EL34 Grid Stopper resistor

[ca7922303]

What value resistor and what pins would be best to put a grid stopper resistor to try to stop oscillation on an EL34 ? Thanks.

[Chuck H]

Pin 5. Resistor must be right at the tube socket pin. anything from 1.5k to 4.7k should be sufficient.

Why do you think this is the trouble? Please give details about the problem you are having.

[ca7922303]

Pin 5. Resistor must be right at the tube socket pin. anything from 1.5k to 4.7k should be sufficient.

Why do you think this is the trouble? Please give details about the problem you are having.

Pin #5 only? I was thinking it would connect to 2 pins like a screen grid resistor?

[Chuck H]

Pin #5 only? I was thinking it would connect to 2 pins like a screen grid resistor?

Neither the screen grid or control grid have any mandate on being connected to an unused pin on the socket. This is done by designers and manufacturers for convenience so that no component ends are floating on a solder joint at the end of a wire lead. With no information about the amp in question I cannot suggest any bridging pins on the socket because it may interfere with what exists now in the amp.

[Enzo]

A screen grid resistor only really connects to pin 4. Pin 6 on a 6L6 is not used, so the empty pin 6 on the socket becomes a handy place to solder something. The resistor is much more secure soldered at both ends than at just one.

[ca7922303]

Neither the screen grid or control grid have any mandate on being connected to an unused pin on the socket. This is done by designers and manufacturers for convenience so that no component ends are floating on a solder joint at the end of a wire lead. With no information about the amp in question I cannot suggest any bridging pins on the socket because it may interfere with what exists now in the amp.

It's a Laney TT50H. Finally got it working and now it's oscillating, red plating and power loss

[Enzo]

What kind of oscillating?

[catalin gramada]

Disconect the PI outputs to power tubes. It still osscilate? If Yes than check the OT wiring track (keep away ot primary wires from inputs wires, secondary common directly to output jacks and from those point to nfb retour) . 100 ohm screen grids close to the socket should be able to cure any . If osscilation stoped with PI disconected check then the PI stage. First wiring track, specially the wiring from OT to nfb injection point.

[Jon Snell]

Pin 5 already has a 4k7 grid stopper, why would you need another?

[ca7922303]

What kind of oscillating?

Only way I know to describe it is a high pitched squeal that increases as drive/volume and master volume are about on 10. It's accompanied by both tubes red plating and output loss of power.

[ca7922303]

Pin 5 already has a 4k7 grid stopper, why would you need another?

Here's a photo of V7/V8. I'm not seeing any resistors attached to pin #5?

[ca7922303]

Neither the screen grid or control grid have any mandate on being connected to an unused pin on the socket. This is done by designers and manufacturers for convenience so that no component ends are floating on a solder joint at the end of a wire lead. With no information about the amp in question I cannot suggest any bridging pins on the socket because it may interfere with what exists now in the amp.

Would 2-5w 4.7k resistors with one leg soldered to the green wire on one el34 and the blue wire on the other(both pin #5) work?

[pdf64]

Here's a photo of V7/V8. I'm not seeing any resistors attached to pin #5?

Aren’t the components under the black sleeving the grid stoppers?
I assume they connect to pin5?
If so, what’s the resistance between the green or blue wire and the respective socket terminal.

[jack briggs]

Here's a photo of V7/V8. I'm not seeing any resistors attached to pin #5?

They're heat-shrinked.

[ca7922303]

Aren’t the components under the black sleeving the grid stoppers?
I assume they connect to pin5?
If so, what’s the resistance between the green or blue wire and the respective socket terminal.

Your right, they both read 4.7k ohms.