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CBM PET 710 WITH BASIC PROBLEMS

thank you very much Eudi, but what is this test specifically for? If the sound is not heard, does it mean that the Sid is broken?

Happy Easter to all !
 
No, completely the opposite...

If you get some ghostly wailing from the machine, it means the CPU is working with the EPROM.

Of course, if you don't get any sound, it means nothing... It certainly doesn't mean that the SID is faulty!

Stop and think. What have we been trying to test out? The CPU and the EPROM and the surrounding support logic.

We have tried a NOP EPROM, but we don't know whether that works or not because (for some reason) we can't see on the oscilloscope what is happening as we expect.

Eudi has suggested a program to get some output from the SID (if all of the planets in the solar system aligns for us) so we don't have to use the oscilloscope.

Dave
 
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on the commodore 64 if the sid fails, it causes a black screen. If you remove the sid, the screen reappears!
 
not really..we have some integrated circuits in common....
I think it's not worth wasting any more time, given my equipment and my lack of knowledge, I think the time has come to raise the white flag.
I think that i ll sell the computer as it is, there will probably be someone who can repair it :(
 
Desperado said:
on the commodore 64 if the sid fails, it causes a black screen. If you remove the sid, the screen reappears!
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Not necessarily. Sometimes it can cause black screen, other times it will just sound terrible if it's bad.

Curious though, has removing non essential chips been considered? SID is on address lines 0-4, and data lines 0-7. If it is faulty it might screw with those signals. (I haven't looked at the 710 schematics and basing that on the c64)
 
eight088 said:
Not necessarily. Sometimes it can cause black screen, other times it will just sound terrible if it's bad.

Curious though, has removing non essential chips been considered? SID is on address lines 0-4, and data lines 0-7. If it is faulty it might screw with those signals. (I haven't looked at the 710 schematics and basing that on the c64)
Click to expand...
Hi, not again...Sid i solded on board...
 
Pass it onto someone with the knowledge and the test equipment to repair it.

Put the original EPROMs back in of course.

Learning opportunities:

1. Do not desolder chips unnecessarily.

2. Do not erase EPROMs without first consulting VCFED members. In fact, do NOT erase original EPROMs AT ALL.

3. Check if the machine is 'rare' and, if so, perhaps think again before even touching it.

4. If you are out of your depth with the repair, STOP...

Dave
 
Are you now going to invest some of your time in learning how to use your oscilloscope correctly?

If so, create a new thread and we can go through it properly without the hassle of trying to 'fix' something in the process (which will actually distract us from the learning).

Dave
 
Thank you all for the help and teachings you have given me... there will be other opportunities to learn how to use the oscilloscope. I'm sorry because I would have liked to understand the problem with this damned computer... but I don't have the skills to find the fault....in the end I am left with doubts.....is the CPU working or is it dead?
 
>>> there will be other opportunities to learn how to use the oscilloscope.

Just to be clear, you need to learn how to use your oscilloscope when you are NOT fixing a faulty computer...

Dave
 
Please Dave help me to repair this bad 710! I need to know if this cpu is good or die :/
 
Forget it.

I don't think it is.

The only way you could do this is to remove the CPU, plug it into a breadboard and write a simple program to store into EPROM (also on the breadboard) that will do something useful (like flash an LED).

However, you will also have to produce the RESET and CLOCK signals for the CPU.

You will also have to wire all of this up.

I don't think your skillset covers doing something like this - you are only going to kill the CPU (if it isn't already dead).

Best leave this for someone else. Please...

Dave
 
daver2 said:
Forget it.

I don't think it is.

The only way you could do this is to remove the CPU, plug it into a breadboard and write a simple program to store into EPROM (also on the breadboard) that will do something useful (like flash an LED).

However, you will also have to produce the RESET and CLOCK signals for the CPU.

You will also have to wire all of this up.

I don't think your skillset covers doing something like this - you are only going to kill the CPU (if it isn't already dead).

Best leave this for someone else. Please...

Dave
Click to expand...
I thought I would find a new 6509 cpu in my Easter egg but unfortunately it wasn't there....maybe can I try with a 138 ic piggyback ?
 
Desperado said:
ALT/CHOP is IN now....
There isn't any manual online...
Need i buy a new digital scope :(
Click to expand...
daver2 said:
And TRIG.ALT button. IN or OUT?

Can you post the manual then (if you have a scan of it)?

I am interested in the operation of the MODE switch.

>>> Time to move trigger probe on Gnd, isn't?

Why, this just displays a horizontal line... To what end?

>>> Need i buy a new digital scope

You cannot handle an analogue oscilloscope at the moment. Until you are able to do, buying a digital oscilloscope will confuse you even more.

If you can't drive a Fiat car correctly, there is no point in buying a Ferrari...

Dave
Click to expand...
ALT/CHOP IN means Chop mode is active, right? Could it be that the oscilloscope has a hard time to keep up switching between CH1 and CH2 at the rather fast time base settings? The posted manual states that the Chop mode is more suitable for slower sweep speeds. I do however not have any experience with analogue scopes, so this is purely speculation from my side.
 
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