Vibrato STILL CHOPPY after flahsing and rebuild. Help!

[danieldempsey]

Hi guys,

Sorry to start another thread about motorboating vibrato but this one's really got me stumped. I've bought and sold several organs and have had to rebuild a few oily scanners. Each time it worked great and the organs went onto happy owners.

However, I've got a C3 now that I just can't figure out. I've flashed and rebuilt the scanner twice and still get very choppy vibrato. Any ideas what I should try next? Recapping the line box possibly?

Thanks and look forward to your wisdom! :)

[geoelectro]

Broken wire, bad cap in delay line, bad coil in DL, short in vib switch assy.

Geo

[BlueOliveB3]

Also make sure the scanner harness didn't get reconnected to the terminal strip on the drawbar base backwards...I made that mistake once after a scanner rebuild... :-\

TP

[Bobmann]

Sometimes zapping is not enough to evaporate the whiskers.
I would start by taking the covers off the switch box...you should be able to do this without any de-soldering. There may be shorts inside there.
If that does not help, follow suggestions above.

I had one once that caused great consternation...turned out to be a couple of those hairlike wires from the coils in the line box had come loose from the terminal. It took a magnifying glass for me to see them.

Bob

[danieldempsey]

Well gents, I appreciate the great info but still no luck.

So far here's what I've done:

-Flashed scanner
-Disassembled and cleaned the scanner
-Confirmed that all inductor wires on vibrato line box are in tact
-Bypassed each cap on vibrato line box with a new one, one at a time
-Reversed the scanner harness in case I installed it backwards
-Opened the box with the chr/vibrato tabs and all looks clean and healthy, no shorts or dendrites detected
-Same for the rotary chr/vibrato switch box, all looks good inside

Still no improvement to the choppy vibrato.

Geo, you mentioned a bad coil in the line box, is there a good way to test for that?

Any other ideas? I'm stumped!

[geoelectro]

You can short each coil one at a time. If you get an improvement in sound on one it is likely open.

Geo

[Tubejack]

So far here's what I've done:

-Bypassed each cap on vibrato line box with a new one, one at a time

I'm no expert on Hammond vibrato, but I looked at the schematic, and I don't think you can eliminate the possiblity of a bad cap by bypassing with a good one. If one of these is shorted or leaking, you would need to disconnect it before testing with another capacitor. They also can't be tested with an ohmmeter without one end being disconnected first (they're shorted for DC by the inductors). I doubt this is the problem you're having, but just wanted to mention it.

Jack

[danieldempsey]

Thank you guys, I'll test the inductors as Geo suggested and then if no improvement I'll just recap that line box and see where I end up! Appreciate the insight!

[T-200]

If you find a bad inductor you can bypass it with a wire. But here's something that SimonB posted me when I had the same problem with my organ:

"Just a little point about bypassing one of the inductors. If you put a wire link across one of the inductors using two adjacent terminals on the top of the line box, then you should also disconnect one of the capacitors. This keeps the impedance of each section the same and ensures you get a clean vibrato. You only need to disconnect one end of the capacitor."

I got rid of the motorboating just with the wire link, but the vibrato was much better after disconnecting the cap.

Jussi

[danieldempsey]

Great tip, thanks Jussi!

[danieldempsey]

Well folks I'm at a loss here. I tried shorting each of the inductors and detected no change, and then I went ahead and recapped the line box and no change. Any ideas what I'm missing?

[danieldempsey]

Just an update, I hired a Hammond tech here in LA who spent three hours looking thru the C3 and could not correct the problem.

He said he's never encountered a vibrato problem like this before and is thinking the line box may have been replaced by a previous tech and may be the wrong unit. Definitely possible because the "open frame" line box in my organ does not match any schematic I've seen for that serial number.

Looks like the next step may be round up a different vibrato line box and see if that corrects it.

[freiburg]

Just an update, I hired a Hammond tech here in LA who spent three hours looking thru the C3 and could not correct the problem.

He said he's never encountered a vibrato problem like this before and is thinking the line box may have been replaced by a previous tech and may be the wrong unit. Definitely possible because the "open frame" line box in my organ does not match any schematic I've seen for that serial number.

Looks like the next step may be round up a different vibrato line box and see if that corrects it.

Just wondering, whether you could resolve the problem in the meantime.

Regards
Christian

[Wes]

I read ... somewhere... something about two styles of line boxes, and that the terminals were soldered in a different order, like offset by one terminal or something.

Does that ring a bell with anybody? Maybe that could be this fellow's issue?

[Hammoog]

I don't think offset by one would produce that big of a difference, or even enough for people to identify. If two wires were swapped, that could do it though. A dirty switch would be the next guess.

The way to get to the bottom of things would be to test continuity between the vibrato line's terminals and the scanner's terminals. A whisker anywhere in this circuit will play havoc because the impedances are very high and the drive is fairly low current.