Phonoland

So, for the record, my meter is a Caltek Instrument CM1200.

After a quick google I still don't know if it is any good as I couldn't find any reviews.

Guy's--
You are "making a mountain out of a molehill" !
First of all, Rob--you have an incorrect schematic--the one you are reading is for a DCC-2 or DCC-3.
The DCC-1 and DCC-4, do not have any resistor in the circuit (which when used, is mounted to the relay socket).
Second. If the 12 volt relay operates, that indicates the problem is most likely in the 24 volt relay. In order to trouble shoot this--it MUST first be determined if the relay is operable. To do so, one must only look at it, when a selection that has been made ( either with the DES, or by using the "battery trick" ), is scanned by the mech. If if fails to pull the armature down, it is either defective (bad coil), or "binding up". If it energizes, but fails to detent the mech--the detent contacts are "dirty-burned-pitted"--in other words, not "making" for some reason. This is a "common failure" caused by incorrect adjustment of the 2M-1 contacts on the mech. Ron Rich

Thanks Ron,

The 24v relay does NOT energize.

I have done some of Rob's tests:

Tested the impedance of both 12v and 24v relay coils. 12v = 152 ohms, 24v = 618 ohms.

The covers on the relays seem to be correct, as the wrapping around the coils are also marked with the voltage. 12v on the 12v and 24v on the 24v.

The voltage at the 12v coil when the mech trips is 25.3 volts.
The voltage at the 24v coil when the mech trips is 25.4 volts (had to trip manually, shorting test point 1, obviously).

I did, earlier in the thread, test a different 24v relay in the juke and still had the same fault. However, seeing as I have several Seeburg's at hand I will try another.

Keith,
Try the following--
Select all Toroids using the "battery trick"--insert 12 volt relay to insure that the mech is indeed detenting at each selection. Once that has been determined, up plug AC for the DCC, and change relays. If the 24 volt relay still fails to energize, swap it with the one in the SHP amp. This should "pin down" you problem--NOTE--do not leave the amp relay in the DCC, and vise verse--the contact blades are ( or should be) "adjusted" differently.
Ron Rich

Thanks Ron,

Just a quick note.

I have just tried the 24v relay from my (working) STD4 and got the same result - not energizing. I tried the original 24v relay from the STD3 in the STD4 and it works okay. The STD4 is a DCC2, but both have 24v relays.

I can still do the battery test, or is this not necessary now?

Keith, as usual Ron has better info.

I do have a question about this:

The voltage at the 24v coil when the mech trips is 25.4 volts (had to trip manually, shorting test point 1, obviously).

What happens if you just let it try to select (w/24v relay) and it fails..What is the voltage at that relay? In theory once a readout pulse hits the gate of the SCS it should start to conduct as long as there is some circuit continuity. So if there should be a measurable voltage at that relay's coil even as the mech continues to scan out. Tapping the trip test point eliminates the whole SCS circuit so it doesn't tell the whole story.

I did a quick search on your meter-it should be fully adequate for any testing on jukes, as long as it is working properly. They don't list the meter's loading on the circuit but this was standardized over 30 years ago for DVM's to beat 10 megohm so as not to load most circuits.


Rob

Kieth, What happens if you sub a known good 24 vdc relay in the non-working DCC ?
If it fails to energize, the DCC has problems, either in the +27 vdc circuit, or the relay socket. I just can not imagine that the SCS circuit knows the difference between a 12 volt relay and a 24 volt relay-- as all that circuit does is provide a "ground" for the relay.
One thought--Check the diode attached to the relay socket--as, if "bad" it COULD prevent the relay energizing--
One other question--On the DCC-2, check the "CODE"--if Code "A", it MUST be updated, or it will mal-function.
Ron Rich

Rob,

With the 24v relay (which we now know works) there is NO (zero) voltage at the coil pins when the mech is scanning after punching in a number. The 12v relay works perfect and selects the correct record every time - go figure?

Ron, on my meter, the diode test and continuity are at the same position on the dial. The diode reads 525 with the black lead next to the black stripe on the diode and 625 with the red lead next to the black stripe on the diode - there is no continuity.

A good 24v relay fails to energize in the DCC4.

The DCC4 from my SQS160 works, I swapped them for a test. Since replacing the original DCC4 the mech now trips at record 179 on its second scan just as it cuts off. Thus, it stops in the clamped position.

The DCC2 is a CODE A. What do I need to do with it?

Ron stated:

If it fails to energize, the DCC has problems, either in the +27 vdc circuit, or the relay socket. I just can not imagine that the SCS circuit knows the difference between a 12 volt relay and a 24 volt relay-- as all that circuit does is provide a "ground" for the relay.

But, an SCS like most other thyristor/ignitron devices requires enough anode potential to fire and conduct.

From Keith's measurements of the two relay's impedance and not knowing the proper impedance of the trip relay for that model, I wonder if the 618 ohms ohms of that relay is simply too high for enough current to latch the SCS.

----Does anyone have a working machine with a 24v trip RY that they can remove and measure the coil impedance?

Ron, on my meter, the diode test and continuity are at the same position on the dial. The diode reads 525 with the black lead next to the black stripe on the diode and 625 with the red lead next to the black stripe on the diode - there is no continuity.

Keith, if you want to diode test the one on at the trip relay the relay must be out of the socket and the PS board disconnected. There are too many other paths and this will confuse the tester.

A proper test on this diode should read about 500+ ohms one way and at least three times (normally infinity) the other.

Rob

Thanks Rob,

With the relay and power board disconnected the diode reads 642 with the black lead next to the black stripe and the meter doesn't move with the red lead next to the black stripe.

Hi Guyz--
Keith,
Are you sure about that diode reading--it should read around (point) .550--if the orange or blue diode.
I just measured a working 24 volt OEM "Sigma" brand relay--618 ohms--
Several brands were used, and something in my memory says that this varied somewhat---
I had a thought---Perhaps, the C3104 cap is going "flat"--if so, it appears to me that it may fire a 12 volt relay but fail with the 24 volt ? Change it, and be sure it is at least a 20 uf X 50 volt cap--some parts books are wrong on this cap call-out---
On the DCC-2 code "A", turn it over and look at the relay socket. If the socket has two diodes soldered to it, it must be modified. If it has one diode, and a 2 watt resistor on it, it has been modified, but not marked "code B" on the front. If it has ONLY one diode on it, it requires a 24 volt relay.
Ron Rich

It feels like we are going round in circles. I just want to recap on what we know and why:

1. The fault is in the DCC. We know because the fault goes away when we sub a good DCC.
2. The fault is NOT with the relay. We know because the fault is still present when we sub a good relay.
3. The fault is NOT with the Power Supply Board. We know because the fault is still present when we sub a good board.

I am going to sub the diode from my SQS160, as it seems to be the only piece left in the circuit which hasn't been substituted. Also, from Ron's and Rob's measurements, it seems like my diode is way out.

If that doesn't work I will look for the C3104 Cap, as Ron has suggested.

Watch this space....

Seems as though one of the tests I did earlier was somehow flawed (or I was attacked by gremlins).

The fault now appears to be on the Power Supply Board after all.

After swapping things around, several times, I now have the jukebox working with a substitute Power Supply Board - original relay, original DCC.

Ron, while the circuit was "live" I tested the C3104 for voltage, and on both good and bad boards the C3104 read an exact 25 volts. Is this still going to need swapping, or should I be looking for the fault elsewhere?

Keith,
I have never tested "voltage" there--just change the cap--
Ron Rich