Reanimating a bricked A1060

[Zweistein]

Hi all,


as referenced in the schematics thread already, I'm dealing with a bricked A1060 sidecar unit that I got with my 2nd A1000.


From inspection of the disassembled PSU, I suspect that most likely the transformer has gone bad. Is this a known symptom and has anybody come up with a suitable replacement as the original part appears to be difficult to come by? Is there any other part that is known to "blow" on these PSUs? The capacitors appear to measure out ok (none short circuited, none obviously blown up) but on the secondary end of the transformer all voltages are zero.



Appreciate any help I can get with this as it would be a shame to leave this unit dead.


Thanks,
Jerry

[Hewitson]

It is rare, but possible for a transformer to fail. Many transformers incorporate an inbuilt thermal fuse, perhaps this has blown?

[Zweistein]

Thanks, I'm about to hack an ATX PSU in shape to hopefully power the sidecar and check if something else got fried in the process. Boards do look healthy whereas the transformer does indeed not look very healthy at all - can't really say but if I were to make a guess it has symptoms of past overheating.
I will desolder it tomorrow and try to figure out if there's a replacement part available - couldn't find anything matching the original brand and type number. Well possible the manufacturer has been out of business for decades.
If all else fails, I'd want to fit in a modern small PSU but it will be difficult to find one that - apart from the obvious 12 and 5V - also has -12V and PWR Good lines.

[Hewitson]

It should be easy to find a suitable replacement transformer. You may have to be creative with mounting it. Of course there's every chance a component in the power supply shorted, causing the transformer to overheat.

Have you considered replacing the PSU with a Meanwell or similar unit?

[Zweistein]

I'm browsing available options at the moment - anything that lets me mount it to the pass-through power connector and keeps the original fan in place (aesthetics, plus the fan is comparatively low-noise considering 30+ years of age) should be fine. First need to prove the rest of the box is still operable, otherwise I'll have more questions than answers.

[Zweistein]

I've checked available models and if it turns out to boil down to only a PSU problem, the Meanwell RT65B seems to be the thing to go for. My problem: The sidecar specs mention a PWR_GOOD signal that the Meanwell doesn't supply - are there any good suggestions how to mimick that signal or will it be "good enough" to just let it give 5V on that pin as well? Considering the HW is pretty old and potentially not quite as touchy as modern ATX boards where a slightly delayed PWR_GOOD may be essential... I don't know, never messed with that level of detail.
In terms of size and stability would be the perfect replacement - I don't think the original PSU has more than 65W.

[Zweistein]

Ok after working my brain and Master Google a bit, I found that what at first sight raised my eyebrows was actually correct:
I fired up the old 1060 PSU and traced the current with a multimeter - when the input of the transformer didn't show any AC signal (which I would have expected), I turned it to DC and it happily displayed 323VDC - which apparently is indeed a high frequency AC as otherwise the transformer wouldn't be able to do very much with it other than potentially generate a lot of excess heat. Anything that isn't technically accurate, please bear with me, I'm not an electrical engineer at all.
Anyway, long story short, the output of the transformer is zero, no AC, no DC of any kind. I therefore have to assume that it is actually blown. Being a fairly antique piece, I haven't been able to make out a suitable replacement part as yet. I do feel encouraged to try my luck with an ATX PSU as first step now. If the sidecar comes alive on that, I shall nickname it "Frankenstein" and probably go for a Meanwell. Still not quite clear as to what needs to be done about the PWR GOOD line, though. Will try to hardwire it to +5V for a start, can't possibly do much harm, can it?

[BLUELiGHT]

Have you tried to have a look at Ian Stedman's page about Amiga PSUs? I see he mentions that on Amiga 3000 and 4000 PWR_OK = PWR_GOOD and it should be connected to ATX pin 8.

Now, the Sidecar was made several years before the 3000 and 4000 and Commodore is known to be mixing things up often, but maybe it's worth trying this (up to you, I don't know much about voltages)

Here's the link: http://ianstedman.co.uk/Amiga/amiga_..._supplies.html

[Zweistein]

Ok, I declare myself officially blind - and that when dealing with electronics, not a good combo...
Just realized that while there is a "PWR GOOD" connector on the 1060 mainboard, it is not actually receiving any input at all. At least not from the PSU but rather from some interface circuit - apparently the A1000 is supposed to hand signal PWR GOOD, i.e. the sidecar may only fire up once the A1000 "says" it's good to go. Muy interesante...
And - glad I double checked - can I just blame Commodore Germany engineers (or the geniuses who designed that PSU) for completely messing up the color coding of the cables? I mean, what did they think:
I can perfectly live with their choice to use blue for the "ground" cables - but why on Earth would they do the 5V lines in yellow (almost everybody else uses yellow for 12V) and orange for 5V. What I thought is the PWR GOOD is actually the -12V and coded in red (which is the default color for 5V lines in all other equipment I own)
I couldn't quite figure out why they would send 12V to the interface board - they didn't, it's clearly 5V. Period.
Going back to the basement, wiring up the ATX PSU and will report back the results shortly.

[Zweistein]

Originally Posted by BLUELiGHT

Now, the Sidecar was made several years before the 3000 and 4000 and Commodore is known to be mixing things up often,

Now I second that and it's probably one of the bigger understatements I read recently

[Zweistein]

Okay I have come as far as:
- A1000 now powers up with the 1060 attached to it
- A1060 power LED lights up
- Filecard controller in sidecar appears to generate heat, so it must be getting required voltage

The disk on the filecard doesn't quite spin up yet - since I do not know the make of this one (apparendly an ancient WD Filecard 30, would assume it's an RLL 3.5'' drive) I can't say if it is only to spin up when the system actually does POST/boots or if something else is still malfunctioning - or (worst but not at all catastrophic case) the drive itself has gone bad. Will be interesting to find a usable replacement in that case.

What's missing now is the PC Install disk - I got several images but have to hook up one of the Amigas to a PC to transfer stuff over - then I hope to hear the long-missed very characteristic chime of a sidecar booting (unless, of course, I get the dreaded "couldn't find library" requesters that point to something being really wrong) - probably will be the evening before I can try.

Forgot: What the A1000 interestingly doesn't do is easily reboot on Ctrl-Amiga-Amiga with the sidecar attached. Needs a power-cycle/KS reload to get moving again.

[Zweistein]

I am - in part - a happy camper: After meddling around with AExplorer, DMS, a faulty disk drive and some other tripwires, I booted my trusty A1000 with a PC Install disk and after a while the good old sidecar "chime" was audible.
I have been able to boot it into the original DOS 3.20 diskette and subsequently figured out that the installed Filecard had a stuck disk drive which is - at least for the time being - spinning when put on a separate power line from the ATX PSU. Currently trying to get it to boot from that disk (as long as it will last - I may need a replacement MFM or RLL drive, these in usable condition should be more than rare by now) - anyway, the 1060 is not broken, it was quite obviously just the PSU's fault.
Will post an update as soon as it runs with a replacement PSU installed internally.