Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Stuff4bikes on December 12, 2021, 12:15:38 pm
-
I have searched and can't find an answer. When rewiring the grids do you use shielded cable and ground the shield at the pots?
And do you ground all pin 1's If they say "shield" but don't show the ground symbol in a pinout drawing?
The tubes in question are 6AK5G and 6Q7G....thanks for any help.
-
Depending on where the 6Q7 is placed in the circuit, I might not even bother to shield the grid lead. But if I did shield it, I would ground the shield at the source end of the signal, in your case, probably the pots.
The 6Q7 is a "metal" tube and the metal is connected to pin 1. So, to use the metal can for a shield you would ground pin 1.
The 6AK5 is a 7-pin mini and has an internal shield that is connected to cathode. Nothing to do here.
-
Sorry sir......its a 6K5G not a 6AK5....
And the 6Q7G is V1 and V2 is the 6AK5 in this...
I have ordered 2 nos 6Q's for this amp, just wanted to know how to wire them up correctly.......the wire on now is crumbling and deteriorating.
-
What I said about 6Q7 also applies to 6K5. Pin 1 should already be connected to ground.
What are you working on? Sounds more like a repair/restoration of an existing amp. If that's the case, I would use shielded cable on the grid caps ONLY if the original used shielded cable.
-
Westinghouse amp conversion came with the two mentioned tubes and some 6K7's and a 6L6.
The wires underneath were so rotted, I gutted it. Through in a turret board, filter board and choke(which turned out to be bad)
And added noise to the circuit.....
I only have like 350v on the plate of the 6L6 but the power, output trans and 5Y4G are the original so I will leave it
That way....
I am using a 250uf cap on the 6L6 cathode and it has a mellow tone.
I believe the cap wires weren't shielded but i have shielded cable on them now grounded at the pots.
I have them pieced together and want to run new wiring to them,
-
alternatives to shielding sensitive grid wires are:
1) a 33k-68k grid stopper soldered right at the grid pin
2) single strand/solid core insulated wire run tight against the chassis between whatever component is in front of the tube and the tube grid pin. Keep this wire at least 1” away from high VAC wires (unless crossing at right angles), or VAC wires carrying high currents. (Solid core because it’s easier to dress where you want it. And keeping it tight against the chassis helps to ‘eat up’ any stray EMF)
-
I couldn't wait for the 6Q's to show up so I rewired the sockets for 6SQ7gt's in V1 and V2. I have a bunch.
I put a RCA 6L6gc in and with the 250uf bypass the bass is very nice with single coils but boomy with my hot
Humbuckers. I am playing this amp through a 1x12" cab with a Motorola golden voice.
I don't play guitar well so my opinion may not be much.
Also had a slight power hum at first then swapped the 6L6 and it went away...