Amiga 4000 problem!!

[redrumloa]

Last night I got an unpleasant surprise. My A4k I am doing the tower project with DIED:-( Everything was working fine, more or less, until I decided to plug in speakers. BOOM total death. Now it won't boot, or even get to the early startup menu. When I turn the computer on I get.
1)A light grey screen that doesn't change or do anything.
2)No HD or floppy activity.
3)The CD-rom acts completely dead when plugged in, won't even eject when the IDE cable is plugged in. If I unplug the IDE cable but leave power it seems normal and respons to eject.
4)Power supply test ok

I seriously doubt a coincidence, something about plugging in speakers caused the death. What blew? Does the A4k have mb fuses like the A3k? I'm going to try to dig out the old service manual, but I am hoping someone here can also give me some clues. I'd really hate to have to buy another A4k MB at this point:-(

[Vincent]

The first thing to do is don't panic.

The second thing is grab a cup of your fave working poison and strip the 4k of every add-on possible.  Boot up and see if you get anything.  If it boots ok add in one of the add-ons then try again.

You'll know this by now anyway, but it's the best way to see what's wrong.  And if you're in a panic, you don't think of this :-)

When my A1200 accel's FPU is playing funny buggers I get the same symptoms as you.  It could be something simple like this (well, "simple" it isn't, but better than a whole mobo going).

[redrumloa]

@Vincent

I did this last night. I stripped it of everything except the A3640. NADA, i am worried :-(

[bloodline]

redrumloa wrote:
@Vincent

I did this last night. I stripped it of everything except the A3640. NADA, i am worried :-(

I blame the PSU.

[voxel]

Hi red :-)

What kind of speakers have you plugged in? I hope it's a pair of self amplified model and NOT an ordinary one...

just for completeness, you used the motherboard audio out to plug it in, right?

[redrumloa]

bloodline wrote:
I blame the PSU.

It's a converted PC AT power supply. It was working a-ok until I plugged in speakers. I tested the PS (no load) and it seems normal except the -12V seems to be -10.46V. That should be close enough?

[SilvrDrgn]

redrumloa wrote:
Last night I got an unpleasant surprise. My A4k I am doing the tower project with DIED:-( Everything was working fine, more or less, until I decided to plug in speakers. BOOM total death.

What do you mean by plugged in speakers?  How did you plug them in?  What types of connections?

[patrik]

@redrumloa:

You dont happen to have the original A4000 PSU to try with?


/Patrik

[redrumloa]

@voxel

Yes they are self power speakers. This A4k mb was modified by the previous owner. He/she removed the original dual rca connectors and wired in a connector to use PC speakers. It is definately the audio I plugged into. I wouldn't rule out a problem with the PC speakers, possibly energising the connector. They are el-cheapo generic PC speakers.

[redrumloa]

patrik wrote:
@redrumloa:

You dont happen to have the original A4000 PSU to try with?


/Patrik

I have a flakey one, but yeah I will test later just for completeness.

[redrumloa]

SilvrDrgn wrote:

What do you mean by plugged in speakers?  How did you plug them in?  What types of connections?[/quote]

See my other post on the speakers. The only thing I did wrong was I plugged the speakers in while the computer was on. I know this technically is a no-no, but who would have thought it really would blow something? :-?

[voxel]

Well :-)

Plugging cables in the sound output plugs when the amiga is on SHOULD NOT be a problem as the Amiga sound circuitery and cinchs are made for.

You should investigate around the modified plug to eliminate possibles shorts, I suggest you mount some Amiga style plugs back instead of the jack the other used.

Making a small adaptator cable or soldering two male cinch connectors to the speakers cable would not be too hard to do :-)

if you find no shorts, it's possible that the sound mixer ic (near the output) or the audio capacitors might be blown :-(

A more horrible thing to might have happened would be the death of paula too :-(

You should pray for the shorts on the plug...

[amigamad]

This A4k mb was modified by the previous owner. He/she removed the original dual rca connectors and wired in a connector to use PC speakers. It is definately the audio

I have a few leads which go from phono to a 3.5 socket would not like modify the computer, is it possible when you pluged the speakers in the motherboard moved or it has shorted somehow to the case.I would also say check the pins in the psu are making good contact and there is no dry joints under the psu plug on the motherboard. :-?

[Matt_H]

I think there was a thread on here a while ago about audio capacitors on the 4000 mainboard blowing up. If these were on the brink, maybe plugging in the speakers while the system was on was too much for them? Try checking those.


Any physical signs of damage to the board?

[CyberHanz]

Seems to me like a short-cut somewhere.
Last weekend I had a zorro card which shorted with the casing.
Resulted in the same symptons you mentioned,
gray screen, completely dead hd/floppy and exactly the same with the cdrom.
Try to remove the audiojack, and try again...