Tuesday, June 16, 2015

Repaired 1053 part, repaired Pertec drive board but more problems remain


I picked up the 1053 margin rack latch part from Dynasty Jewelers this afternoon, after they used a laser welder to put the broken tang back into place. The craftsman wasn't certain it would stand much abuse, but I think I will try to reinforce the back by epoxying a piece along the tang, spanning the joint, as an insurance policy against breakage.

Bottom view of the part with the repaired tag at top left
Side view of repaired part with the tang and weld on the left
I epoxied a support metal piece behind the repaired tang. The repaired part is in place and I am adjusting the carrier return behavior.

Reinforced tang with black metal and epoxy


The parts appear to be arriving on Thursday afternoon, later than I had expected. I stopped by Anchor Electronics, since the parts were very low cost, picked them up today on my way to the mall to retrieve my repaired console printer part.

I installed the parts on the board, tested continuity of those repairs, put the board back into the drive and replaced the blown fuses. It was time to try to power this up again and attempt a startup sequence. However, even though the direct short I found is repaired, there is something else shorted, probably one or more other capacitors on other boards.

The power plug to the main logic board (J210) drops the resistance of the +5V supply dramatically, suggesting we have a short on the logic board probably due to yet another dastardly tantalum capacitor. There is also a big drop when J203 is plugged in, which connects to positional transducers and the positioner lamp assembly. This could be the incandescent bulb whose cold resistance would be low.

The plug J210 goes to the logic board but also passes through to other PCBs through J107. Yanking the passthru plug out still gives me a low resistance, so I will check out each board at a time. If I find more bad tantalum caps, I will probably buy a bag full of new ones and replace all the originals.


Richard Stofer helped me with a review of the Ztex documentation and site; we thought about how to get a loadable fpga bitstream onto the board so that it powers up with my logic design in place.  I have some steps to take, when I get a chance.


After a reader of the blog had mentioned the GenRad Bug Hound, I found one on eBay although not well described. This is often an opportunity to get a very good price, since potential buyers won't find it with searches. Indeed, this worked for me as I bought it for $5.50.

1 comment:

  1. I've never had good luck with epoxy on something like this. Since the weld will hold the part in position, I'd suggest cleaning across the joint well with sandpaper or similar to scuff it up and putting plenty of solder on all four sides. If you get too much, it's not a problem as it can be filed away. The solder would be stronger than epoxy in my opinion. You'd be surprised how strong even 60/40 solder is.