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Amp Tubes





Is there any way to disable the automatic volume control on my Wurlizer 1900?  The volume runs up and down and is very annoying.


On all Wurlitzer 530 and 532 amps, the AVC is controlled by a 12AX7 tube.  Simply unplug this tube and the volume will remain steady.  It is located in the center of the PC board.  Make sure that you do not unplug the 12AX7 closest to the 6L6 tubes, just the one in the center.  Leave it out to cure the trouble.



I bought 4 new 6973 tubes from a mail order supplier for my AMI Continental 2. It now sounds worse than it did!  I put the old tubes back in and the sound was much better.  What's going on here?


Recently I had an amp similar to yours come in for repair.  The customer had also bought 4 replacement tubes.  Just for the heck of it I checked the tubes.  They were NOT 6973s.  The company he bought them from had re-labeled a cheaper tube and sold them as genuine 6973s.  To use the cheaper tubes, a jumper wire must be installed on the tube socket between pins 1 and 8.  The replacements do not have the same internal connections as the genuine ones.  If you have the same problem, the jumper wire should fix your trouble.



I have a Seeburg 222 with a known good amp, I tried it in my Q-100.  In the 222, one channel is dead.  All wiring from the tone arm to the speakers is good.  Why do I have a dead channel?


You have a stuck or dirty mute switch on the mech.  There is a mute switch for each channel, and one of them is either not opening when the mech goes into the play mode, or is covered with dirt or oil.  Clean and adjust the mute switches and your trouble will be cleared.  By the way, do NOT spray ANYTHING on the switches as this may make the trouble worse!  Clean them with a burnishing tool only.



I have a Seeburg KD.  Someone told me recently that this machine might catch  on fire!  Is there anything to worry about?


Of course, anything electrical can potentially develop a short circuit and create a fire hazard.  What I suspect they were talking about are the printed circuit boards used for the amp and selection system.  When the K and L models were designed and built, printed circuit boards were a new technology.  They couldn't forsee what might happen 10 or 20 years later.  The boards are porous, and will absorb moisture.  Also, they are very brittle and heat sensitive.  Often the boards will break down so badly that they start conducting, and this is when the trouble starts!  I have seen several boards that have actually blazed up.  The 2 boards that give the most trouble are the TEU and PAU.  It's always a good idea with any jukebox to never leave the room while they're turned on.



How can I eliminate the automatic volume control on my Seeburg C?


Assuming the amp is in good condition to start with, simply unplug the 6SK7 tube. The same holds true for any Seeburg mono amp through the J.  Or you can remove the .06 cap running from the 6SK7 tube to the 6SN7.  If you have the ability, this is best because unplugging the tube does not disable the entire section.



I would like to connect my Seeburg R to my home stereo system.  Where and how do I tie into the jukebox amplifier?


This isn't difficult.  First remove the back door cover to expose the amp.  Find the mute plug socket, a round 3 pin near the input.  Look carefully at the wiring on the socket.  One is connected to ground, pin 1.  Connect the shield of your cable to this pin.  The center conductor of your cable connects to pin 2.  There is also a 560K resistor connected at this point.  This will be a mono signal, you will have to jumper to both channels on your remote amp.  Most Wurlitzer and AMI amps have an auxiliary output socket mounted on the amp itself.



I have a problem with my Seeburg G that is driving me nuts.  Anytime a record is playing there is a loud hum through the speaker.  When the record rejects, the  hum increases briefly then goes away.  I have tried everything that I can think of and it is still there.  All cables are good and there are no loose grounds.  Where is the hum coming from?


This is a rare problem with an easy fix.  You have a bad mech trip coil.  It is close enough to the tone arm to create a strong enough magnetic field for the cartridge to pick up and send down the line to the amp.  Change the trip coil and it should clear the problem.



My Wurlitzer 1800 occasionally makes a crackling noise through the speaker. I've changed tubes and checked all wiring, but nothing has helped.  It only makes the noise while actually playing a record.  What do I need to do?


You probably have a bad cobra cartridge, or the socket that the cartridge plugs into has corrosion on the pins.  First try another cartridge, but you may have to clean the pins on the socket.  Sometimes the socket itself will have to be changed. If this doesn't clear the trouble, the amp itself is causing it.



I have an AMI F with the original GE cartridge.  I need a new one and have found out that they are not available anymore.  What can I use to replace it?


You have several choices here, but they are all stereo cartridges and will need to have both channels tied together to make them mono.  Use either a Shure M44 or a Pickering NP/AC.  Either will work well in your juke.  Just make sure that you  check the stylus pressure as they track lighter than the original GE.



My 1900 sounds great on old 45s, but when I try to play a newer record it sounds distorted and skips.  What can I do to make it play newer records?


The short answer is not much.  The cobra cartridge was designed for use with 78 rpm records which are much easier to track.  When the 45s came along, the early ones were all mono and Wurlitzer just continued using an obsolete cartridge.  The best thing to do is install a stereo tone arm from a later model Wurlitzer and modify the amp to accept the ceramic type cartridge.  You can then play any 45 you have.



My Seeburg J will lose it's sound halfway through a record.  I opened the back door and saw that the 5U4 tube was going out.  I changed the tube but it made no difference.  How can I solve this?


There is a 4 pin plug on the side of your amp that plugs into the selection receiver. Loosen the 4 mounting screws on the amp and slide it far enough to the side to expose this plug.  Clean the pins and plug it back in.  If this does not cure the problem, you may have to change the 5U4 tube socket.  This is not a difficult item to find, any older TV/Radio shop will have them.



I have a 1600 Wurlitzer with a strange problem:  the top tone arm is louder than the bottom.  Sometimes the bottom tone arm will crackle and pop.  I thought that both were connected to the amp, why is one giving trouble?


There is a small microswitch on the mech that switches back and forth between the 2 tone arms depending on which side of the record is being played.  It is bad and will need to be replaced.



I recently replaced the cartridge in my AMI JAN with a new one, and now I have no bass!  Is my new cartridge bad?


No, you have it connected wrong.  One channel has to be out of phase with the other.  You have a red and black wire for each channel.  Connect a black wire to ground and a red to hot on one channel, then a red to ground and the black to hot on the other.  This will solve your problem.



                                      AMPLIFIER INTERCHANGE LIST


SEEBURG:The field coil type amps will interchange.  A short list includes the A, B, C, G and W.  The non-field coil types will interchange, such as R, J, JL, V, VL & 201. There may be slight mounting differences.


WURLITZER: You are really limited here.  The 530 and 532 will swap.  You can use an amp from a 1700 or 1800 into a later model, but not the other way around. The 501 and 503 are a direct swap, the 800 amp is unique.


AMI: The C, D and E will swap.  The F through I are the same.  Some of the later stereo amps will swap, if they will plug in they will generally work.


ROCKOLA: The 1422 and 1426 are the same.  The 1428 is unique.  Generally on the later mono amps, if they will plug in they will work.