C3 weak chorus

[folkswaggin]

Hope everyone is doing well. Have a question regarding a chorus issue on a C3.

A young, talented keyboard player from my hometown in NC recently returned here after living in New Orleans for the last few years (with gigs are so scarce). Returned to his folk's place and to his C3/147. He started jamming with jazz guitarist Charlie Hunter (also now in Greensboro NC) and called to mention an issue with his organ.

I'm tiring of being stuck inside my house month after month and the thought of checking out a friend's Hammond (instead of changing diapers and teaching kindergarten at home) sounded fantastic so...

The organ sounded fine when chorus or vibrato is off. However once ch/vib switch is on, the volume for that manual dropped dramatically.

No change when I swapped 6AU6 tubes. I happened to have some 470K & 2.2M resistors so replaced plate & screen resistors for the 6AU6 tubes (R7, R8, R19, R20) solving the volume drop but then the depth of the chorus sounds very weak to my ears. He hasn't heard his organ's chorus in years & was thrilled but to my ears, it's off and I wonder where to go for the likely culprit. C1 sounds no different than with vib/ch off & C3 sounds more like what C1 should. Any thoughts to share?

1957 C3, black wooden line box. No noticeable loose wires. Should I lean towards recapping linebox?

I did notice the organ was over-oiled - the scanner/run motor reservoir was filled up halfway with oil (presumably has been for years). That made me wonder if scanner might need disassembly/cleaning. Can oily scanner insulators cause a weak sounding chorus? Perhaps I should take a couple of 9v batteries to each of the scanner's brass screws?

Or should I go back under the AO28? (C12, C13?)....

Am I on the right track? Wasn't sure what to suspect next and I sure do look forward to getting out of the house again real soon....

Take care folks,

David McCracken

[David Anderson]

Hi David,

Sal would remind you that the Chorus mix resistor on these earlier line boxes (R44) is 22k rather than 12k on the last line box version. Playing with that value can make Chorus deeper.

Recapping the line box may help. How much it helps tends to be unpredictable, but it can't hurt. Make sure you have the right capacitor values before you start. Most are 0.004uF. Panasonic does now make a cap in this value.

Unless the scanner is motorboating, battery-zapping will do nothing. Oil in and of itself has no effect on the scanner. It's a persistent myth. Oil only has an effect when it helps move conductive metal particles into the wrong place, causing motorboating.

[Sweet Pete]

Replaced the mix resistor 22K with 12K for deeper chorus.It worked!

[Alenhoff]

I replaced the mix resistor on my B-2 some years ago, and it made a big difference. But it really started to sing when I re-capped the line box. Sounds wonderful now.

[handyczech]

The vibrato switch itself is somewhat complex with many leaf springs. Possibility may be dirty contacts there. Do you agree David?

[Tonewheel]

Just another view here. I'm not a technician, so I asked our elderly tech here, before he retired, to put a pot over that resistor site on my 55 B3. You can get a really SICK vibrato with that, but I have found a sweet spot that I like, It helped when I was trying to copy the sound of Green Eyed Lady when the organist is chording in the background, about 4:40 here: https://www.youtube.com/watch?v=i_i7PKdQJU4

So, if you don't want the chorus to be too pronounced, it's a way to attenuate on the fly.

Also asked him to do the same with percussion.

[David Anderson]

The vibrato switch itself is somewhat complex with many leaf springs. Possibility may be dirty contacts there. Do you agree David?

I have never found that to be a problem.

[enor]

Dendrites in the switch box are a very common source of vibrato issues though! Not weak vibrato though - but "motorboating"

[delaware dave]

I also have a 57 B3 and what I like about it is that the C/V isnt overbearing like you tend to hear on a clone. The C/V has a nice purr. C1 however on mine is very light but I'm ok with that. I really don't like the modern clones in that the C/V is far too pronounced for my liking. When I hold a note or chord i want to hear that purr and not a motor boat. I also believe 50's hammonds were more purry than the 60's and up. So for me what you are describing is more normal given that your hammond is also a 57.

[David Anderson]

FWIW, 1957 was the last year of the wooden vibrato line box and the 22k mix resistor. The metal open-frame line box appeared in late '57, so some '57 consoles have the new (and last) version.

[Sweet Pete]

The B2 with silver linebox (1953) has beautiful worn out vib/chorus!With a 12K mix resistor bringing up levels of smoother less bumpy vib/chorus.
C1 a little weak.The rest are perfect!Thanks again geo,that was almost twenty years ago.Still sounds amazing.I change the mix resistor before I shotgun the linebox caps.Have a listen first,after might be too late!On C3 no need to have chorus wandering around creating phasing on low frequencies IMO.And why my daily driver 1962 A102 has the original parts in it! A player that was forced to learn tech by default knows what he/she wants to hear.Helps to know what you are looking for?No amount of tech will replace the experience of playing,a bit of both for best results.Learning to repair AND play a Hammond is totally normal.
This C2D is a bit too prominent on the outer octaves vib/chorus wise.Perfect in the middle though.What can you do?

[David Anderson]

Dendrites in the switch box are a very common source of vibrato issues though! Not weak vibrato though - but "motorboating"

I guess it's not inconceivable, but I've never encountered it.

[enor]

Behold exhibit A ;) Late 60s UK A-100. Got a call from a friend. Organ is in a tv studio and chorus has started motorboating. Limited time until they were going on air so I zapped it which cleared up the issue; but after a week the problem was back. Did a proper planned service call where I rebuilt the scanner which didn't appear dirty enough to cause a short so I opened up the switch box to find this on the covers, touching the switch reeds. Cleaned it up and the organ has been working fine on swedish tv every Sunday for about a year and a half now without issues.

[David Anderson]

I will grant that that is the furriest switch box I've ever seen.

But the thing is that the physical spacing of contacts is greater inside the depth selection switch box than inside the scanner. The Achilles' heel of the scanner is that 1/32" gap between the stator vane locating pins and the scanner body.

[enor]

I have actually never seen a dendrite in a scanner. Ever. Sometimes they're oily and dirty but no dendrites

[David Anderson]

It's not really dendrites in the scanner; it's tiny particles of the metal plating on the scanner body that slough off and get into the wrong place, namely between the stator vanes and the scanner body. If that weren't the case, cleaning scanners wouldn't fix the problem.

Mike Smokowicz of Trek II says the narrow spacing between the stator vanes and the scanner body is the key.

[geoelectro]

I had a "first" problem with vibrato on an A-100 recently. Ya'll know I like flashing Hammonds. (even nosy customers)
Anyway, there was no difference between vibrato and chorus. V1 sounded like C1. V2 like C2 and V3 like C3. Absolutely no difference. I know the chorus switch opens up a short to ground allowing a resistor to be in the circuit. So in this case, the short was always there no matter what. I measured between ground and the common buss on the delay line and with vibrato, 0 ohms. With chorus, about 17 ohms. I was long on the call and about out the door so I thought about flashing that buss. I did and bam! Chorus returned.

45 years in and I still see new things...

Geo