Crate V5 mods... anyone?

[jim p]

Here is a list of things to check and ohmmeter to see if the connections are correct.


With the op amp out you should have C24 C25 and C26 removed with a jumper from pin 3 of the op amp to the junction of R1 and R2 with R2 removed. That is the signal from the guitar to the first triode. Pin 7 of the op amp should be grounded C27 removed R27 should be removed with a jumper from the junction of R27, R7 and R15 jumpered to pin 6 of the op amp. C6 should be installed R15 should be installed. If you ohmmeter from the tip of the ¼ inch jack to pin 7 of the 12AX7 you should read the value of R1 47k also check to ground should be 1 Meg. Ohmmeter pin 2 of the 12AX7 to ground you should have zero with volume pot turned down to 250k at volume at full clockwise. From pin 2 of the 12AX7 to R9 should read approx 500k to 600k.

Another source for amp modifications and help is over at sewatt.com

[Christopher Whitlow]

Here is a list of things to check and ohmmeter to see if the connections are correct.


With the op amp out you should have C24 C25 and C26 removed with a jumper from pin 3 of the op amp to the junction of R1 and R2 with R2 removed. That is the signal from the guitar to the first triode. Pin 7 of the op amp should be grounded C27 removed R27 should be removed with a jumper from the junction of R27, R7 and R15 jumpered to pin 6 of the op amp. C6 should be installed R15 should be installed. If you ohmmeter from the tip of the ¼ inch jack to pin 7 of the 12AX7 you should read the value of R1 47k also check to ground should be 1 Meg. Ohmmeter pin 2 of the 12AX7 to ground you should have zero with volume pot turned down to 250k at volume at full clockwise. From pin 2 of the 12AX7 to R9 should read approx 500k to 600k.

Another source for amp modifications and help is over at sewatt.com

You are awesome! I know already that one problem will be me not realizing I interrupted the flow when I did the second mod by NOT replacing c6 or c15. Amazing what you miss when you dont know what to look for. I have a multi meter and will check values at those critical points a Bnd replace my missing parts in the signal path then report back. I have the book mentioned above on it's way and Im learning a bunch from the pdf that explains amps in the 70's and before. When I recieved this amp free I decided this was my chance to learn how they work and boy howdy am I a learnin! Thnx again folks!