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Should I be excited? Bag of power NPN's Thoughts/Rambling
Should I be excited? Bag of power NPN's Thoughts/Rambling
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Old 14th January 2020, 08:05 PM   #21
livingdeliberately is offline livingdeliberately  United States
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Wink More Parts bin treasure for sure.

Years ago I maintained RCA TR-70's and still have the huge regulated power supplies as well as associated transistors of plug in modules. It will be fun revisiting the bins as the parts are all top shelf. I still use a pair of BA 72A's out of TR-70 for microphone amplification... high quality studio output.
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I'm a silver haired solder slinger building things the old fashioned way!
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Old 14th January 2020, 09:05 PM   #22
Tubelab_com is offline Tubelab_com  United States
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Location: West Virginia panhandle
used in portable power inverters aboard fire trucks.
Many of the big inverters that I ran across in my early years of salvage collecting used big germanium transistors since their low VCEsat was an advantage over silicon.

Motorola made some 50 amp germanium PNP's in the TO-36 package specifically for inverter use. I tried them in a guitar amp using the same totem pole design, but they shorted the first time I "set the controls for the heart of the sun."

I could be wrong about the output stage of the EV receivers. They could have been quasi symmetrical, but I seem to remember keeping just one kind of output transistor for them. It was one of those HEP replacements from Motorola. They didn't sell well, but I had to fix nearly every one we sold.

All of this stuff happened while I was a teenager with minimal technical training. I didn't know what I was doing, but I learned what doesn't work rather quickly. Fortunately parts and dead equipment were plentiful at the time I was learning. Between the scrap yards, the county trash dump, the dumpsters behind several large electronics plants or import houses, and the AS-IS table at Olson's (that's how I got hired), I rarely had to buy any parts. When I did, there were surplus houses.
Tubelab, it's 5 year mission. To explore strange new tubes, to seek out new circuits and topologies, to boldly go where no tube has gone before......
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Old 16th January 2020, 06:02 AM   #23
PB2 is offline PB2  United States
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Default Stacked, Quasi, Triple

A power amp schematic that I came up with as a young teen. The front end looks mostly
similar to the Tigersaurus but I added a beta multiplier that was copied from another amp.
I wasn't sure where to connect the collector of the beta multiplier transistor since I really
didn't know what I was doing at the time. Not going to ground was probably copied from the
Ampzilla or Dyna - not sure.
I also looked at the Dyna ST400, Ampzilla, Leach double, and perhaps a big Heathkit so it
probably came from one of those. I knew that without voltage gain in the output the front
end shown would not work and I never had plans to build the whole amp. I did build the
output stage and drove it from the 16 ohm tap from a tube amp to get more voltage. I was
worried that the small 5W drivers would not provide enough current drive so I made it a
triple. This is a stacked, quasi, triple output stage:
I had built a chassis, power supply and bought heatsinks for a scratch built Tigersaurus and
that served as the test bed for this. I didn't complete the amp until years later when I
bought the correct output devices for the Tigersaurus.
Picture is of the amp with a Hafler 500 on top of it to show the size - I still have it.
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File Type: jpg STACKED QUASI TRIPLEs.jpg (106.9 KB, 27 views)
File Type: jpg PB TIGERSAURUS.jpg (5.8 KB, 25 views)

Last edited by PB2; 16th January 2020 at 06:22 AM.
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