Kustom_Bart Messages: 601 Registered: October 2010 Location: Greenville, MichiGUN
Senior Member
looking for transistors for K100 they are the ones for q126 rca 38869 and q127 rca 38870 is there another part that will cross for these two parts that you know of off hand? Or is there a supplier for these two pieces that you know of.
Those part numbers are the main driver transistors for the power amp. I've been using a 2N3440 for the NPN (38869) and a 2N5415 for the PNP (38870).
They need to have a small heat sink attached to the cases.
Edit: I just looked up these part numbers and now the 2N5415 is only being made by one company and they want 12.00 apiece for them.
I guess it's time to switch over to a TO-220 case transistor like a TIP41c/TIP42c. Or maybe a plastic cased one like the MJE340/MJE350. Unfortunately the pinouts are different and will be harder to fit in position.
Kustom_Bart Messages: 601 Registered: October 2010 Location: Greenville, MichiGUN
Senior Member
Thanks guys, my guy was trying to use the 128 and 129 and it wouldn't work, I am guessing the 128 is the issue? I did forward the info to him and he will know what to do. He has been repairing Kustoms for Pleat and I for years, this is a K100 head that belongs to Pleat, so now it will live again.
pleat Messages: 1452 Registered: June 2004 Location: Belding, Mi
Senior Member
Been busy but the amp is question is the K100-2 reverb head. I thought I had given him all the cross transistors but talking with Kustom Bart today I must have missed some.
stevem Messages: 4738 Registered: June 2004 Location: NY
Senior Member
What else was replaced other than the transistors?
Is it the driver board that is motorboating ?
If the tech disconnects the signal input to the driver board does the amp still motorboat ?
A bad electrolytic coupling or gain cap could make for the same issue , or maybe one of those two driver transistors are way above spec !