Gulbransen Theatrum Buzz & Hum Issue

[rustyshackleford]

Hi,

I just picked up a Gulbransen Theatrum Organ from a local charity shop. The Organ cost me £20 with free delivery and I'm really happy / Impressed with the look and sound & functions it has.

There are a couple of issues I have with it and I was wondering if anybody else has had similar problems & whether or not it could be simple to fix.

The main problem is there is an rather large buzz coming from the speaker system and the jack output of the organ. Whenever I've tried to record the organ using the jack output, I get a nasty electric shock from the opposite tip of the jack lead. Its as if the organ has become live. I have also recieved a little shock from some of the components of the equipment I'm using to record with, Mixers etc. So the result is the signal is drowned in hum. If I unplug the jack the same frequencies are buzzing from the speakers in the organ.

I was wondering whether this is a grounding issue similar to the kind found with record players? and whether such a problem is easy to fix?

Any advice is much appreciated

[andyg]

Could be a ground issue, but as you're getting shocks, and given the age of the instrument (plus Gulbransen's reputation for unreliability) I think it's more likely that the power supply needs a rebuild. I wouldn't use it until it's fixed.

Repairs will probably cost way more than the organ is worth, which is probably around the £20 you paid. And it will still be worth the same when it's fixed. Easy to fix? Depends on how good you are with high voltage electrics. You'd also need a copy of the schematics.

Too late now, but our oft-stated golden rule is never buy an organ with a fault, unless you're 100% confident that you can fix it and don't mind paying out.

I'll let some of our resident Gulbransen experts chip in with some ideas.

[tucsondave]

The service manual for the U.S. version shows death caps (.01mfd, 1.5 kv) from both legs of the AC input to organ circuit ground. That might be a place to check. If one was shorted or leaking the chassis would be electrified.
The U.S. model did not have a grounded AC plug.
It does not show wiring for the UK model.

td

[rustyshackleford]

Thanks for the replies, I have a friend who could take a look at this and its good to know to start at the power supply. I think its probably worth more to me than the actual street value as I'm using it to record and its a pretty useful instrument. The leslie speakers, reverb, lamps are all in good condition, I couldn't find the fault with it when I bought it and it took a little while to figure that there was a buzz there, but on a piece of equipment this old thats expected. I've already had some really great results while recording from it, just want to clean the signal up a bit, and obviously prevent shocks and other equipment from being damaged.

If any one has any more advice on this problem it would be great to hear? if somebody had this issue and resolved it maybe.

Will pass any info on to my repairs man.

Many Thanks

[andyg]

Just a quick thought. The organ doesn't have an output jack as such, so I guess you've been using the headphones socket?

If so, that won't give you the organ's true sound. For that, you need to record it with mikes to capture the sound of the leslie. If you know that already, sorry, but there are plenty of people who don't!

But you could always record it straight and then add a leslie simuation in software.... :)

[rustyshackleford]

Thanks andy, yeah I just assumed the output would be suitable for a jack lead, that makes sense as when i inserted the jack lead there was no sound. so i had to pull it out half way (like on some mixing desks) to get the sound out. Haven't had a go at micing it yet / or plugging some head phones in so will give that a try. Thanks again for the great advce!

[andyg]

It's a stereo socket, so try a stereo 1/4" to 2 x mono 1/4" 'Y' splitter lead running to the desk/recorder.