Heathkit Transistor Substitution

[Vunce]

I started working on a Heathkit AP-1800 Preamplifier that lost the left channel. The included documentation of this preamp is very thorough, but many of the transistors have a proprietary Heathkit part number that I can't find information or datasheets on.
There many of these two BJT's used:
SM07275 (NPN) Heathkit Pt#417-283
SM62186 (PNP) Heathkit Pt#417-284

I pulled several and tested with a Peak DCA75 analyzer.

NPN's: Hfe 220-320, Vbe 0.770V, Vce 0.040V
PNP's: Hfe 230-285, Vbe -0.765V, Vce -0.070

BC547B/557B could be a possibility, but with so little info known about the originals, I'm not confident enough about this choice.

The PNP's have the dreaded black legs up to the transistor base with webbing connecting the three legs.
Any information would about substitute BJT's be greatly appreciated.

 

[Conrad Hoffman]

I don't get that concerned about black leads if everything is working properly. I certainly wouldn't change anything that's working, though if I change one channel, I change the other to match. You can start with the supply voltages to determine what you might need, plus a bit of thinking about the circuit. Since you can use the Peak to get some idea of hfe, it should be easy enough to test replacement candidates.

 

[Vunce]

Yeah, I probably put the cart before the horse and fixated on those two part numbers in case a couple are kaput.
I agree with you, as long as they are working as they should, they will stay.

 

[akimmet]

The black stuff just looks like plastic flashing. I don't see any corrosion on the leads themselves. Absolutely nothing to be alarmed about.
It is only a coincidence if some are bad.

 

[akimmet]

According to this page: https://www.qsl.net/w6ovp/heathkitparts.htm

417-283 SMO7275 NPN 40V 800mA 300MHz
417-284 SM62186 PNP 15V 200mA 850MHz

However these specs do not look right to me.