Hittin’ A Lick
I was down to the final issues on this SMC3 I’ve been working on for three months. One of them being a very common problem with the mechanism at rest, when activated, just goes the wrong direction. This one was doing that. Whenever the mechanism was at rest on the right side with the box turned off and then powered up the mech would scan left, reset, then back right to home. Selections were fine.However, if the mechanism was at rest on the left side when the box was turned off and then powered back on the mech would try to go left and hang up. I would have to turn the jukebox off, use a finger on the motor coupler and roll the mech to the right a few inches then power it back on. When I sell a jukebox to a customer it can’t come with funky directions in case this or that happens. At least not in this shop.
So, I thought I would order this new replacement PCC interface board that Victory Glass has recently came out with. I got it and all was good as far as the problem just iterated. Board looks good, is typical of today’s boards in that it is processor and software driven rather than TTL. All was right in the world until I turned the juke off while playing a record. Let me tell what is supposed to happen when that situation comes up. There is a small board in the CPA unit that will reject the record and then the mech goes merrily upon its way if the juke is powered on while in Play position. It does this because when the mech is powered back up with a record clamped it might be turning in the wrong direction for the record side in which case it will play backwards and never trip. I imagine it didn’t take too many operators hollering at Seeburg before they came out with the retrofit reject board.
I turned the juke off in Play position for some reason. When I turned it back on the mech tripped, I could hear it pop, but the motor did not spin up. It took several messages and a video to convince Victory what was happening. Turns out their reject board doesn’t work and they never thought to check for that particular operation. I was told he’d get right on it and find a solution. In the meantime another problem cropped up. The record position started coming up 3 spots off. If I played 160 the mech would pick up 163. If I put the Seeburg board in then the mech picked up correctly. I adjusted the detent point spacing and the new board worked fine for a day then went 2 spots off. Apparently the detent debounce circuitry needs work as well. Well, this was enough. No telling what other problems will crop up. I waited three weeks for a response hoping I would be sent a board that worked properly only to be told he was working on something else, no time for the interface board. This was time my customer had to wait as well as the box is sold. He has been patient as can be. Thank you Tracy. I’m sending the board back.
I take “hittin’ a lick” to mean I got something done well in a short time. The first “lick” was my original interface board. These interface boards can be a bear to troubleshoot in that I would have to drag the scope, meter, and schematic to juke-side and spend a lot of time signal tracing. There is a shorter way that I have touched on before. The time honored practice of “shotgunning” or just replacing chips willy-nilly. I did a little better than willy-nilly. Looking at the schematic for the PCC board I could see that the motor direction control was dependent upon the detent switch and of course the limit switches. These signals fed through U1,U4, U7, and then U3. A bunch of NAND and NOR logic gates. Basically all this is used for scan direction latch, scan control, and finally play control as to which direction the motor spins. I replaced these four chips as an educated guess and the board worked! No more off/on motor problem. This made me very happy. To say the least.
The second lick was the MCU3 I got off ebay for a song. I got lucky. No one else bid on it. The 3’s came out when Stern started making the SMC2’s and was used in all the SMC3’s. I manage to repair these MCU’s enough that this was a good chance to take. The case was clean, there was no battery acid damage which is practically shocking. I dis-assembled the three boards and went over them looking for problems. I tested the transistors, cleaned the legs on the processor. No real problems found.Clean boards. When I tried the computer the mech actually scanned and it reset to 00. Was I going to get this lucky????
No, I was not. I actually was able to make a few correct selections then the MCU went off the rails stopping at 100 and playing every record like a tormat that has been charged. Mick sad. Something was heating up apparently. I let a few hours go by and practically the same thing happened again. I have several of these MCU’s that I haven’t been able to repair but one thing I did do was check all their processors in one good MCU that I had so had a pile of good processors. Again, going through schematics I couldn’t find any particular circuit responsible for making a selection. It’s there, just couldn’t see it. So I did the next best thing and swapped the 40 pin processor out. And By Jimminy it fixed the MCU. Mick glad!
One more problem now that I got it running. The buttons and display were acting weird. Any buttons I pressed gave either a one or a five with only a few digits displaying. Luckily I have several working display boards which also house the selection buttons in the same pile of boards previously mentioned. I swapped in a good board and all is well. My $40 MCU3 is good to go. These are hard enough to find working. One can pay almost $400 for a Gen2 CPU and I have had to do that a few times. It feels sweet to add a working MCU to the stockpile. I hit a good lick!
My Seeburg Life 