Help with Rock Ola 1446 - 5U4 wont power up - No sound coming out of speaker

[cru...@msn.com]

Well my wife wanted a Jukebox, so I thought, should not be a big deal to restore one. :). Its now 2 months later (150+ hours) and there is light at the end of the tunnel, but I'm stuck now and I can't figure it out.

The jukebox worked ok (Selector pin, blown speaker, and turn table issues) before I tore her down. I completed all of the basic repairs and all the cosmetics, but did not touch the amp or power distribution unit, since someone had done a basic rebuild on it 10 years. I did change the cable between the amp and power box, because the insulation was breaking inside the cable. Upon reassembly everything works fine except no sound came out of speaker.

I found that the RU4 tube does not glow when the record is playing, but all other tubes glow. The start relay works properly and I have around 40vac on one set of contacts and 12vac on the other. Voltages at the RU4 do not seem to change at all when I manually press the start relay and close the contacts.

The Schematic says I should be getting high voltages on certain pins of the RU4, but the highest I see is around 40vac, with or without the start relay engaged.

I would be greatly appreciative of any help. I wanted to give the Jukebox to my wife for mothers day, but that looks in jeopardy now.

Thank you for your time.

Clark

925-980-8392
cru...@msn.com

[John Robertson]

Have you tried another 5U4 tube? It may have an open filament...a tube
tester is handy here.

Also check that the speaker plug grounds the center tap of the power
transformer HV windings - this is shown on the amplifier schematics.

John :-#)#

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[cru...@msn.com]

HV center tap off of the red wire from transformer is soldered to ground and measures 0 ohms. The 5U4 filament pins measure 0 ohms not sure if you can measure a tube that way. I ordered a 5U4 wont be in until next week.

Thank you,

Clark

[lino...@yahoo.com]

The best advice I can give at this point is to review this schematic:

http://arcarc.xmission.com/PDF_Jukebox/Rockola/Schematics/1448.pdf

And make sure you have AC coming in from the power supply unit to the amp. Check also the plug from the speaker as this will interrupt the primary of the amp's power tran if not certain jumper pins are not making contact. This is intended to keep the amp from functioning if the speaker is not connected.

Rob/NYC

[cru...@msn.com]

I have 40vac coming into the amp. I did replace the 5 ohm resistor jumpered between pins 5 and 2 on the speaker plug and measured continuity between pins 1 and six on the amp plug where the jumper wire is soldered in.

The only readings that don't make sense are no change in voltage at the 5U4 tube when the start relay is manually triggered (I don't think I had the speaker connected though when I did this). I think the issue is there is no high voltage being outputted. I'm not sure if that is from the 5U4 being bad or voltages coming out of the transformer. Would you happen to know what voltages I am suppose to be reading coming into the 5U4, when the juke is idle and when it is playing a record?

Thank You,

Clark

[lino...@yahoo.com]

Clark, 40 volts into the transformer is way too low. On the two primary leads into the amp power tran (two black wires) should see whatever your full line power is (110-120 etc).

Again, look at the PDF and the unit, trace those two black wires back through the relay, the inter-unit plug and to the line cord.

BTW: Once you have proper AC going into the tran you should see close to 400vdc at the first filter capacitor.

Rob/NYC

[cru...@msn.com]

Swapped out the 5U4 and filed (cleaned) out connector holes for speaker and amp, 5U4 still does not light up or output any high voltage.

All voltages appear good except going in and out of 5U4. So I think it has to be the transformer. I'm getting 44vac out of 4 wires and 0v out of another from the power transformer, that cant be right. Any one know of a different way to test the amplifier power transformer or have a spare one to sell? Schematic says its a 18594 power transformer.

Any help would be greatly appreciated.

Clark

[cru...@msn.com]

Hi Rob,

I rechecked the voltage going into the Transformer at the 3 A fuse and its 118vac. Only thing I can think of now is the transformer is bad. :(

Clark

[John Robertson]

Hi Clark,

OK, first of all where are you measuring the 115VAC? If you look at the
schematic in the previous email (which you should have quoted from) you
will see that the power route is a bit circuitous. For there to be
115VAC at the 5U4's transformer you have to have:

A) Speaker plugged in to jumper pins 1 (black) & 6 (white) and then...

B) cable plugged into Power Distribution Box so that pins 3 (black) and
2 (white) get the power from...

C) black wire on transformer AND red-green power return on Start Relay
Contacts which all connect to the right side of the three sockets (Dome,
Door, & Service).

Anyone of the above missing will stop power getting to the transformer
AND unless you measure the voltage for the transformer at the 3A Fuse
(transformer side of fuse holder) AND pin 1 of hte speaker plug you
don't know for sure that you have the required voltage.

Sorry about the 5U4 red herring, I didn't have a schematic handy at the
time. 0 Ohms is OK for reading across the filament pins (5 & 2) of the 5U4.

[cru...@msn.com]

Hi John,

Thank you for your response. I ended up creating a bench test to check the transformer out and applied 115 directly to the primary windings. All voltages checked out perfectly and resistance across the windings was also good. The 5U4 also lite up. So I went back to ground zero and checked every contact.

What I found was gunk/corrosion in the amplifier connector pin receptacles. I thought I had cleaned them out properly before, but it appears that some weird gook was in the pin holes. I cleaned them out again and filed the holes and the amp came alive. All voltages are good now and the 5U4 is glowing like a night light.

Thank you everyone for your help.

Clark

FYI. I now have a issue with the woofer not working but the horn working properly. The field coil measures out at 6k and the voltage is 340. The voice coil is reading open, but the darn thing was working 2 months ago. All the safety switches and relays have to be good if the horn is working, so I'm a bit stumped. If I measure resistance across pins 2 & 4 on the speaker plug I should be reading the voice coil? How else can I check out the voice coil?

[cru...@msn.com]

I wanted to post here and offer a sincere thank you to everyone that assisted me in getting our rockola 1446 working. The last issue ended up being the voice coil leads on the woofer. I sent it in to Neals speakers and he did a great job rebuilding the speaker.

The Rockola 1446 looks awesome and sounds even better. All the hard work paid off!

Thank you again!!!

Clark