Troubleshooting a Gray Box

Today I fixed a problem that has been bothering me for over a year. My good ole test box, the STD4, had an intermittant problem of not selecting any 200’s. I thought variously the fault lay in the gray box, black box, Digital Control Center, either of the two large boards in the Digital Control Center or a wire problem going to the DCC. I even got different results depending how cold it was. Last winter when I did work in the garage doing testing I couldn’t get any 200’s. This will play out as we will see.

I would swap something out and seemingly fix the problem. I am lucky to have known good components to be able to swap with. It is normally the fastest approach to getting a problem down to a unit. With intermittant problems it takes time, patience, and sometimes luck and even then it is frustrating. But, then the problem would crop up again. I thought I traced it down to internal wiring in the DCC chassis once. That chassis is still laying by the juke as I replaced it with another chassis to observe. I swapped out the complete board set in the DCC more than once and came to the conclusion it sure wasn’t the boards. Same with gray box and black box. Did I have bad tormat wiring?

Sometimes there was no problem. It got so that whenever testing units such as the black and gray boxes or different DCC boards that I would hit 266 first and see if it picked up. If it did then I went about my normal numbers selections for testing.

I have been testing refurbished and repaired black and gray boxes a lot the last couple weeks. A few days ago when I went through the stacks picking out gray boxes to refurbish I found a finished, sealed one! Did I put it back in the stack because of a problem? Dunno…normally I’ll put a piece of tape on it with a brief explanation of the problem. This one wasn’t taped. So I put it in and no 200’s! ???? I tried another gray box and it picked 200’s. So I marked it and determined that whenever I tested gray boxes I’d test this one as well and see if this particular gray box had a problem or perhaps something else.

Today was gray box time. I had two board sets I finally got clean cases for and needed to do final testing. I tear the gray boxes down and give the boards a visual inspection, clean the terminals, re-assemble them bare and test in the jukebox being sure to insulate these bare boards. Once any issues are repaired and they pass with bare boards then they are cased back up with the screws installed and tested once more fully assembled. If they pass the seals go on and they are stacked up for sale.

I installed the first gray box, hit 266, and no 200’s! Hit 222 real quick. No luck. I popped the next gray box in and had 200’s!! I started moving the cable and gray box around. When I lifted it about a foot above the mechanism shelf- no 200’s. If I laid the gray box flat-200’s. If I turned the gray box on its side no 200’s.

The gray box or Digital Receiver Decoder accepts selection information on the four data lines from the black box and the control center. It determines whether the selection is a left or right side ( 100 or 200 ), which group of tens, and of course, which record in that group of tens. It charges the tormat for the selection made, triggers the write-in pulse and pulses the play or scan control add coil sending the mechanism on its merry way.

OK. I broke out my gray box schematics and started looking. Examing the pinouts for the upper board revealed nothing that could be so specific. Looking at the bottom board pinout was a different story. Here are all the groups of ten labelled 0-7, all the unit digits from 0 to 9. Pin 10 is labelled Hundred Digit 2. Pin 9 is Hundred Digit 1 incidentally. I pulled pin 10 and immediately saw the cause of all this trouble. I don’t know how it happened but the wire right at the crimp got cut, pulled, or squeezed. The plastic insulation was barely hanging together. The wire strands had been cut. Here’s the rub…..when the wire lay flat or not pulled away the cut ends butted together and provided enough contact to be able to select 200’s. The temperature difference? It had to be that the wires contracted just enough when it got cold enough to not be able to make contact. I made sure to examine the other wires for similar damage and found none.

These are very special pins. Seeburg used them in all their flat molex connectors including the SHP amps. I’m down to less than five new ones I bought 20 years ago. They are for when a new pin is really, really needed. They are called some kind of aviation pin and are ridiculously high. I mean dollars for a single pin. I chased them down last summer and have forgotten their name. I have several flat molex connectors with 2 inch tails from tearing down old chassis for just such a need. I pulled a used pin and soldered it in place on the number 10 wire. I made sure the tang was up and inserted it. Problem fixed.

The chassis that has been laying by the jukebox for a year? It’ll get dusted off, re-populated with boards and make someone a very good replacement. The gray box that somehow wound up in the waiting for repair stack? It’ll still get tested for awhile. I’ve seen gray boxes not pick up one certain number before. When this happens the fault is in the processor on the upper board. I’ll test this gray box long enough to be certain it is OK before I offer it to anyone.