30 replies to this topic

[Esc]

No, I am not getting any video. I haven't ruled out a chip problem since I don't have a spare 2600 to test with. (I have a 7800)

[cwilkson]

Esc said:

No, I am not getting any video.  I haven't ruled out a chip problem since I don't have a spare 2600 to test with.  (I have a 7800)

Whoops...I thought it was a 2600. (Sears Telegames II is a 2600, I believe.) There are several of these threads that are similar...starting to get them confused!

Do you get different behavior when using a 7800 cartridge vs. a 2600 cart?

-Chris

[Esc]

No , what I meant was that I don't have a spare 2600 unit to swap chips. My only other spare unit is a 7800. The unit that is having problems is a Telegames II ...

[cwilkson]

Esc said:

No , what I meant was that I don't have a spare 2600 unit to swap chips. My only other spare unit is a 7800.  The unit that is having problems is a Telegames II ...

Whoops...again.

Got it now. You can substitute the TIA from the 7800 into the 2600 with no problem. They are the same chip. Same with the RIOT (6532). The processors chan't be swapped though. The 2600 uses a 6507, and the 7800 uses a custom 6502.

If they are socketed, try swapping the TIA from the 7800 to the 2600. Usually marked as CO104444 or UM6525.

Hmmm...you only see static. It might be a simple tuning issue. I don't have a Telegames II here, so I don't know exactly where on the motherboard to look, but there should be a tuning inductor (big orange tower, or similar) someplace near the RF section. Try *gently* adjusting that while watching the TV...see if anything happens. If you don't know what I'm talking about, take a photo of your motherboard and post it or PM it to me. I'll mark it up and send it back.

One last question. What test equipment do you have available? Do you have access to an oscilloscope? Let me know.

-Chris

[Esc]

The chips on my 7800 are soldered (aren't most 7800's soldered?) and I don't want to desolder the chips on my 7800. I guess I'll just wait for a spare 2600 to acquire.

Yes, I'm familiar with that tower. I'll try adjusting it.

The only test equipment I have is a Multimeter.

Thanks for the help!

[cwilkson]

Esc said:

The chips on my 7800 are soldered (aren't most 7800's soldered?) and I don't want to desolder the chips on my 7800.  I guess I'll just wait for a spare 2600 to acquire.  

Yes, I'm familiar with that tower. I'll try adjusting it.  

The only test equipment I have is a Multimeter.  

Thanks for the help!

Yeah, desoldering a 40-pin chip is *not* fun. Especially if you expect to reuse the chip! You might ask around here...I think CPUWIZ has some spare TIA chips...he would probably sell you one.

Keep us posted on the results of retuning the RF oscillator.

Good luck!
-Chris