DeArmond (Rowe) Guitar Amplifier Model R25T Restoration

[misterc57]

Picked up a R25T combo with no speakers this week. I believe they were only made in 1960. I hope to get it operational. Looks like work had been started and then abandoned.

Original PT is gone and not a clue what is in there now. I was told it came from a TV. Choke and OT look original and OT tested okay with the 9V battery test.

No schematic has been found yet.

The amp has some encapsulated sections called erie packs. Supposedly there are 4 packs.

I plan to start on the power section. Test the PT which I have removed (not even sure it is suitable). I also will be looking for a schematic (any suggestions) I can use as a guide for the power section. a 1960 era amp using 5AR4, filter choke, (2) 6L6GC, (3) 12AX7.

Suggestions and comments much appreciated.

Thank you, Mark

Edit. I do not think the PT even has enough sections to support a guitar amp.

[misterc57]

Power Transformer?

I need to order a power transformer for this amp. I have never spec'd one before and these are my considerations.

• Not sure what plate voltage is needed for the 6L6GC pair, a Fender Bassman 50 for comparison is running 445V at the plates. So I am going with that for now.
• GZ34 requires a 1.9A minimum 5V winding
• (2) 6L6GC, 1.8A + (3) 12AX7, 0.9A, will require a minimum 2.7A 6V winding
• bias tap
• top mounted

The ClassicTone Power Transformer # 40-18066 seems like a candidate, but I am not sure if I am missing any considerations. It is stated to be a 20W PT, so maybe not...
Suitable for use in the following amps: General Purpose 20W, Deluxe, Deluxe Reverb, Tweed Tremolux style amps

A PT for a Fender Super Reverb should do the trick spec wise? See second pdf. However it is not a "top mount" style.

Thoughts anyone? Thank you


40-18066.pdf

MT-FENDER-MOJO762EX.pdf

[mozz]

Where are you buying classic tone? Thought they were out of business?

[misterc57]

Where are you buying classic tone? Thought they were out of business?

Oh you are correct. I was focused on specs and failed to look at availability.

Anyone have a PT recommendations for this amp?

Thank you, Mark

[g1]

Any numbers on the output transformer? Might give an idea of the power output of the amp.

[mozz]

95W on the input side. So maybe 40-45 out?
Edit: I would try to find something with a 5v 3A rectifier winding, just because 5U4gb are much cheaper and common than a 5AR4.

[misterc57]

Any numbers on the output transformer? Might give an idea of the power output of the amp.

T-708
549-6029

Is power output also a consideration in choosing a power transformer?

Thank you

[misterc57]

I would try to find something with a 5v 3A rectifier winding, just because 5U4gb are much cheaper and common than a 5AR4.

So those tubes are interchangeable?

Unsure if I am leaving a consideration out of my search like power handling.

Although unavailable, I thought the ClassicTone would have worked, or was I missing something?

Thank you

[misterc57]

I prefer to keep things as originally designed but I am also open to converting to a SS rectifier if needed.

[Helmholtz]

Unsure if I am leaving a consideration out of my search like power handling.

Although unavailable, I thought the ClassicTone would have worked, or was I missing something?

The HT winding of the Classic Tone has a current rating of 120mA.
From this it follows that max. continous output should be 20W to maybe 25W.

For comparison, the Hammond replacement PT for a Fender SR is specified at 300mA.
https://www.hammfg.com/files/parts/p...f?t=1697661948

[mozz]

Here are pictures of the original part numbers.
https://southsideguitars.com/product...Tan-p538587947
R25 was a 2x10, 6L6, cathode biased thing all its own. These amps used oversized transformers which is what sets them apart from most any other 5, 15 or 25 watt amp at the time.
Also sold under the Martin name brand.
Since these seem to sell for $5000 area i would try to find something that fit as close as possible to the original mounting.

• Where date is noted: Transformers, speaker codes, potentiometer codes.
• Speaker 1 Brand/Model: Jensen P10Q
• Speaker 1 Size: 10"
• Speaker 1 Code: 220 030
• Speaker 1 Cone: Original
• Speaker 2 Brand/Model: Jensen P10Q
• Speaker 2 Size: 10"
• Speaker 2 Code: 220 030
• Speaker 2 Cone: Original
• Output Transformer brand and/or codes: 549 6029
• Choke Transformer brand and/or codes: 549-6023

[misterc57]

The R25T is grid bias with both 6L6 cathode is a direct connect to ground.

Let the Erie pack mysteries begin.
There is a bias wire that routes through the "outer 6L6" (the left tube socket in picture) pin 6 to the Erie pack, and from the Erie pack are two wires (one to each 6L6) pin 5.
I guess this is the grid bias resistor? The outer 6L6 grid bias R measures 250K and the inner 6L6 measures 233K.

See pic for all this.

[khmassey]

This shows the bias supply on the left

[misterc57]

So this project is going to be a long burn. I just received schematics from another owner of this amp model.

See attached.

[misterc57]

and it looks like they are showing the component values inside the PACs!