Installing a bridge rectifier into a wurlitzer 530 amp?

Hi guys,

I'm not an electronics guru by any means, but I know how to solder and put new things in place. Can anyone give me a quick rundown on the proper way to install a new bridge rectifier into my wurlitzer 530 amp? A local guy here who builds guitar amplifiers, rebuilt my wurlitzer 530 amp. I have great sound out of it, but the mechanism moves slower than slow, and when you insert a coin into the jukebox, the coin credit unit just clicks. The only way the juke is working is if I fire a pin manually, but it's moaning and groaning to get the job done. I'm pretty sure the way he put diodes into the amplifier was wrong or perhaps the values. I'm not an electrical guy by any means, but if someone could help get me back on track, I'll just fix this myself. Please help me understand how to reverse what he did and do this right.


1. What bridge rectifier is needed on this amplifier? Can someone just point me to a radioshack link? I don't know what an amp is or how many volts are necessary. If you can just post up a link to the best one to get, I'll solder it in myself.

2. What is going on in the pictures below? Is that 4 diodes I see with a resistor after the fact? Can I fix my issue just by modifying what he already has in place? I don't want to burn anything up in the amp or machine, so I'm being cautious.

I wish I knew more about this stuff, but I just want it fixed so I can go about listening to my jukebox again.

Even being an experienced service tech, those photos cannot tell me over the internet what or where a problem lies.
And it seems to me that if the amp "sounds good" that the mechanism problem is elsewhere.
And that cannot be fully realized by me either over the internet.
My meter is here, your probem is miles away.
The "net" cannot solve everything.
Find someone who has experience and specializes on these jukeboxes, and not a guitar-man.

"hirdlej" It looks like your man got a bit confused here. I don't want to be more specific without having the unit in front of me, or at least more information.

I can offer you a schematic for that section of the 530 amp:

http://s1192.photobucket.com/user/Rob-N ... sort=3&o=0

The pertinent area is at the extreme lower left and the rectifier bridge. It look like he added a power resistor in series with the output of the new rects. In an amplifier supply this would normally be advisable, here it is not necessary. Excessive drop through this resistor --may-- be your only problem, but since the wire colors don't match the schematic I'm not sure if he connected to the proper secondary of the transformer. There is also the question of the cut orange wire.

With this schematic, it is a simple matter of using a meter and tracing out the proper connections.

Rob/NYC

MattTech wrote:Even being an experienced service tech, those photos cannot tell me over the internet what or where a problem lies.
And it seems to me that if the amp "sounds good" that the mechanism problem is elsewhere.
And that cannot be fully realized by me either over the internet.
My meter is here, your probem is miles away.
The "net" cannot solve everything.
Find someone who has experience and specializes on these jukeboxes, and not a guitar-man.

Hi Matt,

Thanks for your response. Here in Minneapolis we do not have any "jukebox amplifier" repair guys that I know of. Most of them send their amplifiers out to get rebuilt, then give them back to the customer. The cost of shipping would have tipped me over budget for the time being, so I tried my best to find a local tube-amp guy that I was comfortable with.

I'm very compitent mechanically and great with my hands. I also have a nice fluke multimeter and can provide you with any readings needed to help troubleshoot this. If you guys would be so kind to tell me what I need to check, and where it needs to go, I'm sure I can correct this issue myself.

This is the 2nd time he's looked at this amp and hasn't gotten the power part figured out.

Is it safe to bypass that resistor for testing? Would there be a chance of baking something if it's not in the circuit? Is there a value of some sort I can check before attempting this to find out? Any assistance is greatly appreciated.

This thread seems to be centering around the amplifier.

But the earlier complaint:
I have great sound out of it, but the mechanism moves slower than slow, and when you insert a coin into the jukebox, the coin credit unit just clicks. The only way the juke is working is if I fire a pin manually, but it's moaning and groaning to get the job done

Seems to be the mechanism has issues - maybe due to lack of service?

MattTech wrote:This thread seems to be centering around the amplifier.

But the earlier complaint:
I have great sound out of it, but the mechanism moves slower than slow, and when you insert a coin into the jukebox, the coin credit unit just clicks. The only way the juke is working is if I fire a pin manually, but it's moaning and groaning to get the job done

Seems to be the mechanism has issues - maybe due to lack of service?

I have gone through and completely redone the mechanism. This is a fully restored machine minus the electronics. The mechanism motor and mechanism has been cleaned, relubed as it should be.

I have another amplifier here (an old original one) as a spare and it'll walk circles around this amplifier as far as mechanical performance goes. This is definatly a DC power issue since the turntable and cabinet lights are operating as they are supposed to.

Since you have two amps, I suggest that you take them both to your "git-tar guy", and have him figure out what he
"donedid" to ruin your DC supply-- Ron Rich

Ron Rich wrote:Since you have two amps, I suggest that you take them both to your "git-tar guy", and have him figure out what he
"donedid" to ruin your DC supply-- Ron Rich

lol you guys are too funny. Is it worth the 2 hour round-trip again for the 3rd time to get this sorted out? Or is it just easy enough that I can sort this out myself? Something tells me it's close and has something to do with the rectifier. I might just hook the original one back up since it worked fine before the rebuild. I can at least follow wires here and there and use the original amp side by side as reference.

About 35 years ago I used to own a Wurlitzer 1700 jukebox. It had the symptom of very sluggish-to-no motor movement. The 1700 used a selenium rectifier mounted on the outside of the amplifier chassis for the motor power circuit. I temporarily disconnected one of the DC output wires from the rectifier and inserted my multimeter in series with that wire and the rectifier. I was showing almost no current coming out of the rectifier when the motor should be running. So the selenium rectifier was shot.

I went to Radio Shack and got a 276-1173 bridge rectifier and mounted it to a 274-688 terminal strip after completely removing the old rectifier. That fixed my problem.

Got the problem fixed, it was the arrangement of diodes. I had him hook up the original selenium rectifier. It's all better now

hirdlej wrote:Got the problem fixed, it was the arrangement of diodes. I had him hook up the original selenium rectifier. It's all better now

So much for those "I wanna play technician" guitar amp guys.
Maybe they should stick to playing crappy music in their parents garage.