Silvertone 1484 - Tremolo Chirping / ticking

[LooseChange]

I have a 1484 on the bench and when you turn the tremolo up, it chirps with the speed setting.
Any ideas how this can be stopped?
Tube is good.


Schematic:
http://www.el34world.com/charts/Schematics/files/silvertone/silvertone1484.pdf

[Tiny_Daddy]

Chrrping as in bursts of self-oscillation? Are the filter caps good?

[LooseChange]

Yes, replaced all.

[Tiny_Daddy]

Still doing it if you pull the reverb driver tubes?

[tubeswell]

did you try another trem tube?

[LooseChange]

Tried a few tubes... All the same.

Still doing it if you pull the reverb driver tubes?

Still does it with that tube pulled.

I'd have to say it is really more like a ticking.

[Tiny_Daddy]

Does it tick the same regardless of the trem strength setting> You may need to  change the routing of a wire.

[HotBluePlates]

Do you have a scope? If so, could you look to see if the trem oscillator is clipping?

[LooseChange]

Does it tick the same regardless of the trem strength setting> You may need to  change the routing of a wire.

It changes in the first half of revolution. The ticking starts at a higher tone and settles after the half turn to a lower tone.

Do you have a scope? If so, could you look to see if the trem oscillator is clipping?

No scope available.

There is a fix for trem ticking on a Fender. I need to look that up.

[sluckey]

...

[LooseChange]

I'll try that.

[LooseChange]

Fender mod did not work BUT....  I figured it out.
Lead dress. The wire that goes from the tube to the LDR runs halfway across the amp. Directly by the grids of the power tubes too.  I rerouted and all is good.

I've worked on MANY 1484's and I have never run into this before.

Thanks for the help!

Amp back to the owner.

[Willabe]

You Sir, are good!     Always enjoy following one of your combat missions.


         Brad       

[Platefire]

Aw! I love a good trouble shooting story with a happy ending. I was wondering what it would turn out to be? Good Job!

[Willabe]

BUT....  I figured it out.

Lead dress. The wire that goes from the tube to the LDR runs halfway across the amp. Directly by the grids of the power tubes too.  I rerouted and all is good.

                Brad     

[LooseChange]

Tiny was the one who suggested a re-route... The big question was which wire!  I guess well. 

I really like solving these type of puzzles. But I do have my limits. This one came in under that limit.

Thanks for all your help.

[TerryP]

A very late post, hopefully useful to others with this problem.
I had the same issue, chirping & ticking affected by tremelo setting.

Fortunately I had a 'scope and high voltage probe, so could look to see what was happening.
There was parasitic oscillation on the tremelo neon, bursts or continuous depending on tremelo setting. Frequency on mine was around 20kHz, but any extra capacitance (such as meter probe) on the node would give an audible squeak/squeg. My theory is that the neon was forming a relaxation oscillator with the capacitance of the connecting wire and circuitry. I isolated this capacitance with a 220k resistor in series with the neon's leg, wired between the leg and adjacent tagboard. All traces of the oscillation disappeared, along with all the audible side-effects.

[HotBluePlates]

Now that's a handy trick!! Thanks for sharing!