Seeburg Jukebox Troubleshooting

Flippers.com

Click here to order Parts

index

sitemap

advanced

site search by freefind

The Google translation may have errors, the original information was in English only.
(If you don't see the Google Translate's "Select Language", then your browser is blocking google translate...so enable googleapis.com)

Seeburg Tormat Readout Testing

This is a Seeburg LPC series control center - the battery test using an AA (1.5VDC) battery with the negative of the battery to the clean metal chassis and tap the positive end of the battery with the tip of the Tormat Plug (RCA Jack). When done correctlyALL selections should be set and the machine should play every song. If the machine does not select and play at least two songs then let it scan and stop, do the battery test again, but do not start the mechanism.

For the LPC, which uses two Tormat Amplifers, you can use a Dual Trace Oscilloscope - connect the inputs to the capacitor going to the 2050 tube(s) and remove the tubes.

Set the scope to AC, about 20ms/div sweep, and 5v/div (adjust for your scope)

Now make any selection (you have pulled the 2050s I hope) and IF the amplifiers are both working correctly you should see something like this...

Schematic (PDF) showing normal voltages for a typical tube Tormat system.

Jukebox trouble shooting

Symptoms

When a selection is made, the mechanism scans, picks up a record, plays it, starts to put it back into the magazine, plays it again, etc.

When a selection is made, the mechanism scans, picks up the record, immediately rejects it, moves on to the next selection, picks it up, immediately rejects it, etc.

When a selection is made, the mechanism scans twice, picks up nothing, and stops.

The mechanism includes a �Safety Plunger�, to insure that damage to the record or the mechanism does not occur from a warped record. The Safety Plunger is mounted at the rear of the carriage, on the side facing the record magazine. When the record is in the process of being transferred back into the magazine, the Safety Plunger is released to move into the area formerly occupied by the record. A warped record will prevent this from happening, so the clutch cannot shift back into scan, resulting in the record being transferred into play again. This will repeat until the obstruction is removed or the power is turned off. Years of inattention, no cleaning and no lubrication will result in what lubrication is left turning into a sticky mass which prevents free movement of the Safety Plunger, duplicating the action of a warped record. The solution is to dis-assemble that portion of the mechanism (usually requiring that the magazine be removed to gain access), clean away the �gunk�, lubricate and re-adjust whatever was dis-assembled. The mechanism Operation and Adjustments manual for your jukebox does a very good job of detailing which adjustments affect others, and which adjustments must be correct before making another. Before attempting to clean up your mechanism, get a copy of this manual. It's available from: Always Jukin' or Victory Glass Before cleaning the mechanism, remove the motor, trip solenoid, cartridge, trip switch, and memory unit. Use a water-based degreaser followed by plenty of fresh water, and make sure it dries completely before doing anything else.

The mechanism trip solenoid is used to trip from scan into play and from play into scan. Thus there are two circuit paths to energize the solenoid, one for Select Trip and the other for reject (or Mute) Trip. There are wiring differences between mechanisms used in the various jukeboxes, so I'll refer you again to the manual for yours. Generally, mechanism switch 3M12 is closed in play to complete the record reject path from the amplifier's Mute Trip Relay. Another switch, 3M11, is closed in Scan and Transfer to energize the Mute Trip Relay, which mutes the amplifier so that all the clicks and pops of record transfer are not heard. If either switch is misadjusted so that both are closed at the beginning of record play, the record will reject as soon as the tonearm sets down.
Switch S1103 is the switch mounted to one side of the tonearm Cradle Frame. It closes when the tone arm reaches the lead-out groove of the record, to begin the transfer cycle to put the record back into the magazine. If this switch is shorted, or the cabling between it, the reject switch in the Volume Control Assembly, optional PRVC, or the Mute Trip Relay in the Amplifier is grounded this can occur. To check for this, turn the power off and manually put the mechanism in play with a record on the turntable. Turn the motor coupling until the tonearm just sets down, and rotate the coupling a few turns more to insure that the mechanism is completely in play. Use your ohmmeter set for continuity to check between the non-grounded end of S1103 and ground. If there is continuity, either a switch is misadjusted, or a switch or the wiring is shorted. To narrow down the cause, eliminate the amplifier/volume control from consideration by unplugging the Mechanism cable (usually a 6-pin orange connector) from the amplifier. If the short goes away, the problem is in the amplifier, volume control, or PRVC (a likely candidate). Otherwise the problem is in the mechanism.

The classic �scans twice, plays nothing� problem can be caused by the Tormat Write-In, Read-Out, or Trip circuits. We must eliminate two of the three possibilities, to determine which circuit has the problem. First, check the Write-In voltage (usually labeled 'Write-In Source' on the control center or selection receiver test terminal strip). For the digital machines (black/gray or red boxes), the voltage measured at this point will be about +125 VDC. For the solid-state machines, this voltage will be +395 VDC or +150 VDC depending upon model and number of selections. For the tube-type machines, this voltage will be -300 VDC. The Techie Stuff section of this website talks about how the Tormat works, so you should check it out before proceeding. If you measure significantly less than the correct voltage, check the Write/Read supplies in the control center or selection receiver. Given the symptom, it is probably reasonable to assume that the other supplies are functioning properly, but it doesn't hurt to check them, too. There should be test terminals for these supplies on the same terminal strip.

Disconnect the RCA plug sense loop connector from control center or selection receiver. Connect the negative side of a C or D cell battery to the center pin of the plug, while grounding the positive side of the battery to set all toroids to the selected state. (Note that if you use this procedure on a tube-type jukebox, you must reverse the battery connections.) Plug the sense loop connector back in and manually scan the mechanism. It should now trip at each record, transfer, and play it. Upon reject, the mechanism will move to the next record, and repeat the cycle. If this does not occur, the problem is in the Read-Out or Trip Circuits. If operation is normal, the problem is in the Write-In circuits, to be covered later.

Read-Out or Trip?

If the problem is in Read-Out or Trip, we must continue to eliminate one or the other. First, verify that the Read-Out timing is correct. Turn the machine off and disconnect the mechanism plug from the control center or selection receiver. Move the carriage to one end of the magazine, remove the records at that end and also remove the mechanism carriage cover. Set your ohmmeter for continuity and connect it between L1100 and ground. This is the inductor that is mounted to the Detent Timing switch next to the motor. Either side of the inductor will do and any decent ground should do. Slowly rotate either the turntable or the motor coupling a small amount and note which way the carriage moves. Now check the Contact Block Actuator slide or reversing switch (depending on jukebox model) to make sure that it is in the correct position for the direction of carriage travel you have chosen. Note that some models (most notably, LPC1 and LPC480) only perform Read-Out while traveling in one direction. For those models, make sure you are moving the carriage in the Read-Out direction. Slowly move the carriage until you get continuity, then stop. Now if you sight down between the metal record separators, you should see the Transfer Arm Head perfectly lined up with (centered on) the magazine record separator. If so, the timing is correct for this direction of travel. If not, fix it. There are several inter-dependent mechanism adjustments which affect this timing. They include: Magazine - Horizontal Position, Transfer Arm 1, Tormat Memory Unit Position, Read-Out Contact Block 1, 3, and Detent Switch. Any one not correct will make this timing incorrect. Perform this check at each end of the magazine and in each direction for those machines doing Read-Out in both directions.

Once the adjustments are correct, an overall indication of correct Read-Out functionality can be determined by connecting the correct polarity probe of an analog voltmeter set for voltage on the 200-400 VDC scale to the 'Read-Out Source/Read-Out Load' terminals of the control center or selection receiver. The other probe should be connected to ground. Plug the mechanism cable back in, apply power, and start the scan. You should see your meter dipping from the high voltage while the carriage is in the magazine area, and a steady high voltage (which should be approximately equal to the Write-In voltage) at the magazine ends while reversing direction. The dip occurs each time a toroid is read out. While in the magazine area, you should get a voltage reading of between one-third and one-half the voltage read at the magazine ends, with the voltages equal while moving in both directions. For the digital machines, this voltage should be between +55 and +60 VDC. Note that a digital voltmeter will not help here. If the voltage reading is constant, there is a broken connection between this test terminal, the mechanism Detent Timing switch, the contact block, the Tormat rivet connections, and ground. If you measure zero or significantly less than the Write-In voltage, the problem is in the control center or selection receiver power supply or wiring. If the voltage reading is off in one direction but not the other, the problem is usually caused by a bent or pitted contact block contact, or a misaligned Tormat. If the voltage reading is low or high in both directions, re-adjusting the Detent Timing Switch should solve it, but keep in mind that dirt or pitting on these contacts could result in a valid voltage reading but not enough current to Read-Out the toroids. If you are using a neon indicator connected in place of the shorting link between the 'Read Out Source' and Read Out Load' terminals of your control center, you can get a correct indication (neon lamp flickering) but no Read-out due to dirty or pitted contacts. If your box has the symptom that selects properly in one direction but not the other, and these readings are correct for the good direction and not the other, suspect a broken or mis-adjusted contact block contact for that direction. It is also possible that the contact block is not making contact on one side of the Tormat due to worn carriage rollers. If your readings are correct and there is still no trip, the problem is in the Trip circuit. Thanks and a tip of the hat to Ron Rich for contributing to this section.

Trip Circuit Problems

If you've gotten to this point, the problem is in the trip circuit. The next thing to do is to eliminate either the Select Trip Relay or the trip circuit, which may use either a thyratron or SCS as the active device. Unplugging the RCA plug and plugging it back in while the mechanism is in scan will usually cause a trip to occur due to the noise induced as you disconnect and reconnect the RCA plug. You should be able to force a trip by connecting the positive end of a C or D cell to the gate of the Trip SCS, with the negative end of the battery grounded. If this is the case, the Trip circuit is probably okay (check the input components to make sure) and the problem is most likely an open sense loop or intermittent RCA plug connection (see below).

The control center or selection receiver should have a set of three adjacent screw terminals, marked 'Read-Out Source', 'Read-Out Load', and 'Trip Relay'. Note that several of the 100 selection control centers do not have the 'Trip Relay' test point. The first two should be connected by a shorting link. Turn off the power and loosen the screws securing the link. Rotate the link so that it now connects the 'Read-Out Load' and 'Trip Relay' terminals, and tighten both screws. Re-apply power and manually place the mechanism into scan. It should now trip at each record, play it, go back into scan, trip at the next record, etc. If this does not occur, the problem is in the Select trip Relay, Trip Solenoid, mechanism switches 2M11, 3M1, or the associated wiring. If the trip/play/reject cycle functions normally, the problem is with the Trip circuits.

A very good possibility to check is the sense loop RCA connector, especially the ground contact between this connector and the PC board. If your machine uses the Pulse Amplifier, check the resistors and capacitors inside for changed values due to aging. Another possibility is a broken wire in the sense loop. For the solid state machines, check the resistors and capacitor in the SCS gate circuit for correct values. The sensitivity of the SCS gate is partially determined by its anode voltage, so check to insure that the SCS power supply (usually +27 VDC) is correct. For the solid state machines, check for a bad ground connection between the RCA jack and the control center chassis, and also check continuity between this jack and the trip circuitry on the control center PC board. Check for continuity between the RCA plug center pin and shield. This should measure no more than a few ohms. If you do not get continuity, the plug itself is the most likely culprit.

The Tormat has no moving parts inside, so theoretically nothing should go wrong. It is possible, however, that some of the wires may have gotten frayed over the years. If so, the most likely place is where the cables exit the Tormat. To gain access, remove the four screws holding the cover to the ends of the Tormat. The black plastic contact rivet memory block at the end opposite the cable exit is screwed to the metal baseplate using two screws. After you remove these and the screws holding the cover, you can gently remove the memory block, followed by the cover itself. Be careful that you do not snag any wires when removing or replacing the cover. Obviously, the warranty is no longer in effect.

Write-In Circuit Problems

Here's how to determine if you have a problem in the Write-In circuit. If your machine uses a remote control stepper and it can be bypassed, do so by disconnecting the Tormat cables from the stepper and connecting them together. Connect your analog voltmeter to the control center or selection receiver test terminal marked 'Write-In source' and ground, being sure to observe the proper polarity for your machine.

Establish credit and make a selection. You should see the voltage at this point momentarily dip as the write-in capacitor is discharged through the Write-In triggering device and the selected Tormat Write-In loops, followed by the voltage slowly building up again as this capacitor charges. If the measured steady-state voltage is significantly lower than the expected voltage discussed above, the problem is in the control center or selection receiver power supply circuitry, a leaky Write-In capacitor, etc. Try to isolate the power supply by unplugging the gray box (black/gray box jukes), Write-In relay (red box jukes) or Pricing Unit (all others). If the low voltage still remains, the problem is in the power supply. Otherwise the problem is in the Pricing Unit or selection circuitry. If the Write-In triggering device is shorted or some other current path to ground exists, or there is a problem in the stepper (if your machine uses one and you cannot bypass it) the Write-In voltage will go to some lower value once the connections are re-established.

Won't make any selections

If the Write-In voltage is correct but doesn't dip for any selection, the problem is in the triggering device, pulse-forming network, or the Tormat ground return. For the tube and non-digital solid-state machines, the triggering device is the segmented switch located in the Pricing Unit. This switch is closed as the subtract solenoid energizes. For the black/gray box machines, the triggering device is the Main Trigger Silicon Controlled Switch (SCS) located in the Gray box. The red box machines use a Write-In relay, located in the Phono Power Center. If the voltage never dips, this means that the Write-In circuit has not been completed to ground. Check the triggering device first, followed by the pulse-forming network. All machines use a network to shape the Write-In pulse. This circuit consists of several inductors, capacitors, resistors, and a voltage clamping device. The network is wired between the triggering device and the selection circuits and can be found in the control center or selection receiver for all machines except the black/gray box jukes, where it is in the gray box. The voltage clamping device will be either a diode or a zener diode, which clamps the Write-In pulse so that its amplitude cannot exceed one-half the Write-In supply. The tube-type machines use a diode connected to the junction of the OA2 regulators to clamp the voltage to -150 VDC. The solid state machines use either a diode to the bottom capacitor of the voltage doubler, or a zener rated at one-half the Write-In voltage. The final suspect is the Tormat ground return, which is typically connected through a temperature compensating resistor, located in the Tormat. Note that only some of the Write-In loops common to this resistor. Using your ohmmeter, check for 190 ohms (earlier machines) or 72 ohms (later) to ground through the pins of the Tormat connector which route the Write-In loops to the resistor. Here's where having the manual for the machine comes in handy. There will usually be a simplified Write-In circuit diagram which will identify which loops common through the resistor. If you get this reading on none of the pins, the resistor or the connection is probably open. Not getting the reading on one pin implies that loop is open. Keep in mind that the ground return to the control center or selection receiver is sometimes made through this same cable, so make sure you check for continuity all the way back. Also remember that some machines have a shorting link in the control center or selection receiver which completes the ground return.

Missing or additional selections

Successfully making some selections but not others indicates a problem in the selection circuits themselves. All non-digital machines use a latched push-button selector in which the depressed push buttons each complete a current path through the Tormat. Poor contact on these switches or the connectors between the selector and the Tormat could be the cause of the problem. Clean, adjust, and lubricate as necessary to correct the problem. The digital machines use SCSs to complete these paths, and there could be a problem in one or more of these circuits. They are located in the gray or red boxes, depending on type of machine. Remember that all machines must complete a pair of Write-In circuits (letter/number or (hundreds/)tens/units digits) for a toroid to be selected. If one path is complete but the other isn't, Write-In will not occur. Each of the two paths consists of the selection device, one or more cable connections between the device and the Tormat, the loop of wire through the toroids, and a common connection which either goes back to the selector or through the temperature compensating resistor, depending upon machine and selection loop. Any open or high resistance connection here can cause the problem. By making several selections, you should be able to see a pattern emerging which should lead you to the faulty circuit. For example, if you cannot make any selection with '5' as the number or units digit, suspect the circuitry associated with that digit. Latched push-button selectors have each button wired in sequence from the one before it. Pushing a button disconnects the circuit from the remaining buttons, redirecting the Write-In current to the selected circuit. Suspect a problem in the sequencing circuits (which are links between switches on the selector push button assemblies) if you cannot get any selection greater than a specific number or letter. Another possibility is that you get a different selection, or one in addition to the one you made. This generally happens only on the digital machines, and is usually caused by an overly sensitive SCS firing instead of (first case) or in addition to (second case) the correct one. My book gives a procedure to follow to determine the cause of Write-In problems in the gray box. If this problem occurs on the other machines, suspect a sneak path through the Tormat (perhaps caused by frayed wires inside), an incorrectly wired selector/Tormat (this should have been caught years ago unless someone has recently been digging into your machine), or a problem in your stepper. Perhaps the best way to track this one down is to (armed with the simplified Write-In schematic from the manual) check the continuity between the pulse-forming network, the selection device, and the Tormat to the common connection for each loop. For a 100 selection machine, there will be twenty such circuits; the 160 machines have twenty eight, and the 200 selection machines have thirty. Make sure you do this with the power off!