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Commadore 3040 drive issues

automaticbirds

automaticbirds

Member
Joined
Apr 27, 2023
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23
Location
Cheltenham
Hi all, so my next project is a 3040 drive see photo. Plugged it into the commadore 3096 at first it had 3 red lights that stayed on, disc did not spin (I have correct IEEE cable). Second time no power to drive at all on switch on. Any advice on where to start? Thanks!
 

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Probably the better move is to start with the PET computer and use the IEEE port test program to make sure the interface is working perfectly first.

Then if the drive malfunctions still (probably will by the sound of it) open it up and perform basic diagnostic testing to make sure all the power supply voltages are normal and a visual inspection too checking for anything obvious. Sometimes in the power distribution system there can be series inductors and resistors which can go open circuit, especially if a Tant filter capacitor downstream has shorted out, so it is worth looking to see if the correct voltage is present at the power supply pin of each IC.

After that if nothing abnormal shows up, there are people on the forum here, familiar with these drives, who will guide you through trying to diagnose the chip or component failure, or possibly some mechanical issues too.
 
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Have you tried powering the drive on its own, without any connection to the PET? These drives are essentially Computers on their own, as such, they can operate independently. So if the drive behaves normally then the issue's your PET. If the malfunction persists, your PET may still have a problem, but at least you'll know if the drive has one too.

Here is a troubleshooting manual I found:


It's for the 4040/2040. But I believe the 3040 is a variant of those. So it might be helpful.
 
Thanks! So starting with the 3040 as a stand alone unit, I disconnected and reconnected all the power cables. The unit now powers up again! All 3 lights on the front, and a slight buzzing from the transformer. I have a multimeter, what should I check first? Thanks
 

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>>> I have a multimeter, what should I check first?

First, find the schematics etc. http://www.zimmers.net/anonftp/pub/.../old/4040/2040-3040-4040_drive_schematics.pdf.

Then measure all of the low voltage DC voltage rails to make sure they are within specification.

There are three (3) voltage regulators providing +12VA, +12VB and +5V.

You will also find the very useful maintenance manuals in the same directory...

Dave
 
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Hi all, so bad news, I was happily typing away on the basic code, when suddenly the pet froze!. I had to switch it off. It now won't switch back on! Image attached of where I got to. Any thoughts on what could have happened? The fuses are fine, the pet makes the startup electric hum, but no chirp and black screen?? There is voltage on the transformer..
 

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automaticbirds said:
Hi all, so bad news, I was happily typing away on the basic code, when suddenly the pet froze!. I had to switch it off. It now won't switch back on! Image attached of where I got to. Any thoughts on what could have happened? The fuses are fine, the pet makes the startup electric hum, but no chirp and black screen?? There is voltage on the transformer..
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I have computers die while I have been using them.

As usual, back to basic checking the power supplies first. Possibly an IC spontaneously failed, the RAM is a common cause. The RAM IC's are generally less reliable than the usual TTL Logic Chip. Though it could also be something simple like a bad connection on a socketed IC, And your computer is not booting and the screen remaining black, so after the supplies are checked, you will want to find out if the CPU is running. Most people use a NOP generator & @daver2's PETTESTER as initial the diagnostic tool and others with RAM/ROM fucntions that Nivag made.
 
Ok thanks both! So I have deconstructed it and cleaned the boards. This is an 8096 board 8032080 with 64k sister board. The 6502 is on the sister. See images, if I move the 6502 back to the main board could this rule out a sister board issue? And make the machine a basic 8032 to test first?
 

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Yes,

That is what I would do in the first instance. Take the machine back to basics.

Just be careful of the IC sockets in the process. I notice that you have black sockets instead of white - not that the colour matters of course, but the construction of the IC socket does...

Dave
 
Ok back together as a 8032 board. All chips reseated. Still black screen, what do I start to measure? And shall I get your pettester Dave? Where do I get that from. I see the ramulator is out of stock. I can measure things in a list and feedback if that works? Thanks!
 

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Ok so power check 1.

J8 power connector:
Pin 8+9 - 16.65v
Pin 1+5 - 18.4v
Pin 1+3 - 9.2v
Pin 5+3 - 9.2v

I can connect the board next if you give me the locations to test 👍🏻
 
I have also tested the main ram 5v and 12v is being supplied
video Ram has 5v
The J7 monitor connector has the correct voltages.
The crt monitor gives a high pitched whine on power.
The 6502 has 5v on pin 8

Would a romulator be the next step?
Don't want to spend the £75 and find out does not work 🤔
 
Don't forget the DRAMs has -5V also...

Use my PETTESTER. It is free!

When you say 'the J7 monitor connector has the correct voltages' what do you actually mean? There are three (3) dynamic signals on J7 - video, HDRIVE and VDRIVE.

It is possible to measure the voltage on these pins - but interpretation of the readings requires some prior knowledge of what to expect.

Dave
 
Your' next move is to check for CPU activity, and a NOP generator, followed by Daver2's PETTESTER. Then the Romulator if the problem remains elusive.

Not that I would do it this way exactly myself because mainly I rely on my hardware skills with scopes and digital circuitry, however it will likely lead you down the right road to where the fault resides. The PETTESTER and Romulator create a guided approach to the problem, much like a fault finding flow chart, to lead a person in the right direction and down the right road. In fault finding, there can be many false clues (or Red Herrings, more than in a Fish & Chip shop) so you need to be prepared for that and not go down too many wrong Avenues.
 
Hi both,
Ok great, so I am not skilled in the EPROM arts but very willing to learn. Do I order an EPROM writer for pc, a 2k EPROM, and then write the binary to it (and where do I purchase these). And just for clarity, where is the edit roms location? Thanks!
 
automaticbirds said:
Hi both,
Ok great, so I am not skilled in the EPROM arts but very willing to learn. Do I order an EPROM writer for pc, a 2k EPROM, and then write the binary to it (and where do I purchase these). And just for clarity, where is the edit roms location? Thanks!
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Assuming you're in the UK (I think you are) I can send you one already programmed for the duration (ie as long as you send it back when you're done). Doesn't stop you getting a programmer/IC for yourself but it'll get you going on the diagnosis of your problem while you're waiting for them to turn up.

Let me know via PM.

Colin.
 
automaticbirds said:
Hi both,
Ok great, so I am not skilled in the EPROM arts but very willing to learn. Do I order an EPROM writer for pc, a 2k EPROM, and then write the binary to it (and where do I purchase these). And just for clarity, where is the edit roms location? Thanks!
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One cheap and sturdy programmer is the GQ-4x. Then you can program some UVeproms like the TMS2532JL and 2716.

It pays to get this for other reasons. For example you can make a duplicate set of ROMs from the files on Zimmers and they can be helpful in fault finding. You can make a duplicate set for the whole computer and fit them, if that clears a fault, then you can remove them one by one replacing them with the originals and that way any defective original ROMs are quickly detected.

Generally, it speeds things up if there is a way/method to quickly eliminate both RAM and ROM problems. Once that is done the remaining faults in digital logic around the CPU can usually be found fairly quickly with the aid of the scope.

The CPU itself is hardly ever the culprit, though given the complexity of them, one might wonder why this is the case. Only very occasionally the CPU can be defective, apparently breaking the rule that "it is never the CPU". But on the other hand, it is like the notion that the crime was committed by the Butler, when everybody knows the Butler practically never did it. But just once in a while they did.

This is why an open mind is important in servicing. Like the model detectives use in solving crimes; Assume nothing, trust nobody and check everything.
 
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