Rickresource Rickenbacker Forum

I just checked the resistance of the pickups on my 4003, and got a meter reading on the bridge pickup that baffled me. The neck pup checks out at 11.5K ohms, but the bridge pickup reads as 154.8 (155.4 with the tone circuit activated) I've never seen a reading like that come up before in my life.

The pickup sounds fine, except I noticed the difference in tone with the cap in the circuit is so subtle, it's almost unnoticeable. The last time I used the vintage tone circuit was when I first bought the bass (about 10 months ago) just to see what it sounded like. I liked the tone without the cap better, so I haven't used it since... But I seem to recall it having a bigger effect than what I'm hearing now... That could be my imagination, I'm not sure, but I have to really strain to hear the difference... Actually, I really only hear a slight increase in volume when I push the pot back in again.

Also, I noticed when I turn the bridge pickup's tone pot all the way down, it kills the volume of that pickup... I don't think that should happen either. I've wired up a handful of guitars and basses in my time, and the only time I ended up with a tone pot affecting the volume was when I had a short in the circuit. I pulled the pickguard off and checked the wiring... I couldn't see anything wrong... All the connections seemed solid, and everything seemed to make sense, but I haven't even looked at a wiring diagram or schematic yet.

I'm not what you would call an electronics expert, or even knowledgeable... I only have a fundamental grasp on how this stuff works, but this seems wrong to me.

Any input would be appreciated.

Others here will be able to explain it better, but you can't take the reading with the cap in-line. Try going directly to the pick-up leads.

Ed, it sounds like your bridge tone .047uF cap from the switch to the tone pot is shorted either internally by failure (highly unlikely) or by the wire leads touching where they shouldn't. I'd look there. Look for a wire lead touching somewhere, but if you do not see that, try ohming across the cap itself - on ohms, it should read open (infinity). If it reads zero, it is internally shorted. This would explain both the reading and the tone pot killing the pickup. Also the lack of difference with the .0047uF cap in or out.

Thanks, John... I didn't see any wires touching anything they shouldn't the last time I checked... Looked like a very neat, solid, wiring job... I'll check the cap, though I do agree it seems unlikely that the cap would go south so soon, but it's an imperfect world... screws fall out, caps go bad... If that's the case, I think I'll just remove it from the circuit, since I never really used it...

Mossman wrote:Thanks, John... I didn't see any wires touching anything they shouldn't the last time I checked... Looked like a very neat, solid, wiring job... I'll check the cap, though I do agree it seems unlikely that the cap would go south so soon, but it's an imperfect world... screws fall out, caps go bad... If that's the case, I think I'll just remove it from the circuit, since I never really used it...

I'm talking about the .047uF cap to the treble tone pot, not the vintage .0047uF cap to the treble volume control that gets bypasses by the pull switch.

Yes, I knew which one you were talking about by its location... I just got the values mixed up... Well, it reads open with the push/pull switch pulled up, but pushed down, it reads .646 (???). Not sure why the position of the push/pull should make a difference. I also noticed that the output of the bridge pickup is greatly reduced when both pickups are active. The neck pickup doesn't seem to be affected at all.

Ed, something isn't right if you are checking the .047uF cap and the tone switch is changing the reading. If you are measuring across the .0047uF cap then the readings are right.

What I've been trying to point out is if turning the Treble Tone pot makes the bridge pickup go silent, then the .047uF cap from the switch to the tone pot has to be shorted. That is the only thing I can come up with to have that happen when turning that pot.

Here is the schematic:
http://www.rickenbacker.com/pdfs/19507.pdf

If C2 is shorted, then R2 and R4 are both just volume controls in parallel.

Yeah, it's the .047 that's the problem for sure. I took the bass to a tech, just to be on the safe side... Let him sort it out.

Should have it back by Monday.

Mossman wrote:Yeah, it's the .047 that's the problem for sure. I took the bass to a tech, just to be on the safe side... Let him sort it out.

Should have it back by Monday.

Let us all know what he finds, please. One for the files.

Well, I just got off the phone w/ him, and he says it's the pickup itself that's gone bad... Not the news I was hoping to hear. Now my options are either; having the pickup re-wound, or replacing it completely.

Ed, something is wrong with that. If the pickup was bad then you would get no sound out and in your first post you said it was working fine except for the strange reactions to the pots. I'd go get my bass out of that guy's hands pronto. Where are you located?

Well, there was a bit of wire that had come loose from the winding... You could see part of it sticking out from under the electrical tape. It was practically invisible... You had to hold it to the light at just the right angle to see it. I carefully unwrapped the electrical tape to get a better look, and there was about a 1" section of the filament that was all loose, and kinked up... I have no idea how it got that way.. The only thing I can figure is; it must have happened when I installed the pickup surround, but I was very careful handling the pickup when I did that... Or at least I thought I was.

This guy didn't do anything but check the wiring, which he said was fine, and he took a reading directly from the pickup, which he said was way off. That's when he noticed the bit of wire peeking out. I guess he just quit at that point... That still doesn't explain why the tone pot is acting like a volume control, and the pickup does work... sort of... It just doesn't have the output it should, even more so when used with the neck pickup. That's what got my attention in the first place.

I'm not opposed to getting a second opinion... I live in north-eastern Massachusetts... Near the NH border. Do you know anyone out this way?

When I bought my '73 4001 that I've since sold, the bridge pickup was bad. It read about 1.5k, yet still had output, however it was very bright. A pickup will still give output unless the coil is completely dead. It sounds like yours certainly has a problem with the loose wire on the coil, it may be able to be fixed though. I'd send it to Sergio if he is willing, or you could try Lindy Fralin who is kind of in your neck of the woods.

Greg

I actually left a message for Lindy's re-wind guy yesterday morning, before I got the bass back, thinking the pickup would have to be completely re-wound. But it looks like it could be unwound just a little, and re-attached to the lead.

Mossman wrote:I actually left a message for Lindy's re-wind guy yesterday morning, before I got the bass back, thinking the pickup would have to be completely re-wound. But it looks like it could be unwound just a little, and re-attached to the lead.

Ed, that is exactly what I would do. If you take off the black tape and save it, there will be two about 1" long pieces of masking tape also to take off - just start at one end then pull gently and it comes off. One piece will be holding the black wire that leads out to the coax to the switch. Carefully remove that and unwind the wire you found loose once or twice to have a length to work with. Carefully scrape it to bare the copper (it is coated) when wind it around the black wire lead and solder it. Lay it back in as you found it, using the masking tape to hold it in place, then rewind the black tape to cover it all. Ohm the coax again and you should see around 11k.

This is really easier than it sounds. Just work carefully.