Fault Finding - Seeburg

Seeburg did things a little differently to others and so the first thing that you will need is a service manual for your model and then some spare time and alot of patience .

Scans Twice and Stops

One fault that often occurs in a Seeburg is that the carriage scans twice and stops without playing the record that you selected. As always you must check that all plugs are seated correctly and all valves (if there are any) are lit up (the 5u4g only lights when the mechanism is scanning). Check that there's a purple glow in both type OA2 valves: no glow can be caused by a weak 6X4 valve in electronic selection models. If no trouble is found and the service switch is in the play position, make sure that the machine has several credits logged in and proceed as follows. On the back door of your (50's) machine are two chassis (not KD) . The Left hand (door open) is the Tormat Selector Unit (T.S.U.) and the right hand the amplifier. For exact locations and positions of valves etc.you should refer to the service manual for your particular model  of machine.

On some models about halfway down the T.S.U. is a long thin cover which,when removed, reveals the "test terminals" lettered A-H - usually situated near the "pulse amplifier". Remove the terminal cover as you will need to use these terminals to help you establish the location of the fault.

Remove the memory unit output plug from the pulse amp. then connect one end of a 'jumper' wire to test terminal C leaving the other end free.

Make any selection and ,while the mechanism is scanning,  momentarily connect the free end of the lead to the input of the pulse amp, making sure that you connect with the centre of the socket.

The mechanism should immediately trip to play. If the mechanism does not trip to play this could mean that you either have : 1. A trip fault or 2. A pulse amp fault. The obvious way to test for this is to replace the 2050 trip valve and/or the pulse amp 12AX7.They are the two most consistent offenders although any of their associated circuitry could be at fault.

One neglected capacitor by the would be restorer is the 0.05mfd inside the pulse amp.  - worth changing!

However if the mechanism did trip, reject the record and let the mechanism scan to a standstill. Remove the jumper wire from C and carry out the following :

Momentarily connect the tip of the memory unit output plug to the positive of a good 1.5 volt battery with the case of the battery held against the corner of the pulse amp (i.e. negative to earth). This simulates making all selections on the tormat. Replace the memory unit plug into the pulse amp input and make any record selection. When the selection is made,regardless of number/letter, the mechanism should immediately trip and play. If so , reject the record and check if the next record plays - the battery has effectively made every selection and all records could be played if desired. If the mechanism trips on at least two records pull out the memory unit input plug, reject that record and allow the mechanism to scan and stop before replacing the plug again.

You now know that the 2050 trip is working , the pulse amp and both OA2 valves with the 6X4 are also OK.

Consulting the manual for your machine will tell you the position of the "Universal Pricing Unit" this is what Seeburg call their credit unit. Remove its' cover to check that the relays and trigger switches in it are clean and their contacts are functioning correctly. It is also worth checking the relays and contacts in the Stepper unit if there is one. The relays known as timing relays are worth a check as just one contact not making on these can also cause a 'write in' fault.