my new baby.....

Rockmonton

Rockmonton

Infected with Altecitis
heres a northern electric r4a with the patent of 1935, with tow threaded inputs ofr a crystal mic and a phonograph...... from an old race track courtesy of brent. two 6L6G's a 5y3, a 6sn7 and two 6J7's its gonna make one hell of a guitar amp with the huge transformers and coolness of being from a time when canada was running at 25 hz instead of 60
 
cool find :thmbsp: many people dont know that us canucks had northern electric and the good old usa had western electric which were one of the same.that output iron looks pretty stealthy and should make one great guitar amp.good luck with your project.
chris
 
yep i've gotta open it up though i'm almost afraid, i gotta wake it up slowly after i replace the frayed cord.... the caps are sprauges believe it or not..... it should make one hell of an map, but i'm not too sure how much wattage it can take as the transformers are huge, but maybe not so great...... i think it'll look just awesome on a dark stage at one of those midnight coffee shop gigs.....
 
heres an inside shot...... pretty simple but the schematic is messed so i'll be using this one as an online sorta tutorial for DIYers on what to do, heck why not.... i'm gonna have to redraw the schematic and everything so why not......
 
I would do a complete recap and probably new pots.... check out the great wire wound srep down resisters and the cool wiring chassis. Art.....
 
yep i will do that pretty well automatically...... well actually i'll bring it up on the variac then test each cap see how bad they are... the reistors are pretty cool and pots i will too . its pretty crude having the volume controls right after the input jacks, but they didnt have much better back then.... i am probably gonna keep most of the design though and just change the positioning of some of the components..... as well as tune up the tone controls to be just like the old tweed fenders.... and the outputs should be nice...... its a tank at 45 pounds though..... and most of the outside appears to be covered in oil from something, but not anyof the transformers or caps but probably from being stored in a garage, anyone have any good ways to clean that off?
 
ok this is getting really weird, the schematic inside doesent match the amp, and i'm looking at ati and there are parts that arent even on the schematic like a 920K resistor from [in 8 of a 6j7 to the filament on a 6sn7..... and two resistors that go red red whit which would be 22000 Mohm..... which just cant be!


EDIT@ as i'm working feverishly late into the night, i've got it all sorted out now..... except the 22000mohm resistors...... i'll check em with the meter tomorrow.... but so far i've got this thing mapped out to a tee...... i'm gonna change the tone setup from the crude old style cuts..... to a slightly more modern tweed ampeg sorta feel...... along with dpeending on how it soudnds maybe bumping up the gain on one of the 6j7's to get some more bite..... we'll see soon.... i like the way this oen is built, it has the oen channel normal volume control, bass and treble and then a phonograph input, the way the phonograph input works is PERFECT for runing a line in from another preamp to use this as a low wattage power amp....... the circutry i found ahs been changed otu a bit to run on 6l6's and assumably at a bit higher wattage so if i can find my dummy loads i might bother to check..... now that i've got it traced out however it looks like your very classic very standard audio/guitar tube amp..... like amazingly similar....... just gotta see now what the 6j7's sound like!

oh and your probably wondering why i'm up on christmas mornign working on a tube amp, well it was a christmas present, but my parents have to be gone by about 4 in the mornign so i have to watch my sister when my ma drives my dad to the airport and thne comes bakc hoem so i figured it'd be easier just to stay up til about 6 and then sleep till2 or 3 in the afternoon, and yes we already opened presents tonight in our wacky european ways...... enough rnating for tonight, i'm gona go find sometihng else to entertain me
 
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Rockmonton said:
two 6L6G's a 5y3, a 6sn7 and two 6J7's its gonna make one hell of a guitar amp with the huge transformers and coolness of being from a time when canada was running at 25 hz instead of 60
Click to expand...
Great find!

A word of caution on those 25hz xformers. As you know, they have an oversize core to prevent saturation at that very low frequency, so in a sense they are coasting at 60 hz (or is it 50 where you live?). But my experience with a pair of monoblocks with 25hz-rated power transformers leads me to believe that the oversize core does not necessarily translate to much of a under-rating for current capability. In other words, you might think from the size that you could run the output tubes in full class A, with greater current draw, and the transformers wouldn't mind -- but I think they are still limited by the winding gauge, and core size doesn't change that.

Or maybe this was already clear to you, and I'm the only one who had to learn this empirically. Short version: Duncan's PSUD II software is a much better predictor of xformer capabilities than size and weight. :)
 
tubino said:
Great find!

A word of caution on those 25hz xformers. As you know, they have an oversize core to prevent saturation at that very low frequency, so in a sense they are coasting at 60 hz (or is it 50 where you live?). But my experience with a pair of monoblocks with 25hz-rated power transformers leads me to believe that the oversize core does not necessarily translate to much of a under-rating for current capability. In other words, you might think from the size that you could run the output tubes in full class A, with greater current draw, and the transformers wouldn't mind -- but I think they are still limited by the winding gauge, and core size doesn't change that.

:)
Click to expand...

You can't draw more *current* from the windings when you run them at 60Hz instead of 25Hz, but what you could do is run the transformer at 250VAC at 60Hz instead of the 115V at 25Hz. This will make all secondaries produce twice the rated voltage, at the same rated current. Of course the rest of the amp's power supply will need to be modified to deal with the twice as high voltages. This is more meaningful if you are looking at a 25Hz transformer on the shelf, considering its use on 60Hz in a new project. For a given level of power, a transformer's core size is inversely related to the operating frequency. This is what makes switch mode power supplies attractive, small core transformer running at something like 50KHz.
 
wa2ise said:
For a given level of power, a transformer's core size is inversely related to the operating frequency. This is what makes switch mode power supplies attractive, small core transformer running at something like 50KHz.
Click to expand...

Also why old military electronics (military only? beats me) used 400hz systems, with tiny core xformers for tube power supplies to save weight on planes etc. Weird trivia, but I like it.
 
Just a note, Northern Electric (now Nortel) was once wholly owned by Bell Canada. Their only relationship with Western Electric was through an arrangement between Bell Canada and AT&T that allowed Northern to use Western patents. Eventually Northern went their own way and developed their own systems. About that time everyone down here assumed that AT&T had sold off Bell Canada which caused no end of laughter in Canada.

Rob
 
nice to know the info! wow...... hres my tone circut i'm planning on putting on..... if i can do it okish in ascii

.1 47pf
-----------||--------------||-----
......................|......................|
......................|......................|
......................\.....................|
...........220k..../.....................|
......................\ ....................|
....................../.....................|
......................|.....................|
......................\.................... /
...........1M......./.......120K......\
......................\ <--^^^ --->/ 2M
..................... /....................\
......................| ....................|
......................\ ....................|
...........22k....../.................. _|_
......................\ ...................__ 470PF
....................../___________|

voila! the output is at the pointer on the 2 meg pot
 
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