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weird AY160 problem
Hey guys.
I'm working on an AY160 that's got a problem I've never seen before. Whenever the box is in PLAY mode and the mech is scanning, it will trip and play random records that were not selected. There is no pattern to the random selections. The problem occurs even if the memory is cleared (using the battery trick) and no selections are made with the keypad. In fact, it occurs even if the big plugs for the keypad and the main tormat connections are unplugged. This leads me to believe that the problem is in read-out, and not write-in. There is one thing that makes the problem go away: Unplugging the sense loop connector from the pulse amplifier. With that unplugged, the mech scans the full rack without tripping. This led me to suspect the pulse amplifier. So. I've rebuilt the selection receiver, including the pulse amplifier. In addition to all new caps, I replaced several resistors that had drifted out of spec. The old 2050 and 6X4 had internal shorts, so I got new ones. The transformer puts out all the voltages it should. Could the OA2 tubes cause this problem? My understanding is that this tube is essentially just like a zener diode. Each shows a voltage drop of about 145 volts, so didn't think it necessary to replace them. Could it be the Tormat itself? I've probably worked on 30 or 40 Seeburgs and haven't seen a bad Tormat yet, but there's a first time for everything. Could it be the little transformer inside the pulse amp? It doesn't look broken or melted, and it has continuity through its coils -- but I don't know any way to test it beyond that. Demonic possession, perhaps? --- gruggy --- |
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#2
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weird AY160 problem
On Nov 3, 8:51*am, Gruggy wrote:
Hey guys. I'm working on an AY160 that's got a problem I've never seen before. Whenever the box is in PLAY mode and the mech is scanning, it will trip and play random records that were not selected. There is no pattern to the random selections. The problem occurs even if the memory is cleared (using the battery trick) and no selections are made with the keypad. In fact, it occurs even if the big plugs for the keypad and the main tormat connections are unplugged. This leads me to believe that the problem is in read-out, and not write-in. There is one thing that makes the problem go away: Unplugging the sense loop connector from the pulse amplifier. With that unplugged, the mech scans the full rack without tripping. This led me to suspect the pulse amplifier. So. I've rebuilt the selection receiver, including the pulse amplifier. In addition to all new caps, I replaced several resistors that had drifted out of spec. The old 2050 and 6X4 had internal shorts, so I got new ones. The transformer puts out all the voltages it should. Could the OA2 tubes cause this problem? My understanding is that this tube is essentially just like a zener diode. Each shows a voltage drop of about 145 volts, so didn't think it necessary to replace them. Could it be the Tormat itself? I've probably worked on 30 or 40 Seeburgs and haven't seen a bad Tormat yet, but there's a first time for everything. Could it be the little transformer inside the pulse amp? It doesn't look broken or melted, and it has continuity through its coils -- but I don't know any way to test it beyond that. Demonic possession, perhaps? * *--- gruggy --- Not really that unusual. If you look at the contact block on the mech that rides under the Tormat, you'll likely see sparking as it scans. This causes random pulses that trip the machine. Two causes: Corroded center contact rail (long flat piece between the individual contacts) Or worn grounding contacts that have lost intimate contact with that plate. If the plate is corroded you can attempt to clean it with some -mild- abrasives (crocus cloth) and check that the contact plungers are making solid contact.. With power off, pull down on the plunger block and see if the plungers have enough over-travel to remain in contact for at least 1/8 inch. If its just worn plungers you can raise the block by loosening the two screws that attach it to the mech arm and sliding it upwards slightly. Check also that the tormat has not been bent due to some asshole using it as a handle. You can eliminate the center contact plate by running a wire from it to chassis ground. If you do this, you should also disconnect the two plunger wires that touch it (middle of block) and insert a approx 3 amp fast blow fuse inline with the new grounding wire. Rob |
#3
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Quote:
I have also seen a worn clutch also give this fault. Regards Alan Hood ami-man UK |
#4
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weird AY160 problem
Rob -- Thanks for the tips! I had already looked at the contact block and tormat and they seemed okay, but I will give them more attention. That ground-wire trick seems like a good idea too; the center strip did look a little discolored. --- gruggy --- |
#5
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weird AY160 problem
I went back to this thing yesterday and got it working. On closer inspection the tormat contact plate was pretty grungy with old grease. Cleaned it, lightly polished it, and did the same for the contact block pins. It works great now! Thanks again to both of you for the advice. --- gruggy --- |
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