybe didn’t need replacing but some legs were really weak and broke off easily)

Job well done I’d say. Pretty scary for a PC Engine Duo like this that externally was in barely used and nearly scratch-free condition, all case screws had that distinct “virgin snap” too. Even the CD drive works perfectly after fixing that via by C149, didn’t need to do anything else to it.

Thanks so much for your help Keith Courage, you’re still the Duo repair wizard!  :clap:

PCB pics:



https://imgur.com/a/mgi451I
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Is this the same for all 3 of the 4558 Audio op amps? There is one near the AV jack and two others on the bottom part of the board near the heat sinks.

Yes the higher voltage can be a bad op amp but also a bad ground for one or more of the capacitors can do the exact same thing. Also, check for shorts in the via holes near the op amps as more often then not, the problem is a bad connection through a via hole. I only change out an op amp once it seems apparent that all connections through the board are good.

You can repair shorted vias by soldering an extra capacitor through the holes.
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I tried to get all the cliff notes info into the title to get to the point.

So I have a black PC Engine Duo, it has been fully recapped (console5 Kit), its current problem is the audio amp circuit seems to be at an oddly high voltage in general. All the op-amps show 11v on the VCC pins and as much as 11v even on the op-amp Inputs and outputs. All the 22uF caps in the same area are around 5.7v to almost 6v. I understand the voltages should be more like half those values? (7v op-amps, 3.5v caps)

The audible symptom is (tested with a Hucard), the audio plays for about 1 single note of music then goes completely dead.

I read elsewhere by Keith Courage that oddly high voltage on the caps can mean a failed op-amp chip? Should I replace all the op amps with new ones? Or is there a problem with the cap kit install and some 11v line is bridging with the op-amp power circuit?

Lastly, I’m fairly certain the audio wasn’t working properly before the cap kit but honestly, the audio is always not working on these broken Duos before the recap so at this point I don’t pay that much attention.
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I'm out of town for a bit, but I look forward to replaying this when I get home.  It's a goody, much like CF2, the good and the bad.
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TG-16/TE/TurboDuo Discussion / Re: Game of the Month: August 2022 - Cosmic Fantasy
« Last post by seieienbu on August 05, 2022, 12:24:31 PM »
I played this in college after downloading it from the old DC++ hub.  It was grind-y to be sure but I recall liking it alright.  This is the only Cosmic Fantasy (I think) that I don't own so I went ahead and bought a copy off of ebay.  I'll play some when it comes in though I honestly don't know if I can find the time to beat it in a month these days.
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TG-16/TE/TurboDuo Discussion / Game of the Month: August 2022 - Cosmic Fantasy
« Last post by geise on August 05, 2022, 11:58:19 AM »
COSMIC FANTASY


Time to play through this series. I've only ever finished CF2 which is kinda silly since I've never played through the first. Encounter rate aside I enjoyed CF2 and will get back to it again after I finish this one. This was a game I didn't pick up till recently. I got it from one of you lovely folks for SS this past Xmas. Don't think it will be a super long game, but I have been wanting to play it for a good while. Hope others are in an RPG mood.
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PC-FX Discussion / Re: How long does memory formatting last?
« Last post by DragonmasterDan on August 01, 2022, 02:49:32 AM »
I don't know about the first question, but I know the BMPs take a pair of AAAs and presumably have a cap to hold them over for a few minutes while you change batteries.

Thanks, it was kind of a bummer to lose what save data I had, I may just see about picking one up.
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PC-FX Discussion / Re: How long does memory formatting last?
« Last post by Necromancer on August 01, 2022, 02:17:43 AM »
I don't know about the first question, but I know the BMPs take a pair of AAAs and presumably have a cap to hold them over for a few minutes while you change batteries.
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