SWTPC Stereo Tiger Repairs

@wg_ski How's the Onsemi BD parts for speed and Cob? Same question for their MJE340/350?

There is of course the 2n5551/2n5401 that are available from all the usual sources.
I'd go with Onsemi, not sure if there's a better brand.
This would also probably work fine for the VAS and comp.
I seem to remember a high beta version from Fairchild, don't remember the designation anyone ?
 
I’ve been buying Infineon’s mosfets - price for what I need has been better than ON (Fairchild) or IR. But probably the longes lead times I have ever seen on ANYTHING. In not sure I’d call 200 beta “high”, but where it’s critical 200 is better than 40. That’s where a lot of MPSA42’s end up.

Never tested the ON BDs for speed. I had a few Fairchilds in a mixed bag, and a quick Cob check was around 30 pF. It was mostly STs, which were tested by the seller and they came out surprisingly high. As did the SGS-marked MJE340’s. After that I sought out STs for those types over others. I did test Moto MJE340’s many moons ago and fTs were never over 20. If you wanted faster the devices to use were MPSU10/60 (now unobtainium Unless you trust NTEs, so you put ST 340/50 in those old Peaveys and BGWs). Fairchild may have been faster - they were KING of epitaxial planar small signal devices back in the war between the two.
 
In general, one should be able to replace those old RCA40409/10 with modern driver types, usually the TO-126. There isn’t anything “special” about them other than the hermetic metal package. Their SOA curves are deceiving - most ANY driver type will have its Ta-limited SOA be strictly thermally limited, but the Tc limited will have a second breakdown limit. 40409 is no exception (10 watts at Tc=25, but NOT at full vceo, but 1 watt at Ta=25 all the way to full vceo). Most any fast 126 type will do one watt to full vceo, or at least up to 200, 300 volts.

There were more than one series of 2N types in the metal can intended for audio amp drivers. Some of them were 100 MHz types, others dog slow. The only places to get those these days are second source makers (At too high prices), E-bay, or some surplus pile. Prices there have skyrocketed too - gone are the days of getting one for 50 cents or a buck. No sense in seeking those out anymore either, when a reliable BD139 can be had for that.