Shazaam! That fixed both channels, voltages and all. I have no idea how that worked, but it did. On both channels
2.4 v across 220ohm R27 will give you a current dissipation of 10.9mA. The build guide recommends a target of 2-5mA. If you double the resistance of r27 to 440ohms or even 500ohms that will bring you down to between 4,8mA to 5.45mA.
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.
No luck. Ironically, I think I have a life time supply of 220 ohm resistors. I will drum up an order and include some 500 and 680 ohms, I thought about lifting one end and sticking another in series but that would cut in half the watt rating, right? They are tiny resistors.
3 x 220ohm in series gives you 660ohms over 2.4v = 3.63mA. Golden! And that pushes the wattage down to 0.008 Watts. I think you will be okay!
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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