receiver 1769

[peterd51]

Hi,

Am I right in thinking that the Wallbox / Jukebox send the pulses into the receiver 'Signal' wire on pin 2 to make the selection?

If so, are these pulses of 117v AC from pin 3?

Seems a bit high to me but that's what the service manual says it is...

Regards

Peter

[Ron Rich]

Hi Peter,
I am not sure of which model(s) you speak--117 is way too high for a wallbox to "send", IMHO ??
Ron Rich

[peterd51]

Hi Ron,

It's in a 466, but the same Receiver is used in many others.

As it's switching a transistor on & off I would have thought it would be DC rather than AC.

My next search will be on the transistor properties to see if I can find a voltage range there...

Regards
Peter

[Ron Rich]

Hi Peter,
I don't know RockOla's too well, but I doubt they could get away with a wallbox switching that high a voltage, in the mid 1960's ?
That must be an error in the manual --- Ron Rich

[peterd51]

Hi Ron,

yes, the transistor is an NPN rated at 7 volts base-emitter.

I've not seen +5v on the jukebox but I know there's one on the wallbox.

So my next step will be to get a battery box with three 1.5v cells, connect to signal and ground and tap a pulse or two to see if anything responds. It should do at that voltage and it's low enough to not do any damage if I get it wrong.

I'll use a battery first so I can check if there's any excess voltage coming back out of the jukebox, I don't want to blow the wallbox as that's working OK.

That's a job for tomorrow!

Regards
Peter

[Ron Rich]

Hi Peter,
Let us know what you find/found --
Thanks, Ron Rich

[peterd51]

Hi Ron,

receiver no go...

I didn't fancy taking it out of the bowels of the machine but I went for it in the end, it wasn't as bad as it looked.

First I spent a bit of time looking at the connection plugs, testing wires, etc, and struggled a bit as I seemed to have a socket missing. Clearly shown on the wiring diagram but the connections on the Receiver and Power Unit didn't match up.

Then I found that Rock-Ola decided to put two plugs into one cable at the Power Unit, and at the other end they took the cable directly into the receiver with no plug. Well done guys, you fooled me there!

Anyway, the fault is obvious...burnt out component, probably a resistor. Some more testing to do on my workbench.

Regards

Peter

[Ron Rich]

Hi Peter,
That appears from here, to be a 2 watt resistor--or, what remains of it ! These are somewhat prone to frying, as this one did, without any other problems--however, look for fried wires and other components too-- Ron Rich

[peterd51]

Hi Ron,

yes, 56 ohms and I guessed a couple of watts due to it being bigger than the others.

Also the transistor, 2N3054, has been blown.

Both on order from Ebay, as we don't have any component shops locally, and they should be here for the weekend.

Obviously I've not tested everything yet but the components close to these two all check OK up to the relay coils.

This are on the other end of the wiring that I suspect someone connected 240v to at some time.

While I'm waiting for the post I'm thinking of popping the power unit out of the 466 so I can power up the Receiver and I can emulate the transistor switching by tapping an earth on the collector wire to see if the relays kick in.

Regards
Peter

[Ron Rich]

Hi Peter,
OK--have fun !! Let me know what happens--
Ron Rich

[peterd51]

Hi Ron,

I had a 'revelation' late last night...

the wiring diagram that I have is old, faded (like my eyes), and even using a magnifying glass I've struggled to read it at times (especially wire colour codes).

So I've been tracing wires and components and drawing my own diagrams. Checking the 'signal' wire into the blown resistor and transistor, then into the Time Delay and Pulse Train Step Coils all looked OK.

I started following the 117v AC wires into the transformer, secondary connects to chassis (Common) and a diode to give half-wave rectification, but that's the negative end of the diode...so it's negative DC voltage on the top rail.

This rail connects to the transistor base via a 10k ohm resistor to bias it 'off', and it also connect through the coils to the transistor so that could be the emitter rather than the Collector. Seems I had the transistor the wrong way around in my mind!

In that case to switch that transistor 'on' needs a 'more positive' pulse, or a '0v / common' pulse rather than a voltage.

So I connected up the power unit...

117v AC into the transformer, 28v AC out.
-38v DC after the diode

and tapping a single 'Common' pulse onto the emitter wire kicked in the relays, and the Write-in Scanner started to rotate.

So the Wallbox sends 'Common' pulse trains into the Receiver on the 'Signal' wire...

and it looks like my 466 will be fully working once I get the new components installed!

Regards
Peter

[Ron Rich]

Hi Peter,
Most of the wall box systems used a "common" pulse to operate--I did not know if RockOla changed it or not ?? Good luck, I think you are close !
Ron Rich