Model A connector pinout?

[stanchfi]

I'm still trying to get my Model A running. I found pinout listings (http://www.captain-foldback.com/Leslie_sub/pinouts.htm) but how do I tell which pin is pin 1?

thanks
-James

[Logan]

There's probably an easier way to tell (since there's a dot on it) but generally the inside of those connectors (where the wires are soldered) are numbered

edit: i opened the 6 pin connector from my model A and they aren't numbered, but the pin to the left of the dot (facing as in your photo) is a black wire (which should be 1 according to the captain foldback pinout) and the pin to the right of the dot is a red wire

[Tim Rinkerman]

http://www.captain-foldback.com/Hamm...R40_QR40_1.gif

[Drawbar Dave]

it's all explained in the service manual too. Google HSM495 for the restored version.

[stanchfi]

Thanks, I hadn't looked through the "restored" version of the service manual.
For future reference, on the plug, pin 1 is to the left of the dot

[Drawbar Dave]

Has your A still got the hardwired 6 core cable coming out of the side of it? I removed mine as I didn't trust it and fitted a B3 style outlet box from TrekII on the back instead.

[stanchfi]

Ya, the original cable from the looks of it. Its on the list, though I'm hoping to get the thing running before putting more money into it

[stanchfi]

I finally got around to taking a look at this. I looked at the female plug at the end of the cable, and 3 wires had come off. One ac power wire, and the red and black signal wired (pins 1 and 6) The AC was no problem, but I could not tell the difference between the other two, so I took a guess and soldered them in place.

Now I'm getting a hum out of my tone cabinet (Never worked before, so this is an improvement, but so sound when pressing keys. Would this indicate I guessed wrong on which signal wire goes where?

[David Anderson]

Hammond Organs like the Model A used a balanced line output, so it doesn't matter if 1 and 6 are reversed. However, with old cables, it's common for the insulation between the red and black signal wires to break down inside the cable, causing a short, which will stop the signal. Or you could have some other problem somewhere in the signal chain. There's not enough information for us even to begin guessing what it might be.

[stanchfi]

Thanks. I think I'm going to have to bite the bullet and get a new cable and connector

[David Anderson]

Thanks. I think I'm going to have to bite the bullet and get a new cable and connector

I can't guarantee it's the cable, but are you really shocked that an 80 year-old cable might be bad? If so, you're in for a lot of unpleasant surprises. Resurrecting electronic instruments this old comes with a price tag.

[stanchfi]

So I got a replacement cable, and am pretty sure I have it wired up right.


Unfortunately, when I powered it up, there was some high pitched squealing out of the tone cabinet. I shut it down, and then tired again. No squeeling, but also no sound when pressing the keys (Tone wheels spinning, presets were on, volume pedal - tried up and down, tone cabinet volume up)

There is a low level hum from the speaker cabinet, all the power amp tubes were glowing, and the non-shielded pre-amp tub was glowing as well.

What I have done so far.
-replaced tubes in the power amp
-re-capped the power amp\
-replaced the cable from the organ to the cabinet

Would re-capping the pre-amp be the next thing to try?

thanks
-James

[tpappano]

If you have a voltmeter, one critical thing to check is that you have "B+" voltage between the B+ terminal and ground on the preamp. A *positive* 200 volts (approx.) should be on the B+ terminal. The organ preamp gets this voltage from the Leslie or tone cabinet, and won't do much without it, or if it's backwards.

[Drawbar Dave]

So I got a replacement cable, and am pretty sure I have it wired up right.


Unfortunately, when I powered it up, there was some high pitched squealing out of the tone cabinet. I shut it down, and then tired again. No squeeling, but also no sound when pressing the keys (Tone wheels spinning, presets were on, volume pedal - tried up and down, tone cabinet volume up)

There is a low level hum from the speaker cabinet, all the power amp tubes were glowing, and the non-shielded pre-amp tub was glowing as well.

What I have done so far.
-replaced tubes in the power amp
-re-capped the power amp\
-replaced the cable from the organ to the cabinet

Would re-capping the pre-amp be the next thing to try?

thanks
-James

I would not apply power to a preamp of that age without changing the capacitors first. Just personal preference with an 84 year old amp.

[muckelroy]

First of all, the color of the wires attached to the preamp tells us nothing about "did I wire this correctly"? We can't see how you wired the other end of the cable, or anything in between. The danger here is whether you got the B+ and the AC voltage wired to the right place. The 1 visible tube glows, so perhaps your AC voltage is wired correctly.

Do you own, or know how to use a multimeter (to check voltages, ohms, and continuity?)

The 2-tube preamp needs, at minimum, its paper coupling capacitors replaced. The problem here is that you can't isolate the problem to the preamp or the power amp without the tools to measure, at minimum, voltages. The preamp needs B+ voltage (should be around 200V DC) to operate and produce sound. You would then need to clip lead a known-good amp to the preamp's G and Ground output, and listen to the preamp on its own to see if sound comes out of the preamp successfully or not.

What model of tone cabinet are you using? They all have their own quirks, and maintenance needs.

[stanchfi]

I wired the connector per the manual.


I believe the same as the old connector, though with the old wires, they all looked yellow/brown.

The cabinet is a Glentone 25B I'v posted info on it here - https://organforum.com/forums/forum/...e-tone-cabinet

Yes, I have a multi-tester and am ok with it. I'll check for voltage at B+ tonight. Since the pre-amp tube is glowing I assumed it was getting the proper voltage (Though I may be confusing plate voltage with heater voltage)

One of the things that is confusing me is the Gnd. and the two Gs. Since Gnd is Ground, are the two G's positive left and right audio signals?

Thanks again to everybody!