• Please review our updated Terms and Rules here

CBM 3040 Repair

W

Wreck

Member
Joined
Jul 2, 2020
Messages
31
Location
Basel, Switzerland
After a rather long absence, I have a bit more time at hand presently, and I am spending it to learn a bit more about electronics & old computers.

I have a couple of 3032s & one 2001 (all working). Recently I had the opportunity to acquire two disk drives; one being a CBM3040 which was sold as "defect".

Below is a first "shot" at what I am doing at the moment; I think all the power supply to the relevant parts is OK, as far as I can see.
  • Functioning CBM 3032 with BASIC 2
    • IEEE Test BASIC PRG performed; „end of test“ displayed, no failure message.
  • CBM 3040 opened, checked GND connection of board to case.
    • Power ON; VR1 & VR2 U/S, replaced, now good readings of +12V at CR7 / CR8.
  • Voltage readings P6
    • PIN1 +5.14V
    • PIN2 GND
    • PIN3 +12.05VA
    • PIN4 GND
    • PIN5 +11.98VB
  • Behavior of drive;
    • PWR ON, all three LEDs stay RED
    • Both drives spin up but wont stop
    • Sometimes the stepper motor drives the heads „home“ to the stop
    • When entering, on the CBM, the command „LOAD$“,8,1 the message „searching for $“ appears but stays on until shutting down the CBM3040. Then the message „loading“ appears. This can be interrupted with the RUN STOP button.
  • Voltage reading P1 (floppy analogue board)
    • PIN13 +12VA
    • PIN14 GND
    • Voltage reading P8
    • PIN13 +11.96VB
    • PIN14 GND
  • 6502
    • PIN1 (VSS)
    • PIN2 (RDY) HI
    • PIN3 (CLK1) YES
    • PIN4 (IRQ) HI
    • PIN6 (NMI) HI
    • PIN7 (SYNC) LO
    • PIN8 +5.13V
    • PIN40 (RST) LO then HI after PWR UP
    • 6532 (UE1)
    • PIN20 +5.11V
    • 6532 (UC1)
    • PIN20 +5.11V
  • 6522 (UM3)
    • PIN20 +5.12V
  • 6530 (UK3)
    • PIN20 +5.12V
  • 901467(UK5, DOS1.0)
    • PIN24(VCC) +5.10V
  • 901468-06(UL1, DOS1.0)
    • PIN24(VCC) +5.11V
  • 901468-07(UH1, DOS1.0)
    • PIN24(VCC) +5.12V
  • 6504
    • PIN4(VCC) +5.10V
From the above I conclude that moving to checking the ROM contents might be a good idea, this will be possibly quite painful as I have three different EPROM burners (Galep III, a XGECU866 and a rather old haaga1000 (can burn 2532s), but most of my TMS2532 eproms seem to be defect.

I will keep you updated on the progress; if you have any idea or further input, I would really appreciate :)

Joe
 
>>> PIN7 (SYNC) LO

This indicates that the 6502 CPU is NOT executing instructions. It has probably halted.

Dave
 
Unfortunately, not. All three LEDs stay on. Both drives start to spin up, and both stepper motors "wreak" their heads "home". This whole maneuver lasts for maybe one to two minutes, then both motors stop, but all LEDs stay on.
 
I will try and focus on the ROMs as they are "fairly" easy to dump & compare with existing files. But either my old EPROM programmer is acting up, or all the 2532s I have are. I don´t seem to be able to erase them with my UV tool.
 
daver2 said:
There are 6530 adapters of course if it turns out that one of these is duff.
Click to expand...
I guess the only way to find out is to check the other ROMs. For now I need to consider acquiring a reliable EPROM programmer. Either all my stock 2532s/2716s/2732s are faulty or the programmer is...
 
Happy Easter!

Slowly having some success with programming the EPROMs; by using my old Galep III with old software I am able to burn TMS2532s with a 2732 adapter. I will try to burn some BASIC eproms and use them in the 3032 just to see if they work OK. Next step would be to read the EPROMS in the 3040 at UK6, UL1 & UH1 (also with an adapter) and compare the contents with the files from Zimmers.net.
 
OK so not much to do today, except that the CBM3032 developed a hiccup with the RAM, so had to drop in a PET ROM/RAM board.
Also punched in the code below to see if there is any reaction;
10 OPEN 15,8,15
20 INPUT #15,E,E$,T,S
30 PRINT E,E4,T,S
40 CLOSE 15

The return yielded only "0", nothing else.
 
Thinking about reading the ROMs, am I correct as follows;

2332ROM(901468-06)--->adaptor(2332-2732)--->read in EPROM Programmer

This "business" about EPROMs is mind boggling :)
 
Unfortunately, I have very little time for my projects nowadays, but a small update;

I made the little adapters to read the 2332 ROMs (UL1 and UH1), and the GCR ROM, results below;
  • 901468-06(UL1, DOS1.0)
    • The dump matches the file from Zimmers.net
  • 901468-07(UH1, DOS1.0)
    • The dump matches the file from Zimmers.net
  • 901467(UK5, DOS1.0)
    • The dump matches the file from Zimmers.net
I am waiting for my PCBway order of the RRIOT adapter, as I would like to test the remaining ROM and then proceed with further steps.

Interestingly, the behavio(ur) of the drive changed when turning it on; initially all three leds turn on, followed by a "blink" of both drive 0/1 leds (which stay on), but the error led goes out. The drive motors spin, but no head movement
I checked continuity of the socketed ICs, they seem good as far as I can tell.

When typing in the load"$",8,1 command, the CBM displays a "searching for $" message, followed by a ?File not found error.

Joe
 
OK So I found some time and went on to continue with the CBM3040 troubleshooting.

The RRIOT adaptor arrived from PCBWay yesterday, so I soldered one together today (a bit confused about the required capacitors value, hope I got it right). Also not too sure about the EPROM (I burned a 2732 with the .bin file from Zimmers).

In a nutshell; no change in behavior of the drive after inserting the adaptor.

So I went on checking the 6502 again, all good as far as I can tell (I need to manufacture a NOP Tester now, I think). When I looked at the 6504 I found PIN3(IRQ) first going HI for a few seconds when powering up the drive (both motors work for around ten seconds, then stop). When the motors stop PIN3(IRQ) goes LO.

Not sure what that means, but maybe somebody has an idea?

Thanks,

Joe
 
If the /IRQ pin goes permanently low, it probably indicates that the associated CPU has given up executing instructions...

That is one possibility. There are other scenarios of course...

Can you post a link to the schematic for the adapter you have used, and for the EPROM image?

Dave
 
You must log in or register to reply here.
Back
Top