G2 no sound

Hi,

I have built a G2 kit and after completion I measured according to layout with good values. But when plugging in my guitar I get just a very low volume - I can barely hear the guitar if I get vey close to the speaker.

I wonder if it could a problem with the OT secondary?
How do I check this?

Regards,

Jonas from Sweden

Zitat von MAD;325178

Hi Jonas and welcome to the forum!
Just plug in a speaker cable at the output plug socket and measure the resistance between ring and tip of the other plug of that cable (with the amp turned off!). What resisitance do you measure? When connecting a speaker, do you hear any hiss/hum or is it absolutely quiet?
Regards,
Martin

Hi Martin,

Thanks for your assistance.
I checked the resistance and it was ap. 0,9-1.0 Ohm.
No - I don't get any hiss or hum noise.

Regards,

Jonas

Zitat von MAD;325187

Hi Jonas,
the resistance ist OK, please take out V2 (amp turned off) and easure the primary resistance of the OT (pin 6 of the tubes socket against the red wire of the OT and pin 1 of the tube socket against the red wire of the OT). Does the measurement changes, when SW1b is turned on/off?
Regards,
Martin

Ok resistances are (amp turned off and V2 removed):

157 Ohm between pin 6 of V2 and red wire of OT
111 Ohm between pin 1 of V2 and red wire of OT

It doesn't matter in which position the SW1 is (Fat/Smooth) - I get the same readings.

Regards,

Jonas

I checked all voltages once more:

C10+ : 245V
C9+: 233V
Heater: 6,44VAC (measured at V2 tube pins)
TR2 red/red: 193,5VAC

V1 pin1 177V (166 ac. to schematic)
V1 pin3 1,48V (1,7)
V1 pin6 177V (166)
V1 pin8 1,47V (1,7)
V2 pin3 4,8V (5)
V2 pin6 243 (237)

Values for 1V3 and 1V8 seem too low - what could be the reason for that?

Also 1V1 and 1V6 are a little high but only slightly.

regards,

Jonas

Zitat von MAD;325187

Hi Jonas,
the resistance ist OK, please take out V2 (amp turned off) and easure the primary resistance of the OT (pin 6 of the tubes socket against the red wire of the OT and pin 1 of the tube socket against the red wire of the OT). Does the measurement changes, when SW1b is turned on/off?
Regards,
Martin

Hi Martin,

Have you had a chance to check my measurements?

Regards,

Jonas

I have checked the wiring many times without finding any errors.
Doesn't the fact that I can hear the guitar at a vey low volume help you to isolate the possible source of problem(s)? At max volume I have checked the tone and fat/smooth switch and they seem to work.
Could the V2 tube be defect?

Regards,

Jonas

Upon resoldering the V2 connections I meassured the resistor R9 to 220 Ohm (should be 220 kOhm). Color code is red, red, brown which matches 220 Ohm.

From what I understand this means less signal goes to the power amp tube thus resulting in a very low volume ?!?

Does this resistor have to be 2W or can I replace it with a 1/4W?

Regards,

Jonas

Zitat von eBernd;325962

Yes, you can ;D

Regards,
Bernd

After replacing the resistor against a new one with correct speccs the amp works and sounds real sweet.
Thanks for the help.

Regards,

Jonas