Noisy reverb , Princeton copy

spev11

I’ve built a Princeton copy ( modulus kit). Got it working but the reverb is unusable as it’s super noise, very loud hum as soon as you turn the knob. I’ve not got a foot switch for it yet. Checked connections, been in with the chopstick and nothing so far. All the preamp tubes bar
the 12at7 reverb drive are a smidge loose but it doesn’t seem to affect the operation. I did have a faulty 12ax7 which displayed a similar hum problem. Can I substitute the 12at7 for one of my spare 12ax7 for the purpose of elimination? 

BlackbirdCabs

I am in no way qualified to help, but I had this problem once and it was a simple case of the red and black connections being the wrong way round.

spev11

ive swapped em so many times im dizzy   
all the schematics and build plans have slight variations on wiring for the in/out sockets and the footswitch so I've tried all of them. I'm happy enough to order a 12at7 to be honest but was hoping to whack a 12ax7 in for testing purposes

ICBM

You probably need to rotate the tank relative to the power transformer. If the PT and reverb transducer coils are aligned on the same axis it will induce hum in the reverb transducer.

That may be awkward from a layout point of view, but if it’s on the floor of the cabinet now, try it on the inside of the lower back panel, or vertically on the side wall. Make sure the output end is furthest from the PT.

spev11

It’s in a head box so not a lot of room, it buzzes and hums with the tank outside and far away from the amp.i will go,in and recheck everything but it’s driving me mad ( the buzzing is loud enough to make it unusable 

RiftAmps

I bet your RCA sockets aren't grounded

spev11

The diagrams all make the assumption that they ground to the chassis via the socket but I’ll whip em out to check there isn’t an insulation washer or similar in the way, I can run grounding wires to a nearby tab if need be

RiftAmps

spev11 said:

The diagrams all make the assumption that they ground to the chassis via the socket but I’ll whip em out to check there isn’t an insulation washer or similar in the way, I can run grounding wires to a nearby tab if need be

I spy isolation washers

spev11

I figured as they were on the outside and over the back panel that’s the proper place. It’s all a learning curve, I shall go move em and check the grounding again, ta very much

spev11

ah I hang my head in shame, i'd put a bloody washer either side of the socket, the ground tabs on two of em were chassis side . I've removed them, retested and bingo , its playable, there's still a bit of hum so i'll shuffle the tanka around a bit and see if that sorts it. 
Ta everyone for all the help that i've had and undoubtedly will receive. This was a huge step up from the pedals I've built but I'm so pleased (and excited that its working).

stylesforfree

spev11 said:

ah I hang my head in shame, i'd put a bloody washer either side of the socket, the ground tabs on two of em were chassis side . I've removed them, retested and bingo , its playable, there's still a bit of hum so i'll shuffle the tanka around a bit and see if that sorts it. 
Ta everyone for all the help that i've had and undoubtedly will receive. This was a huge step up from the pedals I've built but I'm so pleased (and excited that its working).

The issue with reverb tanks is that sometimes, depending on the environment, some buzz and hum is unavoidable. I have had amps that hum and buzz but when miked up the hum and buzz isn't really present on the recording. Of course when playing at certain volumes for your own personal pleasure it can be hard to accept it for what it is. There's plenty of quiet tube amps with quiet reverb tanks out there but my experience is that some buzz or hum is always present.

spev11

Forgot to update, fitted the tank in the bottom of the headshell I made, made the grounding washers for the reverb in and out work and its running fine and its exceptionally quiet. I have only solid state amps at home to compare it with (I have a Fender Vaporizer at work that I may bring home) and its very quiet indeed. 
 Just need to knock up a footswitch now, nothing fancy, just two switches with led's so I can switch the reverb and trem on and off.

thermionic

I think getting LEDs to work with such a switch may not be straightforward...

Chris.B

Well done @spev11 it sounds like a great project to undertake, especially with the cabinet making. It must be great to play through something you created yourself. 

spev11

thermionic said:

I think getting LEDs to work with such a switch may not be straightforward...

i'll chuck a button cell in to power em (or a 9 volt supply, seems a bit overkill mind)

hywelg

You can buy 9v battery boxes that only require you making a square cut out in the pedal housing. I did that to power the LEDs in my DZ30 channel switch. I also put a switching 9v jack socket so if I had a supply then it would save the battery. 

thermionic

I did think that would be possible, sounds like a very good solution.