Problem Tetris boot repair help needed

[obitus1990]

Hello all! I recently purchased a non-working Tetris bootleg on the cheap, and now need to repair it. It started off with a white screen with a constant buzz. The CPU was determined to be good, and I noticed that the nearby crystal had a broken leg. I replaced that but it didn't do much different, so I probed around on the board and found a bad logic IC that had stuck outputs (I can't remember which, since I am at work right now) and replaced it and the board would then boot to the game. Clock/reset/5V all functioning as they should. The board WILL lock up periodically as it gets hot, and I think this may have to do with a previous owner having cut the 5V and GND pins on numerous ICs, probably trying to figure out where as short was, then soldered them back together. I am thinking these weak joints open up when they get hot, causing the lock ups. I have gone back over some (but not all) of these joints to check them, only to find that only the tiniest stub of pin was left exposed on each IC where it was cut -- in other words, they were cut practically flush with the IC and a very poor joint was made when soldering. So, I took out the dremel and exposed more of the leg and got solid connections when resoldering. I plan to eventually replace these ICs once I have the board working in stable fashion again.

One notable problem is that it will not save settings or high scores. Entering the settings menu by flipping the appropriate dipswitch to on initiates the self tests then brings me into the menu. If I attempt to save any settings, the board will lock up. I have swapped out the EEPROM with no changes to this behavior. Selecting to "initialize" the EEPROM from the menu will do the same. Any suggestions on where to look to find this bug?

Thank you!

 

[obitus1990]

It's this variant of the board:

 

[bones]

I'll check my bootleg out for high score saving, something in the far wrinkles of my brain says this may have been an inherent problem with this bootleg but I'll check when I get a chance. Also they do run very hot,my 2nd one died last year and this one has lost some of the notes in the tune ????

 

[obitus1990]

I'll check my bootleg out for high score saving, something in the far wrinkles of my brain says this may have been an inherent problem with this bootleg but I'll check when I get a chance. Also they do run very hot,my 2nd one died last year and this one has lost some of the notes in the tune ????

Any chance to take a look at your board?

 

[obitus1990]

After probing around and using SLiCE where needed, I found a few bad ICs that carry both the /EEROM and /UNLOCK signals (from the Atari Tetris schematic) both of which are required to write to the EEPROM that saves the settings and scores. As a result, this now works. I also eliminated all the heat related lockups, which were a result of the numerous VCC and GND pins having been cut by someone who must have been looking for a short. When the board got hot, a joint on one of the 7432s on the board would open up and freeze the board up. Cutting away the casing to expose the internal track for that pin on the IC then soldering directly to that fixed the issue.

The only remaining problem is the sound. It seems to be missing one channel, so I am not sure if it's an amp or one of the programmable sound generators that are at fault, or something else entirely. Sometimes, the sound will get very loud after completing a level then stay there, while it was at a normal level prior to that.

 

[Mc-Q]

re-cap the audio section and see if any are missing

 

[obitus1990]

All the caps have been replaced, no difference. I used my audio probe to check the output pins from each of the 76489 programmable sound generator ICs, and each one had static on the line, so it's not the amp. The schematic for a genuine Atari board isn't helpful here, since the POKEY is used for sound there, versus here with the sound generators and a 7489 MPU. So I've kind of hit a brick wall as to where to look next.

 

[Lurch666]

Do you have an audio probe?

 

[qjuk]

… a 7489 MPU.

I’m not familiar with this board, but the 7489 sounds like it could be a 64-bit ram chip, not a MPU.

7489‘s are often used in sound circuits and they often go bad. I would certainly look at this as a possible culprit.
I once had a faulty 7489 that started off by giving weird sound effects when it’s first powered up from cold, then would cure itself when the chip was warm. Your chip could be doing something similar but in reverse.

 

[obitus1990]

Sorry, I meant 8749 (NEC branded).

@Lurch666 yes, I have an audio probe and checked the output pins on the three programmable sound generator chips (76489), and found static corrupted sounds there as well.

 

[Mc-Q]

8749?
microcontroller - do you have a universal programmer to read it?

 

[obitus1990]

8749?
microcontroller - do you have a universal programmer to read it?

I have two USB based programmers (TL-866II+ and Xeltec Superpro 601p), but, neither list it as a supported device. I think I remember reading that the programming voltage for one of these is 21V, which neither programmer is capable of producing, so maybe that's why they aren't supported for simple read operations.

 

[Mc-Q]

i sold my 866II+ and got a T56 instead - i wanted to program 42pin eproms without an adapter and jumpers

the T56 probably wont do it either though - i have OLD programmers for older devices.
i would use a Micromaster1000 for mcu's like that.

 

[obitus1990]

I built a programmer to read the contents of the 8749, using an arduino. File contents verify against the files in the bootleg version mame files. I did, however, notice that this board was made without one of the 76489 sound generators. SO I installed a socket in this unpopulated spot and added one. It made the sound about 90% better, because without that IC, the game is missing one of the sound channels. There's still some static when checking the output pins of the sound generators with an audio probe, and some times the game goes inexplicably loud on some sounds. There's no logic IC between the 76489 and the 8749 pins that control the sound generators, so, there's nothing there to potentially go bad. Were these boards just generally crappy in sound compared to a genuine Atari board with real Pokeys?

 

[Mc-Q]

maybe it's a protection thing,
Atari had a bad habit of wtiting code that did random nasty shit if the protection-check failed.
this was to make clone makers think they messed up the cloning rather than the software hacking.

the tempest "bug" involving the last 2 digits of the score clocking up the credits was a protection check thing.!!!!

 

[TheOriginalCDV]

I have two USB based programmers (TL-866II+ and Xeltec Superpro 601p), but, neither list it as a supported device. I think I remember reading that the programming voltage for one of these is 21V, which neither programmer is capable of producing, so maybe that's why they aren't supported for simple read operations.

I built a programmer to read the contents of the 8749, using an arduino. File contents verify against the files in the bootleg version mame files. I did, however, notice that this board was made without one of the 76489 sound generators. SO I installed a socket in this unpopulated spot and added one. It made the sound about 90% better, because without that IC, the game is missing one of the sound channels. There's still some static when checking the output pins of the sound generators with an audio probe, and some times the game goes inexplicably loud on some sounds. There's no logic IC between the 76489 and the 8749 pins that control the sound generators, so, there's nothing there to potentially go bad. Were these boards just generally crappy in sound compared to a genuine Atari board with real Pokeys?

Hey Obitus,

An old thread, but I hope you can assist.

I have this exact board, with what looks like (at least) one faulty GAL. I am unable to match to a Mame set, in the hopes of finding the GAL contents. Can you please confirm which Mame Romset matched with your board.

Input to the GAL from 74ls74 is corrupt.

Thanks!

 

[bones]

Old thread I know but I forgot to post a pic of my boards, I will say that one of these also only had 2 of the 76489's installed and one of the installed ones had gone faulty. Both now sound the same, so just for future reference here are the pics of the pcbs. As for the gal chips,I'm unable to read these and wouldn't fancy desoldering them.

 

[TheOriginalCDV]

Thanks for the update. I am not looking to get you to desolder your GAL’s (that would be above and beyond!!) But interested in which Mame Romset matched yours, as sometimes people add the data from other programmable chips (such as PROMs).

Do you recall which Mame romset you used?

Thanks

 

[bones]

Unfortunately apart from the 2 x 76489's on 1 pcb which I recently did and the big ram on the other which was done probably 30+ years ago everything else is soldered directly onto the pcbs. I can see that one has 2 pcb tracks cut and the other was manufactured with a 5mm gap instead so 1 is obviously an earlier production version. Other than removing chips is there any other way to get the info you need like in the test mode during boot up ?

 

[Martinmurphy30]

Tetris (bootleg) - PLD Archive

No guarantee they work but the dumps are available here.👍