Hi,
The issue: The "more drive" circuit is not working.
Three amp techs have looked at the amp without results. Link to schematic
http://www.thetubestore.com/lib/thetubestore/schematics/Fender/Fender-Hot-Rod-Deluxe-Schematic.pdfI have replaced many of the components in this circuit.
Test point readings:
Per schematic
TP 31 +1.37 +1.07 +1.07
Actual
TP 31 +1.36 +1.09 +1.09
Per schematic
TP 32 +.548 +9.76
Actual
TP 32 +.498 +9.78
Per schematic TP 33 +16 -13.5 -13.9
Actual TP 33 +16.37
-10.17 -10.17Per schematic TP34 -13.0 -5.46 -4.96
Actual TP34
-11.88 -12.11 - 12.11Per schematic TP 35 -.54 -10.0
Actual TP 35 -.51 -9.5
Per schematic TP 36 -16 -16 +16
Actual Tp 36 -16 -16
-16I have verified all resistors and zener diodes and changed any that were out of value. I replaced the op amp which was a 4558 on the board from the MFG but shows a 4560 on the schematic. The only difference in the two op amps is the slew rate. I replaced the two JFETs and Q3 and Q4 transistors. The push button switches are working correctly.
It is obvious that the voltages at TP33, pin 7 of the op amp are not correct. TP34 is not correct, and the voltage at TP36 does not change to positive.
I can provide any other measurements that may help.
Anyone have any ideas of what to do next?
Thanks,
Billy
EDIT...sorry about the schematic...you will need to go to the link
2nd EDIT...the 4558 op amp that was in the amp would not work correctly. I installed a 5532 and that works. Other strange issue...the combo LEDs are not red and yellow but red and green which makes yellow when both are lit and shows red when the green LED is turned off.