Seeburg not selecting

Hi Ron

I'm not sure how to know if the relay energizes or not?

I cleaned 2M1 and checked it was making good contact.

If there was an open circuit between 2M1 and the relay would that not have stopped the 12 volt relay from working?

I plugged the 12 volt relay back in (naughty), just to check what was happening. As soon as the carriage hits the selected record slot the relay trips. With the 24 volt relay, the relay does nothing as the carriage moves past the selected record slot.

Keith,
Remove the relay cover, as above--open your eyes, and you can see if energized or not---Do not operate the 12 volt relay in that DCC, --you will burn it up !
Ron Rich

Okay, then I would have to say no - it is not energized, as the relay is no different when the power is on or off, or whether the jukebox is scanning or not. There is 25.7 volts at the two wires going to the coil, but the relay never moves.

Keith, looking at Pg 25 (pdf doc I linked) The simplified "sense and trip relay" diagram shows that if you short Tp-1 of Tb3100 on a DCC42 (27volt source) the trip relay should actuate.

I would first try this with the original relay installed. If mech does not trip suspicion falls on:

10 The 150 ohm resistor -or whatever value may have been subbed.

2 )The relay coil itself.

3) A sagging voltage from the p.s. -In this case measure the voltage across the relay coil itself while tapping Tp-1 to ground as above.

If the relay trips and mech coil actuates as normal you are now looking for a sag in the SCS circuit. Check the resistor values there.

You are correct in that since the mech trips with a different relay installed, that removes all suspicion from the TM contacts and other intervening connections.

Rob

Thanks Rob

I shorted Test Point 1 on the test strip and the relay tripped.

I am not sure which resistors I should be looking at for the sag, or what the values should be. Are they in the Grey Box? If so, I could swap the Grey Box from my SQS160 if it is the same.

Keith, the trip relay and SCS circuits are shown as integral to the main power supply board in the DCC. That is under another board on the side nearest the test points on the front of the unit.

Again, look at pg 25 on the manual-PDF. The circuit is extremely simple and if no mods have been done, troubleshooting should be straight forward.

The grey, black boxes have no involvement here.

Rob

I think I'm lost, really lost....

I have tried to check as many values as possible from the diagram on page 25 for the "Sense & Trip Relay". All the measurements I did seemed to match pretty close to the same measurements on my SQS160. I even swapped the Power Supply Board to eliminate all those components, but it didn't fix the problem.

I'm wondering if it will be best to swap the whole DCC with the one from my SQS160 or my STD4. This still won't tell me what the fault is though.

Keith,
I only have one question for you--is the relay energizing when it scans past a selected space--or not ?
Ron Rich

Thanks for your reply Ron.

I'm pretty sure it is NOT, but just to be certain I will double check that the next time I'm in the shop.

NO, the relay DEFINITELY does NOT energize.

Keith, I imagine this is frustrating 'been there. It points up the shortcomings of trying to do remote troubleshooting. If I had the machine in front of me we could have solved this in a few minutes.

Based on what you have said so-far, the "wrong" relay (12V) works in this circuit so, let's try something down'n dirty.

Before we do that, test the impedance of both the 12V and 24V relay's coils. If you have not already, check the 150 ohm resistor in series with the relay coil (R3191). I believe you mentioned earlier that tapping the trip test point (Tb3100) caused the mech to trip with the 24 V relay but this does not include the slight resistance introduced by the SCS and an off value R3191 might just lower it enough to be unreliable.

Connect your meter to the two terminals on the relay socket that go to the relay coil. Place the 12V relay in the socket, make a selection or use the battery test. When the mech trips quickly check the voltage at the relay coil. You'll only have a few seconds before the voltage is cut be the mech.

Now do the same with the original 24V relay in circuit. The voltage should near the spec'd 24vdc.

The reason I suggest trying first with the 12V relay is that an open coil on the 24 volt relay will not provide enough load on the SCS circuit to give an accurate reading.

If Ron can chine in with the correct coil impedance for the relay, that might solve some of this.

I wouldn't be shocked if someone put the wrong relay with the right cover in there. This was fairly common with the relays on the Rowe steppers. the covers would be removed to de-pit them and placed back on the wrong relays. If I were prone to drinking, that would have done it.

Rob.

Thanks again for your great input Rob,

Funny you should mention that 150 ohm resistor (R3191), of all the components on that circuit diagram from page 25 that resistor was the only one I couldn't find. Do you know where it should be located physically?
Because I couldn't find it I measured from test point 5 to the relay and got a reading of 17.8 with the meter set to 20k ohms. If I can locate that resistor I will test it directly.

I also need to test the battery in my meter, as I know that can have a huge affect on ohm readings.

Keith, it sounds to me like you need to get a decent, basic digital multimeter. These are available at places such as Radio Shack for $25 and up. If you feel the one you have is OK with new batteries, I still suggest you buy some resistors to test the resistance ranges. Get the following values: 10 ohm, 100, 1000 and 100,000 and I megohm. this will only cost a few dollars and allow you to verify with reasonable accuracy, the resistance scales in your meter. Rat Shack sell 10% tolerance and they are usually much better than that -adequate for this sort of work.

As for the 150 ohm resistor, from the diagram it would seem to be on the mainframe and not on the P-S board. I have not had one of these sets in over 20 years so..not the real expert here.

Again, have you measured the coil on the 24 volt relay? Probably best to wait till you have proofed your meter.


If you measured 17.8 K-ohms from the test point to the coil terminal on the relay, I suspect your meter is -way- off, -with that amount of resistance in the circuit even the 12V relay wouldn't not work with only 27V supply.

Rob

Keith, I may as well explain where I'm going with these tests.

I suspect that the 12 volt relay is correct. Here's why; If the supply voltage is around 27V and the relay coil is in the vicinity of 150 ohms with the 150 ohm resistor in series, the relay would only see approx 12-13 volts including a slight loss thru the SCS. A 150 ohm resistor in series with an average 24 volt relay would be too big for it to operate. Either the schematic is wrong (would not be the first time) or the 24 volt relay is.

An accurate meter will clear a lot of confusion in this matter.

Rob

Thanks Rob,

I will test my meter. You should also keep in mind that there maybe a certain amount of user error on my part - while I am no dummy, I am originally from a computing background and not electronic. Methodical troubleshooting is no problem, but sometimes reading schematics and even getting the meter on the right setting can be hit and miss. Although, as you said, the circuit for the trip sequence is very simple, so I am confident with what I have tested so far.

Last time I used my meter I noticed that there was a manufactures name on there, so I am going to look at it again and see if I can find a model number - that way I can search on-line and see just how good, or crap, it really is.

While reading your last post I remembered that I had measured the voltage at the coil pins of the relay while the jukebox was idle and the voltage was 25.7 volts (noted in one of my previous posts). I think this is why Ron was saying that leaving the 12 volt relay in there would burn it out?