| Author |
Topic: Issues with a 1963 Blond fender 6G6-B |
Paul Smith
From:
Ma
|
Posted 16 Jul 2022 1:25 pm |
|
Wondering if anyone has an idea where to "look". I have a static sound im trying to pin point. Im in channel 2 which is the "Normal channel", no tubes in channel 1 which is the Bass channel. I have 2 good/tested 12ax7 tubes in v3, and the phase inverter socket. If I pull the v3 tube I still get static, If I pull the PI Tube, leaving V3 in place the static goes away. Does this pinpoint that the problem is possibly somewhere in the PI circuit? any help would be appreciated.
Also, this happens with my guitar (lapsteel) is not plugged in, so its not my guitar rig
thanks in advance,
Smitty |
|
|
|
Ron Forrest
From:
Logan Ohio, USA
|
Posted 16 Jul 2022 9:06 pm
|
|
Smitty,
I think by pulling the phase inverter tube you are basically disconnecting the signal to the power tubes. So the static sound you are hearing would go away because there is no audio present in the output stage.
Id be more concerned with the tubes being out of channel one. They could possibly share a ground or some other component thats not seeing the correct voltage with them absent.
Most of the time noise, static, or hum in a tube amp is caused by aging capacitors, bad shielding or bad grounds.
Im definitely a tube amp repair expert but i've my fair share of noise amps and 99% of the time its been a bad ground or bad caps. |
|
|
|
J Fletcher
From:
London,Ont,Canada
|
Posted 17 Jul 2022 4:18 am
|
|
| Can't say without hearing what the noise sounds like , but a frying sound is usually a bad plate load resistor . |
|
|
|
Paul Smith
From:
Ma
|
Posted 17 Jul 2022 8:15 am
|
|
Thanks for the replys, Im going to replace the plate load resistors, starting at V1, if the noise goes away, I will stop replacing resistors. I will continue in this fashion right through the PI if I have to.
I will report back as to weather or not it was the plate load resistors. |
|
|
|
J Fletcher
From:
London,Ont,Canada
|
Posted 18 Jul 2022 3:38 am
|
|
| Static and frying sounds mean different things to me . If you are going to replace plate resistors, I would start at the PI tube since that is the most likely source of noise , based on your description. Jerry |
|
|
|
Ken Fox
From:
Nashville GA USA
|
Posted 18 Jul 2022 11:37 am Plate load resistors
|
|
I learned a good way to identify bad plate load resistors from a book called “Hip Hop Amps, by Gerald Weber”some years ago
With amp head on the bench and connected to my bench speaker I place a jumper from ground to the plates (pin 1 and then pin 6) one at a time
This effectively turn of the tube and safely takes the plate supply to ground thru the 100k plate load resistor
If the noise goes away then you have found the offending plate load resistor
If you are not an experienced tech I do not recommend doing this or any other work in a tube amp chassis. |
|
|
|
