I salvaged this heatsink from a dead power supply (not my build). The four Motorola(?) 2N3055 have actually survived.
Strangely, all four have exactly the same very high hFE of 221. Is that normal? Specs mention hFE 70 max.
I might leave it as it is and build a 2-channel quasi-comp retro amp. I've already laid my eyes on Elvee's Circlophone.
Would anyone suggest other preferred schematics?
Thanks,
Jacques
Strangely, all four have exactly the same very high hFE of 221. Is that normal? Specs mention hFE 70 max.
I might leave it as it is and build a 2-channel quasi-comp retro amp. I've already laid my eyes on Elvee's Circlophone.
Would anyone suggest other preferred schematics?
Thanks,
Jacques
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Different data sheets show differences for these old devices. You will be measuring Hfe at low current wheras the data sheet measurements may be at 1 amp and at some frequency such as 1kHz.
They are what they are.
They are what they are.
It is not unusual for old power devices to show fairly high beta at low currents but then to exhibit significant beta droop. Note that fT is another story.
That sort of characteristic may be useful for a Class A headphone amp or somesuch. 3055s would seem a tad too big for something like this though, I'd rather go with 3-4 amp types then.
That sort of characteristic may be useful for a Class A headphone amp or somesuch. 3055s would seem a tad too big for something like this though, I'd rather go with 3-4 amp types then.
Be aware that you still need chassis/transformer/cabinet/preamp/rest of power amp and supply components, etc. , all costing some 10x to 20x more than what you already have.
Like finding a wheel and tyre and building a car around that.
Doable of course, but much of a better deal if you already salvaged, say, at least a suitable power transformer and can recycle/kludge a chassis, both being the most expensive parts of an amp.
Like finding a wheel and tyre and building a car around that.
Doable of course, but much of a better deal if you already salvaged, say, at least a suitable power transformer and can recycle/kludge a chassis, both being the most expensive parts of an amp.
Thank you for being protective. Actually I built my first amp from scratch (including the case) in 1981. You were probably not born yet 🙂 !
Hfe 200 at 10mA, 7 at 5A. Yes, 7. How bout we blow a set of driver transistors, ok?
The Circlophone or other 25V rail amp would be fine, but don't go higher unless you have enough to parallel a few. Unless you do want to blow the drivers.
The Circlophone or other 25V rail amp would be fine, but don't go higher unless you have enough to parallel a few. Unless you do want to blow the drivers.
The idea was to treat these old dudes respectfully without any violence in mind.
Such as use them a nice-sounding medium power amp with a different or novel topology and maybe learn something new in the process.
I just learnt here about beta droop; what will I learn next ?
Such as use them a nice-sounding medium power amp with a different or novel topology and maybe learn something new in the process.
I just learnt here about beta droop; what will I learn next ?
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