A1200 Rev2B stopped working

[Intuition]

I got my remaining A1200 and 1084 out a few nights ago and they miraculously still worked and I played Superfrog with my daughter.

There's an issue with the keyboard connector missing the top part so I ordered a 3D printed one of ebay and a pair of DiagROMs just in case. The Amiga LEDs don't light up at all either.

The morning after I noticed a high pitched whilsting coming from my office and the 1084 had been left on over night so I switched it off.

Come the weekend and the DiagROM pair get delivered. I removed the 3.0 chips and installed them.

Switched on the 1084 and the whistling is really loud, the LED doesn't light up either. Dead flyback transformer I assume.

The A1200 when powered on does nothing. No drive clicking at all. I replaced the DiagROM pair with 3.2, same issue. Put 3.0 back in, same issue.

I know it takes forever and a day with no HDD to boot so I added an old one, I believe having no keyboard attached can cause issues but it booted Workbench and Superfrog successfully the other night so I don't think that is the issue.

Could it be dead caps or possibly another issue?

Could the 1084 being left on all night have fried the 1200 board when the flyback transformer died?

Anyone in NL know where I can get it recapped cheaply?

I'm currently trying to find my 25 to 9 pin null modem adapter so i can see if DiagROM tells me anything.

Thanks in advance.

[8bitbubsy]

Leaking capacitors is very likely. You may have rushed the cap leak process by using it after all these years. A1200 is one of the Amiga models where the surface-mount caps are almost guaranteed to leak at some point.

Regarding the 1084, it sounds to me as if the HOT (horizontal output transistor) is shorted. This probably keeps the PSU in protection mode. I wouldn't think a dead flyback would prevent the power supply from running, but I could be wrong here.

BTW: If you change the flyback, you should also change the HOT.

[huggy70]

First things I would recommend: is the PSU working? Perhaps try another one or measure voltages but even then under load the voltage may collapse. Check Supply voltage on all ICs with multimeter and proper ground connection. Look for possible corrosion in sockets.

Don't bother with caps or even recapping before failing part/area is found, you may bring in additional faults. Even with failed cap board should boot ok. Of course look for some leakage around caps an possible damage to traces or vias. Did you place the roms in correct position (lo/hi rom?) and with e.g. gap on first slot?

I recapped my 1200 (2B like yours :-) last year for the first time after I bought it new in 1993 and there was not a single sign of corrosion or leakage on the board or near/under the caps.

I found A600 boards by far worse. I recapped one a600 where the solder on one IC of the audio circuit was so corroded that it just popped of just by grabbing it firmly with tweezers, the solder pads where all intact but it took me some time to make them accept some new solder again.

[Intuition]

Thanks for the replies.

I've since fitted the ribbon connector for the keyboard to rule out that and still no change.

Even with failed cap board should boot ok.

This concerns me as the caps don't look like they've leaked at all, so it's probably something else.

I don't have another power supply as this is the only Amiga I have left in my possesion (My A3000 is back in the UK and I sold all my other stuff years ago), though the HDD spins up and the caps lock light works when I tap it on and off.
I have no idea how to even use a multimeter, electronics is not my forte!

I sent a message on tsb.space about getting it recapped but got no reply yet.

Anyone know of another place in The Netherlands where I could get it done and whatever else might be wrong fixed?

I'm keen to get it working again ASAP so I can buy a PiStorm32 and start coding Amiga stuff again. UAE just doesn't feel right and my Amithlon box has been dead for a long time too.

I'm not too concerned about the 1084 dying as I can use a TV I guess.

[Intuition]

Originally Posted by Boing-Ball

How did you remove the Kickstart ROMs? You didn’t use a screwdriver and levered them up and possibly damaged the traces underneath by chance?

That thought occurred to me as I did use a screwdriver, but the traces don’t appear to have any damage too the naked eye at least.

I’ll zoom in with my phone later and double check.

It seems I own every cable known to man except an RF cable to connect it to my TV so I’ve ordered one so I can have some form of feedback hopefully.

If I connect the floppy ribbon the wrong way then the floppy led stays on permanently.

The HD led never lights up at all, nor does the power led.

[huggy70]

I have no idea how to even use a multimeter, electronics is not my forte!

Ok so your options are limited (connections are ok, roms in the right place and working, power ok). So what are your expectations? Even if you could diagnose a dead cpu that won't help you further and finding a dead trace is a pain in the arse even with proper knowledge. And then you will need to get someone to repair it.

This is why I like the A500 so much. Important chips are in sockets and everyone could simply swap them around for a check. in A1200 not so much.

I think simply recapping won't get you a working machine
Probably:Power supply, CPU, Alice

[Intuition]

Originally Posted by huggy70

Ok so your options are limited (connections are ok, roms in the right place and working, power ok). So what are your expectations? Even if you could diagnose a dead cpu that won't help you further and finding a dead trace is a pain in the arse even with proper knowledge. And then you will need to get someone to repair it.

This is why I like the A500 so much. Important chips are in sockets and everyone could simply swap them around for a check. in A1200 not so much.

I think simply recapping won't get you a working machine
Probably:Power supply, CPU, Alice

I took a zoomed in look at the rom sockets and there are superficial scratches but they look quite old as though they’ve been there for quite a while rather than recent.

RF cable should arrive today so I’ll connect to the TV and see what happens.

[HomeLate]

Are the ROM-sockets still in a good condition? If you have a multimeter, do all the traces near the ROM-sockets still work? You can use the Amiga PCB Explorer on the www to check all traces.
Cap leakage can cause issues, but I never had a dead 1200 caused by capacitor leakage and I repaired/recapped a lot of Amiga's. Best bet is to hook up a serial null modem cable and check if Diagrom gives any output.

[Intuition]

Originally Posted by HomeLate

Are the ROM-sockets still in a good condition? If you have a multimeter, do all the traces near the ROM-sockets still work? You can use the Amiga PCB Explorer on the www to check all traces.
Cap leakage can cause issues, but I never had a dead 1200 caused by capacitor leakage and I repaired/recapped a lot of Amiga's. Best bet is to hook up a serial null modem cable and check if Diagrom gives any output.

I’m away from home at the moment but when I get back in a couple of weeks I’ll get a new multimeter and start testing all the traces.

I haven’t see any signs of cap leakage at all so it’s very odd.

I did manage to get the TV to tune into the RF modulator output and it just gas a grey screen with corruption/distortion down the far right of the screen.