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TG/PCE Repair/Mod Discussion / Re: PC Engine GT weird Sound Problem
« Last post by RyuX on July 28, 2021, 02:22:20 PM »
So today I added a PAM8610 Amplifier and now I get all the volume I want on my speaker.
I also replaced the speaker with and now everything is just working perfectly.
It just seems the OP-Amp is too weak to really drive a speaker  O0 :thumbsup:
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I've been so bad playing this game this month. Did a few runs at the beginning but nothing lately. I will get some time before the month is over. I really need to work on the 2 min run. I have really not done much with 2 min on this game for over a decade. I forget most of where stuff is.
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Been giving SSS a good run this month, no clear yet and stuck on stage 6.
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TG/PCE Repair/Mod Discussion / Re: PC Engine GT weird Sound Problem
« Last post by RyuX on July 24, 2021, 11:43:56 AM »
Hey

The speaker will behave the same even when hooked up directly to the OP-Amp so its no bad trace.
Also the Headphone output (which is the same as there is no separate circuitry for the speaker) sounds very good.

I checked continuity from the opamp all the way to the capacitors - audio jack - flat cable connector for the controller board up to the speaker connector which is all good.
I think the NJM2073 is just too weak to really drive a speaker properly and maybe my PC Engine GT is outputting normal speaker volume and I was just expecting more which isn't really realistic with just one low power op-amp.

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TG/PCE Repair/Mod Discussion / Re: PCE CDROM2 (White) Troubleshooting
« Last post by Keith Courage on July 24, 2021, 09:02:42 AM »
Do the caps first to know for sure. Sounds more like bad caps to me.
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TG/PCE Repair/Mod Discussion / Re: PCE CDROM2 (White) Troubleshooting
« Last post by SonicBlastMan on July 23, 2021, 09:42:03 PM »
Thanks - you dont think it sounds like a dead/dying laser then (what I'm most worried about)?
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TG/PCE Repair/Mod Discussion / Re: PC Engine GT weird Sound Problem
« Last post by Keith Courage on July 23, 2021, 05:23:54 PM »
Usually it's a bad trace causing the problems you are speaking about. I'd check all the via holes near the headphone port to make sure there isn't a short.

However, what's the condition of the headphone port? Does it have burn spots on the back of it from someone bumping with a soldering iron when changing the caps? The headphone port itself does the switching of the audio amp for louder volume when no plug is inserted. If the port gets heated up too much the internal switch can fail and then the speaker has weak volume.
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TG/PCE Repair/Mod Discussion / Re: PCE CDROM2 (White) Troubleshooting
« Last post by Keith Courage on July 23, 2021, 05:20:44 PM »
Caps might be your issue plus possibly needing a little lens adjustment via the pots on the side.

yes, those 4.7uf caps are known to go bad. They actually deal with the headphone audio but when they short out, they cause CD lens reading problems.
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TG/PCE Repair/Mod Discussion / PC Engine GT weird Sound Problem
« Last post by RyuX on July 23, 2021, 06:01:59 AM »
Hey Guys, my name is Patrick and I am from Austria.
I love the PC Engine and used a PC Engine DUO-R for a while now.

I recently bought a broken PC Engine GT and started replacing all of the caps and resoldering the whole board.
Now everything works as it should except for the Speaker.
The sound in the speaker is low and distorted - I already tried another speaker with the same result.

The OP-AMP NJM2073 gets the proper voltage and outputs the sound into the capacitors (which I replaced) and all of the traces are fine.
The Audio Socket bridges that mute the speaker when a headphone is plugged in are also ok.
The Headphone sounds very clear and loud and it seems that there is no separate circuity for the speaker as it only takes one of the channels from the headphone socket and routes it to the controller board.

I would need a reference from a known good/perfect PC Engine GT to evaluate if mine is too low on volume or not.
I tried a separate PAM8302 Amplifier board but because of the way the PC Engine handles its audio the PAM8302 will only work with an external power source that does not share the same ground (never had this problem before with any other handheld but on the PC Engine GT I can't get it to work as it will pull down the 5V rail to 2,2V even though the PAM8302 only draws around 0,05A in standby when measured on my lab supply).

So if the headphone sound is perfect - all of the traces and connections to the speaker are as well and even the speaker got replaced - could it be that this is it ? I mean by design its not supposed to be any louder ?
Because of the way the NJM2073 works it is also hard to find a replacement without making your own OP-AMP PCB but maybe I will end up making one.

Does anybody also know how the Sound Input (coming from the sound chip) into the OP-AMP is specified (how many volts amplitude etc.) ?
Would be really helpful.  :dance:
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TG/PCE Repair/Mod Discussion / PCE CDROM2 (White) Troubleshooting
« Last post by SonicBlastMan on July 22, 2021, 02:17:52 AM »
Hello all,

I hear this is the place to come for PC Engine help  ;)

I recently bought a fully loaded briefcase system and the CDROM2 has a few issues.

Symptoms:
- Disc spins and laser moves no issues, unit is a little noisy when trying to read the disc. Disc is sat in place properly so not rubbing on the tray. May be laser?
- Takes time to read a disc (original game or audio cd). Game normally just shows the main game screen then struggles to get any further. Audio cd takes time to read tracks but usually gets there eventually. Have more luck on middle/later tracks
- Audio through headphones/TV is scratchy/low

Otherwise in good condition. Middle gear replaced already. No obvious signs of cap deterioration

Questions:
- What symptoms would be present if the laser was dead/needed replacing? Hoping my symptoms dont indicate laser replacement
- If pots need adjusting, how exactly should I start that process? ie which pots to try first, turning pots clock/anti-clockwise? I've ensured the pots are at the approximate position as mentioned a few times in various threads/videos
- Would a recap help my issues?

Cap kit is on its way, I'm hoping that covers most/all of my issues...

Really appreciate any advice!

Thanks in advance

EDIT: upon closer inspection, I found 3 or 4 4.7uf caps near the volume wheel that look highly suspect. Dull, brown fur on the legs of the caps and in close proximity on the board itself. Anyone know what these caps are responsible for?
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