I do have a variac at my disposal . Would this help? Maybe I should just remove the limiter and chance it, or remove limiter and bring her up slowly with the variac.
Just worried about the voltages on the preamp tubes. If there is no voltage drop across the dropping resistor strings, then these tube swill be seeing 400+ volts on the plates.
andresound wrote:However, the volltages (with bulb limiter) at the B+ = 196, then B2 - B5 are all 183v !!! Shouldn't they be dropping in increments?
If you are still in standby mode, then the voltages down the rail will all be about the same since there is no current draw (unless you have a bleeder resistor somewhere). Switch into play mode and remeasure. I also recommend a 60W bulb.
I thought $%£@! it! And removed the bulb limiter. Been on for 30 min and no smoke! Transformers are cool. Heater supply is 6.2v ac. Bias is - 48v pin 5
Secondary = 639 ac
B+ = 424v
Voltages are high on preamp!!
V1 pin 1 409.4 v
V1 pin 3 6.52 v
V1 pin 6 409 v
V1 pin 8 6.52 v
V2 pin1 410 v
V2 pin 3 8.92 v
V2 pin 6 411,5 v
V2 pin 8 8.97 v
PI pin 2 297.3 v
PI pin 3 & 8 106.1 v
PI pin 6 277.7 v
PI pin 7 66.9 v
Something wrong here guys!! Any ideas? Amp is very quiet and no sound with an input. Highly imbarresed
I find that 40W bulbs glow too bright for larger amps (50W and 100W). While it isn't as safe, I typically use a 60W bulb in my limiter so I can tell the difference between normal current draw and s short.
Well, that's some progress anyway. Can you post or point to the schematic you are using, and post voltages for pins 1, 2, 3, and 6, 7, 8 for the preamp tubes, and 3, 4, 5, and 8 for the power tubes?
martin manning wrote:Well, that's some progress anyway. Can you post or point to the schematic you are using, and post voltages for pins 1, 2, 3, and 6, 7, 8 for the preamp tubes, and 3, 4, 5, and 8 for the power tubes?
Your voltages look reasonable except for the loop send stage. Pin 2 should be about 28V and pin 3 should be about 30V. Check the wiring and component values around there.
To see if that's where your signal is dying you can try jumping over the FX loop by pulling that tube and connecting a clip lead from the input side of the send pot to the input of the master volume (Level) pot. Turn the send and return pots all the way up.
Can you post a link to the schematic? The image above is fuzzy.
Checked my wiring for the 1000th time and reveresd some faults. I now have sound coming through (very soft). The return pot of the FX loop is acting like a master volume. The send pot makes no difference.
The tone stack seems to work.
The drive pot of the OD introduces a wired sound that (if the drive pot is not full open), and i put a finger on the blue cable from the relay board to the 0.01uf, the wired noise goes away. Also if I play a note, the wired sound seems to follow the fequency of the note played The higher I turn the drive pot, the lower in frequency the wired sound becomes!
Will try bypassing the FX loop. So just to be clear, clip lead from wiper (centre lug?) of send pot, to wiper of i meg level pot (OD master?).
. Would this help? Maybe I should just remove the limiter and chance it, or remove limiter and bring her up slowly with the variac.
But still to high on preamp.
The higher I turn the drive pot, the lower in frequency the wired sound becomes!