Vintage electronics thread

[HFWR]

I worked on some old pinball and bowling machines for a part-time job in the early 80s. Miles and miles of bundled wiring...

One of these days I'm going to build a guitar amp, probably class A. Like to putz. Don't remember enough RF/AC circuitry to tackle old radios and such.

[ls99]

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Originally Posted by youbet OH boy....... this is a good thread! Wish I had more digital pics ready to post. These pics were taken of stuff I'm selling or have sold: Collins S Line - 75S3-C 32S-3 312b-4 516F-2 Collins 51S-1 Drake C Line - R4-C T4X-C Drake 2-B Hallicrafters SX-100 Misc mountain of other "stuff" qualifying me as a guy who needs to thin the collection! This is primarily ham radio related, not quite as vintage as the example above, but vintage just the same.

The Collins' bring back memories. Had one in a cubbyhole on the ship with a Griefkit (Heathkit) 1 KW SSB amp.

While I was tech on a research ship, also ran the ham radio station for scientists passing data back to Lamont observatory in NY, and phone patches for the lonely folks via a schedule with a ham on Long Island NY. The call sign begun with X, can't remember the numbers, it was an experimental setup to allow operations just outside the ham band.

In those days the ship's radio officer (sparky) could only send and receive messages via RCA Morse Code telegrams, for a huge fee. He also kept daily several 2 hr radio watches on HF 2182 for emergencies. No satellite phones then.

I think the maritime services have done away with the Radio Officers. Satellite comms have made things dialup now.

By the way my only vintage gear now is a tube EICO RF sweep generator. It runs good but need about an hour to stabilize so the frequency drift stays within a few Hz. Next is a Marconi SSB AM HF marine transceiver on 2182 , 4125 and a few more rock bound (crystal oven) frequencies.

[ERD50]

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Originally Posted by HFWR One of these days I'm going to build a guitar amp, probably class A. Like to putz.

Are any guitar amps Class A? I know tubes are preferred by many for the particular way in which they distort. Class A eliminates the 'cross-over distortion' of switching through zero and handing off the signal from one device to the other, but that distorion is pretty minimal for guitars I would think. A little bias minimizes it.

Unless you are going for maximum clean sound, or just want to do it because you can. Class A will heat a room though! Probably not such a good thing in Texas?

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Originally Posted by Gumby a 1936 vintage capacitor analyzer.

So now you can test capacitors made in 1936?

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I tested all the old paper capacitors I had replaced and found, not surprisingly, that they leak like crazy, so it's a good thing I didn't just turn it on when I first got it.

I guess so!


Cool project, a friend had (IIRC) a Heathkit capacitor tester with that 'magic eye'. I don't know why he had it, other than to put a cap on and show people the magic eye - it was pretty cool.

-ERD50

[HFWR]

Quote:

Originally Posted by ERD50 Are any guitar amps Class A? I know tubes are preferred by many for the particular way in which they distort. Class A eliminates the 'cross-over distortion' of switching through zero and handing off the signal from one device to the other, but that distorion is pretty minimal for guitars I would think. A little bias minimizes it. Unless you are going for maximum clean sound, or just want to do it because you can. Class A will heat a room though! Probably not such a good thing in Texas? -ERD50

Well, most class A guitar amps are AB, but with only one power tube, it would be class A, no? I studied the implications some years ago, and have since forgotten, but have some old lab books and schematics for if/when I actually decide to do this...

Is the Vox AC-30 really class A?

[Keim]

I built some 2A3 Single Ended Triode amp kits and pre-amps put out by www.bottlehead.com. They sound fantastic, and were fun to do.

Not technically vintage, but certainly in the spirit of this thread.

[ERD50]

Quote:

Originally Posted by HFWR Well, most class A guitar amps are AB, but with only one power tube, it would be class A, no? I studied the implications some years ago, and have since forgotten, but have some old lab books and schematics for if/when I actually decide to do this... Is the Vox AC-30 really class A?

Well, the line blurs as you go from Class-B to Class-AB with higher and higher bias currents. Looking at that article, and another I found, it seems like some consider that if you bias it heavy enough the push-pull pair are operating together as Class A.

That's not the defintition I'm familiar with from school (long time ago and I may have forgotten or fallen asleep), or from the Hi-Fi world. I recall Class-A as being a device (or parallel devices) biased right in the middle and it would swing from + to - rails. It always used the same amount of average power supply current regardless of the amount of signal fed into it. IOW, if an 'ideal' Class A amp was biased at 1A, and it could swing to zero and up to 2A, it would draw 1A idle and over one cycle of input it would also draw an average of 1A (average 0A and 2A).

A Class AB would draw its bias current at idle, and then it would draw more when a signal is applied. The blurry line is when you bias it all the way up to 1A as in our class A. I think distortion products would still be slightly different (not better/worse - the ear determines that), as the conduction shifts from one device to another, versus being on a continuos slope of a single device. I don't know which sounds better for guitar, but those sites should give about as many opinions on that as asking what SWR is best would here.

Bottom line, it would be cool to build your own, regardless what form it was in. Or multiple and compare. Once you retire, you're gonna need something to keep you busy

edit/add: I have not worked with tubes much, but I think some of those power tubes are two devices in one glass envelope. So 'one tube' could be a push-pull pair? A dual Triode/Pentode?


-ERD50

[HFWR]

Many guitar preamp tubes, such as the 12AX7, are dual triode, but popular power tubes, such as 6v6, 6L6, El84, and EL34, are single pentodes.

[Nodak]

Quote:

Originally Posted by Keim I built some 2A3 Single Ended Triode amp kits and pre-amps put out by www.bottlehead.com. They sound fantastic, and were fun to do. Not technically vintage, but certainly in the spirit of this thread.

The amp in the bottom of that Scott radio of mine is 35 watt class A using 4 2A3s in a push pull cascaded config.

[Gumby]

I am a sucker for old stuff that still works (or has been made to work again), especially old test gear. As I mentioned earlier, I recently restored a Model CB-1-60 capacitor analyzer, originally built in 1936 by the Solar Manufacturing Corporation of Bayonne, NJ. I also have working Variac Model 200-CM built by General Radio Corporation of Cambridge, Mass. in 1935, and a working Model 630 tube tester built by the Jackson Electric Instrument Company of Dayton, Ohio in 1937. My multi-meter is a Simpson model 260-2 from the late 40s.

So what's your oldest working equipment?

[HFWR]

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Originally Posted by Gumby So what's your oldest working equipment?

[Gumby]

Maybe I should have been more specific -- ". . . electronic equipment?"

[REWahoo]

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Originally Posted by Gumby Maybe I should have been more specific -- ". . . electronic equipment?"

Yep, that's probably better. For a moment I thought about responding to this...

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Originally Posted by Gumby I am a sucker for old stuff that still works...

...with "What a coincidence - so is my DW!"

[ERD50]

RE: Class A, AB, etc...

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Originally Posted by HFWR Many guitar preamp tubes, such as the 12AX7, are dual triode, but popular power tubes, such as 6v6, 6L6, El84, and EL34, are single pentodes.

Makes sense then. So if one of those single power tubes is the output of a guitar amp, it seems it would have to be 'Class A' then. You gotta have two to tango for a push-pull Class B/AB. At least as far as I can determine.

I was just surprised they would run them that way. A Class A really sucks up the power.

-ERD50

[Gumby]

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Originally Posted by REWahoo Yep, that's probably better. For a moment I thought about responding to this......with "What a coincidence - so is my DW!"

Don't tell me -- she's a steampunk fan.

[Ed_The_Gypsy]

Bellingham, Washington, has a nice radio museum, started by an ex-Microsoftie, I gather. It covers electronics up to but not including transistors. If you are in the area, check it out.

[ls99]

My Grid Dip Meter.

Made by Measurements, later to become Boonton. Made about 1948-49. Had it about 30 yrs. Works like a charm, use it often. Never thought about how old it is until yesterday's query by Gumby. Looked it up, actually found a downloadable manual. Never had a manual for it. Now I do, yay!GridDipMtr.jpg Model 59 Sno 582

This thing just works, never had a lick trouble with it.. Read in the manual that all tubes were conservatively rated, they are still the original. Works up to 400 Mhz, now I'm curious, the manual said the made a tuning head for it that was good to 800 Mhz or more. I'll start looking.

[bruce1]

Here is my oldest working Radio 1926/27 Westinghouse Batteryless. The second is my best working, a Phonola with a pair of 6F6 in Push Pull Configuration.

[bruce1]

These are a pair of homebrew receivers from the twenties or early thirties

[bruce1]

The New Westinghouse 55

[Gumby]

Wow! That's quite a collection. My oldest audio stuff is a turntable from 1957 and a receiver from 1963 (both Voice of Music made in Benton Harbor, Mich.)