rockinrob86
Well-known member
I am working on this echoplex, and I traced a sine wave from the input to pin 8 on v2b. If I look at the plate on v2b, it is all wacky and messed up, so something is clearly happening here.
I then measured voltages, and am seeing 350v(?!) at pin 9, the cathode. I see that voltage back at pin 5 of the 6c4 oscillator, and can trace it around the line. Looking to where that line comes from (the cap can) I see that the rectifiers are putting out around 380, and both R29 and R28 are barely dropping anything. The power transformer is stock.
I have another working EP2 that also runs hot due to higher modern voltages, but it is running more like 300 vs 260 on the schematic.
My questions are - what would cause the 100 ohm and 3.9K ohm resistors to not drop voltage - I realize if there is not current being pulled, then they will not drop, but the tubes are in and everything looks alright?
I do not hear massive 60 cycle hum with it plugged, but it appears the record and erase heads are not doing anything. Playback works and the guitar signal comes through.
What should I look for next? I am assuming 350v is frying the cathode in the 6eu7s. The 350v is present with both v2 and v3 removed. I just realized I did not check if V2A is normal, or V1, but based on the unit's operation I am thinking probably.
