Mystic 478 Profit Setter fails test

[turbohobby7d]

I just purchased this gem for my wife, and have been cleaning up all sorts of issues. When doing the diagnostic per the service manual, when all the switches are off (A,B,D) the display responds as expected by counting to 99 and staying there. However per the next part of the process, D3 is switched to on, and the test button depressed, however the display then counts to 35 then resets and counts to 99 and stops. Any idea what component on the profit setter I should be looking at? I have had the board off and visually inspected it, also had to do a fair amount of cleaning to get all of the dip switches to work as expected.

Thanks in advance for your help.

[jukenorman]

Clearly there is some life there in that it's responding to commands. I'm not sure that much can be determined by what you've written, although I confess that I haven't gone to the manual to check. What happens when you use it, can you add and subtract credit, for example? Can you input a selection? You will have checked that the 9.6V supply is OK?

Norman.

[turbohobby7d]

Jul 29, 2024 9:13:36 GMT jukenorman said:

Clearly there is some life there in that it's responding to commands. I'm not sure that much can be determined by what you've written, although I confess that I haven't gone to the manual to check. What happens when you use it, can you add and subtract credit, for example? Can you input a selection? You will have checked that the 9.6V supply is OK?

Norman.

I am able to add and subtract credits with the buttons, as well as add credits with the coin changer. However when I make a selection it doesn't play, and doesn't remove a credit.

The machine will play both sides of the 5 selections when you run through logic board test.

[jukenorman]

For starters, if you look through the forum, similar type problems have come up before that might assist you. Other than that, you need to follow the operations sequences in the manual to discover where exactly it is getting stuck. For example, sequence 8 or sequence 9; it's all too vague at the moment to make any kind of judgement.

Norman.

[turbohobby7d]

It appears that I am stalled between sequence 8 and sequence 9.

[jukenorman]

LOL, are you determined to provide the absolute minimum of info? As a wild guess, you could replace the tri-state bufffer IC704 (MM80C97N) which would prevent the selection info being relayed through to the logic module. Note that it is a guess and although obsolete, it shouldn't be overly expensive.

Norman.

[turbohobby7d]

Thanks for all of your help thus far, and I apologize for my ignorance. My expertise is not electronics, but have plenty of experience in PLC'S and logic controllers for industrial equipment, and worked as a mechanical design engineer for many years. I know not relevant to jukeboxes.


If I follow the sequence of operations all the way through the completion of sequence 8 everything is normal. But that's where it stops.

Is testing the component you referenced the next step? If so I will research how to test it.

Thank you, Levi

[jukeboxmarty]

Ignorance? I think not! It takes time to grasp the correct terminology and methodology required to repair these things.

We just need to gather enough information so we can point people in the right direction.

The profit setters are not my strong suit, so I'm probably not the one to help you... but if Norman has the info he needs to guide you along I'm sure you'll make some progress.

[jukenorman]

Hi Levi,
If you have worked on PLCs, the you will have knowledge of logic states which probably gives you a good head start over a lot of people! I have very fond memories of the Texas Instruments 5TI - is that before your time? Anyway, there are a number of things you could do. If you searched the forum, you will have noted that poor solder joints are a common problem in these jukeboxes so you could look at that.

A nice simple check for you - the same chip as profit setter IC704 is used in logic board IC403. If you install that in the profit setter and it runs the self test, then you have identified the problem.

Other than that, it's mainly checking logic states with a logic probe. The hot circuits are marked on the schem-a-grams.


Norman.

[turbohobby7d]

Evidently I've spent too much time on the farm lately. Like a bull in a china cabinet I broke the component taking it out of the logic board. Thankfully just one pin on the component itself, not the board.

So now I wait for a new one to arrive.

Thanks for the help thus far.

[jukenorman]

Oh no, that's unfortunate! It wouldn't have been quite so bad if you had trashed the one in the profit setter that we thought might be suspect! How pessimistic were you; did you order two? I actually have a little special tool for removing these ICs although I never seem to use it!

Norman.

[turbohobby7d]

I ordered plenty! Lol. The only ones I could find that were in the United States, and didn't seem sketchy to order was a batch of 20. The price was low though. $25 with shipping I believe.

[turbohobby7d]

I guess I should rephrase my statement, I was able to swap it in the profit setter, however I got no results, display was dead. So I put the pieces back where they were initially removed from to re check, and went back to my original scenario. It was the second time I removed it from the logic board that I broke it.

[jukenorman]

I cannot see how that chip affects the display - is the 9.6VDC (pink wire on the plug from the power supply) OK?

Norman.

[turbohobby7d]

Voltage is good on the pink wire at the power supply because that's where I checked that I had exactly 9.6v. I can check it at the other components as well.