Guyatone Imperial-el cheapo weekend buy

[Madison]

Took a chance on this in the recycle store.
It an extension cab I suppose.
1-12ax7
2-6CA7s (EL34s)

Good-
Speakers seems pretty alright

Bad- Blowing fuses.
Half wave, voltage doubler, I think..........
Wasn't expecting that!

It doesn't blow fuses with tubes out.

Not even sure where to start!
Can someone give a little advice here.

Love to get this thing going, might be perfect for my Fender Rhodes.

[Madison]

2

[Madison]

3

[Madison]

4

[Madison]

5

[Madison]

Ok, got it working.
It was red-plating.
Replaced the .1 caps going to the grids.

Sure doesn't have much umph!
Stuck a distortion pedal in front of it and it picked up pretty good but would imagine it could have more power?

Add a tube?
Make a preamp?
I am working on a stand alone reverb right now, don't know if it could be enough to push it?

I played just the speakers through my 50 watt head and they can certainly take the abuse.

Here  are some voltages:

EL34s
1-x
2-x
3-438
4-434
5-  -31
6-  -32
7-x
8-x

12AX7
1-146
3- can't seem to get a decent reading here.Replaced the cap and 3.3K resistor, no change.
6-128
7-88
8-86

[Willabe]

I'd trace from the main amp in jack to the 12AX& socket and draw it out to see what's going on with it.

Looks like it may be just a 2 tube PP power amp including the PI? (Which is part of a complete a power amp.) If so it makes me wonder why they labeled the input main amp in instead of pre-amp in. 

Someone else posted about an extension amp something like yours not long ago. Was it Plexi 50? IIRC it took it's input signal from the main amps extension speaker jack? But it might have been a SS unit?


                  Brad        

[spacelabstudio]

I'd trace from the main amp in jack to the 12AX& socket and draw it out to see what's going on with it.

Looks like it may be just a 2 tube PP power amp including the PI? (Which is part of a complete a power amp.) If so it makes me wonder why they labeled the input main amp in instead of pre-amp in. 

Someone else posted about an extension amp something like yours not long ago. Was it Plexi 50? IIRC it took it's input signal from the main amps extension speaker jack? But it might have been a SS unit?


                  Brad        

It sounds like from your description that it's intended just as a power amp, so it's probably expecting a hotter input like you'd get from the output of a preamp.

Chris

[eleventeen]

Congrats, that looks pretty cool! During the phase where you are just looking at it and imaging where you could go with it, I'd be thinking about adding a preamp and or tone stage (or both) Looks like a nice chassis (eg; hunk of metal) with room to add a toob or two....and have a "power amp input" where you could insert your Rhodes signal. Depends upon your ambition and how much $$ and effort you wish to sink into it; the great thing is that these things will patiently wait for you to decide whether you want to impose major or only minor surgery. If your preference is towards EL34, stay with them, I'd consider changing to 6L6. Give us another pix so's we can look at the size of the output tranny & gauge its musculature. 

[sluckey]

I would probably just fix the power amp as is and build a separate preamp unit to just sit on top.

[P Batty]

Guyatone stuff from that era is pretty good,  I suspect that may be part of a stereo-guitar amp setup, they were known to create some odd stuff...

[HotBluePlates]

I wonder if the Atlas Ohm resistors with the dogbone-like shape are carbon comp resistors like the old dogbones of the 30's.

[terminalgs]

Sure doesn't have much ump

12AX7
1-146
3- can't seem to get a decent reading here.Replaced the cap and 3.3K resistor, no change.
7-88
8-86

Based on voltages on the 12ax7, I'm guessing section 1 is gain, section 2 is a cathodyne pi.

I'd add a another twin Triode with at least 1 gain stage.  If you make it an external enclosure, I'd    run it off this amps power supply.  PT can probably handle another 300ma 6.3v.

Looks Japanese made.

[PRR]

Yeah, it's just a Power amp.

Like a Crown DC300, but only one channel, but with speakers, but ~~40 Watts.

Guitar right in, you don't have enough signal to get a fraction of 40W. Booster helps; might need two boost-pedals to really wail. That's silly. Steal the first two triodes and knobs from a favorite amp, box it on top. (Let people 'think' you get all that sound from one small bottle.)

Or plug it to the PreOut jack on your small amp to play large venues. It can probably tap a Speaker out, IF you add a 100K volume control in front of the Guy. But keep a speaker-load on the small amp, and do NOT turn this amp's Vol up much.

[Madison]

Going to go with a preamp me thinks up front I think.

Just building the 3 tube Hoffman reverb......hopefully finish this week.
Can't wait to try that in front.
If that's a no go, going with a preamp.

It is fun to look at it as a just a normal 2x12 speaker cab.

PT/OT pretty beefy.

[Madison]

chassis out

[Platefire]

Did I understand you had a Fender Rhodes Piano that you would like to try it with. With the electric piano already having a preamp seems like it would be perfect to plug that into power amp/speaker???
Does the Piano have a preamp out? Platefire

[Madison]

Did I understand you had a Fender Rhodes Piano that you would like to try it with. With the electric piano already having a preamp seems like it would be perfect to plug that into power amp/speaker???
Does the Piano have a preamp out? Platefire

No pre amp out/electronics.
Just a plain jane Seventy Three.

[Platefire]

Well, nice find anyway! It's been a long time since I found a good old amp. Plate