Rustling noise help

[bluesguitar]

The noise voltage could be so erratic that your meter can't settle on a value. What does it do when the red probe is not touching anything? If it's different when you touch the board that might mean that something is there. Do you have access to another meter?

Have you gone over all the solder joints related to the cap job?[/quote]My multimeter acts identical touching the board as it does when the red lead is touching nothing. Have tested different locations on the board. Nothing. I don't have access to a different multimeter, but I have no evidence that mine is malfunctioning. Will probably resolder the filter cap eyelets pertaining to this circuit as a next step. It just seems, to my way of thinking, that if the tone is fine, then the problem is not in the components of the signal chain.

[Reeltarded]

Frittering could even be the filter caps already cycled. I have 50 year old caps working just fine and trashed a couple that were bad in 1 year. The ground bus could be nearly disconected and look like old resin and solder. No evidence and reads closed on a meter but isn't a good joint.

The problem sounds just like mild waterboard, but ground side issues in filtering and bias sections act like that too.

HERE is what you do

Can of freeze spray or compressed air with the tube tip thing and do little squirts (with the can tilted over if compressed air) just the slightest of taps on the button at every joint and component while the amp is running and idle condition all knobs at 0. Wait at least a couple seconds before moving to the next spot. Include all components, joints, grounds, and pots.. but not tube sockets.

[Structo]

This is where a O'scope can really help you as you can see exactly what is happening on each stage.

If you don't have one or access to one, then a listening probe can really help.

[Richie]

could you post some good pics of the board? it might help if people could see the board. If you tap on the chassis does it effect the static noise? Make it happen or stay the same?

[bluesguitar]

could you post some good pics of the board? it might help if people could see the board. If you tap on the chassis does it effect the static noise? Make it happen or stay the same?

I'll see if I can upload some pictures later. In the mean time I will explain one change I had to make when replacing the resistors to get it up to spec. Keep in mind that the amp operated fine afterward, and I stored the amp confident that all was fine. At the lead coming off #1 pin (plate) of V2 it connects to an eyelet on the board. There is a 100k resistor coming from that eyelet going to an eyelet half way across shared by another 100k resistor coming from pin #6 of V2. The resistor from pin #1 has an extra long lead that dives down into the shared eyelet, travels under the top layer of waxed board and comes up into an eyelet on the ground side shared by a wire that goes to the cap can. Because it was too difficult to fish the new 100k resistor under the board and up into the eyelet at the negative side of the board I ran it on top of the board. This is my only concern as to a mistake I may have made and the only thing different from how it was originally. Again, the amp tested fine after this work. Anyone know why fender ran some leads under the board, and how important this is?

[jelle]

Not important, it just looks nicer to have the voltage supply wires tucked away, that's all. Nothing to worry about.

That is not your problem. But, you may have a broken wire there...

Look forward to pics as well. Good call Richie, there might be something else as well.

Jelle

[jelle]

Mr. Bluesguitar, where are you located? There may be a competent forum member in your area who can diagnose this in minutes. I am in north NJ, and am willing to diagnose this for free. I love these old Fenders.

Jelle

[bluesguitar]

Mr. Bluesguitar, where are you located? There may be a competent forum member in your area who can diagnose this in minutes. I am in north NJ, and am willing to diagnose this for free. I love these old Fenders.

Jelle

I appreciate your offer, but I live in rural Kansas 75 miles from the nearest tech(Salina). That's why I'm learning more on my own.

One more clue- If I remove V2 I can play the amp thru V1 with no noise problem at all.

[jelle]

Sure, just trying to help.

Your observation is actually quite typical for conductive board issues around the reverb mixer input. Thing are crowded in that area of the board.

It could be something else too. Like a bad tube...

Quick test: Can you place the V1 tube into the V2 spot and tell me if you can play the Vibrato channel without noise? (Do not stick the other tube in V1)

[Reeltarded]

Progress!

[bluesguitar]

Sure, just trying to help.

Your observation is actually quite typical for conductive board issues around the reverb mixer input. Thing are crowded in that area of the board.

It could be something else too. Like a bad tube...

Quick test: Can you place the V1 tube into the V2 spot and tell me if you can play the Vibrato channel without noise? (Do not stick the other tube in V1)

Can't test it now. Have to be somewhere. But, I can almost certainly rule out a bad tube. Swapped all preamp tubes with known good ones, and still have the noise.

[Milkmansound]

One more clue- If I remove V2 I can play the amp thru V1 with no noise problem at all.

ok next test - does the noise follow the volume knob?

if not, than its isolated to the side of the tube that is post volume knob - this eliminates the tone stack, a plate resistor and also the cathode resistor on V2

so its got to be something off of pin 6-7-8

[Richie]

sorry my quote edits never worked..lol



""""""ok next test - does the noise follow the volume knob?

if not, than its isolated to the side of the tube that is post volume knob - this eliminates the tone stack, a plate resistor and also the cathode resistor on V2

so its got to be something off of pin 6-7-8""""""


I think he said earlier it doesn't matter or is not effected by the volume control.
And if that number one channel doesn't have the noise, and you know that tube is good, i'd still try what Jelle suggested and pull it, and try it in V2,just for the heck of it. If it still happens, Then move on.






"""""One more clue- If I remove V2 I can play the amp thru V1 with no noise problem at all."""""


So, that's good. Is this with all other tubes in place but V2? V1 and 2 share a cathode resistor, So that could be ruled out on V2,when just that tube is in. Both share same power supply cap,so that should rule that out.
Seems its more so in the function of the tube. The cathode off pin 3 and or bypass cap. did you change the 100k [tone slope] resistor going to the treble cap/tone caps on V2? Its the one right off the plate resistor. Is/was it CC resistor?
Since its making the noise at idle, with no signal, V2 in, and with other tubes in. Since you don't have a scope or other test equipment. I'd change those if the tube swap didn't cure it.
If you have a conductive board, or have a hard time trying to get a reading, what you can do, is with all tubes in, turn up the channel volumes, you can do one at a time or both. And hook up your meter like you would be testing voltages in the amp.
But all you have to do is lightly rub the board with the probe. if you hear a static noise, or closer you get to a problem area, or one that has most voltage, you'll hear the static louder.

[bluesguitar]

[quote="jelle"

Quick test: Can you place the V1 tube into the V2 spot and tell me if you can play the Vibrato channel without noise? (Do not stick the other tube in V1)[/quote]

I did this test and still had noise. Tube in V2, no tube in V1.

[bluesguitar]

One more clue- If I remove V2 I can play the amp thru V1 with no noise problem at all.

ok next test - does the noise follow the volume knob?

if not, than its isolated to the side of the tube that is post volume knob - this eliminates the tone stack, a plate resistor and also the cathode resistor on V2

so its got to be something off of pin 6-7-8

The volume knob does not affect the rustling/static noise. It does not get louder with volume increase.