Amiga 2000 black screen

[JACK98]

Hi all,received an german Amiga 2000.im aware these models do not have a good reputation.it is a basic system,no cards etc.The rev motherboard is rev 6.when i turn it on i do not get any display,i wait for couple minutes and still no display.There appeared to be battery leakage but according to seller it was cleaned up and cured.i tried connecting to my tv with scart lead,and also tried A500 modulator but still no luck.i hope i can resurrect this amiga .is it true you can swap chips from A500 to test them?.

[deicidal]

Have you tried the monochrome video output on it? When you turn it on does it appear to work like disk access?

[JACK98]

hi,tried mono video,no display.no disk access either,doesn't sound good

[prowler]

Does it do anything when you switch it on? (Power or Drive Activity LEDs?)

If it's really dead, you should check the PSU rails with a multimeter.

[JACK98]

only get the power light which stays on and does not flicker or dim etc.no other response its a bare bones system so no hd etc.

[prowler]

But it has one or two floppy drives, right? No activity on those either, even with floppy disks inserted?

If you have a multimeter, at least check that there is +5V DC present between the brown and black wires on the floppy drive power connector(s) and +12V DC between the red and black wires.

[Jope]

If all the voltages are correct on the PSU connector, try changing the tick jumper on the motherboard.

[prowler]

Here are the A2000 PSU pinouts:
http://pinouts.ru/Power/amiga2000power_pinout.shtml

[JACK98]

good news friends.i had a suspicion and read from other accounts before that sometimes reseating chips can solve problems.i did this and happy to say my A2000 started up.thank you all for your contributions

[prowler]

That's great news, Jack! Well done, mate!

[deicidal]

Glad you got it sorted, really need to get back on top of my a2000 project

[JACK98]

is the sound low on these models?.i read elsewhere that the sound is low on A500's in comparison of A1200.there's no crackling noise symptom anything that on the A2000.but maybe im going deaf from playing music too loud

[source]

On the 2000 nd 500 there is a low pass filter that could be turned off and on with software. The power led would dim.

[Loedown]

When you pushed the chips back into their sockets the ideal way would have been to remove the A2000 motherboard and put it onto a static free flat bench, otherwise you run the risk of cracking the motherboard because you're applying pressure to the chips which aren't necessarily supported by the stand offs.

As the A2000 audio circuit is nearly identical, if not identical to the A4000 & A1200 circuits, they suffer exactly the same way as the afforementioned parts.

The audio circuit has a Vref or offset to the op amps, if this voltage isn't right then audio will be low too or non existent. This voltage should be close to or exactly 2.5V DC

[JACK98]

thanks all for reply's.sound is ok,tried another game.F17 challenge and the sound was perfect.so that software was bypassing the filter,game that was giving me low sound was rainbow islands

[Hewitson]

Originally Posted by Loedown

As the A2000 audio circuit is nearly identical, if not identical to the A4000 & A1200 circuits, they suffer exactly the same way as the afforementioned parts.

Dont believe this to be the case at all, unless you are not including the LPF in that statement.

[Loedown]

Originally Posted by Hewitson

Dont believe this to be the case at all, unless you are not including the LPF in that statement.

Sometimes I get the impression that you're always up for a verbal stoush

The circuits are very similar, only difference is that the A2000 uses through hole parts where the A1200 / A4000 are SMT

[Hewitson]

Originally Posted by Loedown

Sometimes I get the impression that you're always up for a verbal stoush

Thats not far from the truth

[Loedown]

Originally Posted by Hewitson

Thats not far from the truth

Behave yourself or I will unleash my Flamoooorz Mad Skillz on your sorry arse

Somewhere is a great diagram of what to expect and where in the Amiga 500 audio circuit, I have no idea of the link. With a CRO and the circuit you can't go wrong.

[Matt020]

Originally Posted by Loedown

The audio circuit has a Vref or offset to the op amps, if this voltage isn't right then audio will be low too or non existent. This voltage should be close to or exactly 2.5V DC

I have an A500 that has a lower volume level than my A2000 and A1200. Its not too low, its just lower...

What will cause the voltage drop from this 2.5v?