Noisy Princeton Reverb Clone

[fiddi]

Princeton Lead Dress

Hi

pretty made - really good looking.

Nice build.

I made about 10 of them from scratch - most quiet amp type - Leos best masterpiece.

Here is my advice :

just look forward to exactly place your lead dresse where the

originals had it - watch old photos of real ones and do exactly lay the wires where they had it 1965.

And use shielded cable for grid wires.

And take a look at the preap tube - V1 - there are several wich are noisy.

Just try differnt ones.

[blewgrass]

Update

Update: I cleaned up the lead dress and grounded the tone stack to the chassis like the original picture above. There is still some hum in the reverb section so that will be my next order of business. The help on this forum has been extremely useful so thanks for all the responses.

Steve

[blewgrass]

It's all about the reverb

More sluething is bringing me back to the reverb circuit. All the noise is gone until I advance the reverb knob. I will start switching tubes and see what that does.

Any other ideas about reverb noise?

[tubeswell]

More sluething is bringing me back to the reverb circuit. All the noise is gone until I advance the reverb knob. I will start switching tubes and see what that does.

Any other ideas about reverb noise?

Grounding.

[blewgrass]

Thanks tubeswell, but could you be more specific on grounding with regard to the reverb circuit? Are there certain wires in the reverb circuit that look problematic on my layout pictures? I added the chassis grounding already as most of you suggested and it had great results.

[tubeswell]

Look for ground loops in the verb circuit.

Where is your RT secondary grounded?

Where is your recovery stage grid leak resistor grounded?

Where are the other reverb circuit grounds (cathodes, level pot, driver grid leak, decoupling cap ground etc) grounded?

I find those BF amps with the cap can damn fiddly for grounding. Are you using a cap can, or have you gone to separate filter caps?

[blewgrass]

Thanks for the heads up tubeswell. I am way behind you on this material, and truth be told, don't really know jack about electronics, other than some basics and the safety info on how to discharge the caps to avoid zapping myself with the DC voltage.

The cap can is still in play the way you see it wired above, except I've twisted the wire pairs that were previously running around the front of the eyelet board exactly like the '66 version you posted. I also grounded the other two points in the preamp section to the chassis like in your picture.

I also found that the shielded reverb tank cables were coming unsoldered at the shield area on the connector so I clipped and stripped those out and now the reverb is back on track, but still as you turn the reverb knob up there is a small amount of hum, but not as much as before.

Is there always *some* hum in the reverb circuit, or should it be dead silent? I also have the issue of the amp head output being very close to the transformer... I have a traditional combo cabinet on order, which may further quiet the amp... in other words, she's almost where I want her! I love the tone of this thing! Currently I have a Weber California 10" with light doping and no aluminum cone. Shweet, other than that little bit of hum..

Steve

[Bruce / Mission Amps]

I hate to tell you this but out of the last 10 CE Dist, Mallory multicap clones, 4 of them have now totally failed and raw buzzy hum was the issue.
A 40% failure rate is completely unacceptable and I will never use another one again.
They claim no one else but me has complained and I say that has to be 100% bullshit.
So what I am telling you is, don't rule out the basic CE Dist filter cap being bad even though it still could be another ground/hum problem.
As an example, I can't tell from your photos but are your shielded audio cables grounded at the signal source end like they are supposed to be?
And where are all the grounds on that terminal strip next to the PT?
Are the first preamp stage's grounds all grounded to the input jacks?

[blewgrass]

Wow Bruce,

Thanks for the heads up... and thanks for turning my attention to the grounds on the terminal strip. This amp is not my build, but other than a few problems, I assumed it was OK... perhaps an incorrect one. I will check all of the things you mentioned.

Since the amp is very quiet without reverb engaged, I am assuming the cap can is good, but I don't know.

Overall the amp is working very nice now, and I think most of the issues are in the reverb circuit, and possibly the proximity fo the tank to the PT.

I'll try to load a picture

[Bruce / Mission Amps]

Wow Bruce,
Since the amp is very quiet without reverb engaged, I am assuming the cap can is good, but I don't know.

Overall the amp is working very nice now, and I think most of the issues are in the reverb circuit, and possibly the proximity fo the tank to the PT.

I'll try to load a picture

OK... if it doesn't make noise with out reverb then the cap is probably OK for now. The reverb tank being right up on top of the PT can be an issue in a head cab.... yet the BF Bandmaster Reverb didn't have an awful lot of hum.... slightly bigger cabinet though.
I assume you know to keep the tank's RCA jacks forward, toward the front of the cabinet and as far as possible to other side of the PT.
Sometimes using a smaller value reverb level pot helps too as most player don't use the Fender reverb level above 3-4.... they're just looking for some room reverb/ambiance.
Try putting a 100K resistor across the two outside legs of the pot.