Electro tone PER 200 Percussion Unit Transformer

[Drawbar Dave]

I have picked up a PER200 unit minus it’s transformer. I would have had to change to a 230V transformer for the UK anyway.



Looking at the schematic the dc voltage should be 350VDC after the rectifier. Can anyone suggest the secondary ac voltage I would need from the transformer to get this DC voltage. Also can anyone tell me what sort of current rating I would need for the transformer? I am not able to work this out from the schematic.

Thanks and Merry Christmas :-)

[bnelson218]

Using the 1.414 formula I'd say around 248 volts.

[Doddy.van.Straaten]

You may try Electronic Instrument Service. Bob as I understand it from Hammond Organ forum postings was involved in the company.

http://tonewheel.com/

[Drawbar Dave]

Using the 1.414 formula I'd say around 248 volts.

Hmmm I wonder if 230V ac line voltage would work.

[Doddy.van.Straaten]

Hmmm I wonder if 230V ac line voltage would work.

The circuit diagram clearly shows a full-wave rectified value of 350VDC, the output of the smoothing capacitors shows 260VDC is being delivered to the circuitry.

[bnelson218]

Hmmm I wonder if 230V ac line voltage would work.

Hmmm...good point

[Drawbar Dave]

Hmmm...good point

I just don’t know what the tolerances are in the design of the circuit. I won’t receive the PER 200 in the post for a week or two so I can’t test the theory until then, but if I only needed a 6.3 filament transformer for the heaters and could use line voltage straight from the ac panel for the rest, that would be fantastic. I would have 345 vdc after the rectifier, right?

[tpappano]

Whoops, just realized that the original power transformer is missing.
Recalculating...

[tpappano]

You should *not* attempt to derive B+ direct from the AC line. This would make the organ a dangerous electrocution hazard and cause problems with connections to other equipment. You definitely need a transformer of some sort.

If a 230v transformer similar to the original can't be found, perhaps a 115v version combined with a small 230v to 115v stepdown transformer would work.

[Drawbar Dave]

You should *not* attempt to derive B+ direct from the AC line. This would make the organ a dangerous electrocution hazard and cause problems with connections to other equipment. You definitely need a transformer of some sort.

If a 230v transformer similar to the original can't be found, perhaps a 115v version combined with a small 230v to 115v stepdown transformer would work.

Ok understood. Any idea what kind of current rating I need to be considering when searching for a transformer?

[tpappano]

It looks like the B+ current requirement is about 15 ma, so you would want a transformer rated 25 or 30 MA secondary current at 225 to 250 volts.

[tpappano]

I was just commenting on the HV secondary. Obviously, the 6.3 volts must be provided for the filaments, whether from the same transformer or a separate one.

[Drawbar Dave]

It looks like the B+ current requirement is about 15 ma, so you would want a transformer rated 25 or 30 MA secondary current at 225 to 250 volts.

Great that gives me some direction. Thank you very much!

[tpappano]

You're welcome! Depending on whatever transformer you actually get your hands on, you have some wiggle room to play with the resistors between the filter caps (the 4.7k and 1k) if your transformer voltage is a little too high or low. It is sad, all sorts of components like these use to be 'on the shelf' of your local electronics supply house. Now you really have to get creative restoring older equipment 8)

[Drawbar Dave]

https://www.organforum.com/forums/sh...l=1#post297260

Hi yes I read that thread, originally thinking he was talking about the little signal transformer inside the chassis, but now I notice the poster is from a 230 volt country, perhaps they are talking about the PT after all.