I’m working on a Bally -17 MPU that has been worked on before. Whoever worked on it before obviously lost several solder pads removing U10. He did a decent repair job except the socket he used is not quality. Sometimes it won’t boot past the 4th flash. If I press on U10 it will boot. I need to replace the U10 socket but the problem is he soldered most of the pads on the top side.

How do you remove sockets that have been soldered on the top?

Thanks

Bob

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Thanks guys,

I don't think a desoldering tool is going to work for the ones with the missing pads. There's nothing left to heat up except the pin itself. I think my only choice it to cut up the socket and remove the pins one at a time. Not a task I'm looking forward to.

Bill, BTW I modified my YiHua desoldering tool. I replaced the pump and worked on fixing every vacuum leak. I'm now getting over 23 inches Hg and it will hold a vacuum for over 60 seconds. It really makes desoldering easy now.

Thanks

Bob

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Thanks Bill, I tried heating the pin only (in most cases it was all that was left). It didn't work for me - but I'm not that talented. I tried cutting the pins with my snipping tool but I was worried I might be causing harm to the board. Next I shielded the board with sheet plastic, got out my dremel tool and cut off the pins and plastic housing. Then I could heat each pin and pull them out. Slow and messy work but I got it done.

That board is really in bad shape. It's going to take a lot of work to get it going again. Some pads are missing on both sides. If you don't hear from me for a while you'll know where I'll be.

Bob

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After a few days of stitching and jumpering I got the new sip sockets installed. I checked for continuity and shorts and all seemed fine. I installed the PIA and it didn’t boot. Sometimes I get one or two flashes. A couple of times I got several flashes. It did boot before when I messed with the U10 but I usually only got three flashes. I removed the PIA and re-checked all my connections. I found a couple of places that didn’t look right and cleaned them up. I even added a jumper where I thought it didn’t make good contact. Now (with the PIA removed) I’m only getting solid on LED.

I’m beginning to think the solid on LED in non-related to the U10 repair. If I had a short or bad trace at U10 (with the PIA not installed) shouldn’t I at least get a flicker then off?

I hate to give up on this thing – that would mean it won.

Thanks

Bob

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Skidave, slochar, I didn’t think U10 played a part in getting the first flicker so I think I must have a reset problem at this point. I believe my broken trace issues are resolved with the replacement of the U10 socket. The main problem with the original socket was it was cobbled together from pieces of several machine sockets. If you look closely at the first photo you can see the socket was 4 pieces of a machine socket that he cut the centers out and made into sip sockets. Some pin sockets are higher than others. The problem wasn’t so much flexing the board but was more to get all the U10 pins to make contact in the socket. In hindsight what I should have done was solder a new socket on top of the old socket.

Quench, I’ve used the light behind the board but I don’t see anything that looks suspicious. I now keep a halogen bulb on my bench for that purpose. I’ve also used my analog meter to swipe all the connections. Good eye on the possible bridge. I saw that too and checked it with a meter and it showed open – but I cleaned it up anyway. Yes, the trace repair is on the back of the board.

Budwin, That’s the method I used to remove the original socket. But I learned at my age not to trust my steady hands so I protected the board with 0.04 sheet plastic. Messy but it worked.

Thanks guys, I’ll head back down to the shop to find the reset problem.

Bob

I’ve checked several times and several methods for shorts or opens on U10. Everything seems to be connected properly. I’ve gone through every step on PinWiki. All voltages check and everything that should be pulsing is pulsing. I removed every IC except U9 and U11. I installed Leon’s test ROM and followed every step on PinWiki for the test ROM. Again, everything checked.

I then logic probed all pins on U10 socket. Pins 2 – 20 were all High – no pulsing. Pins 21- 40 seemed normal (either high pulsing, low pulsing, or high and low pulsing). Except pins 23 and 39. On those pins I got nothing – as if my probe wasn’t touching anything. I understand 39 is ground but shouldn’t the probe indicate low? And I’m not sure about pin 23 (CS). I check continuity on those two pins and they both have continuity to the proper trace but I didn’t check the schematic to find where those traces connect. Remember this was done with Leon’s test ROM installed.

Does anyone have any suggestions where to look? I’m lost at this point.

Thanks

Bob

Looks like we fixed another one. I don’t know why I was thinking pin 39 was ground – Maybe I was thinking U9 where I was also using the logic probe.

I know where I screwed up with pin 23 now. Pin 23 has traces on both sides (solder side and component side). I knew I had continuity on the top side (that goes to U11) but I didn’t check continuity on the bottom (which goes to U17). I knew I was on to something when pin 23 showed nothing on the logic probe but I didn’t check the schematics.

A quick little trace repair and it booted perfect.

Thanks to everyone for all your help – especially Quench for heading me in the right direction.

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