Commodore CBM 8032-B

[RonTurner]

Here is the commodore CBM, it doesn't work at this stage...


The capacitor underneath has failed, this has pushed live wires against the chassis

[Gibsaw]

The capacitor underneath has failed, this has pushed live wires against the chassis

Oooh, very nearly had your entire collection available as a deceased estate.

[tezza]

Good one.

Interesting that there is no labelling of Commodore badges on the machine. Is that normal?

[nzswift]

The label has fallen off at some stage of its life....

[RonTurner]

I have pulled the whole thing apart, and cleaned the motherboard for a start, visually it looks really mint after a clean.

This is the 80 column model.

[nama]

Scary looking cap!!!!

[RonTurner]

Scary looking cap!!!!

It's not needed so I cut it off,

I pulled the CPU and put it into one of my Apple //e and it works ! Best / cleanest pins I have ever seen on a CPU in fact.

PS: I corrected the name of the computer, sorry about confusion but the 4000 series are called PETs and 80xx are CBMs.

[Update] after reinstalling the CPU it is now beeping on power up, the RAM has failed so it's going to be easy to fix, the biggest problem going forward is that the monitor has no picture at the moment, I need to wire up a composite video out so I can connect an external monitor, anyone done this before? Incidentally the apple monitor 2 is the same size and shape so it will fit the CBS case if all else fails.

[tezza]

There is something about pictures of mint-condition motherboards of vintage computers. I love to look at them. They are a form of art.

Hmm...I know nothing about wiring up these things for composite video. I'm sure the knowledge is out there though...

In my experience it's usually the circuitry around the screen rather than the screen itself that's failed. The Commodore Section of the Vintage Computer Forums often discusses problems like this: http://www.vintage-computer.com/vcforum ... -Commodore

[nzswift]

I'm so pleased this has gone to a good home......
Go Gav!!!!

[RonTurner]

I'm so pleased this has gone to a good home......
Go Gav!!!!

No, Thank you

Here is a closer look at the motherboard (I have not looked into the monitor yet),

I agree Tezza, the picture can disappear even because of parts on the motherboard, like if the character ROM has lost proper contact in the socket.

I have gone over the PCB with a new tooth brush.... I firmly believe dirt and dust is rust food.

[RonTurner]

I soldered an IC socket onto an IC clip to come up with this device for piggy backing 4116's,

Patent pending ...

[Clym5]

I soldered an IC socket onto an IC clip to come up with this device for piggy backing 4116's,

Patent pending ...

That's just brilliant! I'm gonna have to make one for C64 RAM ICs...

[RonTurner]

Voltages test results:
+12v
+5v
-5.1v
Simple testing shows the RAM is getting +12v etc.

I soldered an IC socket onto an IC clip to come up with this device for piggy backing 4116's,

Patent pending ...

That's just brilliant! I'm gonna have to make one for C64 RAM ICs...

Thanks, if it works let me know

I tested the 4116 in my Apple europlus motherboard, piggy backing any of the chips did not stop the apple 2 from working, I tried dozens of 4116's on the motherboard until I found a dead one, on this I tried the piggy backer and it did not fix it, ambiguously the piggy backing did not stop any RAM chips from working.


So far progression timeline (also known as regression in this case) goes as follows:

* initially the computer chirped and had a garbled picture, after a few seconds the picture went out (but it still chirped).

* when I got it home it chirped, then it stopped chirping so I cleaned the motherboard then it started chirping again.

* then it stopped chirping (I promise I did not even touch it !).

apparently from here there can only be progression as all the regression that is possible has already happened .

So I took the CPU out of the CBM and put it in my Apple 2 and the MOS CPU still works anyway, re-tested the voltages (alls well), I'm going to need some cleaner solvent for the sockets (I suspect IC sockets due to intermittent failure) so in the meantime I will keep cleaning the outside.

When I push the IC's into the sockets they make that crunching sound, I'm going to replace them with quality wire wrap sockets.

[Gibsaw]

I'm glad I'm not the only person for whom "piggybacking" seems inconclusive.

Is it really that simple? I could be talking rubbish, but wouldn't you have to lift some pins on the chip being tested?

[RonTurner]

I'm glad I'm not the only person for whom "piggybacking" seems inconclusive.

Is it really that simple? I could be talking rubbish, but wouldn't you have to lift some pins on the chip being tested?

It proves it doesn't always work.

I tested the reset pin on the CPU , it goes low for half a second on power up.

There are also signs of activity on the address and data bus's, also there is activity at the RAM chip select etc pins.

CR1 and CR2 get very hot (located near PSU plug).