Phonoland

Hi all: got a Seeburg Encore back round music system. uses a BMA3-56 amp. Missing the power transistors but found that I could sub out ones from a parts TSA 1 that I have. the problem is the driver transistors. I cannot find GC113a. I cannot find a cross either. Any help would be appreciated. Thanks Mark

Mark,
Give me the Seeburg part #, and I can probably come up with a sub--
Ron Rich

Ron:

I think the Seeburg number is 309411 for that transistor.

Sorry--I have no cross number for that one---try NTE---
Ron Rich

Thanks for responding. yep the Seeburg number is 309411. it appears it was made by TI. it is a germanium npn. it goes in opposite the pnp gc102a. Mark

Mark, you have probably seen this doc':
https://www.flippers.com/pdfs/Seeburg_H ... erence.pdf
It shows the device to be a GC113a and gives the spec's.

That is really all that is needed to at least look for a suitable replacement. The complicating factor is that it is a germanium, those can be hard to find in a particular configuration.

Using higher voltage and current transistors is fine and since this is a low power driver, I wouldn't worry too much about a heatsink. The collector voltage in that amp is probably nowhere near the spec on that list so you might have a bit of flexibility there.

More important is to be careful in [powering up the circuit after whatever replacement you do use. I suggest a 25 watt bulb in series with the AC at that point.

Replacing the entire driver-final chain with commonly available silicon types has been my approach in old PA and consumer amps. Biasing must be increased and the gain is higher so feedback sometimes needs to be changed.

Sorry i couldn't be more specific.

Rob/NYC

What I'm finding are these two crosses:

PNP Germanium, T05 case = NTE 102

NPN Germanium, T05 case = NTE 103

The Seeburg cross reference guide says 309411 is a GC113A and that it's a PNP Germanium.