BUZZ IN SILVER JUBILEE

[TIMBO]

Hi guy's, This is a part of this thread http://www.el34world.com/Forum/index.php?topic=11494.0 as i am still unable to find this buzz but i think i am slowly working my way to it.

I have done lots of rehashing and the buzz is still the same buzz ( thinking by at least changing some wiring i thought that it might change the sound or the volume and might give me a idea to the location of it 

DISCONNECTING BITS

Thinking that it is (with the help of others)most likely to be in the grounding somewhere.
The grounding is as the attached schem. The grounding of the cap cans, circuit board, pot buss,etc. was tried in many different ways but did not change the buzz in anyway (sound or vol)
The next thing i tried was to do some disconnecting in this order :-
Tone Stack at treble wiper - no change
Vol pots at wiper - NC
68k resistor at V1 pin2 - NC
.68 cap V1 pin3 from turret on grounding trace - NC
2.7k resistor V1pin3 from turret on grounding trace - NC
10uf V1pin8 from turret on grounding trace - NC
1.5k resistor from turret on grounding trace - REMOVED BUZZ 


With this being the possible location of the buzz i am unable to see a correction as the info that has been available to me is not presenting anything that could be the cause, other than it being not able to connect the cathode grounds of V1 & V2 to separate Cap grounds  Thanks

[LooseChange]

DId you disconnect the relay and see if this was your buzz source?

[Geezer]

DId you disconnect the relay and see if this was your buzz source?

I suggest you try this (LC's suggestion)....just unhook the power supply to the relay & see if the buzz diminishes. Of course, you will only have access to the "normally closed" side of the relay during the test.
I had the same "buzz" problem once with a relay whose power supply was "isolated". I grounded the "-" side of the supply thru a 50 ohm resistor & the buzz disappeared.

G

[LooseChange]

Geezer. Lift the ground just a bit... Nice.

[Geezer]

Yeah, I was trying 2x 100Ω resistors from various spots, then connected them BOTH (parallel) to ground from the neg/common footswitch lug of the FS jack & the buzz was gone, thus the 50Ω....I just left them both connected, since it worked so well.
I was just like Tim, trying anything I could think of, when I stumbled onto this solution.
Of course, this will only help if the buzz is getting in thru the relay circuit.

G

[TIMBO]

Thanks guys, The schem is the relay circuit i am using.I disconnected the the neg wire at point "A" wonce before and this did not remove the buzz. Thinking that the circuit (diodes and cap being close to the preamp ground) was the problem, I moved the diode and cap to the tranny end and had wires running from there to the relay (on the main circuit board ) thinking that it would be better to have the relay on the main board as to keep wires short for the amp circuit.

Trying your suggestion again i disconnected the neg wire and the buzz remained.
Disconnected both wires and well, I DON'T FREAKIN BELIEVE IT,  BUZZ GONE    and amp is almost dead quiet but not able to try the OD to see what effect it does have as it was really bad when switched to OD.

I have seen other circuits that have the relays on the main board so i did not think that the relay would have an effect.

So any ideas or is removing the relay off the board and running wires from it the only solution.

Thankyou o cleaver ones 

 

 

[TIMBO]

Is this what you are suggesting.

[Geezer]

Is this what you are suggesting.

If your entire relay circuit is NOT connected to chassis/ground anywhere (including footswitch jack insulated/isolated) then yes, that is my suggestion.
You don't have to use 50R....try a 100R, or 47R....whatever close you have on hand. Put the resistor on clip leads to give it a try.

Hope it does the trick! 

G

[Geezer]

OR, if you DO have the relay circuit grounded, then place the 50R (+/-) between the circuit & ground.

G

[TIMBO]

Thanks Geezer, The circuit is isolated from the chassis, I was wondering if another type of circuit ( hoffman type ) would be any better,

Thanks

[Geezer]

Did you try the resistor to ground?

[Tone Junkie]

Geezer could this cause a hum  problem and only effect one side out of a two channel switching schem.
Thanks Bill

[TIMBO]

Hi guys', IT WORKED A TREAT  Used a 51ohm.In clean mode without a lead plugged in and all knobs at half you had to put your ear at the speaker to hear if it was on.Plugged the guitar lead in and it did increase a little bit, plug the guitar in and touching the strings and the buzz would reduce. Flicked to OD and the buzz would increase a little ( but bearable )but i thinking that this could be the nature of the circuit. Now that the source has been found i can tidy up some of the mess i made trying to find the little bugga.

Thanks to all, it was another great learning experience 

[Tone Junkie]

I love your head box Timbo thats just plain cool.       
Bill

[jojokeo]

You need to always plug in a chord or jack into the input socket to hear what the amp's floor noise is as nothing should be heard when it's shorted w/out anything there.
The noise floor should aways go up when the high gain gets switched and is normal as well as when you turn up your vol knobs. The grounding info (and work you've done) we discussed ealier will still pay off for you now besides the buzz geezer helped you with.
Glad it's all fixed up, you're happy, and your amp is a success Tim! 

[LooseChange]

Nice job on the amp! It looks great.