Go To:

Home page

Amp Repair

Amp Tubes





In the 1955 model year, Seeburg introduced the first all electronic selection system with the V-200. The system was based on the IBM computer memory design which was state of the art at the time. It worked by magnetically charging small coils of wire wound around a circular core. These coils and cores were called toroids. In fact, the system was called "tormat memory," derived from the name toroid.


There were no moving parts associated with this system other than a contact block that rode the bottom of the memory unit. To say that it was highly advanced for the time is a serious understatement! It caught the other manufacturers off guard. Of course, this wasn't the first time Seeburg made a quantum leap in jukebox design, but this one was big.


There was one small problem, though. Like the other manufacturers, it caught the operators off guard, too! Very few technicians understood how the system operated. Fortunately, it was very reliable (other than a few bugs in the very early machines) and the same system remained in use almost untouched for the next 20 years.


Which brings me to the ticking time bomb title of this column. There are actually Seeburg's out there that haven't been serviced since they were new. And that is really a problem because the system works at very high voltages. It has a power supply similar to an amplifier, but with one big difference: amps use a negative ground system, the tormat system is positive ground. It's easy to install capacitors backwards which will fry the power supply.


The real trouble is that few people realize that the tormat receiver MUST have periodic service. In fact, it's more important that it be serviced than the amplifier. The danger is the filter capacitors, and to a lesser extent the 6X4 rectifier tube. The caps start leaking, causing the current drain to rise. Eventually the caps short, and/or the 6X4 tube fails. This runs about 400 volts into a dead short. The fuse on the primary of the power transformer usually doesn't blow, so the transformer burns to a crisp. Sometimes you can actually watch the smoke run up the back of the juke! It's a smell you won't soon forget.


The transformers were readily available when the jukes were new, most will actually interchange. But next month we're already into 1999 and it's been over 40 years since the first ones were made. Now they're in short supply, and getting more expensive by the day. Soon, there won't be any more, and jukes with bad transformers basically won't be repairable.


The point of this colunm is to warn Seeburg owners: if you have a V through DS, you may be living on borrowed time. The safest thing that you can do is change all filter capacitors in your receiver now. At the same time, be sure to install a new 6X4 tube. This is the cheapest insurance you can buy. Heed this advice so your juke will continue to work for years to come.


If your amp needs service, you can count on the fact that the receiver needs service also. If you have repaired your amp, and didn't repair the receiver at the same time, do it immediately. The only warning that the system is failing is when it starts skipping selections, or plays too many. When it's getting ready to really cause problems, it will work for a few records, and then fail to select any more. The most dangerous situation is a juke that has been stored for over 3 years. Too many people will pull a juke out of extended storage, and actually plug it in without checking any of the electronic systems. This is what we used to call, "tuning for maximum smoke."


Think I'm overstating the situation? Last month I received 5 selection receivers for service that were un-repairable due to bad transformers and associated circuitry. That's 5 jukes in one month! Believe me, the owners didn't want to hear that it could have been avoided.


It is easier to keep an amplifier going, transformers are still in fairly good supply for them. Also, amps don't seem to fail as drastically as a receiver. The fuse on an amp is for the amp alone, but the receiver fuse is for the entire machine. If it were practical to fuse the high voltage section of a receiver I would recommend it, but the plain truth is that it just won't help. Only periodic service will do the trick. Next month I'll be discussing capacitor values in detail. I've had several requests lately to explain how and why capacitors are rated and marked. The newer numbering systems have confused many readers that do their own work. I'll make up a chart which should be easy to follow. Any questions? Give me a call during normal business hours and I'll try to help.