My Hammond M-3 Organ is not earthed! Is this safe?

[bails]

I was replacing the power cord on my 1960 M-3 organ last night (because the original one has turned to dust) and found there was no earth connection, only an active and a neutral.

I realise this was the standard configuration in the US in 1960, but because I had an original three prong power cable, I assumed someone would have earthed it once it arrived in Australia. This is not the case, and I was wondering if I should do this myself, or leave it as is.

Is it just a matter of connecting the earth wire to a random point on the chassis, or is there more to it?

[headbanger]

Captain Foldback would know.

Here's the schematic page. There are a couple of versions.

[urlhttp://www.captain-foldback.com/Hammond_sub/ha ... matics.htm[/url]

[bails]

Thanks for the link.

This is however also a general tube amp question, not specifically a Hammond question. Perhaps I should have titled this topic: "My Old Valve Amp not earthed! Is this safe?"

Most of the Hammond forums seem to be populated by players more than techies, and the schematics don't tend to show layout so I wouldn't know exactly how the amp should be earthed, or whether it's even worth doing. I'm sure that earthing old amps is a fairly common procedure, but I'm not sure if it is as simple as soldering the earth to a random point on the chassis, or whether there are other factors to consider.

[headbanger]

Bails,

I have a L series which should be similar config, I'll have a look.

Just my thoughts but I don't think it's a problem, nowhere should you come into contact with metal parts when playing a Hammond - unlike a guitar amp.

[admin]

Bails: Here is a response to a question I posed to the company handling Hammond organs parts these days.

Hi Peter, Yes. The original organ power cable was not a 3 wire type, so hopefully there is no trouble with the power transformer. It is possible that if there is any leakage in the transformer, you might have a problem when you connect the 3rd lead to ground, Frankly, I would not worry about making the connection.

Jerry J. Welch
Organ Service Company, Inc.
1210 West 55th Place
Countryside, Illinois 60525
Phone 708-352-8011
Fax 708-482-9626

[rictified]

JMHO but I ground (earth) everything including old amplifiers, radios, transmitters etc. (I'm a ham radio operator) . I've never had a problem with power tranny leakage I'm not even sure what the organ co. means by that unless they have bypass caps to the chassis as some old radios had (which usually eventually leak). This stops a potentially lethal electric shock, if a hot wire touches the chassis now the chassis will be hot, if it is grounded it will blow a fuse instead alerting you to the problem. Also you will have less hum as the neutral and hot wires will always be in the correct sides.

[admin]

Bob: That was may original take, but these are the Hammond Service folks and so I felt obligated to pass along the official policy.

[soundmasterg]

The old US amps with 2 prong cords should all be changed to 3 prong these days. However, they need to be rewired when doing this so that the fuse and switch are on the black (hot) side. The neutral wire (white) should go straight to the transformer, and the green (chassis ground) should go to it's own bolt on the chassis at least an inch away from any other chassis grounds. They will work if you don't change around how they did the fuse and switch but they aren't correct that way and can be a potential safety hazard.

Greg

[rictified]

Hopefully anyone that undertakes this will already know that, if not they should have a qualified tech do it. The hot wire always goes to the switch, takes the short path. I understand why you printed that Peter, I probably would have also, being as it comes from the Hammond Organ Co even though I disagree with it.

[soundmasterg]

Yes, I would say that it is critically important that AC wiring is correctly done in an amp, or it can be very dangerous, and if anyone who is considering working on anything which needs some AC wiring changed, and they don't know everything they should about the subject to be safe, then find a tech and have them do the work. Safety first is the most important rule to follow.

Greg

[bails]

Does anyone have a genuine early 60s, 'Made in USA' fuse holder that I can add to the power supply chain?

Doesn't need to be from a Hammond, but I'd hate to put in a shiny, new Taiwanese one on such a nice old amp.

Preferably the type with screw cap, which gets drilled into the chassis (like so many Fenders of the same era), rather than push-in automobile type.

[jnbass]

As a matter of practice I ground ALL my old stuff.

What's a lil extra voltage among friends...