Cbm dual drive 3040 disk - two red lights

[Desperado]

Monitor the 6502 SYNC pin and apply a manual RESET to see if there are any signs of activity on SYNC at all. It will be brief...

No signs of activity...always low signal

 

[daver2]

OK,

Can you check the 6502 CPU pins:

37 - Input clock - 1 MHz.
39 - Output clock - 1 MHz.
6 - /NMI.
4 - /IRQ.

And report back the results. You may need to use your oscilloscope for the clock pins.

It all sounds like repairing a PET so far doesn't it?! Exactly the same process...

Dave

 

[Desperado]

37 - Input clock - 1 MHz.
39 - Output clock - 1 MHz.
6 - /NMI.
4 - /IRQ.

4-6: High
37-39: low

 

[Desperado]

It all sounds like repairing a PET so far doesn't it?! Exactly the same process...

Yes but in this case is more difficult process

 

[daver2]

>>> Yes but in this case is more difficult process.

So far we have done the same things - check the power supplies, check the RESET signal. Now we are checking the other important CPU control lines.

>>> 4-6: High

This is correct.

>>> 37-39: low

This is NOT correct. You should have a 1 MHz clock. No clock, no CPU executing anything (exactly the same as a PET).

Did you use your logic probe or oscilloscope for this measurement? Your logic probe may not be good enough.

Dave

 

[Desperado]

Did you use your logic probe or oscilloscope for this measurement? Your logic probe may not be good enough.

i used logic probe, ok now i check with scope!

 

[Desperado]

Yes!! With scope i can see 1 Mhz waveform on pins 37 and 39!

 

[daver2]

So, you now see that all test equipment is not equal!

If you look at the manual for the logic probe, it should have an upper frequency limit that it will work up to. You can't exceed this and expect it to work...

My next move on a PET would be to install a NOP generator and observe for pulses on CPU pin 7 (SYNC). Same thing here, plus look for pulses on the address decoder UB3 (74LS42) pins 1 through 7 and pin 9.

You should also observe the same square waves on the address bus of the 6502 CPU. Just the same as the PET!

Dave

 

[daver2]

Write all of this useful information down in a notebook for later...

Dave

 

[Desperado]

So, you now see that all test equipment is not equal!

If you look at the manual for the logic probe, it should have an upper frequency limit that it will work up to. You can't exceed this and expect it to work...

My next move on a PET would be to install a NOP generator and observe for pulses on CPU pin 7 (SYNC). Same thing here, plus look for pulses on the address decoder UB3 (74LS42) pins 1 through 7 and pin 9.

You should also observe the same square waves on the address bus of the 6502 CPU. Just the same as the PET!

Dave

Yes Dave i can see waveform with scope on cpu pin 7 and on cpu pin 9 to 20.
Also i see pulses on UB3 pin 1 to 7!

 

[daver2]

And UB3 pin 9. Did you miss that one?

Dave

 

[Desperado]

And UB3 pin 9. Did you miss that one?

Dave

yes pulses also on pin 9!

 

[daver2]

It sounds to me as though one/both of the ROMs have failed.

Perhaps we can pickup on this tomorrow again. I have packed up for the evening. It is just too hot!

Dave

 

[Desperado]

Yes tomorrow!
It's possible burn eprom also for this drive?
Good evening!

 

[daver2]

Yes, but you will need adapters for them as they are non standard devices.

Dave

 

[giobbi]

Yes tomorrow!
It's possible burn eprom also for this drive?
Good evening!

you can sent the attached gerber file to PCBway or jlcpcb.com (I found jlcpcb far better, faster and cheaper than PCBway) and ask them to make some adapter (tip: buying 10 will have the same price of 5...). They will work as 2364 to 2764 adapters; soldering a 74LS04 (SMD) on the PCB it will work as ROM-EPROM replacement for CBM disks that need an inverter on the /CS line; if not, you can simply jumper with some solder the pin #8 and #9 of the 74LS04 pad and it will work as 2364 to 2764 adapter for any other scenery (like C=64 etc.)


of course you can make an adapter using a DIL 74LS04, a couple of sockets and some wires, but this way will be faster and better.
Sorry for the bad silk and design, I made it for my personal use and I didn't spend too much time on that ;-) -- however I can certify it works 100% on 8050 and 8250 drives.

 

[AndyG]

Retro innovations have made up adapters where you can configure /cs0 and /cs1….. where are you located?

Are you convinced the RIOT IC is OK?

 

[daver2]

CS1 (pin 20) is active LOW.
CS2 (pin 21) is active HIGH.

>>> where are you located?

Desperado is in Italy.

Dave

 

[Desperado]

Are you convinced the RIOT IC is OK?

no, im not sure that Rriot is ok....i have one Rriot replacement but i think that i need correct eprom firmware to burn!

 

[Desperado]

On the original RRIOT ic i see 901466-02..... if i wanna try to use the replacement board, need i download same bin file to zimmer and burn it on the eprom? Correct?