C64 basement treasure. Sadly floppy 1451 not working... anyone have any ideas?


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Hi there people!

I recently aquired a C64 which has been sitting in a work colleagues basement for 30 years. I got a MIDI Interface and a 1451 Floppy with it (I believe it's a first gen 1451, it has a solid eggshell case, an internal power transformator and that weird latch mechanism to lock the disk in, not the more common lever variant).

I was super excited, that the breadbox still works and was eager to load some of the floppies that came with it. Sadly the drive won't respond correctly.

When I turn on the floppy, it resets the head like it should, while the red led is lit. then the red led goes out as it should, leaving only the green power led on. I then boot the c64 and the drive resets again, like it should. The serial cable seems to be working and I think a fault in the c64 is unlikely, as it communicates with the drive.

then I load"$",8 and the drive will not budge, not even the red led. c64 either displays "drive not present" error or "searching for $" and hangs until I run/stop + reset.

I read that there are two likely culprits to the problem. There is an inverter ic 7406 that likes to die and cause this error, which I have exchanged. I got the drive working for a short while and it was reading and loading floppies like it should. when I came back in the evening it stopped responding again... I'll try exchangin the 74SL14 beside the aforementioned IC next.
 
ah yes, I tried that first. but as I said, after changing the IC it was working for a short while and registered as number 8. the jumpers on the pcb are also not cut.
 
Did you replaced the 7406 with the exact same chip? If a chip like that dies, they are probably drawing quite a lot on it, newer version (with letters after the 74) while being a drop in replacement functionality wise, exhibit different electrical and time performances... Since it was working for a short while, the culprit seems to be the 7406, the question is "did the replacement died by itself or did something else (like that other chip you mentioned) killed it"... I haven't took a look at schematic so these are just general remarks...
 
Are you willing to spend money? If so, one option is that there are carts out there that emulate disk drives, so you can load D64s from USB/SD card.

I just wish my C64 still booted :(
 
Are you willing to spend money? If so, one option is that there are carts out there that emulate disk drives, so you can load D64s from USB/SD card.

I just wish my C64 still booted :(

I have ordered an sd2iec device, but that does not change the fact that the floppy drive is broken. I'd still like a working floppy...

@elwing that is an interesting thought. the 1541 was originally designed for 220V and now in Europe we have 230V standard, which sometimes fluctuates even higher. maybe the replacement has just died. the 7406 is an inverter (NOT gate), so it doesn't do much but turn 1 into 0 and vice versa.

Could it be the serial cable? The drive responds when I turn on the C64, but couldn't this still be a wonky connection?

thanks for all the input!
 
I had a couple not fully formed ideas, but it seems the pieces don't really fit for the one that kinda made sense*. I will let this voice around in my head for a bit and see if I can come up with something even somewhat in the right direction.


*It doesn't help that I have no hands on experience with C64 hardware, which might give me specific troubleshooting ideas, and I am not rally familiar with how it all works (I have read somewhat detailed technical comparisons of floppy drives, however I never moved the C64 stuff to long-term memory since it fell outside of my main areas of interest. At this point in time we really should be doing whatever we can to potentially help others that appreciate and use old computers...).


TL;DR I really wish I could help you. I will think about it.
 
that is an interesting thought. the 1541 was originally designed for 220V and now in Europe we have 230V standard, which sometimes fluctuates even higher. maybe the replacement has just died.

The Europe wide standard is 230V+-10%, which means anywhere between 207V and 253V - in practice just like the old days the majority will tend to have around about 220V and us in the UK will be closer to 240V - they didn't rebuild the power stations and transformers when the regulations changed.

Plus I'd be surprised if an american company didn't use the same transformer and regulator across Europe, so including the UK. C64s ran just fine on our nominally 240V mains too.
 
Sorry, I wasn't imply supply issue, trough, that is still a possibility, but I would expect worst result if it were the case... I was just thinking that 7406, 74LS06, 74F06 as example, while being dropin replacement do not have the same electrical performances, some might output more current, other have slower slew rates and such, from what you're saying, I suspect the replacement burned, the first question is: is it really the case? the second question is why? the two most obvious cause would be that you have a short after caused by something else, but it might just also be that the original part was able to output more current than the one you have... there's lot of possibilities when talking about possible failure cause... do you happen to have some schematics?
 
Have the electrolytic caps been checked?How old they are I would replace them anyway.
 
+1 for trashyMG, electrolytic caps are the component that ages badly... A quick look for bulking caps is a nice idea, a check with an in circuit esr meter would be even better for caps checking...
 
There's the electrolytic cap plague issue from the late 90s till the late 00's, and I'd replace those automatically, but something made in the late 80's? I'd only replace those if they weren't working or were clearly leaking. Though in this case it might be safe to assume they're a problem and replace them anyway, so I don't really know.

But I'd leave ceramic caps alone fwiw.
 
It's not just bad 90s caps from knock offs that plagued the industry, but All electrolytics eventually dry up over time, if kept cool they don't leak or expand, but they definitely could change electrical properties overtime. It really does depend on the quality of the caps, but it's still something that could go bad even if they don't look like they're bulging or leaking.
 
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FWIW, it wasn't knock-off caps that caused the 90s-00s cap plague, it was knock-off electrolyte bought by legitimate cap manufacturers.

I was thinking as I wrote that that the 80s caps in my kit stored in the loft all still works, but thinking further on that I've not really tested some of that stuff in 10 years now. And my gamegear predates the cap plague, yet most of the SMD caps in that have visibly leaked.
 
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