Should I be excited? Bag of power NPN's Thoughts/Rambling

I'm an old tube guy here having to re-learn things I have long forgot. Tube projects are on stand by while temporary nerve damage gets sorted. Just a little to shaky to be anywhere near high voltage DC :eek:, so low voltage projects are king for now. I literally have a warehouse full of vintage audio parts saved from "The Golden Years" and deal with the "Where do I start" with to many Ideas. While preparing a low watt germanium amp, I have run across a bag of 20 Motorola 69-206's NPN Silicon power transistors.

Vceo 80V, Vcb 80V, Veb 5V, Ic 50A, Ib 15A, PD 300W
For high power amplifier or switching applications.
These were sorted, precisely measured for close leakage and bagged a very long time ago.

ALL Measure exactly 2 micro amps Icbo leakage, but the Hfe/ AC Beta measures...
28
47
57
75
45
26.5
70
37
90
52
45
40
90
49
46
37
39
48
52
57
Possible JLH amp? 2,4 or 6 devices per channel?

What do you think?

Your input is kindly appreciated good or bad.
Thank you
 
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U230421

Disabled Account
2017-02-07 1:54 pm
You might consider an OTLcircuit (NPN's only) based upon known tube circuits.

Pair them up:

1 26.5 28
2 37 37
3 39 40
4 45 45
5 46 47
6 48 49
7 52 52
8 57 57
9 70 75
10 90 90

1 are spares
2 are front end inverters
3-4-5-6 are first in end stage darlingtons (L+R)
7-8-9-10 are second in end stage darlingtons (L+R)

pm me for a drawing of a possible circuit
 

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
The Sony TA1010 is an interesting all NPN design.
 

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Motorola 69-206's NPN Silicon power transistors..... The basic data I posted originally was a cross reference on the NTE site, but I do not think it is correct.

69-206 is either a house number for a large contract order, or part of an internal part number. Either way the exact specs are unlikely to be found in a published data book.

I worked at a large Motorola plant for 41 years. Even with friends inside the semiconductor division I could not find out what some of those numbers were.

If a large manufacturer wanted to buy some semiconductors from Motorola and wanted them marked XYZ-123, they could get them. If they didn't want the numbers released, they stayed secret. Usually they were just ordinary parts with special numbers, but there were plenty of "specials" and grade outs too.

Parts made for use inside Motorola had a long part number. Transistors started with 48-xxxxx and IC's were 5-1xxxxx. The last 3, 4 or sometimes 5 digits, and the date were the only marks on the part.

Your 69-206's could be an internal number ending in 206, made in 1969. If that's the case I doubt that they are really 50 amp 300 watt parts.

When you finally blow one up, cut the case open and check out the die size. You can guestimate the power and current rating from the die and wirebond sizes.

I bought a big box full of house marked RCA transistors in 1969. I found them quite hard to blow up, so I cut one open. That led me to believe that they were ordinary 2N3055 die selected for high breakdown voltage.

The Westinghouse 2N3773's that I found in a military scrap 400 Hz power converter were a killer find though. Made for a wicked 1200 watt amp in 1971. Can't discuss it here due to it's non-safe power supply.
 
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I bought a big box full of house marked RCA transistors in 1969. I found them quite hard to blow up, so I cut one open. That led me to believe that they were ordinary 2N3055 die selected for high breakdown voltage.
40636's, maybe?

The Westinghouse 2N3773's that I found in a military scrap 400 Hz power converter were a killer find though. Made for a wicked 1200 watt amp in 1971. Can't discuss it here due to it's non-safe power supply.
But you might want to share the power amp's circuitry without the PSU?
Best regards!
 
40636's, maybe?

That number sounds familiar, but I can't say for sure until I find the box that the remaining parts are in. I have moved twice since I packed them. I remember buying them from a surplus shop in the late 60's. I got a 100 piece bulk pack Styrofoam container for $20. They must have been hard to blow since I still have some left after 50 years!

When I was preparing to move everything I owned about 1200 miles after my Motorola career ended, I trashed things I didn't want to move. This amplifier was one of the casualties. It was a "booster" made to be driven from the speaker terminals of a 5 to 10 watt guitar amp. It used 6 of those transistors and made about 250 - 300 watts into a 4 ohm load at an untold amount of distortion.

I was about 16 or 17 years old when I made it. I used a jig saw and a nibbling tool to cut the chassis. My construction skills and tools have improved a bit since then. It had been stored in a shed outside for 40 years or so, but I plugged it in to see what would happen. As expected one of the filter caps started spewing it's guts, so I kept the heat sinks / transistors and tossed the rest.

But you might want to share the power amp's circuitry without the PSU?

The 250 watt amp seen here, and the 2N3773 amp I made shared the same schematic. It is the utterly simple driver transformer "totem pole" design from the mid 60's often seen with germanium transistors. I started making them as a kid using the big TO-36 doorknob transistors lifted from car radios in automotive junkyards. I wound my own driver transformers using three strands of Radio Shack enameled wire on whatever transformer core I could find.

This amp used 6 X 2N3055's. Three in parallel, each with their own emitter resistors, on the top, and 3 on the bottom. Power was a bridge rectifier running on a 75 volt 4.5 amp transformer (about 100 volts). A large cap was placed in series with the speaker since I didn't have a bipolar supply.

The BIGGIE was made from a heat sink that I found complete with 24 of the 2N3773's some time in 1970. They were wired in the same manner, as two banks of 12 parallel transistors and operated from rectified 115 volt line (about 150 volts). An accidental short across the output set the speaker wire on fire, but did not blow any parts! It was used as the PA for a rock band in their outdoor shows, driven by a Kustom 100 watt PA amp. The driver transformer provided isolation from the line for the input side.

The circuit is the same as the 2N2147 drawing. I just used bigger parts. The 2N3055 version used an old 6.3 volt heater transformer for the driver transformer core. The BIGGIE used an old power transformer for the core.

I did not have any means of measuring distortion or accurately measuring power output at the time I made these. I was 17 or 18 years old with a VTVM set on AC volts. My "load resistor" was a long piece of wire wrapped around a piece of plywood, or the heating element from a household heater.
 

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wg_ski

Member
2007-10-10 5:21 pm
The transistor in question is probably a 2N5686. Which is a double-die version of the 2N5886. The breakpoint for s/b in the SOA curve is at 30 volts, with a second breakpoint at 50 volts above which it falls like a stone. Good for +/- 35 volts in class AB, or +/-25 in class A. Above that you’d have to do some kind of series stacking, which does not work well without PNP’s. Maybe you can get it to work, I’ve tried and all I make are power oscillators and smoke bombs (and the same circuits converted to complementary work the first time).

The single die version is reportedly just as rugged in normal class AB service. Having the second die in there really doesn’t buy anything at elevated voltage. As a saturated switch they both conduct and share currents, but not as well in linear amp service.
 
I built an experimental quasi (all NPN) stacked output stage back in I want to say
1969 but it might have been the early 70s.
Drove it off the 16 ohm tap of a tube HiFi amp in order to test and listen to it.
I had bought 8 large heat sinks with what I guessed were Bendix house brand
2n3055 s. I cut one open to check die size and tested them for Vce breakdown
for 100V at least. Had a +/- 64 volt power supply and used the standard
config for a quasi PNP where they were required. I had seen stacked designs
but not quasi, it was original as far as I know. I have the schematic around
here somewhere.
The plan was to build a Tigersaurus but these were free and I wanted to try
out the idea.
 
I built an experimental quasi (all NPN) stacked output stage

ElectroVoice built some solid state home stereo equipment in the early 70's. It was junk, and blew up if you looked at it funny. The higher power versions used a stacked transistor design with all NPN plastic output transistors AFAIK. It was the worst of the bunch.

They also made some of the best guitar amp speakers of the period.

I ran the service department at the largest Olson's Electronics store in the US in 1971 and 1972. Olson's came out with a house branded guitar amp called the "Mighty O," built by Electro Voice. It used the same flash bang stacked output stage that was seen in the high powered home stereo sets, but had a nice EV SRO-12 speaker inside.....ALL blew up if abused.

I left Olson's for the career at Motorola on the first work day of 1973. After finding some like minded individuals at Motorola who played guitar and made loud things, I went back to Olson's and made a deal to buy ALL of the Mighty O's (dead or alive) from all three south Florida stores for cheap...….we stripped them of their speakers, and trashed the rest.....I think we used the cabinets from a few for some Tiger based guitar amps.