Anyone Recognize This Noble Amp from the 50s?

[Jecarroll7]

See attached pictures - I have a Noble accordian/guitar amp from the 50's? from the Noble Accordian Company in Chicago.

As I understand it, Ampeg, Valco, Danelectro and Supra all may have manufactured amps for Noble under OEM agreements.

If I had to guess I'd say Ampeg as the regulator/power stage looks remotely like the Ampeg Jet J12B, although the knobs look like Danelectro

Problem is a resistor between the OT center tap and pin 4 of the 6L6 power tubes is fried beyond recognition.s

Trying to track down a schematic or value for the resistor.

Attached is a photo of the front of the amp, the other is of the fried resistor in circuit. Never blew a fuse, I think the resistor just gave out. Looks like 1/4 watt but other schematics of similar design suggest the resistor should be of heavier wattage.

Additional Information - There is a stainless steel control panel with Pots, Resistors, Caps and (1) 12AX7 above the speaker

The aluminum chassis with the below tubes is below the speaker. The two are connected with an audio wire, and a 5 prong multi wire twisted voltages cable.

The amp uses the following tubes:
V1 - 6SJ7
V2 - 12AX7 (plus another one located on the control panel)
V3 - 6SN7
V4/5 - 6L6GC
V6 - 5Y3

I hope someone has seen this before. Any help is appreciated. Thanks

[Jag]

Did you see this, dumb.org » ’57 Nobel Twin Twelve?

Maybe look for a Dano 1396 schematic. I'm on my iPhone right now so couldn't really dig too much.

[Jag]

Apparently Danelectro also built the Silvertone 1396. Does this schematic look similar to your amp, http://www.webphix.com/schematic%20h...rtone_1396.pdf?

[Prairie Dawg]

I ressurected a defunct 1396 a few months ago. What an amp.

Gut shots here

Judybox Revival: Resuscitating A Silvertone 1396 Twin Twelve

[Jag]

Nice one PD! I've got a 1395, real odd-ball but has a really cool tone.

[Jecarroll7]

Jag,

Appreciate the help. Do you happen to have the schematic for a 1395? The 1396 got me close, but my amp has a single speaker and I'm hoping the 1395 schematic is a closer match.

Thanks

[Jag]

I've never been able to find a schematic for the 1395, it seems to be a pretty rare amp. It's basically a 1394 in a 1396 cab with a 15" speaker. I've never found a schematic that matches exactly. I've been meaning to draw my own but never seem to get around to it.

[Jag]

That picture is one of the 6L6's? That resistor looks like it goes to ground, it may be the same ground as the OT CT but it would be more accurate to say it goes to ground than the OT CT.

Can you post a more inclusive picture of the guts.

[52 Bill]

A better photo would be great. I don't think that the resistor or the output transformer lead are connected to the grounded mounting lug of the terminal strip. It's hard to see, but it looks like it's one over from the grounded one.

In any case, the resistor connects to pin 4 of the tube. Are both pins 4 connected together on the 6L6's? Is there only one of these screen grid resistors?

[Jecarroll7]

Jag,

There is a Sams Photofact schematic available for the 1395 at https://www.samswebsite.com/en/photo...ndex/id/150701

[Jecarroll7]

Okay, replaced R25 2.2K resister with a new carbon comp 1/2 watt

Okay, replaced R25 2.2K resister with a new carbon comp 1/2 watt, played fine for a couple minutes and then toasted the new resistor. Did not blow the fuse.

Schematic attached.

1/2 watt seems light supplying two 6L6 tubes, but then again the resistor I pulled out was 1/2 watt and lasted 50+ years.

Did the old carbon resistors handle more current relative to their rating? Or do I have something else going on in the amp?

Not seeing anything obviously wrong with other resistors/caps, tubes all check out on my Hickok. Plug in a 1 watt and follow the smoke?

BTW: The resistor is not soldered to a grounded lug.

[Jag]

Something is causing a lot of current to go through that resistor. My first guess would be a short in one of the output tubes (sorry, I should have thought to mention that before) but could be a bad filter cap or OT.

Build a lightbulb limiter (you can do a search on this site for instructions), pull all tubes, except the rectifier, and power up with the limiter in line. If the bulb lights brightly, you've got a short somewhere and my bet would be a bad filter. If the bulb is dim, it's probably a tube.

Give that a try and let us know what happens.

[Jecarroll7]

It Seems To Be Working, its been playing now for about 20 minutes.

It Seems To Be Working, its been playing now for about 20 minutes.

Replaced two filter caps which tightened up the ripple quite a bit.

I didn't build the limiter, but that is on my list. I did pull the tubes which stopped the current draw long enough for me to check caps.

It would be nice to have an LC analyzer with load/leakage testing ability, I see one in my future.

Appreciate the help from everyone, especially Jag.

[sangandongo]

Did you see this, dumb.org » ’57 Nobel Twin Twelve?

Maybe look for a Dano 1396 schematic. I'm on my iPhone right now so couldn't really dig too much.

This one belongs to me. I actually think it's more like a 1392 based on the schematics. The RMS output is about 35W. I had a cap short at the choke recently. It blew out the choke. They are now available on Mercury Magnetics for replacement if you ever require one - they cloned mine. Anyhow, this amp is amazing. Here it is in action: Old Bottle Black - La Morena - Floyd's Place, Seattle - 04/20/2012 - YouTube

[Jag]

Cool!