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No progress on this :( Might be a sixty clone candidate when I get time, but that said, is there a c64 equivalent of amiga pcb explorer anywhere?

I think there must be a broken trace or dry joint, if I flex the board then the system boots... These things are sent to test us

Desoldered CIA 2 on the hunch that it was killed by a hotplug, and the system started into basic at first power on post desolder. Cycled the power and it's back to that screen... scratches head.

BTW here's a link to the symptom as described by the pictorial fault finding guide -> https://www.pictorial64.com/fault.htm?id=u8_1

Same issue with diag test cartridge initially, but then some garbled cycles and eventually a cyan border and just white background. I can make out during the cycling that some of the screen patterns match what I'd expect from diags so some code is being executed at least. Exact same issue with...

I have a c64C which is showing a very similar fault to this: The pictorial fault guide suggested that this fault could be caused by a faulty 7406 (U8) or 2 other 74LS14s - because I have the parts & wishfully thinking these may be relabelled on the 64c I replaced U23 (74LS14) & U22 (7406) -...

Great to see you got it working. I'd love a 1084 or a 1901, but they go for silly money here in the UK.

Always great when the frustration ends, well done.

I guess it depends what you wish to use it in, they work just fine in 1541's. But yeah 6522 equiv, not 6526 as I wrote - braino moment.

6526 is available as brand new part still -> https://www.mouser.co.uk/ProductDetail/Western-Design-Center-WDC/W65C22N6TPG-14?qs=opBjA1TV901DbgJ9rfcBoQ%3D%3D&countrycode=GB&currencycode=GBP

Are you able to update the firmware on the older pi1541?

Excellent, glad you got it fixed.

I'm by no means an expert but I think I'd be targeting UF3.

You could work outward from UC1, there's a data in pin where a serial stream comes in from the read head, it's get's differentially amplified by the 2 592's and then more so by the 311. UC1 then essentially deserialises the data stream and pops it out 8 bits at a time to UC2. I'm not sure...

Got to be worth trying to replace the trimmer pot or the newtronics control board first - there are a lot of drives out there with dead heads so I would've thought it may not be too hard to obtain. I don't know the pot value I'm afraid. I had an alps with a very slower spindle motor, but it...

If the head resistances check out then Frank's post above is spot on for the parts that could be at fault, it's scope time, or substitution with known good parts to address. Similar issues I've seen on 2 Alps drives were a failed gate array in one instance, and failed 592 in the other.

Mechboard64 is the only replacement that I'm aware of, it aint cheap.

Resistances should be as per the service manual: https://www.classic-computing.org/wp-content/uploads/2016/01/15401541_SERVICE-MANUAL.pdf Extract here: There's a reasonable troubleshooting guide in there, but I tend to use Ray Carlson's chip fault finding guide from here ...

Further to this, I managed to source a spare spindle motor. I fitted this which fixed the slow motor issue, but although I could load a disk directory (slowly), no larger programs would load successfully. Given that a directory was working, clearly this was not a logic issue, but rather a...

Looks correct to me. Have you checked the resistances of the r/w heads? It's uncommon for Alps heads to fail but certainly worth doing. Also, it may be that some of the circuitry has become inadvertently damaged, UC1 plays a big part in controlling the movement of the stepper motor (as does...