Dead Derringer 030 card

[darkage]

Hi All,

It seems my newly arrived CSA Derringer card is dead.. d'oh! :deadhorse

I have confirmed my 68000 cpu works fine, I've cleaned up the board with isopropyl, tested a number of 72pin ram (about 7 different types) even though I dont think this matters as memory is not auto config I believe, I've re-seated the 030 but I dont think this matters as well since the select jumper to pick the 68000 doesn't seem to work. I've tested with a multimeter to see if power is being supplied to the board which it is

Other than that I've tried everything, the only thing I can think of is reflowing all the joints with my smd rework station.

Tracks on the board seem fine but Im guessing this is a 4 layer board so not all tracks are visually inspectable.

Any suggestions?

 

[Zetr0]

if the jumper is not working that should give you a good indication to the faulty chip.

these cards use a simple cpu-hand-shake to swap CPU's, some might put this code in a GAL or PAL (tricky to get hex data for these), but some might use a simple logic IC (this being very repairable)

I would track down where that jump goes to and look at the problem from that position first.



I have reviewed some images of the card.... theres quite a bit of soft-logic GAL chips, as well as a lot of tantalum capacitors on there, it might be wise to check them out first.

 

[darkage]

I see your logic, makes sense to start off from the jumper that informs the board which CPU to use.

Yes there is alot of GALs on the board. I guess if one of them is dead then the board is impossible to revive as they contain locked code.

I thought you had to watch out for electrolytic cap's for aging. Do tantalum caps have a significant breakdown failure rate?

Im starting to think its a good time to buy a logic analyser, I always wanted an excuse to buy one.

I guess the first goal would be to troubleshoot electronically if its possible for just the 68k cpu to become responsive to the system and whats preventing it if not.

 

[rkauer]

In fact, there is little board that can read programmed PAL/GAL chips, but it is expensive and cannot read all types of programmed chips.

I'll post here where to find it, but if one PAL is knackered then the board is not useful.

[EDIT] here it is!

 

[darkage]

Whao thanks rkauer!

I never really dealt with PAL/GAL's before, except for learning about them in school many moons ago.

Looks like this will be my next board in my 'to fabricate' list. Fingers crossed the chips are alive.

In fact, there is little board that can read programmed PAL/GAL chips, but it is expensive and cannot read all types of programmed chips.

I'll post here where to find it, but if one PAL is knackered then the board is not useful.

[EDIT] here it is!

 

[rkauer]

If they are alive and can be readable by this lovely board my best advice is saving the contents of all chips and program a GAL device with the code.

PAL & GAL chips only reliably hold the program for up to 18~20 years. Also GAL chips don't dissipate much heat (PAL chips heats a lot) and then you'll have the hardware for many more years to come.

Save the Amiga hardware while you can!

Some years back I started spreading the capacitor replacement idea, now it's time to save the GAL/PAL chips.

 

[darkage]

Save the Amiga hardware while you can!

Hahah! I know the feeling now, after the dead accelerator and now what seems to be troublesome A590 *maybe dead*. I now know you have to be careful when buying these aging hardware oh:

I think my next course of action would be to build the PAL/GAL board and test each logic chip for functionality, at least thats the first step that doesn't involve alot of guess work. Straight forward check & test.

Cheers!

 

[rkauer]