Old Standel SI15b outputs

[randomair]

Does anyone have any experience working on Standel SS amps? I am trying to cross-reference their NPN output transistors. Below is a picture of part of the schematic.

[Enzo]

In a case like this, before I try to find something in my notes, do you still have a good one? If so, check its junction drops with your meter on diode test. If it measures close to .5v, then it is a silicon transistor. If it measures about .2v then it is germanium. Out of circuit measurements of course. In circuit there is only about 15 ohms emitter to base, and that would cloud your reading.

ANy other numbers on the parts? The S2773 is a SDT9203. Or was.

And before you cross them to NTE 284, look at the spec for the 284 compared to the MJ15003. Then try to justify paying four times as much for the NTE.

You want them all the same, so if you replace any, replace them all. I think yours are silicon. If the amp is runnning on like +/-35-40v, then most any 100v or better part will work. MJ15003 is common and cheap, and you can get real ones from relaible sources.

[randomair]

well the info on the transistors is: DELCO GM 7299803 6708. I am assuming "6708" is a date code. The readings I am getting on the one I yanked is:

neg lead to collector, pos lead to emitter: .090 and dropping (slowly but steady)

neg lead to base, pos lead to emitter: .130 and dropping (slowly but steady)

neg lead to base, pos lead to collector: .128 and dropping (slowly but steady)



...it even comes equipped with the GM patent number stamped on the side, for transistor packaging, fancy that!

[Enzo]

On diode test? SOunds shorted. Try resistance.

Was this amp making DC or humming loud?

[randomair]

Yeah, this was the diode test, I will try the resistance test and see where that ends up. There is a slight bit of of hum, but the one thing this amp is doing which I have yet to track is the normal channel is extremely quiet. I will need to measure the output voltage of the "blue epoxy" module that these amps were so famous for. The output voltage should read -23 volts.

[Fragger]

A schemetic for Standel`s infamous epoxy module can be found here

[twango2]

Standel 50 J 12 V schematic

I'm in need of a schematic for my 1955 (?) Standel 50 J 12 V.
In particuar the input vibrato stages.

Anyone help? input one sounds great but the vib channel hums because of a wiring mistake on my part.

greetz

twango2