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TMNT Repair Log


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I had a TMNT PCB on the bench tonight, the video below shows the graphics fault.

 

 

I did a quick once over of the board before looking up the schematics and when I got to the Mask ROM at K27, I found pin 14 had no output.

After checking the schematics there should definitely have been and output there.

 

The mask ROM has been removed and socketed but none of my burners can read/program them (27C400 equivalent), is there anyone that can help me out and possibly burn a new for me?

@poidapoida

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If you can burn a 27C4096, and your programmer can turn off its chip-id check, then you can use one of the 27C4096 to 27C400 adapters out there. They'll normally also work with the 27C800, 27C160 and probably the 27C322 chips as well. You do need to split your roms into 512KB chunks and switch banks to program each, but any hex editor can do the splitting.

 

https://oshpark.com/profiles/thepoorstudenthobbyist

 

That page has a few variants, though one of the 27C322 versions is advised. The SMT one has the component values marked, but they're the same values for the through-hole version. The thing in the bottom right is a 2PDT switch with 2.54mm pin spacing.

 

I could program for you if no one else puts their hand up, but i'd have to check if i have any 27C400's left.

 

related: Can someone with Eagle convert the below file to a gerber?

27C4096_to_27C400_adapter.zip

Edited by buttersoft
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  • 2 weeks later...

K27 Mask ROM was replaced and some improvement but still had graphics issues.

Found the dip settings for testing the Mask ROMs and it indicated H4 and H6 were faulty.

 

nZAbNnE.jpg?1

 

5 x 27C400 ROMs were ordered and with the help of @Arcade King they were programmed.

I replaced K6 first an the graphics fault was gone.

All of the Mask ROMs were removed, socketed and replaced.

When testing previously the voice sounds seemed a little scratchy. After soak testing for a while the voice sounds disappeared and the music and sound effects would drop in and out.

This was traced back to a dodgy tantalum cap in the audio circuit and once replaced all sounds were restored and clear.

 

 

I was given an adapter board that converted a 27C4096 chip to the equivalent pinout of the 27C400, the board was modified in reverse so I could drop a 27C400 into the socket and plug the board into my TL866 in order to read/program ROMs for TMNT boards.

I drew it up on EasEDA last night, a pull up has been added to the Vpp line and a cap across the power rails.

 

HMPPuye.jpg

 

Link to Gerber: https://drive.google.com/open?id=11htaPgsfhXriqRSElJWaYJl9MqkHeyD5

Link to Schematic: https://drive.google.com/open?id=1DIQvCWvMb9GeYDGDZZcLlHM2fk3cTiMA

Edited by Kaizen
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I was given an adapter board that converted a 27C4096 chip to the equivalent pinout of the 27C400, the board was modified in reverse so I could drop a 27C400 into the socket and plug the board into my TL866 in order to read/program ROMs for TMNT boards.

 

Is that different to the ones i linked to? I've been using those to read and write 27C400 chips... and the 800/160/322 chips too, with the programmer set to work with a 27C4096.

 

Not that i'm not enjoying the repair log by itself, of course :)

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The board will only do the the 512k 27C400.

For the larger eproms you'll need the board with the dip switches or jumpers to program them.

 

That part i understand, it was more a question about any functional differences for programming, and why you made a 27C400 adapter yourself when you'd need another one to do the other chips.

 

Then again, i spent almost as much designing and making my PC Engine hucard repros as a turbo everdrive would have cost, and they don't work nearly as well and look totally backyard, so i really shouldn't be hassling you for looking to do your own designs and programming because i understand the urge ;)

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Cheaper programmers cant generally do non Jedec standard roms (I think it was Jedec). A simple example is a 2732 vs a 2532 with an adapter you can program 2532's as 2732's.

The same goes with a 27c4096 to AM27C400 a simple adapter can be used. Most inexpensive modern programmers can do the more common 27C4096 which are not pin compatible with the AMD AM27C400. Its very confusing with the 4 meg 16 bit roms because some brands can be called 27c400 and have the same pinout as the 4096 and also not to be confused with the 8 bit variant.

 

Never heard of or used adapters with dip switches to program these. :unsure

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Never heard of or used adapters with dip switches to program these. :unsure

 

See post 2 in this thread :) Along with this guide to using it. The guide is for a SNES rom on a 160 or 322, but the principle is the same. You get your larger rom and use a hex editor or rom utility to split it into 512kB chunks. Dip switches are for address lines A18, A19 and A20. 27C400 roms don't use any switches bar the chip-type switch being set away from 322. 27C800 chips use A18 (two chunks of 512kB), 27C160 chips use A18 and A19 (four chunks), and for the 27C322 chips you throw the type switch over to change the wiring, and use all three dips. You just have to remember where you're up to when programming.

 

There are at least half a dozen different types of 27C4096 to 27C400/800/160/322 adapter out there. I bought one that turned out to be in beta, and had to redesign a chunk of it :/ You can make cut down version of the adapter with fewer switches to handle whichever chips you want, of course. It just seemed easier to me to get the 322 one so you can do them all.

 

These would be standard version of these chips, i don't know anything about the 27C400 variants you're talking about. I've been programming SNES roms and Amiga kickroms with mine.

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See post 2 in this thread :) Along with this guide to using it. The guide is for a SNES rom on a 160 or 322, but the principle is the same. You get your larger rom and use a hex editor or rom utility to split it into 512kB chunks. Dip switches are for address lines A18, A19 and A20. 27C400 roms don't use any switches bar the chip-type switch being set away from 322. 27C800 chips use A18 (two chunks of 512kB), 27C160 chips use A18 and A19 (four chunks), and for the 27C322 chips you throw the type switch over to change the wiring, and use all three dips. You just have to remember where you're up to when programming.

 

There are at least half a dozen different types of 27C4096 to 27C400/800/160/322 adapter out there. I bought one that turned out to be in beta, and had to redesign a chunk of it :/ You can make cut down version of the adapter with fewer switches to handle whichever chips you want, of course. It just seemed easier to me to get the 322 one so you can do them all.

 

These would be standard version of these chips, i don't know anything about the 27C400 variants you're talking about. I've been programming SNES roms and Amiga kickroms with mine.

 

Yep, what he said.

 

I wanted to get some practical experience in designing PCBs so that was the main reason I drew up the schematic and did the board layout.

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