Hammond M3 and HR-40 connection

[mwd]

I acquired a M3 from a local church. They were playing it the week before as they brought it out of 16 year storage to sell it but when I went to pick it up and it would just buzz and 'thunk'. In my extremely limited knowledge I don't think it's spinning up and I doubt it has been oiled in years. I ordered some oil and will start trying to figure out. The main reason for my post is they also gave a HR-40 Tone Cabinet, but no cable. I know they had this hooked up and using it back in the day. The organ has a 5 pin connector and the tone cabinet a 6 pin. Both male and female.

I know there is potential for high voltage and I have schematics for both the organ and the tone cabinet but I am seeking just general understanding of operations. Does the organ provide power to the tone cabinet? Does the cable carry both signal and power? I have contacted church to please look for cable near where they found the cabinet but there is a probability I will have to buy one or have one made. Any assistance appreciated.

[Jaim]

Use the standard 5 to 6 pin cable. On the 6 pin end you will have power on pins 3 & 4. Balanced signal on pins 1 & 6 and ground on pin 2. The M3 requires a Leslie kit to interface a tone cabinet or Leslie. Is the 5 pin connector in a box of some sort and do you have any switches on the front rail?

There are many threads about getting the TWG up and running.
Do a visual inspection of the power cord - these tend to deteriorate.

BTW - you will get more visibility if you post in the Hammond group.

Jim.

[mwd]

Thank you Jim. I have a switch on the front that changes from internal to external speakers or both. The cable connector in the back is not in a box but a lid may have been removed over the years.

[Jaim]

In the box, the Blue and grey wires are AC power going to pins 2 & 4. Pin 3 is ground (black). The balances signal (red/black) in on pins 1 & 5. I don't recognize the box type. Where do the red and black wires come from?

Again - you will get more visibility if you post in the Hammond section.

Jim

[myorgan]

Moved per Jim's request.

Michael, Moderator

[enor]

That's a neat little interface, of a type I haven't seen before. Good catch!

[David Anderson]

All I would add is that I never take anything for granted in Hammond hookups for tone cabinets, especially if something appears non-standard. For example, the bass channel of the HR-40 amp needs a ground reference that would usually be provided by the organ preamp's output transformer. Does this kit provide that ground reference? Why are there capacitors in the box?

[mwd]

Thank you for moving this post. I did not want to double post and I figured since I bought it from a church it was a 'church organ'...lol. I will see if I can track the red/black wires. The good news is I got it going yesterday after a couple of drops of oil. The folks at the church said they would keep an eye out for the cable that they used. I'm not comfortable just plugging stuff in especially with vintage gear.

[mwd]

Where do the red and black wires come from?

So those wires come from the Auxiliary volume control in the black box on the front.

[Jaim]

The M3 only has a speaker output. The HR 40 requires a balanced input. The Leslie 8010 kit was used to interface a M3 to a 122 type leslie which has the same type of input (Type 6H) as a HR 40. There needs to be a transformer with an 8 ohm resistor across the input to provide a balanced out.
1. The speaker output from the amp is on the 5 pin plug. Where does it go?
2. It appears that in the 5 pin connector box, only the 5 pin connector is used. True?



Jim

[David Anderson]

Some M3s have what amounts to balanced output from the output stage, particularly the earlier ones with field-coil speakers that do not have negative feedback from the secondary side of the output transformer. However, the Bass Channel of the HR-40 amp needs a ground reference that would normally be provided by the console organ preamp's output transformer. Only M3s below SN 90485 have a center-tapped and grounded output transformer secondary, according to the manual, but I would check it to make sure. The M-series manual is somewhat vague on where changes occur relative to serial number.

If it's an unsuitable M3 model, you can always use the same transformer used in Leslie 8000 kits and sold by TWG to get a balanced signal while keeping the internal speaker load on the M3.

[mwd]

My serial is 1158XX. Whereas XX is between 50 & 99. Jaim I can't answer questions 1 & 2 because I've never hooked it up to anything. I assumed the church had used this M3 with the HR-40 cabinet they gave me over the years but maybe they didn't. I asked them to take a look around, as they cleaned up, for the cable and as of yet no luck. Attached is a more direct downward look on the box to see some of the connections.

I don't have to have the HR-40 hooked up if it needs further modifications to work. Thought I would use it to create a stereo image for recording in my studio since they threw it in the deal. I would have more benefit if the 5 pin plug could give me a TS or TRS out (or both). I would love to be able to shut off the organ speaker and feed to a pre-amp I use for direct recording, use FX, go direct to mixer or use headphones without blowing anything up because of load balances or ultra hot signals. I am thinking I have the beginnings of that possibility with this connector and the box in front that switches internal, external or both.

[geoelectro]

I believe this schematic is for this kit,
Geo

[Jaim]

Ah - Thanks Geo. I knew somebody would recognize this.

Jim

[mwd]

I have the complete pdf manual this schematic is in but wasn't 100% sure it was correct. Considering it is probably what I have can anyone give further input as to what I need to do to make the HR-40 work? Just order a 5-pin to 6-pin cable? Precautions?

[Jaim]

Acquire a 5 to 6 pin cable.
When was the last time the HR40 was powered up? 16 years ago? I wouldn't do it without taking a look at the amp and even then I would use a variac.

Jim

[David Anderson]

With regard to the HR-40, here's what I'd do. I'd unplug everything, including all tubes or at least the rectifiers, and test the power transformer for secondary voltages. I'd test the chokes and output transformers for continuity/DC resistance. Then I'd replace all the paper dielectric capacitors (and any severely drifted resistors). The HR-40 doesn't use any electrolytic capacitors, only the oil blocks. I might test them, too, but then I have an old Heathkit Condenser checker that allows me to test caps like this at full voltage.

I might make an exception on the paper capacitors if they are the kind in brown plastic cases, but the ones in metal cases do leak and fail.

The longer I've worked on this kind of gear, the less I use my Variac. It can be useful in equipment where electrolytic capacitors may have de-formed over time, but there aren't any in this amp. The oil block caps don't deform.

Past a certain point of experience, you have a pretty good idea of what the problems are likely to be. I think it's a better use of one's time to get in there and do a clean sweep, especially since no one cares about original parts in an HR-40 amp. There's no point in using your output tubes to see if caps are leaking by watching them red-plate, at which point, they are damaged. Replace the coupling caps to their grids and be done with it :-)