Trem ticks only when signal from guitar is applied

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JD0x0
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Trem ticks only when signal from guitar is applied

Post by JD0x0 »

I have a SF MV twin reverb that I've been trying to get rid of the tick in the trem for a while now. After adding a 22nF de-thumper cap, getting rid of board conductivity, and replacing all the caps, the trem still ticks under certain conditions..

With no signal from the guitar, it's fine. After a chord is hit there will be a notable high pitched 'tick' that rides with the trem. Is this a sign of a bad roach?
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martin manning
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Re: Trem ticks only when signal from guitar is applied

Post by martin manning »

Does this occur on either channel or just one? Is there DC voltage on the intensity pot that would indicate a leaky 0.1u coupling cap on V4a, or 0.047u on V1b? Have you tried bundling the trem leads and separating them from the tone stack leads?
Stevem
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Re: Trem ticks only when signal from guitar is applied

Post by Stevem »

How old are the power supply filters?
That circuit may not be decoupling enough from the other preamp circuits so for now if you have another filter just jump it across the filter for the phase inverter section and see if that helps .
Stock Fenders with 4 gain stages on just 1 filter is asking far too much!
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JD0x0
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Re: Trem ticks only when signal from guitar is applied

Post by JD0x0 »

martin manning wrote: Mon Aug 28, 2017 10:42 am Does this occur on either channel or just one? Is there DC voltage on the intensity pot that would indicate a leaky 0.1u coupling cap on V4a, or 0.047u on V1b? Have you tried bundling the trem leads and separating them from the tone stack leads?
It ONLY occurs on the vibrato channel, WITH the tremolo engaged. The issue is with the effect engaged.

Entire amp has been recapped. (Yes, Including non-electrolytic poly/ceramic)

V1b is normal channel. Shouldn't have an effect on trem channel and again, amp has been refurbed. All caps are new. v4a is reverb recovery, no? As I've said, issue only occurs with the Tremolo engaged and signal applied to the amp. The amp does not tick with the trem engaged and the guitar volume down/off. Hit a chord/note with the trem engaged, and the ticking comes in very noticeably. Everything else in the amp is peachy. Reverb sounds great, vibrato channel sounds great. It's the tremolo ticking ONLY while playing it, it's almost unusable.

I'll have to check the trem pot for DC, I didn't notice any static/crackling when playing with intensity control, though. I tried to isolate the Trem circuit's lead dress (well all stages, really) but perhaps I can make some improvement, there.

These symptoms are not a sign of a bad roach? It's just about the only component in that circuit I didn't replace.

How old are the power supply filters?
Like 6 weeks old...


Thanks guys!
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sluckey
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Re: Trem ticks only when signal from guitar is applied

Post by sluckey »

These symptoms are not a sign of a bad roach? It's just about the only component in that circuit I didn't replace.
Just replace it. Then you'll know.

Sometimes substitution is a valid troubleshooting method.
Stevem
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Re: Trem ticks only when signal from guitar is applied

Post by Stevem »

I can't see any reason why the roach itself would make a ticking in the circuit!
If this tick was not a issue until you recapped the amp then look no further!
How have you determined that the board is not conductive?
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!😊

Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Firestorm
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Re: Trem ticks only when signal from guitar is applied

Post by Firestorm »

The tick comes from the neon bulb in the roach flashing. Sometimes a new bulb helps, but the principle causes of the tick leaking into the signal are conductive board or lead dress; the trem leads should be dressed well away from the tone stack leads. You might even try shielding them.
JD0x0
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Re: Trem ticks only when signal from guitar is applied

Post by JD0x0 »

Stevem wrote: Tue Aug 29, 2017 11:20 am I can't see any reason why the roach itself would make a ticking in the circuit!
If this tick was not a issue until you recapped the amp then look no further!
How have you determined that the board is not conductive?
It was an issue before I recapped the amp. It was ticking and thumping all the time. It has improved in that it now doesn't tick at idle, and zero thump whatsoever.


I've metered the board many times and in the process of refurbing the amp fixed several conductivity issues.

I was previously getting 1-2VDC on the board right around the trem circuit. In addition to that it had about .6VDC around the tonestack. All plate resistors had at least 1VDC around the eyelets. Measuring High voltage eyelets ranged from about 5VDC to over 50VDC, in this one spot far off corner of the board, not even near an eyelet. Weird right? I've gotten that entire board under 1VDC. I think last I checked I was getting ~.05VDC on the board near the trem circuit. That's why I'm very reluctant to think it's the board anymore.
To note: It doesn't seeming getting the board from 2VDC to .05VDC near the trem circuit had any notable effect on trem noise. I would've expected bigger issues with that much leakage, honestly. The amp had a surprisingly low noise floor considering the conductive issues. It's still quiet except for this one specific ticking issue.

I've addressed the lead dress around the tubes quiet well, but I believe the issue might be the dress from the intensity/speed pots to the board. That area of the amp is a complete clusterfuck because of the poor layout. (Again, I'm astounded how low the noise floor in this amp is, especially considering a bumped the gain up quite a bit..) It's very possible I'm getting bleed over when I start playing. I'm not sure how much I'll be able to do without rewiring the amp
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Stevem
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Re: Trem ticks only when signal from guitar is applied

Post by Stevem »

Don't forget the sub fiber board sitting right on the chassis.
Remove the top board hold down screws and lift that board off the sub board and see if the issue still takes place.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!😊

Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
JD0x0
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Re: Trem ticks only when signal from guitar is applied

Post by JD0x0 »

Stevem wrote: Wed Aug 30, 2017 12:42 pm Don't forget the sub fiber board sitting right on the chassis.
Remove the top board hold down screws and lift that board off the sub board and see if the issue still takes place.
The board is currently raised on standoffs to help rule out possible conductivity issues between the main board and insulation board. I did this after noticing oscillations and static noises when putting downward pressure on the board, before I had worked the amp.
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Stevem
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Re: Trem ticks only when signal from guitar is applied

Post by Stevem »

It would not be the first time a tube socket was slightly conductive either!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!😊

Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
tweedeluxe
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Re: Trem ticks only when signal from guitar is applied

Post by tweedeluxe »

Cut open the optocoupler and replace the bulb with a red LED. For me, when all else has failed, this has always fixed a noisy fender tremolo.
JD0x0
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Re: Trem ticks only when signal from guitar is applied

Post by JD0x0 »

tweedeluxe wrote: Sat Sep 09, 2017 3:17 am Cut open the optocoupler and replace the bulb with a red LED. For me, when all else has failed, this has always fixed a noisy fender tremolo.
I think I'll have to try this. Do you know the recommended fV of the red LED. I think I have a bag here, but the fV on them ranges a bit.
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JD0x0
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Re: Trem ticks only when signal from guitar is applied

Post by JD0x0 »

Ended up swapping to a 'real' board instead of the paper one, and the issue is gone. Cleaned that damn board half a dozen times and could only get it to stop being conductive for brief periods, then the issues would return, and I could measure more voltage off the board.. Kind of sucks, looks like I'm going to have to do the same thing to my newest Silverface.
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Stevem
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Re: Trem ticks only when signal from guitar is applied

Post by Stevem »

Before you go thru the project of replacing the oil tag board go to the string of 3 disc caps in the Trem circuit and on one side of the .022 cap there's a wire going over to one of the Trem control pots ( Green wire likely) unsolder it from the pot and pull it out of the mass of wires its run with.
Reroute it in a L shape above the board down towards the PI section and take a 90 degree turn back to the pot and solder it back on and your issue should be gone!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!😊

Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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