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CBM PET 710 WITH BASIC PROBLEMS

Now I have deleted them and will try to write them again with the zimmer files.
 
That is why we do not do anything that we can't reverse without using STAR:

Stop.
Think.
Act.
Review.

This includes erasing EPROMs and desoldering components WITHOUT either good cause or we are completely stuck without replacing something to help with the fault finding.

Unfortunately, you have now destroyed what was on the original EPROMs by erasing them without saving the original contents first. In fact, I would never have erased the old ones anyhow, I would have purchased new blank devices to program.

Never, ever, erase any original EPROM without backing it up and making it available to the comunity. You never know, you might have come across some code that has never been imaged before.

So, what labels did you have on the EPROMs, which one(s) did you erase and re-burn, and what did you burn into them?

Let's see if we can undo what you did...

Dave
 
Ok, I had these on the labels:
 

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I downloaded these from zimmer.
 

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They look to be the correct variants.

So, the first obvious question is: Have you burnt the individual files into the EPROMs correctly?

Verify the burnt EPROM against the file using your EPROM programmer.

Have you inserted the EPROMs correctly in the machine?

The correct way around and the correct EPROM in the correct socket?
 
daver2 said:
They look to be the correct variants.

So, the first obvious question is: Have you burnt the individual files into the EPROMs correctly?

Verify the burnt EPROM against the file using your EPROM programmer.

Have you inserted the EPROMs correctly in the machine?

The correct way around and the correct EPROM in the correct socket?
Click to expand...
Yes...but maybe i have too old eproms?
 
That is why you have a verification function on the EPROM programmer and I have just asked you to verify the EPROM contents against the files they were programmed with.

Have you done this or not?

Or are you just guessing again?

Facts, not guesses or supposition!

Dave
 
So, if they are fine, they programmed and verified OK - didn't they?

So, when you inserted the EPROMs back into the sockets, have you installed them correctly and/or have you disturbed the connections from the daughter board (that the EPROMs are installed in) and the PET itself?

Dave
 
Yes i have inserted in correct way...
 

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So, what is the SYNC pin doing on the CPU when you power the machine up?

It mostly worked before you erased and reprogrammed the EPROMs, and doesn't now. So there has to be a cause and effect here.

Dave
 
daver2 said:
So, what is the SYNC pin doing on the CPU when you power the machine up?

Dave
Click to expand...
I checked and it's not present...I suspect wrong voltages at the main connector Cn5 but unfortunately I can't find the diagram to check how much they should be.
 
So the CPU has stopped.

Measure the low voltage rails (e.g. +5V) to see if they are correct.

Check various ICs (e.g. CPU, ROM, a few RAM devices and a few bog-standard TTL devices).

You can find the pinout from the associated data sheets.

>>> but unfortunately I can't find the diagram to check how much they should be.

So this is another learning opportinity. Find all of the relevant documentation for a machine BEFORE you start poking around with it.

is there a clock and a RESET signal I would be asking myself.

Power, clock, reset signal (in that order) for ANY machine you repair.

Dave
 
daver2 said:
So the CPU has stopped.

Measure the low voltage rails (e.g. +5V) to see if they are correct.

Check various ICs (e.g. CPU, ROM, a few RAM devices and a few bog-standard TTL devices).

You can find the pinout from the associated data sheets.

>>> but unfortunately I can't find the diagram to check how much they should be.

So this is another learning opportinity. Find all of the relevant documentation for a machine BEFORE you start poking around with it.

is there a clock and a RESET signal I would be asking myself.

Power, clock, reset signal (in that order) for ANY machine you repair.

Dave
Click to expand...
i have 4,75 V on MK4564-15 pin 8 Dram ics..
 
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