FPIII Left channel crackle and static ... helps needed

[Paul Birkeland]

The only one resistor left is the 22.1k ohm connecting pin 8 and terminal 39.  Can it be the LED gone bad?

I'd be doing my best to measure voltages while the noises are happening, to see if any are jumping around.

The LED is likely OK.  If you poke the LED and the preamp makes a ton of noise, it could be damaged.

-PB

[audiblesoundwave]

Thanks Paul.  I chopstick testing the remaining resistor and the led and they seem to be ok as you have suspected!

I am going to try and to catch the "crackle and static" moment for the measurement.

Thanks again,
Milton

P.S. This is the most difficult one that I have encountered in the past 7/8 years with the Bottlehead gears I have.

[Grainger49]

Intermittent problems are maddening! 

[audiblesoundwave]

Is there a way to test out the socket to see it is still good or gone bad?

Thanks,
Milton

[Paul Birkeland]

Do the chopstick test on the tube socket terminals themselves.

[audiblesoundwave]

After a few more days of chopstick testing, I still could not locate any bad "things".

I ending up replaced the left channel socket and all of the resistors and the led.  Very disappointed!  The crackle and static are still there.

From the listening position, the crackle and static in much louder level come in a burst for few seconds and back to crackle, crackle in other time but much lower level.  The attenuator has no impact on the level of the crackle and static.

I used Deoxit Cleaner on the 0D3 socket a couple times.

Any other ideas?  I am pulling my hairs.

Could the 0D3 socket (if it is bad) cause this issue?

With my limited knowledge, I don't think the heater supply and B+ voltage would cause this problem in one channel!  Both channels share the voltage.  Would it?

Thank you so much for your helps and patience with me.
Milton

[Paul Birkeland]

Yeah, your logic about the power supplies is 100% correct, and very useful in this situation.

What kind of level controls do you have on this FP-III?  The old Sweetest Whispers switches are known to eventually go bad.

One thing you could do to test this would be to temporarily ground the output of the SW on the crackly side, then listen to see if the noise is still present. 

Other than that, there may still be a funky connection on one of the terminal strips, or on the actual power supply wiring that feeds from the 0D3 to the offending side.

-PB

[audiblesoundwave]

Thanks Paul.

I grounded the left channel that has the crackle and static and there is still crackle, static, and off cause no music.  What does this mean?

I am using the Goldpoint stereo 10K attenuator and the selector.

I will continue to poke around 0D3 connections again to see any better luck.

Thanks again,
Milton

[Paul Joppa]

I may have missed it, but I don't see any test to confirm this is not downstream of the FP-III - output jacks, cables, power amp input jacks, power amp itself, speaker connections, speaker cable, or speakers.

[audiblesoundwave]

Thanks Paul.

I isolated to the FPIII which is the one generating the crackle and static! I have switched and replaced the 12au7 tubes, 0d3, switched the interconnects between FPIII and power amp, switched the channel connection into my tube mono power amps, switched the source's channel connection into FPIII.  The end result always is the FPIII's left channel has the crackle and static.

I have been trying to isolate the problem within the FPIII.  I have replaced the left channel's socket and resistors. I have also pulled the 1K resistor bridged the two output RCA center pin.  Up to this point, the crackle and static are still there.  I am continuing on poking around as PB suggested the 0D3 connections which I have tried few time.

Anything else I should try, please let me know.  I could have been chasing the wrong direction.

Thanks,
Milton

[Doc B.]

If it is only in one channel and it does not vary with volume you know that it is not the 0D3 or power supply, and not anything ahead of the volume pot. Does the output cap on that channel possibly have some damage? Do the LEDS flicker when the crackle happens?

[audiblesoundwave]

Thanks Doc.

I have also replaced the output cap with new one!  I had assumed the 0D3 and power supply were possibly not he cause last couple days but I am trying any suggestions to isolate the issue.

You just point out a new one that I have not tried which to see the LED (I also replaced with a new one) flicker or not when the crackle happens.  Early on this thread that you suggested to see the 0D3 flicker or not when the crackle happens; so far I did not see 0D3 flicker when the crackle happened.

Anyhow, I will pay attention to the LED!

Thanks
Milton

[Doc B.]

When you grounded the signal from the Goldpoint, exactly what did you connect to ground? My thought would be to ground the actual grid of the tube on the noisy side. If that stops the noise it  would tell you if there was a problem at the output of the pot, or maybe the 220 ohm grid stopper connected to pin 2. That connection would be pin 2 on either 12AU7 socket to the ground buss. If it doesn't stop the noise, then you may have to say "what's left to inspect?" and examine the things that you have not replaced. Another thought would be to wiggle the STP cable that goes from the output capacitor to the RCA output jacks to see if maybe a wire has broken inside the insulation.