Wurlitzer 4100 BP hums, no sound from keys

[Guest]

I just picked up a free Wurlitzer 4100 BP today. The owner said that the cable for the volume pedal had broken about 2 years ago, but up until then it worked fine. It appeared to be a moderately simple fix (though I know very little about organs), so I picked it up.</p>

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When I turn it on, after it warms up, I get a low hum, and it sounds like a note is being pressed. It turns out pressing the bass keys does work, at least somewhat: the pitch of the hum changes, though it doesn't sound like an organ. Pressing the keys on the upper manuals doesn't do anything. After reading a couple posts on here, it seems this might be an issue with power supply capacitors? How easy is that to fix?</p>

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As far as fixing the volume pedal cable, I need to take a better look at it, but it appears to be simply a mechanical failure. Does anyone have any pictures or documentation on what it /should/ look like, or how to fix it? I think one of the wires might have also come loose under the volume pedal too.</p>

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Thanks in advance! I look forward to playing this thing :D</p>

[bluetantra]

Re: Wurlitzer 4100 BP hums, no sound from keys

Make certain the tubes in the amplifier section are good. (A 5U4, two 6L6's, and a 12AX7). The expression pedal works a potentiometer underneath the pedal by means of a cloth cord. It is common for the cord (sort of like the dial cord on old radios) to rot and break from age and use.

[Guest]

Re: Wurlitzer 4100 BP hums, no sound from keys



Those numbers don't match the tubes I saw. On the door in the back that swings out, there were two 12AX7 tubes on the outside, and a 5BC3 and two 7868 tubes on top next to what appeared to be two very large capacitors with metal casings (the numbers started with C). I didn't see any other tubes close to the amp. I don't know how to tell if the tubes are still good, but one of the 7868 tubes looked like this:</p>

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As far as the cloth cord, I see what you're talking about. It appears, also, that the cloth cord is still intact, but simply disconnected. How exactly is it supposed to hook up? There are two posts that I think the ends of the cord are supposed to attach to (one end was already attached, the other not). But when I tried to hook it up that way, one side of the cord was always too short and the other side too long.</p>

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Also, there is a larger grey cable under the pedal with 3 wires coming out of it. One of these wires is bare, and it's not soldered to anything. I was wondering if that's a problem, though I didn't see any broken solder connections.</p>

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Thanks again! I hope I can get this thing in working order soon without too much trouble :)
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[bluetantra]

Re: Wurlitzer 4100 BP hums, no sound from keys



My apologies; you did say 4100BP and it does have a slightly different amp from other 4100 series instruments because of the Spectratone and Reverb features. The rectifier is a 5BC3 and the main amp stages are two 7868's as you've found. You really need a friend with a tube tester or known good tubes. A visual inspection won't determine if a tube is good or bad.I'm includinga scan of how the expression pedal's cord should be wrapped. The perspective is looking up from the bottom side of the expression pedal. I'm also including a scan of the amp schematic - the bare wire shown in your photo of the expression pedal potentiometer should be soldered to ground.</P>


Please be very attentive when working on this organ - there are potentially lethal or injurious voltages in several places; not just the in the amplifier and tone generator sections. The keying busbars underneath each manual carry enough voltage to knock the snot out of you when the power is on.</P>
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[Guest]

Re: Wurlitzer 4100 BP hums, no sound from keys



Ah, thank you very much! If tubes weren't so expensive, I would just replace them :P I'm not sure if I know anyone with a tube tester, but I'll look around. Do they cost much, if I have to buy one? Also, is there a certain spot under the pedal to ground that wire? I can't spot it.</p>

I'll definitely not be working on the organ while it's plugged in ;)
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[OrgansR4Me]

Re: Wurlitzer 4100 BP hums, no sound from keys



Many old tube organs are being parted and there are numerous auctions on Ebay for tubes. The ones you refer to as expensive are usually resales after someone has won a lot. Watch for whole organ listings where you get multiple tubes (sometime more than a dozen) at a time and you'll get the best deal. You may end up with some you won't need but then you can possibly trade them or resell them. Ocassionally, tube testers become available on ebay as well. They don't cost much because most people don't need them.</P>


I have two. One I bought on Ebay and the other was given to me by a neighboring family who had a dear departed father who had TV repair business on the side in the 50's and 60's. I have only had to use them a couple of times. Replacing tubes with another known good tube is really alot faster. And cleaning tube sockets and the tube ends can go along way to restoring the function of a tube. (Be sure to let the socket dry throughly after applying alcohol or another electronic cleaner.) My first tube organ was an Allen S15 and my second was a Conn 720. Both worked well after cleaning and I've seldom had to do a tube replacement.</P>


I once bought a Baldwin 54 that was not functioning only to learn that a tube had been completely removed from the organ. I went to the shelf where I stock my tubes, put in the new tube and the organ was one of my best bargains. One word of warning. When you get this organ fixed you'll find another that needs you!</P>

[Guest]

Re: Wurlitzer 4100 BP hums, no sound from keys



Well after messing around with all the toggles, I actually was able to get sound from the keys (I didn't try very hard before). However, some of the keys still appear to be dead, and some of them are crackly. Is this just a matter of cleaning contacts or something? Or is it a deeper issue? Also, when I turn on Spectratone or Reverb, I get a sort of pop sound, and adjusting the reverb amount pot is crackly too.</p>

I didn't get the expression pedal hooked up yet; I cannot find where to ground the bare wire, but unfortunately, the wire is about to break off. Any suggestions on what to do about that? Also, turning the expression pot manually while playing didn't seem to affect the volume, but I'll have to double check on that.</p>

I noticed that the tubes got pretty hot after playing it a short while. Is this normal?</p>

There's still a hum when playing. It sounds like a dissonant chord being played constantly in the background.</p>

Thanks everyone for your help so far. What should my next step be in getting this beautiful organ into full working order?</p>

[OrgansR4Me]

Re: Wurlitzer 4100 BP hums, no sound from keys



Tubes were notorious for their heat -- thus the name Toaster used by tube organ detractors!</P>


Playing an organ in is fine as long as you don't hear anything alarming that would indicate something has broken. Especially the Spectratone Belt which may be fairly brittle. As long as you note improvement each time you play you are moving in the right direction.</P>


At some point you want to consider opening the organ and getting excess dust out with a vacuum.</P>

[Guest]

Re: Wurlitzer 4100 BP hums, no sound from keys



Aha, thank you. Well I vacuumed out the inside today. Didn't notice really any change in the playing though; there are still many dead keys. I'm thinking this is a contact issue, because some of the dead keys on the top manual will work if I press on them firmly.</p>

As far as the hum, what could be causing that besides tubes that I could check, if anything?</p>

[OrgansR4Me]

Re: Wurlitzer 4100 BP hums, no sound from keys

You will be getting in deeper going beyond the tube issues, but if you're ready for some greater learning you'll want to go into the amplifier and check the large capacitors. It is very common for them to weaken or fail with age. If you don't feel comfortable doing this kind of work yourself you need to check MITA website to see if there is a tech in your area you could call in.

[Guest]

Re: Wurlitzer 4100 BP hums, no sound from keys



How exactly should I check the capacitors? (I'm assuming they're the two large ones on top of the door next to the tubes)</p>

Hm, this is turning into much more of a project than I had hoped. Perhaps I'll find a free organ that actually works and give this one away ;)</p>

[bluetantra]

Re: Wurlitzer 4100 BP hums, no sound from keys



Since you're hearing a hum (roughly about the pitch of B natural is 60 Hz. AC hum), the capacitors are starting to fail. The two FP type caps you mentioned need replacing along with a few axial type capacitors also in the amplifier section. They're available from Antique Electronics Supply - www.tubesandmore.com. It would be prudent to also at least check the large resistors in the power supply. Those in my 4100A had drifted somewhat in tolerance with age and warranted replacing. These organs are approaching 45-50 years old and it's normal for these parts to need replacing. It's not difficult to replace any of these, but some skill with a soldering iron is necessary.</P>