The Analogue Turbo Duo clone shipped in time for Christmas 2023. Are you happy with yours ?? Find firmware updates here.
IMG
Main Menu

Recent posts

#51
Thanks for the suggestion Tak-

That's quite a last resort - sure to take hours.  I had a working one to compare, but the owner doesn't want to recap it yet, despite the speaker failing and leakage everywhere.  I had to give it back because I didn't want it to kick the bucket in my hands :/

The issue with oscope probing every pin, is that behaviors are different of course when a cart / game is running.  What I need is a better service manual, that gives more debugging info than "replace all ICs if clocks are bad." (basically what TG-16 service manual says).

I wish I knew:
  • - what is the boot up order? Which pins go high / low on startup (OE, WR, Read, etc)?
  • - does the metal shielding need to be in place for a proper boot?
  • - what pins / ICs are known to go bad with a +5V short?
  • - is there a source for the knobs (volume / brightness) to replace?  some of the plastic got melted on mine with chip removals  note to others - desolder those, dont even try to take out the main CPU (80 chip) with them in there.
  • - can a white CoreGrafx PCE chipset be swapped in?  Or are there revisions to the huson chips + VRAM and Work RAM?  (I actually swapped the *entire* chipset and results were the same).  I'm sorta guessing there's a slight variation.

Essentially what I have here is what appears to be a fully working GT (audio, screen, contrast, high voltage stuff), but a dead PCE chipset.  Would love help from someone who knows that architecture more.
I found this epic write up: (https://www.copetti.org/writings/consoles/pc-engine/) but it's not really repair / failure focused.

What I really don't understand is why the symptoms are the same no matter what I try.  No garbled graphics or sound.  I fear these 80's ASICs dont have the diode protections of 90s logic used in Sega consoles that I'm more familiar with, and just bite the dust at the first sign of a +5V short (such was the case with the controller IC, that's for sure).

I can verify from a working system that it will boot without controller PCB connected (just make sure pins 12 and 8 are bridged on the controller FFC plug if you want backlight on)

Some essential repair resources:
Main IC pinouts:
Hopefully all my debugging and suffering can benefit some other poor soul out there.
Attatched pics of my board, literally one of the cleanest you'll ever see.  Sigh.

Repair log:
  • - Removed all ICs (even RAM) from while PCE and replaced.  All pins checked under microscope.  No difference in symptoms
  • - Removed all electrolytic caps and rechecked all values and pads with DMM on cap setting
  • - Cleaned under all ASICs and RAM and caps, no trace damage I could find
  • - Ultrasonic cleaned the entire PCB in friends $1000k+ cleaner.  Cleaned uup after with 99.9% IPA after
  • - Began removing chipset again to fix my white PCE now, while doing that, melted some of the plastic on knobs :(  they still turn, though.

My postmortum on this guy:
  • - Was given to me for a recap, which was successful on first try
  • - Was given back years later for speaker not working. Likely broken headphone jack (testing seems to confirm this).  Wired up audio signals using retrosix guide and speaker "hiss" comes back
  • - +5v rail was shorted somehow in this test process.  Controller IC was getting *very* hot until it was removed.  Controller PCB replacement ordered
  • - Current symptom ever since then

To help others, I am attaching here:
  • - My board scans
  • - Blank board scans (courtesy of retrosix)
  • - TG-16 service manual
  • - ASIC chip pinouts
  • - Diode probe compare excel I made (comparing good unit FFC 40 pin cable with my bad unit)
#52
Hi there!

When I'm lost as you after doing way too many tests, what I do is to try to get a working one and start comparing every-fucking-pin of every-fucking-ic (or connector/etc :P) with an oscilloscope while running the same game until I find a difference.

Hope you can fix it!
#53
So my friend gave me his childhood PCE GT to fix.  Lots of sentimental value.  and man is it busted.  At some point the 5v rail I believe shorted and it fried the controller board IC.  ordered a new controller board, but I don't know what else it took with it.

I get a yellow and reddish screen, split in 2, with noise lines in the middle (attached).

IMG_20240804_033016.jpg

- Fully recapped
- Fully cleaned in Ultrasonic and manually with 99.9% IPA
- No audio (I can hear speaker hum, and volume works.  I'm confident audio amp output stage is OK.
- +5V rail is good (4.85v)
- +2.5v rail is good (for audio)
- 24mhz clock is good on both ASICs (followed guide from TG-16 service manual)
- H sync and V sync outputting correctly
- Backlight circuitry all tested good, 30V and 24v OK.  All oscope probes of transformer check out too.  Screen seems to be fine.

What I did in addition to above:
- swapped in full Hudson ASIC chipset from working CoreGrafx (white)
- probe (diode) tested every on the Hucard slot.  Compared with working unit, and values seem to be as expected / close (bus pins within range of each other, no obvious shorts).
- swapped in one of the VRAMs from the CoreGrafx as well

I'm at such a loss with this one...the board looks *so* clean.  anyone know of other stuff to look at?  I've poured so much time into this one it hurts.

I'd be so indebted to a helpful benefactor.  Willing to send thank you gifts!
<3

Thanks in advance!



#54
Console Repair/Mod Center / Re: AMP-30 restoration
Last post by elartur77 - 07/23/2024, 05:29 PM
Thanks, Ill try that site to post there the chart..
#55
Console Repair/Mod Center / Re: AMP-30 restoration
Last post by Tak-MK - 07/22/2024, 05:03 AM
Quote from: elartur77 on 07/21/2024, 03:09 PMFor anyone interested I already did a complete recap to the AMP-30 and documented the caps values needed, quantity and locations..

Dont know where else I can put this, if there is a specific place, please let me know...
PCEAMP30-Cap_Chart.webp
Nice! :D Someday I'll buy one for myself to document it too on my website (not only caps).
For now I only can thing of maybe NFG? necretro.org maybe? :-k
#56
Console Repair/Mod Center / Re: AMP-30 restoration
Last post by elartur77 - 07/21/2024, 03:09 PM
For anyone interested I already did a complete recap to the AMP-30 and documented the caps values needed, quantity and locations..

Dont know where else I can put this, if there is a specific place, please let me know...

PCEAMP30-Cap_Chart.webp
https://imgur.com/WRfrFxK.jpg
#57
Console Repair/Mod Center / Re: AMP-30 restoration
Last post by elartur77 - 07/19/2024, 12:29 PM
Quote from: Tak-MK on 07/19/2024, 06:45 AM
Quote from: elartur77 on 07/18/2024, 05:57 PMI was lucky to get one at a very good price, even if it didnt come with the speakers and accesories, but it looks great, I have a normal DUO and Im thinking painting the amp black (dark gray) so they match color with the black speakers too and I think they are going to look good.. or maybe not because Im a fan to keeps things original..aa decisions!

If you try to paint that amp I'm going to appear at your home and steal it to protect it before you notice  :rollin

Haha ok ok.. You are right better to keep it original..
#58
Console Repair/Mod Center / Re: AMP-30 restoration
Last post by Tak-MK - 07/19/2024, 06:45 AM
Quote from: elartur77 on 07/18/2024, 05:57 PMI was lucky to get one at a very good price, even if it didnt come with the speakers and accesories, but it looks great, I have a normal DUO and Im thinking painting the amp black (dark gray) so they match color with the black speakers too and I think they are going to look good.. or maybe not because Im a fan to keeps things original..aa decisions!

If you try to paint that amp I'm going to appear at your home and steal it to protect it before you notice  :rollin
#59
Quote from: Tak-MK on 07/18/2024, 06:19 AMDefinitely no idea... sadly I fixed only two of them and their issue was mostly the low audio level at start.

 I don't know what's going on, maybe I did a bad job with the capacitors.
#60
Console Repair/Mod Center / Re: AMP-30 restoration
Last post by elartur77 - 07/18/2024, 05:57 PM
I was lucky to get one at a very good price, even if it didnt come with the speakers and accesories, but it looks great, I have a normal DUO and Im thinking painting the amp black (dark gray) so they match color with the black speakers too and I think they are going to look good.. or maybe not because Im a fan to keeps things original..aa decisions!