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 Post subject: Northern Electric R4A Amplifier Info Needed
PostPosted: Dec Sun 15, 2019 10:36 pm 
Member

Joined: Apr Sat 30, 2011 2:14 am
Posts: 710
Location: Mississauga, Ontario
Seasons Greetings to All,
I have had this amplifier collecting dust in the basement for many years and with the holidays aproaching I thought I'd finally give it going over and see if I can get it up and running again.
Only problem is I can't seem to find any info on this amp, other than it's fairly desirable.
I can't get into it without a schematic as there are a couple of wires disconnected and I believe someone has put different tubes in it.
I believe I have figured out much if it but the 3 multi section can capacitors have no markings on them and if I knew the values I think I can figure out the rest? If anyone has this amp and could give me this info it would help or if anyone knows where I can get/buy a schematic and parts list for this amplifier it would much appreciated!
Thanks,
Mauro


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 Post subject: Re: Northern Electric R4A Amplifier Info Needed
PostPosted: Dec Mon 16, 2019 1:48 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 4496
Location: Boston, MA USA
Northern Electric was the Canadian subsidiary of Western Electric. I wouldn't be surprised if there is a WECo amplifier identical to this one.

-David


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 Post subject: Re: Northern Electric R4A Amplifier Info Needed
PostPosted: Dec Mon 16, 2019 4:38 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 4915
Location: Rochester NY USA
There's a usable schematic in this eBay listing (if _I_ needed it, I'd capture 4 screen shots using the "magnifier" and paste 'em together)

https://www.ebay.com/itm/Pair-Northern- ... true&rt=nc

Tubes are a pair of 6V6s, 5Y3, 6SN7, two 6J7s, plus an empty socket for mike transformer.

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 Post subject: Re: Northern Electric R4A Amplifier Info Needed
PostPosted: Dec Mon 16, 2019 3:55 pm 
Member

Joined: Apr Sat 30, 2011 2:14 am
Posts: 710
Location: Mississauga, Ontario
Tom,
I actually saw that listing but it was on my phone and seemed unclear. When you mentioned it in your post I pulled it up on my laptop and to my surprise it's very clear! I was also able to read the values of the caps on top of the amplifier!
Thanks for your suggestion.
Would you have any idea what the high voltage should be from the power transformer? At some point it's been replaced and it puts out 800vac unloaded. I would think the voltage for this amp is more likely to be at about 550vac, but not sure? I may have to order another transformer.
Thanks
Mauro


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 Post subject: Re: Northern Electric R4A Amplifier Info Needed
PostPosted: Dec Mon 16, 2019 11:29 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 4915
Location: Rochester NY USA
Yes, that's too high unless a choke or dropping resistor has been added. Even in that case, B+ would be over 500V until the tubes start drawing current... 600VCT is about right, 550-650 would still be reasonable.

Look for a transformer with the same mounting dimensions, best not to have to drill more holes. Alternatively, you could add a choke (maybe 8 Hy, 100 Ohms) between the 5Y3 and first filter cap, and the supply would be about 300V. Of course, that means drilling holes... and it would STILL have over 500V at start-up.

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