emulatorII-list

Found it! It looks like a previous "repair" killed my E II. IC71B has at some point been replaced and a pair of SIL strips soldered in as a socket - for some reason this row of ICs was not socketed on my board. There was a blob of solder between two pins and a couple of lifted pads. I have replaced the socket and made a start on running some wires under the board to deal with the pad problem. There is also some very iffy soldering around the capacitors between IC93 and IC94.

A couple of bypass caps were cracked, but not shorted, though I will replace these too. I'll probably go for a complete recap at some point, but I want to get it running first.

From what I have seen, the E II did have a bad channel, but the "repair" could never have worked as it created a dead short between -15v and GND! I guess this is probably what finished off the PSU.

One more thing. IC65A has at some point also been replaced and socketed (though without the awful soldering), but the chip itself has had every pin on one side broken and a wire lead soldered in it's place. I'm not convinced about the health of this as it almost fell out of the socket when I removed the PCBs...

Kevin


--- In emulatorII-list@yahoogroups.com, "kgslug2" <kevingibson952@...> wrote:
>
> OK, so I now have a working PSU, onto the next problem! There appears to be a dead short (0 Ohms) between -15v and analogue ground (the black and blue wires in the power loom). Having unplugged the digital board I have traced the problem to the output board. Now I need to work out where on this board the problem could be.
> 
> Does anybody happen to know of any component that is likely to fail short across these two rails? I suspect a tantalum capacitor, cut there are quite a few of them...
> 
> I also note that there are quite a few kludges on my board - capacitors wired in series and piggybacked onto resistors. Is this normal?
> 
> Thanks
> Kevin
>