RCA 40315 Transistor replacement for 70's Traynor TR-2 reverb unit

[thetragichero]

i know i'm backing the train up a little but: how have you confirmed that the transistor should be replaced? multimeter diode test (with the transistor removed)?

my quick and dirty test to confirm if the issue lies in the reverb driver/recovery stage or the tank: plug an rca cable between the send and receive. if the reverb knobs sound like a really loud/annoying treble booster, your issue is likely the tank (being a mechanical device with itty bitty wires on itty bitty transducers, likely thrown around by careless guitarists if not even worse, singers (if you can actually get them to load in/out) or drummers, this is not out of the realm of possibility)

maybe i'm just lazy now, but i wouldn't even touch a solid state amp without a lightbulb limiter and scope these days

[drew]

Thanks pompeiisneaks.. I'll wait a few days and see if anyone else has any suggestion. Otherwise, I'll just order that and try it out.. Would be nice to get both transistors from the same source though - Especially at $20 shipping for a $3.00 part..
lol

DigiKey will ship it for free to the US and Canada if you send in your order with a check or money order:
Free Shipping On Parts Orders

[Stevem]

If voltages are low by more then .750 volts ( the conduction point of a silicon based Transistor) then that in itself could be making for a non normal functioning circuit!

You need to chase down why those voltages are off by so much!

I would confirm that r24 and 25 are very close to being dead on the money, especially that 220 ohm one!

[traynin]

I think you solved my problem Stevem - Much appreciated.


Despite being a brand new 5 watt metal oxide, r26 measures 265 ohms instead of 220. either way, I get 10.3 and 14.5 volts at junctions A & B instead of 12 and 18 volts.. Yet, I'm reading exactly 26.2 volts at the transformer output - Pretty well as it should be.

Otherwise, I seem to have a bit more range on the tone pot now for some reason.. Not sure why but I did clean up that mess of factory flux that was all over the board.. Maybe, it has created some kind of undesired conductive path or I did something to improve a grounding situation somewhere upon putting it all back together..

Of course, I don't have a 1 watt 220 ohm resistor on hand,, so the rest will have to wait.

[traynin]

So, in the meantime, it's back to Uncle Doug boot camp and the Bassmaster for this old retired diesel mechanic. - So much more fun than playing with hydraulics or rewiring dirty machinery as I did all my life.. lol

Thanks to all

[mhuss]

Sorry, a little late to the party. The NTE part will probably work well, but for future reference, the main things to look for in a replacement transistor are (1) VCE is the same or greater (2) Current gain (Beta or hfe) is in the ball park and (3) power dissipation is the same or greater. Note that a different package may have different heat sinking requirements. In this case, any small heatsink that will fit the NTE is probably fine.