Hello folks,
I'm intrigued by Steve Bench's RAT Tube Tester. Details are here under "RAT gm/Mu Tube Tester Project"
Steve's Tube Pages
I'm trying not to worry too terribly much about which types of tubes I'll need to test, as I know I can customize that down the road. What I am trying to figure out first is the plate power supply circuit. The BOM calls for:
1 MPSA92 350v pnp to92 Q1 M 333-MPSA92
2 MPSA42 350v npn to92 Q2, Q3 M 333-MPSA42
The numbers on the far right are Mouser part numbers that now pull up no results, as this BOM was from the late 90's. But, I'm having heck finding an equivalent. I can't find any MPSA92 or MPSA94 transistors which are rated for 350v. They're almost all rated at 300v. Can anyone give an answer to this conundrum? Is this a typo, or if not, which equivalent transistors could I use here?
I've sent an email to Steve, though I'm not sure how often he checks his email, we'll see. Thanks!
I'm intrigued by Steve Bench's RAT Tube Tester. Details are here under "RAT gm/Mu Tube Tester Project"
Steve's Tube Pages
I'm trying not to worry too terribly much about which types of tubes I'll need to test, as I know I can customize that down the road. What I am trying to figure out first is the plate power supply circuit. The BOM calls for:
1 MPSA92 350v pnp to92 Q1 M 333-MPSA92
2 MPSA42 350v npn to92 Q2, Q3 M 333-MPSA42
The numbers on the far right are Mouser part numbers that now pull up no results, as this BOM was from the late 90's. But, I'm having heck finding an equivalent. I can't find any MPSA92 or MPSA94 transistors which are rated for 350v. They're almost all rated at 300v. Can anyone give an answer to this conundrum? Is this a typo, or if not, which equivalent transistors could I use here?
I've sent an email to Steve, though I'm not sure how often he checks his email, we'll see. Thanks!
Long story short I am not sure that Steffie Bench checks her old email address.
You will need to identify replacement transistors with the correct voltage ratings and sufficiently high beta as well as similar Ft..
Depending on your budget you might also want to consider the uTracer here: The uTracer, a miniature Tube Tester / Curve Tracer. I built one a couple of years ago and now have a hard time imagining how I ever designed anything tube based without it.
You will need to identify replacement transistors with the correct voltage ratings and sufficiently high beta as well as similar Ft..
Depending on your budget you might also want to consider the uTracer here: The uTracer, a miniature Tube Tester / Curve Tracer. I built one a couple of years ago and now have a hard time imagining how I ever designed anything tube based without it.
The MPAS42 and 92 are garden variety low power silicone transistors. There are tons of them on eBay even in sets of P & N. According to my transistor D.A.T.A. reference book they are both 300 volt units. (BVcbo and BVceo) I suspect the figures on the website are in error. Perhaps taken from a erroneous source listing. But since the actual voltage across a device is lower, 300 volts should be good enough. I use a Tek 576 curve tracer to check every transistor I use and have found that often transistors exceed their ratings to some degree.
I think you've explained that bit of the story well enough. Good to know. Anyone have any idea if it's possible to contact her, and how?
Stephie actually responded to my original email so, horray!
I will relay the advice given here:
"There are 350 and 400 volt TO92 parts available in stock at DigiKey. For instance, the KSP44 lists in stock at 44 cents. It is the NPN and a suitable replacement for the MPSA42. Similarly, the KSP94 replaces the MPSA92."
I'll get cracking on this later.
I will relay the advice given here:
"There are 350 and 400 volt TO92 parts available in stock at DigiKey. For instance, the KSP44 lists in stock at 44 cents. It is the NPN and a suitable replacement for the MPSA42. Similarly, the KSP94 replaces the MPSA92."
I'll get cracking on this later.
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