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-   -   1950 Gretsch Electromatic Artist (https://www.diyaudio.com/forums/instruments-and-amps/263505-1950-gretsch-electromatic-artist.html)

MelB 18th October 2014 12:56 AM

1950 Gretsch Electromatic Artist
 
5 Attachment(s)
:santa: Just thought I would share a very cool little amp schematic. All of the resistor values are from the color bands so the schematic should be exactly as intended. Actual measurements were "close". The 20uF+20uF+20uF @450v cap is still holding up. The coupling caps have working voltage 600v and test voltage of 1800v...:eek:. I picked this thing up very cheap. It had a pretty bad hum. I had to replace the small cap on the primary of the power transformer and the cathode bypass on the first stage.

Sounds very nice with single coils, sounds insane with humbuckers.

If you had this amp in 1950 you were the coolest kid in town. If only the volume would have gone to 10 in 1950...;):p

kevinkr 18th October 2014 01:05 AM

Pretty cool, but given the age of the amp I would at least replace the triple section electrolytic and the coupling caps to the output tubes.

MelB 18th October 2014 01:14 AM

I did also put a three prong plug on it.
@kevinkr
Ya I'm going to look into fitting 3 x 20uF caps into the original can that is there. Everything is riveted on to the chassis. Unless someone knows where to get a 3 x 20uF @~450v cap in a can.

vinylkid58 18th October 2014 01:41 AM

A quick look around and this is close as CE gets:

https://www.tubesandmore.com/products/C-EC1020X3-450

There's also a 4 x 20uf @475v by CE.

jeff

kevinkr 18th October 2014 01:54 AM

Vinylkid beat me to it, but that was exactly what I was going to recommend. :D

There is this: https://www.tubesandmore.com/products/C-EC20X3-525
The higher voltage rating cannot hurt. (3 x 20uF/525V)

MelB 18th October 2014 02:22 AM

Hey thanks guys looks like tubes and more is it. The 525v looks like a perfect fit.

jazbo8 18th October 2014 07:11 AM

Are you sure that the tone and volume controls come before the 6SJ7 and not after?

MelB 18th October 2014 01:59 PM

Quote:

Originally Posted by jazbo8 (https://www.diyaudio.com/forums/instruments-and-amps/263505-1950-gretsch-electromatic-artist-post4092691.html#post4092691)
Are you sure that the tone and volume controls come before the 6SJ7 and not after?

Yes quite sure. If you look at the picture of the under side where I replaced the cathode bypass cap (black electrolytic) you can see the bottom of the RCA jack that the top panel plugs into. The brown wire from that goes right to pin 4 of the 6SJ7. You can also see the unplugged RCA cable that comes from the top panel hanging down in the picture.

costis_n 18th October 2014 08:05 PM

Quote:

Originally Posted by MelB (https://www.diyaudio.com/forums/instruments-and-amps/263505-1950-gretsch-electromatic-artist-post4092544.html#post4092544)
I had to replace the small cap on the primary of the power transformer and the cathode bypass on the first stage.

What you replaced is known as a "death cap". It should be removed. Maybe there are two of them, from earth to Live + Neutral.

MelB 18th October 2014 09:31 PM

Quote:

Originally Posted by costis_n (https://www.diyaudio.com/forums/instruments-and-amps/263505-1950-gretsch-electromatic-artist-post4093187.html#post4093187)
What you replaced is known as a "death cap". It should be removed. Maybe there are two of them, from earth to Live + Neutral.

There is only one "death cap ". Looks like it's on the wrong side of the fuse too...:eek:

It would appear every old amp had one....interesting. I will remove it and see what happens.

An interesting thing I noticed in this amp is that they just grounded one side of the 6.3v filament circuit. There is no center tap and no artificial center tap. It is a pretty quiet amp despite that.


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