Rock-Ola 480 Techna end of record Issue

[madpole]

I noticed a very similar post from February 2019 that was never responded to.

I have a Rock-Ola 480 Techna that was been fully operational since I picked it up last November.

The issue is when the tone arm reaches the end of the record.  The reverse relay starts latching and unlatching about 2 times a second and the tone arm stays stationary andthe process to remove the record does not start.

If I manually turn the gripper arm motor and advance it until the record is gripped and placed back into the carousel, the jukebox takes over and is ready to select the next 45.

I swapped out the mech power board and the issue remained.

Can anyone point me in the right direction to start troubleshooting?

Thanks in advance,
Jeff

[Ron Rich]

Hi Jeff,
How about starting with the Factory Service Manual ?? RockOla's usually have a "Sequence of Operation" them-- what happens when the end of record switch is actuated ? Ron Rich

[madpole]

When the end of record switch is activated, the reverse relay begins latching and unlatching faster than one cycle per second. The gripper motor is not energized.

[madpole]

Sequence 17. Music Cycle Ends
1. AS record play is ended the tone arm moves into the record cut-off groove closing the Tone Arm Switch. After a delay of 150ms, the Timing MOdule (PEC 301) SCR conducts thereby energizing the Reverse Relay K302. Relay contacts K302-1 and K301-2 now transfer.

2. K302-1 provides a holding circuit to the Reverse Relay K302.

3. K302-2 causes the Gripper Motor to operate in reverse via Q302 and Q301, and proceeds to return the record to the magazine.

It looks like step2 of this sequence is not working.

[jukenorman]

Hi Jeff,
You've pretty much answered your own question! The relay holding contact K302-1 is failing. You could try taking the cover off the relay and clean the contacts (refer to "sticky") or get yourself a new relay.

Norman.

[madpole]

Norman,
Additional info...

I've swapped out the Reverse and Latching relays with no luck.

I've ran the gamut with two sets of relays and three different Mechanical Power Boards.

The symptoms remained the same across all combinations. It leads me to believe the issue is elsewhere, I just don't know where else to look. The jukebox worked with no issues since I picked it up in November. The issue started on Saturday night.

Is there anywhere else I need to focus on?

[Ron Rich]

Jeff,
L@k at the schematic-- what "holds" the relays ? Does that circuit go thru a switch ? Is the switch "good" ? Are the "swapped" relays good--and the correct style/type ? Ron Rich

[jukenorman]

Hi Jeff,
It will be #1 micro-switch. I've had a look at the diagram and it can't really be anything else - because you've tried replacing everything else! You could absolutely prove that to be the case by linking CR30 to 32V DC before the tone arm switch operates (effectively shorting #1 micro switch).

Norman.

[madpole]

Hi Norman,
I removed the Red-Blue (+32 VDC) wire and the Blue-Yellow (feed to CR310) wire from Micro-switch #1 and placed a jumper between them. This was done prior to the tone arm reaching the cut-off groove.

When the tone arm switch closed, the Reverse Relay began to latch/unlatch more than once per second.

If I removed the jumper during this, the relay went quiet as I expected.

I'm starting to suspect the Timing Module.

I want to test this by running a jumper from the non-banded side of CR309 to the negative lead of C302. This would bypass the Timing Module. Before I do this, do you think this would cause any issues?

Thanks,
Jeff

EDIT: I measured the voltage on the 32 VDC feed to Micro-switch #1 and found it to be 19.6 VDC. It's my guess that 19.6 V isn't enough to latch and hold the Reverse Relay.

Any comments or help will be greatly appreciated.

[Ron Rich]

Jeff,
What "kind of" a relay is it ? If the voltage is supposed to be a nominal 32 volt, my guess is that it is too low---However--- If you can see it "pulling", the voltage to hold it, should hold it, at 20 volts-- Ron Rich

[madpole]

Ron,
The relay is 24 VDC.

There are 3 voltages coming off the regulator board; +32 VDC, -21VDC and +9.6 VDC.

The +32 V is what powers the Mechanism Power Supply Board. What is supposed to be +32 V is measuring 19.6 V on the regulator board. That sounds like a problem.

I have the service manual for this model, but it doesn't include a schematic for the power supply or regulator board. Do you know what a likely cause is or where I can locate a schematic for the power supply and regulator?

Thanks,
Jeff

[jukenorman]

Hi Jeff,
If you can disconnect the output on the regulator board and it still reads 19.6V, then that is a problem. Otherwise there is a danger that another fault is pulling down the voltage. I would be surprised if a real stable 19.6 V wouldn't pull in a 24V relay. I might be able to find a schematic for the power supply - let me have a look later on.

Norman

[madpole]

Norman,
I disconnected the low voltage output plug from the power supply. The 32V comes in at 20.0V. Sounds like that is at least one of the issues.

I ran the 19.6V directly to an unmounted relay. It vibrated, but did not latch the relay.

Thanks in advance for looking for that schematic. I'm wondering if a failed diode or bridge rectifier could be the issue. The 32V is sourced off a 25 VAC winding.

Thanks,
Jeff

[jukenorman]

Hi Jeff,
I'm sorry I don't have a pdf of the power supply. The original manuals came with a large fold out schematic which includes the power supply. I will have a suitable schematic in my workshop filing cabinet and hopefully I can scan that section - but it will be tomorrow. I'm not sure if the 32V rail is regulated. I still say 19.6V would normally be enough to pull in a 24V relay so you could have a rectifier problem.

Norman.

[Ron Rich]

Jeff,
Check with the suppliers listed in our FAQs section for a schematic ! A 24 volt -AC-DC relay ? Either way, most odd to connect it to a 32 volt supply ?? Ron Rich