2600: Swap chips from a 6 switch to a 4 switch?

[carlsson]

I have received/borrowed a 4 switch 2600 with fake woodgrain. It only displays random stripes with noise or black screen, both with and without cartridge inserted. I have tried to clean the cartridge connector, I have reseated the three chips and I have measured the voltages from the 7805, which read out correctly.

 

I've understood that this kind of failure can be the cause of either of the 6507, RIOT or TIA chips. Is it possible to easily single out one of them?

 

I've also got a light 6 switch that appears to be working, but it is lacking both RF cable (perhaps not a bad thing if I would be doing an A/V mod on it anyway) but in particular it is missing the top half of the shell!

 

I suppose the 4 switch shell doesn't fit the 6 switch, which leaves me with the option of transplanting chips. Before I destroy more hardware than required, here are some questions:

 

1. Are all 6507, RIOT and TIA chips equal? Both machines are PAL for that matter.

2. Shall I pull all three chips from the working 6 switch and put them into the 4 switch?

3. Shall I replace one chip at a time, or is that a risk for consequence faults? Once I get the console working, can I replace the old chips to determine which ones possibly still are OK?

4. Shall I try once more to clean the cartridge connector thoroughly before swapping chips at all?

 

[+DamonicFury]

I'm not an expert, but I have swapped around chips quite a bit in 2600's. Based on that experience:

 

>>>1. Are all 6507, RIOT and TIA chips equal? Both machines are PAL for that matter.

As far as I know, yes, you should be able to interchange chips between a 4 and 6 switch. I've certainly done it before.

>>>2. Shall I pull all three chips from the working 6 switch and put them into the 4 switch?

I would to do it one at a time instead... see answer to #3.

>>>3. Shall I replace one chip at a time, or is that a risk for consequence faults? Once I get the console working, can I replace the old chips to determine which ones possibly still are OK?

Yes, do it one at a time. Start with the TIA, if that doesn't bring it to life, try the RIOT. I've never seen a 6507 go bad yet, but there's a first time for everything. I usually like to swap them around until I know which chip is faulty.

>>>4. Shall I try once more to clean the cartridge connector thoroughly before swapping chips at all?

Sure, can't hurt! Fold an index card in half, cut it to the width of the slot, then wet the folded part in alcohol. Fit the card over the pins of a cart, then work it in and out a few times.

[carlsson]

I'll try later and see how it works out. If it was a regular 6502, I would agree that those very rarely go bad (but I've seen a few cases of when that was the exact cause of failure) but I don't know about the smaller 6507.

[Osgeld]

Yes you can swap my money is on the riot, but it could be the cpu I have replaced plenty of them

 

With the systems I return of they don't fire up after a cleaning its almost always one of those two sometimes both

Edited November 2, 2017 by Osgeld

[Keatah]

I understand that there are 14 revisions of the TIA, but they are all interchangeable. Just a bit of trivia that popped into my head reading this thread.

[7800fan]

The only exception to TIA is the Coleco TIA clone for Expansion module and Gemini console. That one has different pinout. CPU and RIOT are the same though.