Adding RC Network to Tone Generator

[steve160304]

Hello, I have a 1953 C2 I've been tinkering with and I have some questions regarding possibly adding an RC network kit to the tone generator. I'm getting some low-end cross-talk that's very noticeable on the highest octave and a half-ish of the keyboard. Now, can I add an RC kit without recapping the entire generator? Or would it be advisable to do both? Also, I've been reading that when you do a re-cap, you also have to recalibrate the TG. Is this necessary? And if so, what does it entail? Also, if I just add the RC network kit, will I need to recalibrate? Any info would he great! Thanks y'all!!

P.S. this is my first Hammond! I'm an instrument repair technician.. So, I have some technical know how.. But, this is all very new to me. I've already recapped the preamp and vibrato line box. So, I'm currently getting a very clean signal from the output. It's really sounding good aside from the cross-talk!!

[Jaim]

Technical Service Bulletin 16 covers the addition of the RC filter networks on tones 37 to 48. On 1 TWG, I added the network to tone 36 as well. The cross talk is easy to hear on phones.

Calibration - listen - is there a smooth transition between tones 36 & 37 and 48 & 49?

Re-calibration involves adjusting the pickup rods.

Jim

[steve160304]

Jim, thanks for the response! Being able to find that service bulletin is a huge help!

[MihevicB3]

The RC networks will load the TG outputs. When I first put them on my B3, I found the volume significantly reduced on freq. 37-48. What I did was to first measure the mv output of the frequencies. Then I installed the RC networks. After I added the net works, I moved the magnetic pickups to obtain the same mv output I had before adding the RC networks.

John M.

[steve160304]

John, thanks for the input! I'm starting to think I may do both and just re-cap the whole thing while I'm at it. From what I'm reading, it seems like a TG re-cap can vastly improve tone.. My C2 will eventually be living in a studio.. So, I'd like it to sound as good as possible for recording..

Btw, would anyone happen to have any good pictures of what the RC network components look like installed?

The RC networks will load the TG outputs. When I first put them on my B3, I found the volume significantly reduced on freq. 37-48. What I did was to first measure the mv output of the frequencies. Then I installed the RC networks. After I added the net works, I moved the magnetic pickups to obtain the same mv output I had before adding the RC networks.

John M.

[Jaim]

TSB 16 has you mounting the RC filters on the back of the TWG. Factory installed filters are mounted on top of the LC filters used on tones 49 - 91. See picture. The green wires are the in and out. The cap is hidden behind the terminal strip. Input is on the left. The first resistor in the schematic is actually resistance wire on the pickup coil.

Jim

[David Anderson]

I know of a few 2-series Hammonds in need of tone generator recapping. This will, in and of itself, decrease the crosstalk. As the paper capacitors age, one thing that happens to them is that their ESR increases significantly. In many applications, this doesn't make that much difference, but, in this filter circuit, it does. It has the effect of widening the filter bandwidth.

Do use Mylar/polyester for recapping since these have similar DF to the original paper capacitors. Polypropylene is 1/10th the DF of paper or Mylar, and it does affect the circuit.

[Bobmann]

John, thanks for the input! I'm starting to think I may do both and just re-cap the whole thing while I'm at it. From what I'm reading, it seems like a TG re-cap can vastly improve tone.. My C2 will eventually be living in a studio.. So, I'd like it to sound as good as possible for recording..

Btw, would anyone happen to have any good pictures of what the RC network components look like installed?

Personally, I do not like to use those terminal strips. I wire the filters in as shown. The terminals on the coil are used as an attachment point only for those tones that have the coil, but the coil is disconnected from the circuit.

Bob