Found these inside a non-working 71B

[MikeSD]

(03-14-2018 09:49 PM)Dave Frederickson Wrote:  

(03-14-2018 09:15 PM)MikeSD Wrote:  What Ref is that? And which bank is it? The only 2 devices I touched are the on back right in the photo above, and the back left (Math), in the photo above. No other RAMs were touched.

Mike, you do have a copy of the schematics, right? They can be found in the H/W IDS and the Service Manual.

To answer your question, U9 is Port(0.3), but how do you know if that's where the issue is? If there were a short on U6 between DIN and DOUT, the Port(.01) RAM, then it may go undetected and U7 would be configured as Port(.01).

I think all you can be certain of is that only three of the four 4k modules were detected.

Dave

I have an old schematic in one of my docs. For some reason my IDS don't have a schematic or layout with refs.

I guess I don't know which it is then, except that only the 0.03 can't be configured. I guess it could be any of them then. The only 2 RAMS I touched were the U9 RAM (and I didn't solder directly to it) but the Math ROM was attached to it. And the RAM on the other side of the board, on TOP. Those are the only 2 RAMS touched.

I'll buzz them out and follow the daisy chain, to try and locate where the fault is. It was working before I put everything in the final place, so likely it's related to the last ones touched. U9 and the one on top, on the other side. I'll pick up with that tomorrow and finish the FORTH.

I'm going to bond down all the wires, where they connect to the board, to keep vibrations from breaking these wires. ONCE it's all checked out.