I've dug through one giant bag of resistors, best I can find so far is 1k, which I could use 2 for 500 I guess. I have more to search through. This resistor sets the bias for the opamp, if I remember right, does this need to be carefully matched 1 % types, or are typical metal films good to go here? search continues. Better start thinking of parts needed coming up in case I need to order some. I dont mind waiting to get the part I want. I have Pearl 2 also. Listening toSalas UltraFSP RIAA, so I can still listen at least. Going back in for resistor hunt.
500 ohm over 2.4v gives you 4.8mA. That should work. Since you have a range of 2-5mA for Class A bias on the opamp, matching is not really that important. Most resistors will be more than close enough. So 2 1K resistors in parallel should be fine. There is no audio going through this resistor.
Have anything in the ballpark of 200ohm? Put that in series with the 220 already there…
Resistor composition is not critical at all in this position.
EDIT: @dpogorman beat me to it, yes, 500ohm would also work nicely.
Resistor composition is not critical at all in this position.
EDIT: @dpogorman beat me to it, yes, 500ohm would also work nicely.
Not my night for physics. I think I might have cooked something. Possibly the opamp. Now, with resistor 220 ohm added in series, I have 2.7 volts
instead of 2.4 I did have. Everything lights up and looks normal. I checked resistor before install, 220ohm.
The reason I think I cooked the opamp is when I first did the surgery, I did it on R26 ( yes on both sides) instead of R27. With variac, I saw it heading north of 10 volts before shutdown. Fixed resistor surgery and now get 2.7. Are there other voltage points to track down whats dead? Guess i should have waited. I cant believe I made the same mistake on both sides!
instead of 2.4 I did have. Everything lights up and looks normal. I checked resistor before install, 220ohm.
The reason I think I cooked the opamp is when I first did the surgery, I did it on R26 ( yes on both sides) instead of R27. With variac, I saw it heading north of 10 volts before shutdown. Fixed resistor surgery and now get 2.7. Are there other voltage points to track down whats dead? Guess i should have waited. I cant believe I made the same mistake on both sides!
Wait a minute....I was measuring that ( the north of 10 volts ) across the "series" R26, not R27.....I have no idea why the slightly higher voltage. Everything lights up. It does a little led blink when first powered up, then all steady on. The new 2.7 IS measured across corrected series R27