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I guess the above connector? Interestingly, P9 on the top image becomes P10 on the lower and vice versa...dont know if I am missing something. With the connectors disconnected, I have "open" between all the pins on p9/p10 respectively. With the connectors plugged in, I have the following...

Hi Dave, I have my 3040 on the bench today, trying to fix a faulty analogue board (one is fixed, can be used as a reference); if you need any readings from myself, please let me know :-) I am an absolute beginner with electronics, so please be patient if I donßt catch up with something. Joe

Hi, Just out of curiosity; did you remove the board from the chassis? If so, did you ground the board as recommended by a service manual I found? Joe

I agree. Without such a device it becomes quite painful and is no fun. Joe

Maybe you could get hold of a SD2PET device? This is a very helpful tool for many things. Joe

If you happen to get hold of the Commodore Test disk, there are a few neat programs, I found it very helpful. Admittedly, I have BASIC 4.0 on my 8032 which helps.

Hi, I am not sure with your PET, but with my 8032 I can use HEADER"Test" ,d0 to format. I have a Commodore "Demo" disk with some useful programs, making life a bit easier for "normal" users. One of the programs is called "dum 3.4" which includes many useful functions such as format, backup...

OK, another day, another update, good news overall; Further troubleshooting revealed Q3 (4401 Transistor) also being defect. I replaced it, and both drives now work as they should; formatting, copying, reading etc all work :-) :) Now since I fixed one analogue board, I am getting ready to fix...

small update; I re-checked the board, and replaced Q2 (4403 Transistor), which now has an 11V output. When trying to access drive1, I can format a disk until an "error#21 read error on 18.04" appears. Strangely the "rattle" of drive1 is more subtle than of drive 0, but who knows. Drive 0 works...

I had an hour or two to get acquainted with the analogue board of the CBM3040. As mentioned before, I have two of these boards, one not working (produce read errors all the time), and the other only "half" working (drive0). I tested both mechanical drives, they both work (reading & writing)...

I think that would be TP1 and TP2 at UA5 (LM592)? Out of curiosity I swapped the analogue board from one drive to the other, and it is now able to read disks (also formatting). As I would like to understand more about what is happening, I will continue with the troubleshooting :-)

Dear Hugo, Thank you very much for your detailed answer. I have done the below work on the drive so far, and it looks quite promising! - General cleaning. - removal of the filter cap in the AC power supply part (the drive is from Germany). - Replacement of C31 near VR2, which was blown already...

Hi :-) In a previous repair attempt of a CBM 3040 I got stuck with three red LEDs. I haven't made any progress on that drive, but I got my hands on another 3040, which has a good mainboard, as I can use the various disk commands to access both drives. Problem now is, I am unable to read...

...Just returned from an overseas assignment, going to continue working on the mainboard over the next couple of days...unless there was some magic self-healing over the past couple of months:-) Joe

Dear Hugo, Thanks for your input!! I can very well visualize the idea of a bug zapper :-) Funnily I just today took my schematics out again and am trying to formulate a plan regarding further troubleshooting of the (beasty) PET. I will beg my wife today to allow me an hour or two in the...

I have a second board ready to take some comparative measures if needed; I wish I could take a week off from work to tackle this beast! Joe

I started a bit of troubleshooting today, but it definitely ain't easy to find this fault. A couple of resistors (R39, R34) not having any voltage (powered through G1/13 respectively H1/6), and the cause probably being the INIT line being pulled low somewhere. After the weekend I will start...

Gents, Thank you very much for your valuable inputs! I might be able to spare a few hours tomorrow to start the search for the holy grail...in the worst case I have a day or two after the weekend, will report back. Joe

So in other words I will have to check every chip having something in common with R12 if it is pulling the voltage low(?), which are essentially the G and H rails. The voltage on G5/11 is 0.65V ( the same as on R12. The "input" voltage of R12 is 4.97V. I am using an EPROM for the moment in...

Just measured R12, the resistance is OK but there is a voltage drop across which can't be right, unless I miss something. Joe