Broken CoCo2

[robcfg]

Hi Everybody!

A friend of mine gave me a non functioning CoCo2. We took a look at it, but there seems to be no damage to the pcb or anything but I cannot see it.

I've uploaded a video of the picture from the CoCo2 in case anyone recognize the symptoms. I start with njo signal, then I power it up, and reset it a couple of times. You can see the ghost of the screen with the border and then the image goes all white...

Regards,
Rob

[zephyr]

Because there's no monitor port on the CoCo 1/2 models this sort of problem can be difficult to diagnose without proper test equipment. Try entering MOTOR ON at the command prompt and listen for the relay click. Although this test won't help with your problem it will help to determine if the computer is functioning.

1. What is the Model/Cat No (26-xxxx on the underside of the computer) of this machine?

2. Is it a PAL or NTSC machine?

[robcfg]

Hi!

Thanks for your answer.

I tried the motor on command and the relay does click, so I guess that's kind of good news

As for your other quiestion it's a NTSC machine with model number 26-3127B.

Regards,
Rob

[zephyr]

That's the excellent Korean made (1985) 64K RAM model with Extended Color BASIC 1.1, so its well worth repairing. I'm just sorry that I can't help you with this problem. Perhaps one of the (very few) forum hardware experts will reply to this one.

Regards,
Steve

[robcfg]

Well, at least you pointed me to a nice test and now we know that maybe it's the rf converter or the graphic chip, I guess, and that's quite an improvement!

Thank you very much, Sir!

[zephyr]

I'm pretty sure that machine will be fitted with a MC6847T1/XC80652P VDG chip, and a MC6885 SAM chip, which seem to be impossible to buy anywhere. If ever you find a supplier for any of those chips, please let me know.

[jmk]

I once had a 16K CoCo2 with a broken power supply. I tried powering it with another computer power supply, but I could not find one strong enough... the result was a picture that was visible but weak. I ultimately broke it with my PSU fiddling, so be careful!

Possibly patronising question:

On the other hand, since it appears to work... you have an NTSC CoCo2 and you are registered in Spain. Are you using it on a PAL television? The behaviour of a PAL TV taking an NTSC signal can be anything from no picture, rolling b&w picture, stable b&w picture to a stable colour picture, depending on the capabilities of the TV.

If you have a TV card in a PC, you could try that. They usually handle all types of PAL/NTSC input or just try different TVs to see if you get a different result.