Fault Finding

With the recent surge of the 'do-it-yourself' type of enthusiast it has become apparent, from the many phone calls received, that some people find fault finding on a juke box confusing - it is actually just a question Of methodically working through the different systems present in a juke box. A jukebox has three basic systems : Making a selection, Playing the selection, and The Sound.

The Sound

The sound can always wait until you have the mechanics working correctly. Best thing to do is disable the amplifier before you switch on and then you will have oneless thing to worry about going up in smoke.

It is also worth considering having your amplifier rebuilt by an expert, like myself, particularly valve types which are now of an age that they could really do with a complete job and not just a couple of caps and the odd resistor changed.

How to disable your amplifier depends to some extent on the make/model. The easiest way is to simply remove the H.T. rectifier valve. You can, on some models, simply pull the supply lead to the amplifier, but this can sometimes lead to a problem if the amp is also supplying the low voltage to the mechanism ! Thought does have to be given - get a service manual it should help, even if it is only when you phone someone for a bit of F.F.A. (free friendly advice) !

The Mechanism

So with the amplifier not worrying you it is now time to look at the mechanism. First you have to understand that the machine is designed to take money. You are not allowed to operate the machine without establishing A credit and this is done by inserting a coin.

The coin is detected by the coin mechanism switches and sends an electrical pulse to the credit unit which can also be called credit accumulator or pricing unit depending on the manufacturer.

The credit unit will not allow you to make a selection if it has no credits established back in the day it was 'No pay - No play'

So it is an important consideration when trying to make your selection - you can put most machines on to free play or manually clock up a credit or two - usually done by locating the add coil (or CREDIT SWITCH) and manually operating it.

This done then you may try to select. If not satisfactory then check that the mechanism can play the selection or as it is often referred to - 'read-out'. To check this you must find a way of starting the mechanism without the pushbuttons being involved.

If this can be achieved then you must also find a way of faking a selection. In Wurlitzer both operations happen simultaneously : each selector pin represents the side of a record and if one of them is made to 'pop-up' this also starts the mechanism motor to turn to that pin.

Pre-Tormat Seeburgs have a similar system but with a start switch separate .

RockOla generally have a start switch arrangement that has to be activated before the machine will scan to look for the selector pin and our dear old AMi also has its' scan control assembly in most models for exactly the same reason.

By establishing that the machine will 'read' the selection and hopefully carry on to the play position you will have demonstrated that at least half the machine works.

You can then concentrate on making the selections? or 'writing' them in via the button bank. I hope that you can appreciate how confusing it could be if you do not establish what is or is not working as most of the time we are looking at the symptoms of the fault(s) rather than at the fault itself.

By establishing that the machine will 'read' the selection and hopefully carry on to the play position you will have demonstrated that at least half the machine works. You can then concentrate on making the selections or writing them in via the button bank.

All juke boxes operate in this way although the actual hardware is different between manufacturers. Before you give up and phone for advice : Get your self a service manual !

Try to find which parts are working by some very basic work. If you can't get your head round it get someone in who can - you know it makes sense.