JMF Spectra

[ca7922303]

Does the one you didn't change measure 470 ohms?

No, it reads 32.5m ohms, so I think I can answer this question maybe. 2nd resistor is dead, replace with same rating resistor as other 6L6.

[g1]

Yes that one is open and needs to be replaced. But be aware that they usually burn or go open because of a bad power tube. So one or both of those power tubes in there may be bad.

[TomCarlos]

I found this schematic on another MEF post.


JMF_Spectra_30T_60T_120T_212T_Original_Schematic.pdf

[ca7922303]

Yes that one is open and needs to be replaced. But be aware that they usually burn or go open because of a bad power tube. So one or both of those power tubes in there may be bad.

Thanks, 6L6s were replaced before working on it.

[g1]

Once that 470 ohm resistor is running that tube will start working again. Then the high voltage will come down a little, but I don't think it will bring down that 494V to a safe level on that 450V cap. So it will still probably need to be replaced with a 500V rated one.

[ca7922303]

Once that 470 ohm resistor is running that tube will start working again. Then the high voltage will come down a little, but I don't think it will bring down that 494V to a safe level on that 450V cap. So it will still probably need to be replaced with a 500V rated one.

Installed 2nd 5w 470ohm resistor on 6L6 pins 4 & 6, power tubes now both read about 450vdc, caps read as follows:
previously 410v now(368vdc) (rated @450v)
457v. (407vdc) (rated@450v)
. 494v. (445vdc) (rated@450v)
265v. (231vdc) (rated@350v)
232v (217vdc) (rated@350v)
Thanks.