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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 23rd Jun 2022, 10:37 pm   #21
SiriusHardware
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Default Re: Dead commodore 4040 disc drive

Quote:
Just tried it again and now it settles at 14.9
That sounds rather low for a mains transformer primary, but then looking back at Colin's thread his was about 33R, which also seemed low.

When we ask for a resistance measurement please use the ohms / resistance measurement range on your meter, not continuity. This is because the continuity position on meters does not always indicate the resistance of the circuit under test, although it usually does. Even where they do indicate resistance they often only indicate up to several hundred ohms and then indicate Overload / Infinite, whereas if the resistance is higher than expected, we need to know what the resistance really is.

Next one: With the unit still unplugged from the mains and the unit's mains switch turned on, measure the resistance between the black wire on the filter and the metal chassis of the drive unit, and the resistance between the white wire on the filter and the metal chassis of the drive unit.

Both readings should indicate Infinite / Overload, although there may be a brief flash of low resistance at the beginning of each measurement as the capacitors in the filter charge up.

If the above readings are OK make up a three core mains lead with a plug on one end and stripped ends at the other and immediately fit a three-section piece of terminal block to those stripped ends. Check the value of the fuse in the plug and if it is not already 3A, fit a 3A fuse, this is important as it will limit the size of the bang / the extent of the damage if anything goes wrong.

Disconnect the black, white and earth wires currently going to the filter and connect them, via the terminal block, as follows:-
Mains cable live (brown) to black wire which went to filter.
Mains cable neutral (blue) to white wire which went to filter.
Mains cable earth (yellow/green) to earth wire which went to filter.

Disconnect the low voltage output connector from the drive unit's PCB and turn the unit's power switch to ON.

Choose a switched mains socket, set it initially to off, plug the mains plug into the socket and switch the socket on. This is so that if something does go bang you won't be hunched over the top of the unit when it does.

If nothing bad happens, switch off at the mains, reconnect the low voltage connector to the drive unit's PCB and switch on at the mains again and see what happens.

Last edited by SiriusHardware; 23rd Jun 2022 at 10:45 pm.
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Old 25th Jun 2022, 5:14 pm   #22
pudwink
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Default Re: Dead commodore 4040 disc drive

Hi all
I have found a spare IEC switched socket that I had lying around so conected that to the power supply as a temporary measure.
I first tried the power without the board plugged in and no bang.
So I have now connected the board and drives.
The drives make a noise then the power light and the two drive lights flash in a repeated 5 flashs then they start again.
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Old 25th Jun 2022, 6:36 pm   #23
ScottishColin
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Default Re: Dead commodore 4040 disc drive

I've not seen that before, but here's the LED codes in the hope this helps you or others:

https://www.vintagecomputer.net/brow...ILqy2j7dAfnmpU

Colin.
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Old 25th Jun 2022, 6:59 pm   #24
ScottishColin
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Default Re: Dead commodore 4040 disc drive

So the implication is that it's a 6502 fault. It could be the 6502, the socket or any of the connections to/from.

You could either plug in your PET 6502 and see what happens, which risks breaking that one too, or you could wait for better advice than mine on looking at the schematics to work it through.

Colin.
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Old 25th Jun 2022, 7:24 pm   #25
TonyDuell
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Default Re: Dead commodore 4040 disc drive

I know the 8050 rather better than the 4040 but they are probably similar.

There are two processors in these units (the 8050 is a pair of 6502s, I thought some of the older units used a cut-down version for the 'drive' processor). One handles the IEEE bus, command decoding, etc. The other handles data encoding/decoding to the disk drive heads.

They communicate via a shared area of RAM (the 8050 is 4K*8 in 2114s). The processor clocks are the inverse of each other, each processor only tries to access memory when the clock is in a particular state so this interleaves accesses vey nicely.

From the mention of '6530' (A ROM/RAM/IO chip) in the fault codes, I suspect it's referring to the drive processor
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Old 25th Jun 2022, 7:43 pm   #26
ScottishColin
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Default Re: Dead commodore 4040 disc drive

My UK3 chip is marked as "MOS 901466-004 1181" not a 6530 at all. Curious.
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Old 25th Jun 2022, 7:53 pm   #27
TonyDuell
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Default Re: Dead commodore 4040 disc drive

Is it 40 pin?

Remember that the 6530 contains mask-programmed ROM, so one used in a particular device may well have a strange number which effectively identifies the ROM contents.
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Old 25th Jun 2022, 7:53 pm   #28
ScottishColin
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Default Re: Dead commodore 4040 disc drive

It is.

Colin.

Quote:
Originally Posted by TonyDuell View Post
Is it 40 pin?

Remember that the 6530 contains mask-programmed ROM, so one used in a particular device may well have a strange number which effectively identifies the ROM contents.
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Old 25th Jun 2022, 7:54 pm   #29
ScottishColin
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Default Re: Dead commodore 4040 disc drive

Back to the problem. You could at pretty low risk I thought no transfer the 4040 6502 to your PET and see if it works in there. That would either rule it out or focus the problem onto there.

Colin.
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Old 25th Jun 2022, 8:07 pm   #30
TonyDuell
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Default Re: Dead commodore 4040 disc drive

If it is a 6502, which I doubt.

The circuit diagrams I've found for the 4040 show that the 'interface' processor is a 6502 at location UN1 but that the drive processor is a 6504 (28 pin package) at UH3 (roughly in the middle of the PCB). It's the latter chip you need to test.
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Old 25th Jun 2022, 8:18 pm   #31
ScottishColin
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Default Re: Dead commodore 4040 disc drive

I have a working 4040 so someone else needs to takeover but I can do comparative tests here.

Colin.
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Old 25th Jun 2022, 10:19 pm   #32
SiriusHardware
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Default Re: Dead commodore 4040 disc drive

One additional suggestion, if you have not already done so, is to check that all the power supply voltages are correct as detailed in Colin's recent 4040 thread.
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