Jaguar hardware fault

[zx81]

Hi all, new guy here!

 

Was wondering if anyone could help me with a problem I'm having with an Atari jaguar.

 

I bought a faulty Atari jaguar off eBay.. it was reasonably cheap compared to a working or boxed one! It was pot luck the guy had a bunch of them with different faults (old shop returns apparently).

 

So when it arrived there was a sticker on the bottom which said "no sound" great I thought! It'll just be a reg1 replacement.

 

We'll things are never that simple, so I power it on and checked the output of the u38 switch mode supply. 5v great, reg 1 also 5v .. but still no sound.. I break out the the ocilloscope to check the DAC is receiving data. And that's when it all goes pair shaped.. nothing but noise was coming from the DAC and that's when I burnt my finger! The game also crashes / freezes after a minute or so.

 

The DSP (jerry) is overheating.. There's also a buzzing noise which goes away after 20-30 seconds. I initially thought it was the inductor for the switch mode supply but I think it's the DSP.

 

There's a lot of connections too and from the DSP is there anything that could cause this or is it a faulty DSP? Is it a common fault?

 

Any help would be appreciated!

 

 

 

[Zerosquare]

Never heard of this issue.

 

Could be a short-circuit on one of Jerry's outputs (tedious to trace).

 

You could replace the chip, but they are neither cheap nor easy to (de)solder and there's no guarantee it'll fix the problem:

http://www.best-electronics-ca.com/custom-i.htm (bottom of the page)

Edited May 20, 2017 by Zerosquare

[zx81]

Never heard of this issue.

 

Could be a short-circuit on one of Jerry's outputs (tedious to trace).

 

You could replace the chip, but they are neither cheap nor easy to (de)solder and there's no guarantee it'll fix the problem:

http://www.best-electronics-ca.com/custom-i.htm (bottom of the page)

 

Thanks for the reply and the link to the parts! I did not think that this part would be available.

 

I checked continuity between ground and VCC at several points on the board, there does seem to be a short I'm getting 19 Ohms of resistance between VCC and GND so I'll need to investigate that, oddly though there's no short on the Audio parts of the circuit (Reg1, DAC or the amp stage)