Jerry garrcia
Tele-Holic
First post in the new Shock Bros….
Been doing my first PTP build ever. A modified GA-5 (Les Paul variant). Different values for the pentodes operating conditions as compared to the original schematic to tame the amp a bit.
So happy when all voltages were as expected and jolly as a kid when I was about to remove the speaker dummy load, insert a speaker and a guitar to rock on.
Hardly any volume. Tried with a different guitar, different speakers, swapped tubes etc. but no difference. Volume about 5-10% of expected. Compared to a 5F1 and this was nothing compared to that one.
So redid the thing with the original specs. No difference. Redid the power supply and altered the preamp section sir maximum gain of the 6SJ7. A tiny difference.
Added a screen resistor on the 6V6. No difference.
Poked everything with a china stick and no difference.
Measured all the resistance and ESR meter of all components.
Fought with the family for a couple of days because I was so frustrated but no difference in the amp volume.
Measured the volume pot and read 5K!!!!
I’ve had this nagging sensation that it wasn’t in the circuit since all voltage were fine and I’ve measured all the components (except for the pot) before I added them.
In the back of my head I remembered that I did use a 5K lin pot for setting a bias before and removed the alligator leads before this build and must have added the pot by mistake.
So inserted the right pot and all went well and my PTP sounded great. Redid the circuit to original specs but kept the screen resistor on the 6V6.
Lesson learned.
Been doing my first PTP build ever. A modified GA-5 (Les Paul variant). Different values for the pentodes operating conditions as compared to the original schematic to tame the amp a bit.
So happy when all voltages were as expected and jolly as a kid when I was about to remove the speaker dummy load, insert a speaker and a guitar to rock on.
Hardly any volume. Tried with a different guitar, different speakers, swapped tubes etc. but no difference. Volume about 5-10% of expected. Compared to a 5F1 and this was nothing compared to that one.
So redid the thing with the original specs. No difference. Redid the power supply and altered the preamp section sir maximum gain of the 6SJ7. A tiny difference.
Added a screen resistor on the 6V6. No difference.
Poked everything with a china stick and no difference.
Measured all the resistance and ESR meter of all components.
Fought with the family for a couple of days because I was so frustrated but no difference in the amp volume.
Measured the volume pot and read 5K!!!!
I’ve had this nagging sensation that it wasn’t in the circuit since all voltage were fine and I’ve measured all the components (except for the pot) before I added them.
In the back of my head I remembered that I did use a 5K lin pot for setting a bias before and removed the alligator leads before this build and must have added the pot by mistake.
So inserted the right pot and all went well and my PTP sounded great. Redid the circuit to original specs but kept the screen resistor on the 6V6.
Lesson learned.
