Newly Built 5F2a, Low and Bad Sound...

[MWJB]

"Well soldering most of things to socket's pins wouldn't be too complex for debugging and finding errors?" The majority of your errors are centred around the fact that you don't have suitable board materials, so dispense with the board as much as you can. There isn't really much that can go wrong wiring point to point, if done carefully (no shorts/blobs of solder dripping on the chassis). This is how many amps were built in the 50's & 60's...even early Fender Champs were built this way.

The eyelet board is more convenient for mass production...as long as it's a proven design.

Those strips wont be any good, can you find any insulated terminal posts (screw one end to the chassis, insulator in the middle & another screw thread at the other end, under which you can stuff a couple of solder tags to connect parts)? A handful of these and your amp is sorted.

[Bruce / Mission Amps]

HV rating of the PT is 700v in total, by the way B+ is 478 if i only install 5Y3 tube rectifier (it is NOS) when i install all tubes the B+ is 395v. Even 395v high for B+?

My tubes are:
5Y3 GE NOS
6v6GT Tung-Sol
5751 Philips Jan

I will check values of the tubes' legs and will post it here soon

Caner, where in the world are you?

[PFCnR]

Caner, where in the world are you?

Bruce i live in Turkey. It is really hard to find electronic components about tube amps. I ordered most of the things from tubedepot.com

[PFCnR]

"Well soldering most of things to socket's pins wouldn't be too complex for debugging and finding errors?" The majority of your errors are centred around the fact that you don't have suitable board materials, so dispense with the board as much as you can. There isn't really much that can go wrong wiring point to point, if done carefully (no shorts/blobs of solder dripping on the chassis). This is how many amps were built in the 50's & 60's...even early Fender Champs were built this way.

The eyelet board is more convenient for mass production...as long as it's a proven design.

Those strips wont be any good, can you find any insulated terminal posts (screw one end to the chassis, insulator in the middle & another screw thread at the other end, under which you can stuff a couple of solder tags to connect parts)? A handful of these and your amp is sorted.

Hello guys,

I rewired the amp today and it really rocks although there is still some humming. ( I just could not leave after i hear the tone ). I just want to know, when i touch the chassis there is no hum unless i touch the strings at the same time. If i do not touch the chassis there is hum and if i touch the strings of my guitar hum sound increases. If i get away from amp, hum sound just increases more.

I have two grounding point,

1) The ground from wall, PT, Filter caps.

2)Everything related with preamp tube, input jacks and volume and tone pots.

I also loaded Artificial CT on power tube.

What else i can check?

The other thing is i played the amp like 20~30 minutes and i have realized that PT is really hot. Is that normal?

Thanks.

[MWJB]

Did you correct the values or the artificial heater centre tap, as Bruce advised - should be 2x100ohm resistors, not 2x 100K?

How does the volume & tone control affect hum, do you still get hum with the preamp tube pulled? We want to try and establish whether it is heater filament hum (common in single ended amps) or whether it is relatd to preamp grounding layout.

Does the amp hum with nothing plugged into it? We want to be sure that the guitar is not contributing to the hum.

Champs & Princetons use small power transformers, they get hot. Hot for your fingers & "hot" as far as the transformers are concerned might be very different things. Can you smell burning?

[PFCnR]

Did you correct the values or the artificial heater centre tap, as Bruce advised - should be 2x100ohm resistors, not 2x 100K?

How does the volume & tone control affect hum, do you still get hum with the preamp tube pulled? We want to try and establish whether it is heater filament hum (common in single ended amps) or whether it is relatd to preamp grounding layout.

Does the amp hum with nothing plugged into it? We want to be sure that the guitar is not contributing to the hum.

Champs & Princetons use small power transformers, they get hot. Hot for your fingers & "hot" as far as the transformers are concerned might be very different things. Can you smell burning?

Yes i corrected the artificial heater center tap 2x100ohm.
The amp gives a little hum if i do not plug my guitar in.
Yes, volume and tone control affects the hum.
There is not even a little sound but PT, when i pulled out preamp tube.
No there is no smoke or something like that but PT gets hot.

[MWJB]

Make sure grid wires (5751 pins 2 & 7) are away from plate wires (pins 1 & 6) and away from heater wires.

Make sure that components are not accidentally grounded to more than one point (causing a ground loop hum).

Power down the amp, connect a jumper wire from the volume pot end of the coupling cap at V1 pin 1, to ground. Power up, still hum? If so try the same trick at pin 5 of the 6V6. We are trying to detemine if there is a particular triode in V1 that is more hum prone than the other.

Is the hum a buzzy higher pitched hum, or a low frequency low hum?

Any fresh pics of the new wiring?

[PFCnR]

Power down the amp, connect a jumper wire from the volume pot end of the coupling cap at V1 pin 1, to ground. Power up, still hum? If so try the same trick at pin 5 of the 6V6. We are trying to detemine if there is a particular triode in V1 that is more hum prone than the other.

Is the hum a buzzy higher pitched hum, or a low frequency low hum?

Any fresh pics of the new wiring?

I am still trying to understand what you meant

You want me to connect a jumper wire from volume pot (but which leg) it is already connected to the volume pot though. And want me to connect the jumper wire to the ground?

Yeah i can take some pictures soon.

[MWJB]

I want you to short out the signal, after the coupling caps (e.g. at the volume pot input/right hand terminal for V1 triode A), one by one to see if the hum pertains to any particular half of V1.

[PFCnR]

Power down the amp, connect a jumper wire from the volume pot end of the coupling cap at V1 pin 1, to ground. Power up, still hum?If so try the same trick at pin 5 of the 6V6

I just done it and there is no hum but not even a sound. (for pin1 5751)

However when i do the same thing to pin5 of the 6v6 hmmm it gives sound like buzzing more than a hum

[MWJB]

"I just done it and there is no hum but not even a sound. (for pin1 5751)" Good. Ok, so we might assume that there is hum related to V1 triode A, cathode pin 3 & the tone/vol pots.

Double check that they all ground at one point, preferably the input jack ground. Make sure that the grounds on the vol pot & 0.0047 tone cap are mechanically sound.

Does your grid wire to pin 2 run close to a plate/heater wire? Rout it away as best you can. Shielding is grounded at just one end?

"However when i do the same thing to pin5 of the 6v6 hmmm it gives sound like buzzing more than a hum" I thought that might happen, lift the end of the coupling cap instead. But sort triode A first, you were only supposed to investigate triode B if grounding the coupling cap didn't kill the hum.

[tubeswell]

However when I do the same thing to pin5 of the 6v6 hmmm it gives sound like buzzing more than a hum

Hmmm... maybe you are amplifying a hum that's in the ground return path when you ground the grid of the 6V6?

[PFCnR]

"I just done it and there is no hum but not even a sound. (for pin1 5751)" Good. Ok, so we might assume that there is hum related to V1 triode A, cathode pin 3 & the tone/vol pots.

Double check that they all ground at one point, preferably the input jack ground. Make sure that the grounds on the vol pot & 0.0047 tone cap are mechanically sound.

Does your grid wire to pin 2 run close to a plate/heater wire? Rout it away as best you can. Shielding is grounded at just one end?

I better take a picture for you all to examine it better

What do you mean by "mechanically sound" ?

And yeah pin 2 and pin 1,3 moves parallel in the chassis. I will re position them then.

[MWJB]

"What do you mean by "mechanically sound" ?" a good sturdy ground connection, check grounded terminals on pots & components with an ohmeter, to main chassis ground. Should read lowest, default setting on the meter. If any look suspect, reheat/resolder, crimping/staking the wire/component to it's location.

[PFCnR]

"What do you mean by "mechanically sound" ?" a good sturdy ground connection, check grounded terminals on pots & components with an ohmeter, to main chassis ground. Should read lowest, default setting on the meter. If any look suspect, reheat/resolder, crimping/staking the wire/component to it's location.

Ok i will do it very soon after i upload some pictures. Pictures will be here any soon