I know that this is a well covered subject in many forums, but I still have a question regarding the operation of this type of tremolo that appears to inject its output directly to the grids of a cathode biased 6v6 PP pair. I've attached the Silvertone version of this circuit because that's what I have to work with.
The circuit is oscillating but my question is, what is the expected strength of the signal at the grids of the output tubes? In its current state there is just a faint amount of audible tremolo even with the intensity fully CW. I've also attached shots of my O-scope as I trace the signal from 6AU6 plate through to the 6v6 grids.
The circuit is oscillating but my question is, what is the expected strength of the signal at the grids of the output tubes? In its current state there is just a faint amount of audible tremolo even with the intensity fully CW. I've also attached shots of my O-scope as I trace the signal from 6AU6 plate through to the 6v6 grids.
Attachments
Peak trem at grid equal to grid-cathode bias is a little too much.
15V p-p on an oscillator with 330B of B+ is remarkably small. Are there any DC voltages at the 6AU6? How far out have the resistors drifted? Disconnect the 1Meg off the plate; does the plate swing better?
And: you will scare the Hi-Fi buffs with tremolo talk. There is a section for guitar amps.
15V p-p on an oscillator with 330B of B+ is remarkably small. Are there any DC voltages at the 6AU6? How far out have the resistors drifted? Disconnect the 1Meg off the plate; does the plate swing better?
And: you will scare the Hi-Fi buffs with tremolo talk. There is a section for guitar amps.
Hi Soundfish616,
You need to clean that poor 'scope's face plate! Pride of ownership, you have to look at it all day after all.
At least use a paint brush and lose the loose dust.
-Chris 🙂
You need to clean that poor 'scope's face plate! Pride of ownership, you have to look at it all day after all.
At least use a paint brush and lose the loose dust.
-Chris 🙂
PRR, thanks for the reply.
I apologize that my labels didn't come through on the photos. The first shot is the plate with a x10 probe, so 150v PP swing. The rest are x1. The last photo is the 6v6 grid. So you're saying thats too much swing?
FYI, here are some measurements I made earlier today:
Airline 9013a tremolo Voltage Readings
FLUKE 87 DMM
6AUA6 Plate
max: 225
min: 192
Ave: 145
6AU6 Screen
max: 60
min: 53
ave: 57
6AU6 Grid
max: -1.8
min: -2.65
ave: -2.25
6AU6 Cath.
0
Two other things I've noticed as I've gone through this amp are that the B+ is intermittently dropping from 350v to 280v (at idle with trem. off), and my 6v6 cathode voltage is consistently riding at 25v (instead of 15v). Both output tubes are testing at 100% and the cathode resistor measures right at 220ohms. I think I'll table the tremolo problem for know and see if I can get to the bottom of these issues.
I'll take your advise and try to migrate this posting to a more appropriate site.
I apologize that my labels didn't come through on the photos. The first shot is the plate with a x10 probe, so 150v PP swing. The rest are x1. The last photo is the 6v6 grid. So you're saying thats too much swing?
FYI, here are some measurements I made earlier today:
Airline 9013a tremolo Voltage Readings
FLUKE 87 DMM
6AUA6 Plate
max: 225
min: 192
Ave: 145
6AU6 Screen
max: 60
min: 53
ave: 57
6AU6 Grid
max: -1.8
min: -2.65
ave: -2.25
6AU6 Cath.
0
Two other things I've noticed as I've gone through this amp are that the B+ is intermittently dropping from 350v to 280v (at idle with trem. off), and my 6v6 cathode voltage is consistently riding at 25v (instead of 15v). Both output tubes are testing at 100% and the cathode resistor measures right at 220ohms. I think I'll table the tremolo problem for know and see if I can get to the bottom of these issues.
I'll take your advise and try to migrate this posting to a more appropriate site.