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

[traynin]

To say that this entire site has been an asset would be an understatement. Otherwise, an old retired grease monkey such as myself wouldn't of had a chance repairing or modifying all those vintage amps I've accumulated through the years in my basement.. But, now, in my efforts to rebuild an old Traynor TR-2 reverb unit, I find myself having to deal withthe notorious transistor and I have absolutely no clue where to start.
More specifically, I'm hoping to replace both the RCA 40315 ( heat sink????) and the other3 X BC109/ BC149 transistors on the schematic below.. And while I finally did manage to find a BC109C ( apparently "C" simply means more gain) , I simply don't trust my capacity to even begin to cross reference a suitable replacement for the RCA 40315.. Can someone suggest a replacement - Preferably, one that I can source either at Moosers or Digikey up here in Canada

[traynin]

OOPS! Sorry, I just realized that only this schem as found online for a newer version of the TR-2 has the "heat sink notation beside the RCA 40315 transistor The schem as found inside my older unit does not - Not sure what it means but, nevertheless, the transistor appears to be the same and I really do need to replace it - Thanks.

[pompeiisneaks]

From what I'm finding in searches the 40315 is a BJT NPN transistor that can be replaced with an NTE 128:

https://www.digikey.com/en/products/det ... QIQAvD_BwE

oddly mouser doesn't seem to find that part at all.

I'm no expert, so take that with a grain of salt

~Phil

[traynin]

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

[pompeiisneaks]

Trying myself to get better at understanding replacements. I don't know what parameters are the 'most' important, but looking at the 40315 datasheet:

https://datasheetspdf.com/pdf/1293847/RCA/40315/1

it says it wants VCEO of 35 volts, but the +18V in the schematic means that's a bit overkill, the VEBO of 2.5 volts isn't available from some I've looked up at that voltage, but they seem higher, so something like this also seems to fit the bill:

https://www.mouser.com/ProductDetail/Ce ... GzOw%3D%3D

I'm still not 100% sure exactly which parameters are the most important here, but ensuring it's over that 18V you're possibly safe, electronically, but is it going to 'sound good'? Not sure.

~Phil

[pompeiisneaks]

I will also point out that this is a tube amp forum, and therefore the number of people versed in solid state electronics is much smaller, so there may not be any other responses in a fast manner, often this kind of thing is better served in some of the forums linked to solid state work like diyaudio.com or the like.

Even those that are versed in this type of thing may not be interested in talking about them, and only focus on the tube side of things. It tends to be a bit of hit or miss here. Mostly due to the nature of this

They might have an instant answer that's more exact in this case than my educated guessing.

~Phil

[traynin]

Yes, I guess I get that pompeiisneaks.. I just didn't want to join some group I'm not all that interested in just to turn around and take advantage of their knowledge.. lol

[Stevem]

The NTE 128 NPN Transistor will work perfectly for the RCAs replacement.
I use these all the time to fix blown out output driver stages in Kustom amps, and all they need it the top hat type heat sink added to them .

Check out pricing from NTE parts direct in NJ as sometimes they have better pricing .

Also as with a tube amp I would replace any electrolytic’s while your in there!

If you can’t find a certain value in a cap remember you can make a non polarized cap out of 2 electrolytic types by joining there positive ends .
All you need to do is make each new cap twice the Uf value of what the single original cap was.

[traynin]

Thanks Steven.. I have already replaced all the caps. But the reverb is rather weak and the "Color" and "Mix" controls seem completely ineffective. So, I thought I'd look into the transistors.. In fact, apparently, the old Lokfit BC149 / BC109 transistors have a very bad reputation far failure.

However, I really would appreciate more info in regards to "heat sinks."

Again, there is no such notation alongside the RCA transistors on the schematic that came with my reverb unit and I see nothing whatsoever that might look like that on the board itself.. There is only mention of heat sinks on the OTHER schem that I found online - A schem that might be for a later version of the unit that had all the inputs and outputs on the front.. Everything is at the back on mine.

I've attached pics of both units and both schems

Any reason why there is no mention on my schematic,, Do I need it and what does it look like..

[traynin]

Could it possibly be because of the nature of the primitive style PCB on my unit and it's own inherent capacity to dissipate heat VS what might be a somewhat more typical PCB on the later model ??

[Stevem]

I would confirm that C3 is not leaky and throwing the bias off to that down stream pan driver transistor by passing some of the up stream 7 volts dc to it.

Does it look like the reverb pan is original?

On the original pan the output jack should not be grounded to main pan case like the input jack is, nor be grounded to the whole units chassis or ground plane.

Is the dry signal output ( non effects ) at least as loud as what’s going into it?

[traynin]

All caps are new except for C6 (mustard .1 tone cap). Pan is original. never been tinkered with and in good shape.. Input equals output volume FX on or off..

Only issue is reverb is quite weak and tone knobs barely effective..

Then again, this is a very primitive transistor driven unit.. It didn't work before I changed the caps.. In fact the lead between C10 and C11 was broken.. Therefore I never heard how it was supposed to sound in the first place..

Perhaps, I expect more than I should.. lol

[Stevem]

No, when that is working right it should sound pretty good as that Driver transistor can pump a lot of current into that tank.

Are the power supply voltages at the nodes good, infact on today’s wall outlet voltages they should be a tad high.

It wouldn’t hurt to check some of the high value resistors like R4,8,11,20 to check if they have drifted higher by more then there tolerance band percentage,

[traynin]

Actually, you might be onto something Stevem.. In fact the voltage at the first BC109 is a tad low at 5.94 V where it should be 7V and I only get 9.14 V at the RCA 40315 where I should get 9 according to the schem..

Then again,, all voltage creep up a tad after awhile

Perhaps I have a drifting resistor

Or, could the fact that I used 680uf and 120uf caps respectively instead of 640uf and 125uf make that much difference

[traynin]

oops, sorry,, I should get 14v at the RCA and I'm getting only 9.14V