Baldwin Zodiac constant noise

[mixthe76]

Hi I was just given a Baldwin Zodiac organ. When I plug it in and turn it on it immediately makes a constant loud noise. It's not a scratchy or static-y noise it just sounds like a note is being played. When I flip any of the switches, turn any knobs, or play any notes nothing makes it go away. I have ordered a service manual for it but would like to know if anyone else has run into a problem like this or if anyone has a recommendation on where to start with troubleshooting. Thanks.

[jbird604]

Baldwin organs are notorious for that very malfunction. Each model has a different arrangement and value of cap, but you'll probably find that the main power supply filter capacitor has opened up. Thus, when you turn on the power, the entire system, including the power amps, receive this hum-laden power instead of the smooth DC that they expect from the power supply.

To find a bad power supply cap, use your volt meter on the AC scale. (Disconnect the speaker so you won't rip it up while you're doing this test.) Turn on the power and put the probes on the large filter capacitors (usually down in the floor of the console). The one that is bad will have a large AC voltage across the terminals. A good power supply filter cap will have no more than a few hundredths of a volt of AC across it.

[mixthe76]

Thanks!!!!! I appreciate the information. I'll have to take a look at that.

[mixthe76]

So I have a bit of an update. I've taken the back panel off, and removed the wires to the two speakers on the right hand side but I can't seem to unplug the speaker that goes to the tremolo. It's inside a wooden housing and I can't access the wires. What should I do?

[jbird604]

If you have the service manual, look for the speaker output connection on the power amp that drives the rotating speaker. But you may be able to just go ahead and replace the power caps, as in my comment below...

[mixthe76]

Also, I'm assuming I am supposed to check across the large orange capacitors?

[jbird604]

Those orange ones are the output caps for the power amps, so they're not the problem. The main power supply filter is the big black cardboard sleeved capacitor BEHIND the power amps. I can just see it in the photo. It looks like it has several sections, and one or more of them will likely prove to be open.

This is such a common failure that I'd suggest replacing that thing pre-emptively, even if you aren't able to test it. It may have three or four different capacitors of different values inside it, but you can replace it with discrete electrolytic caps of the proper value and voltage rating. Can you get a pic of the label engraved on the cardboard sleeve?

[mixthe76]

Gotcha. Here's a picture of it.

[jbird604]

That's it, and possibly the cause of your trouble. Just get a new 4000 mfd electrolytic cap with a voltage rating of at least 60 volts and replace that thing.

BTW, 4000 mfd is not a common value, but it's perfectly fine to use a 4700 mfd, which is a more common value. And the voltage rating can be higher than 60 volts, but be sure not to use one rated for LESS voltage, as it might explode. 75 volts is a more common value. The cap shouldn't cost more than $10, probably less. You don't need a fancy "computer grade" cap, just an ordinary electrolytic from Nichicon or some such brand.

Be ABSOLUTELY sure to connect the wires to the new one properly. The label says "can negative" so group together all the wires that are soldered to the tabs around the rim of the can and connect them all to the negative wire of the new cap, and connect whatever is connected to the inner terminal of the old cap to the positive wire of the new one.

Even if that doesn't fix it, you will have done a useful thing. Those old caps tended to dry out rather quickly and make the organ noisy. It needs replacing for sure, and it doesn't cost much.

[mixthe76]

Cool. Would a certain terminal be better than another terminal (easier to install)? Also by mfd you mean microfarad, correct? I want to make sure I'm getting the right specification.

[jbird604]

Yes, mfd = microfarad. I have used various types of capacitor terminations to replace the cans. It doesn't really matter, as long as you get one with terminals you can easily solder all those wires to. A radial cap with fairly long wires sticking out the end will give you lots of space to solder on several leads. Or a large axial cap would be fine, as long as the wires will reach. With an axial cap at least the positive and negative wires would be separated by some distance for safety.