AV Famicom PPU dead after removal for RGB mod?

[Arkanix38]

Hi all!

I'm finally getting around to NESRGBifying my AV Fami, and after desoldering my (working) PPU I tested it in the new socket and got garbled graphics. I substituted with the PPU from my old spare Famicom and it was displaying properly again. Anyone else had a PPU just up and die for no fu**ing reason?

I was grounded (so no static discharge) and stored the chip on a conductive surface while installing the socket. I guess it was just its  time to die 
The only possible fault (maybe) is that i removed the electrolytic cap in the way of the NESRGB board BEFORE removing the PPU and replaced it with a new cap. Perhaps the new cap had some residual charge :c

[Pit]

There are many reasons to deffective ppu, maybe it's dead, or a pin is damaged....

A friend of mine killed a ppu recently, because he plugged it incorrectly 

[famifan]

probably, the socket itself caused the extra amount of capacitance which the old PPU can't tolerate with.

so there's a chance it still may work without the socket.

what kind of garbled graphics does it produce?
Post Merge: August 05, 2016, 07:06:22 am
AV famicom is relatively newer than other types of famicoms. perhaps it gets CMOS version of PPU. That explains why it's so sensible to parasitic capacitance added by the socket.

PPU from old famicom, isn't CMOS anyway, so it could deal with increased capacitance as well..

what do you think? does that sound convincing?

[Arkanix38]

Might try soldering it into my donor Famicom and give it a go. The sprites load, but out of order so it appears one of the Address Lines isn't connecting properly.

[famifan]

The sprites load, but out of order so it appears one of the Address Lines isn't connecting properly.

http://www.famicomworld.com/forum/index.php?topic=9077.0 perhaps newer PPU is very picky about 74'373

[FAMICOM_87]

The sprites load, but out of order so it appears one of the Address Lines isn't connecting properly.

http://www.famicomworld.com/forum/index.php?topic=9077.0 perhaps newer PPU is very picky about 74'373

Recently I opened my famicoms and NESes so in everyone there was version  74LS737.
and powerpack works only ot the older version ot the famicom (1984) and not on (1988)
on my NES consols is more complicated thay all manufactured in (1987) and it works on one of them but not in other . if someone want to buy flash cartridge I will recommend everdrive over powerpack because of this issue 

About your broken PPU , do not throw it ! Years ago I damaged my PPU and CPU from original PAL NES when try to do over-clock mode on it. 
I replaced them with clone UMC ones from an early clone system made in Taiwan.This clone was with sockets so I decide to put in it the original ones and voala it worked with original Rico ones     then when I noticed that they actually work I bring them back to the original NES and the  again distorted picture and black screen after a several seconds , so the new home for them was that famiclone and UMC ones stayed in original NES and everything is ok that way so unusual

[Arkanix38]

I never throw out any chip in decent condition, they can come in handy for 'in a pinch' troubleshooting. I'm thinking that if the PPU is acting up, it's probably the interface with the socket as suggested before as I see no reason for the chip to have died so suddenly.

I might tinker when I get home, and see if the '373 is LS or HC. I'll try and find some replacements and do some tinkering, maybe the PPU isn't buggered after all and I can have both of my famicoms back in action (use my older Famicom for the microphone and playing Zelda, hey may as well put in an NESRGB while i've got the PPU out, my composite mod had bloody horrible jailbars)

EDIT: The PPU acted identically on all games I tried (SMB, SMB3, RECCA repro, Final Fantasy) when i initially tested, so if the '373 is affected its due to something I did when installing the socket/replacing the electrolytic that is too tall for the NESRGB. Will let you know if the '373 was the offending chip.

[famifan]

my composite mod had bloody horrible jailbars

i thought that was solved a long ago and the all needed instuctables were provided http://www.famicomworld.com/forum/index.php?topic=8080.0

sorry for going out of the topic 

[xIceMan]

Yeah, I once ordererd UMC clones as well since my PAL PPU / CPU was burned.

Here's the list:

UA6527P = PAL CPU
UA6538 = PAL PPU

UA6527 = NTSC CPU
UA6528= NTSC PPU

Aliexpress got all of them and I've tested all. They do work like a charm. 1-1 replacement possible.

[FAMICOM_87]

wow I did not know that the UMC have NTSC versions UMC are very good clones! even better then original  
about  jailbars , I added one cap to reduce them between + and - near the PPU rated at 1000mF 6V (it must be 5V or above , for me 1000mF is good solution it can be less of course, just try ) 
I am very pleased with the results . jailbars actually gone! I even keeped my RF functionality when done AV MOD

[Arkanix38]

I tried caps, Aluminium tape shielding and isolating pin 21 and only saw a reduction in jailbars. They were still significantly noticeable in my case unfortunately. Might grab a couple of UMC clone chips to try out for repairs.

[Arkanix38]

Tried soldering the PPU directly into the Famicom and the graphics are even more scrambled then before. This PPU is definitely dead and I'll probably end up grabbing some of the Bootleg PPUs

Got any seller recommendations xIceMan?

[P]

UA6527P = PAL CPU
UA6538 = PAL PPU

UA6527 = NTSC CPU
UA6528= NTSC PPU

I read that the PAL CPU clone UA6527P has swapped the 25% and the 50% duty cycle sound mode. The PAL CPU UA6538 has swapped red and green colour emphasis modes but so has the original PAL PPU.

[Arkanix38]

Hi,

Would you be able to refer me to the seller you bought your Clone PPU from? I've never dealt with Aliexpress before and i'm tentative to choose a random seller and hope for the best.

Thanks

Luke

[xIceMan]

Sorry for the late reply. PMed you about it. Kinda forgot this topic.

I've been using all 4 ICs and all work great in either Famicom or NES with the corresponding clock speed (crystal), of course.