Princeton Reverb Help

[Paul-in-KC]

All,

Just finished initial assembly of a Mojotone BF Princeton Reverb kit for a friend.

This is the first Princeton Reverb that I have put together - and I don't have any history or experience with them (Princeton Reverbs), but something seems wrong.

Everything sounds find. Clean and quiet. But it seems to be lacking power. Virbrato, reverb, and all tone controls are functioning correctly. But the amp isn't as loud as I think it should be and it doesn't break up at any volume setting.

If anyone has any specific ideas, I would be grateful to hear. I am tying to find voltage specs to check - but having no luck. I did find something for the 65 reissue - but not sure about using that.

Thanks in advance for any ideas or info.

Kid Regards,
-Paul

[martin manning]

I find the reissue schematics to be a good reference. Both AC and DC values are given; see if the DC values line up first and then look at the AC.

[Stevem]

Is the recto tube good, you should have around 400 to 420 volts at the first filter node, also these amps do not have as much gain as even a deluxe reverb even with the same power supply voltage due to the princeton use of a non long tail pair pI section!

[ToneMerc]

I have a 69 "transitional" Princeton Reverb, SF on the outside and BF on the inside. I think what you are describing is relatively normal perse, but I find that the PR will get loud before it starts to break up. What speaker are you using?

TM

[Paul-in-KC]

Thanks guys,

I am still haven't found a good clear print with voltage #'s that I can read with confidence - but the one that I am looking at is labeled as a "AA1164" - and also labeled as coming from Fender, so I think these are the values I should get.

I do find some discrepancies in the pre-amp section so I need to double-check my "jumpers" on the back of the board - but just to clarify...

It looks like the print that I am looking at calls for 200 VDC on pin 6 of V4 and 260 VDC on pin 1. Am I seeing that right?

Thanks again.

[dorrisant]

Yes, you are correct sir.

Tony

[Paul-in-KC]

Boy this is a tough one (for me).

I expected to find an obvious wrong (or missing) connection (on the back), but that was not the case.

I must be reading something wrong.

Does anyone have a clear print for the AA1164 that I could cross reference?

(ideally layout and schematic - but one of the two would be nice)

The schematic and layout from Mojotone are quite clear - but those are the ones I'm misinterpreting.

Thanks.
-Paul

[stuben]

First amp I built was from a kit, an Allen Accomplice kind of, like a deluxe reverb with master volume. When I first fired it up it worked but sounded like a tiny transistor radio! I had mixed up a 470 ohm resistor with a 470K ohm resistor somewhere in the build thereby reducing gain a thousand fold!.

Did you actually measure the value of each part during the assembly process?

[Paul-in-KC]

No - I didn't measure the values during assembly, but I was reading the color codes.

I have measured most of the resistors since, but I'll go through ALL of them.

I do see one discrepancy between Mojo's layout and schematic. Their layout agrees with Fenders - but schematic shows a 100K plate resistor (think that's what it's called) going to pin 1 of V4. But their layout (and Fender's) shows a 220K in that position. And a 220K is what I have there.

Great suggestion though. I'll go through each of the resistors and measure them.

Thanks for the suggestion!

[sluckey]

Does anyone have a clear print for the AA1164 that I could cross reference?

Here's the best I've seen...

http://el34world.com/charts/Schematics/ ... aa1164.pdf

[Paul-in-KC]

sluckey,

Those are beauties!

Thank you.

stuben, you nailed it. I didn't have a wrong value installed, but a 2.7K resistor is only measuring about 50 ohms. That must be what is throwing everything off.

I have a couple of 5.6K that I can tie in parallel to see if that doesn't get things (voltages) back in line.

Thanks all. Watching some SNF, but will post results later.

-Paul

[ToneMerc]

sluckey,

Those are beauties!

Thank you.

stuben, you nailed it. I didn't have a wrong value installed, but a 2.7K resistor is only measuring about 50 ohms. That must be what is throwing everything off.

I have a couple of 5.6K that I can tie in parallel to see if that doesn't get things (voltages) back in line.

Thanks all. Watching some SNF, but will post results later.

-Paul

That 2.7K in the negative feedback circuit would have no bearing on the voltages at the nodes.

You should post the plate and cathode voltages for V1&&V4.

TM

[Paul-in-KC]

Oh poo - thought I was on to something.

Thanks ToneMerc.

I'll post those voltages (V1 & V4) a little later this evening.

-Paul

[ToneMerc]

Oh poo - thought I was on to something.

Thanks ToneMerc.

I'll post those voltages (V1 & V4) a little later this evening.

-Paul

Better yet, also include the AC mains voltage, DC voltage at output of the rectifier and the power tube voltages.

TM

[Paul-in-KC]

Will include those too, but everything up to (not including) V4 looks okay.