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Old 23rd April 2012, 07:46 PM   #1
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Default Old schematic

For information

I've got a somewhat electronic scrap / schematics from an estate (a +90 year man).

I found the schematic here, which I've attached.
There comes several schematics as I have drawn them clean.

Here is one schematic with, for me unknown low-voltage tube, 50B5.
I would probably raise the voltage and use EL90 tubes.
You must be disregarded pin numbers on the tubes.

Regards

Benny
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File Type: pdf 50B5 pp.pdf (10.4 KB, 159 views)
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Old 23rd April 2012, 09:45 PM   #2
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Quote:
Originally Posted by Hojvaelde View Post
Here is one schematic with, for me unknown low-voltage tube, 50B5.
The 50B5 is identical to the 50C5, however, the pinouts are different. That was the big problem with the 50B5: it has the same pinout as the 6AQ5, but that caused problems when using the 50B5 in a series string, as the voltage could be quite high before it warmed up. So they changed the pinout, and made the 50C5.
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Old 23rd April 2012, 10:50 PM   #3
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http://tubedata.milbert.com/sheets/137/5/50B5.pdf
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Old 23rd April 2012, 10:56 PM   #4
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Benny,

The 50B5 data sheet is here.

That circuit is typical of cheap, LOFI, AC/DC designs. It used a transformerless 1/2 wave rectified B+ PSU and a 150 mA. series heater string. It's inexpensive and deadly dangerous. The only protection the owner got was from the floating speaker setup. Notice zero NFB in combination with full pentode mode. That means lots of distortion and wretched voice coil control.

It's not that long ago that folks living in certain localities were forced to use equipment of that ilk. Their house current was "110" VDC.

A good amp can be built around that sort of power tube, but not with that crappy PSU. Bridge rectify "120" VAC. 0B2 regulate g2 B+. You can bank on that design being used with a piezoelectric phono cart. as the signal source. HF info. was already rolled off. The parts values shown will cause HF info. loss, if a full range signal is applied.
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Old 24th April 2012, 07:20 AM   #5
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Hello

Peaceful Eli. I had no intentions of building the amplifier. I showed it just as an example of a design from the late forties, early fifties.

I have found the following designs in the estate.
6SJ7-6N6-6V6 in pp
Something 6SQ7 - 6V6 in pp
6SJ7-6SN7-6L6 in pp
12SQ7 - 12L6 in SE

There are more but I have no overview at the moment.

Benny
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