Vibrolux Reverb Ticking Tremolo

[rf7]

It's the infamous ticking Trem problem in a Black-faced Silverface Vibrolux Reverb. I've tried the .02uf cap to ground, moving/dressing the wires, moving the wax boards apart, etc., and nothing seems to help much.

I actually disconnected the neon lamp and I'm still getting the ticking. So, it's not coming thru the LDR, apparently. And when the speed is set to it's lowest setting, the ticking is very low level, but once the speed knob hits 3, it's back. Pushing the vibrato tube wires together helps a bit, but not enough.

Any further ideas?

I've seen the Fender service bulletin and RG's geofex info, but none of it is really stopping the ticking.

[jrfrond]

If you disconnected the neon lamp and it is still ticking, my guess is that you might have tagboard contamination, or possibly a bad cap and/or resistor in the LFO that is "broadcasting" the sine wave peaks. However, I'd sub a new trem bug in there first, just to totally eliminate that issue.

I'm also thinking that perhaps something is amiss from when the amp was BF'ed.

[mikeboone]

The last SF2BF (Super Rev) amp I worked on with this issue turned out to be lead dressing. Someone suggested to me to tuck the leads from the pot end all the way under the other pots as compacted as possible and it worked like a charm...

[rf7]

If you disconnected the neon lamp and it is still ticking, my guess is that you might have tagboard contamination, or possibly a bad cap and/or resistor in the LFO that is "broadcasting" the sine wave peaks. However, I'd sub a new trem bug in there first, just to totally eliminate that issue.

I'm also thinking that perhaps something is amiss from when the amp was BF'ed.

I completely pulled the trem bug and I've still got the ticking. I can see it on the top of the intensity pot with my scope. It's getting picked up by the PI and then amplified apparently. I even pulled the intensity pot output wire and it still gets through the circuit. All of the caps in the LFO circuit are relatively new, someone has gone thru the amp before me. I've replaced most of the resistors in there and it's still ticking.

The last SF2BF (Super Rev) amp I worked on with this issue turned out to be lead dressing. Someone suggested to me to tuck the leads from the pot end all the way under the other pots as compacted as possible and it worked like a charm...

The amp was already like that. I'm not having any luck with wire dressing at all.

Apparently 2 other techs have tried to fix this problem and no one has got it.

[tubeswell]

If you put a scope on the LFO output, what does the LFO waveform look like?, and then on the output tube grid resistors?

[rf7]

If you put a scope on the LFO output, what does the LFO waveform look like?, and then on the output tube grid resistors?

The LFO output at V5 pin 1 is like a sine wave except it is pointy at the top and bottom of the wave.

At V5 pin 6, which feeds the neon bulb, there is a pointy trough and then the upper half looks chopped off about 1/4 way up, followed by a flat part where the wave seems to rest for one period of the LFO.

The grid input to the tube has a short trough followed by a larger trough and then it climbs up to about 1/4 way past the zero point and then it tapers back down to the zero point. So the grid more closely resembles the output of V5 pin 6. At speed settings above 7, the two troughs become one.

[tubeswell]

Have you tried changing the LFO tube?

(And what are the idle voltages like on the LFO stage's cathodes, grids and plates?)

[rf7]

Have you tried changing the LFO tube?

(And what are the idle voltages like on the LFO stage's cathodes, grids and plates?)

Yes, I've already replaced the tube.

Voltages on V5:
Pin 1: 245V trem on/ 435V trem off
Pin 2: 0V
Pin 3: 2V trem on/ 0V trem off

Pin 6: 357V trem on/382 trem off
Pin 7: 0V
Pin 8: 19V trem on/0Vtrem off

So, with the tremolo engaged, the voltages match the schematic very well.

I think it's getting induced onto the following stages through the 46 year old waxed fibre board.

[tubeswell]

A leaky board ('tweed disease') is a possibility. I have heard that slowly 'drying' the board in a 50 degree oven for 1/2 an hour is a workaround for this - otherwise replace the board.

So it wasn't ticking at first and somehow the ticking just started huh?

[jmaf]

A leaky board ('tweed disease') is a possibility. I have heard that slowly 'drying' the board in a 50 degree oven for 1/2 an hour is a workaround

I've dried carbon comp resistors with a hot air gun in the past, perhaps it works for board as well?