Vox Gremlins (90's AC15 TB).

[Sea Chief]

Opinions may vary, but pots are typically cleaned with a product that includes lubricant. Switch and contact cleaner often has a de ox agent in it. I love my reading glasses. They work for reading information on line as well.

EDIT: I think it's funny that WD40 has a "contact cleaner" now. Since regular WD40 lubricant has always been considered a no no for the purpose.

So servisol.. has lube in, or not? I dont think I'll be able to distinguish between its ingredients to tell, or would take me hours to find out (if you're suggesting I try googling for the answer pdf-? I dont understand the glasses point).

No I would never use wd40: this is all I do know. But yes i think this 'wd contact cleaner' is new stuff in their range.

My servisol.. says on it its 'switch cleaner'. But I have no switches to clean! (so is this of no use for pots? or is a pot a 'variable switch' ?!).

As a result, as usual, I therefore cannot tell my ass from my elbow as to what's best for where. Maybe servisol is a contact cleaner-?

[pdf64]

Hi pdf.. I'd love to have the best/ an array of xyz cans, but I am always watching my wallet: are my servisol & wd40 contact cleaners not sufficient in your opinion then?

As above, we don’t know what exactly your Servicol is.
For many people, reading glasses are a help in reading the small print on product labels.
WD40 is intended to displace water and prevent rust on untreated metal surfaces. It leaves a waxy deposit behind of unknown composition.
It’s good for squeaky door hinges etc, and if I was desperate, I suppose I’d use it on an amp, as I have done in the past. But I’m really not keen on that waxy goop it leaves behind.

[Chuck H]

Ok... Since you've only given me blunt references from the labels to work with rather than research the products for yourself "I" researched them FOR YOU!?!

WD40 "contact cleaner" is said to be a cleaner that dries and leaves behind no residue. So use this for jacks and pin connections.

Servisol "switch cleaner" includes a lubricant. So use this for your pots. It is ok (even preferable for some) to have a little lubricant on a pot track.

[Sea Chief]

Ok... Since you've only given me blunt references from the labels to work with rather than research the products for yourself "I" researched them FOR YOU!?!

WD40 "contact cleaner" is said to be a cleaner that dries and leaves behind no residue. So use this for jacks and pin connections.

Servisol "switch cleaner" includes a lubricant. So use this for your pots. It is ok (even preferable for some) to have a little lubricant on a pot track.

Sorry.. I had no idea servisol wasnt anything but 1 can. If theere are different ones.. apologies (I just assumed you guys just had this stuff, or similar stuff saying 'switch cleaner' on.. therefore best placed to tell me where to use it, rather than me www trawl its ingredients for clues).

Good yes I had thought the contact cleaner likely the one for pin connections, as I bought it specifically for tube pins (noisy twin reverb).

Many thanks chaps. Will report back. SC

[Sea Chief]

Hi chaps. I've got a brand new L O U D gremlin. I wonder if you could help.

I plugged in, volume very low on MV to start, a few chords then a sudden -very loud- !!GRRRRRRRR!! ..turn amp off asap. Tried again later & there on amp turn on.

It is very loud at 0.5 on MV, & rotating the knob increaces it. Its louder/ different than anything Ive known before. Unplugging gtr chord it stays. I checking most obvious: connection to spkr, ftsw connection/ unplugged.. no change.

It's so loud its very disconcerting. Like a sort of 'bad earth turbo'd to MAX' is all I can describe.


Grateful for any ideas- SC

[DrGonz78]

If the noise can be controlled by the master volume then the offending noise is coming from something before it. Try pulling the first preamp tube. Noise still present?

[Sea Chief]

If the noise can be controlled by the master volume then the offending noise is coming from something before it. Try pulling the first preamp tube. Noise still present?

Hi there Gonz..

well that's a reassuring start/ if something before the MV (which I think denotes the power tubes 'gain' stage).

Ok pulled v1.. all fine/ no noise. Replaced with a brand new 12ax7.. !!GRRRR!! noise there on turn on.

Thanks, SC

[DrGonz78]

So it’s not the tube but the noise is either something connected to the tube. Could be any of components or joints that connect to tube or it could a bad ground connection somewhere in the input side. Looking at the schematic I am very confused by the gain pot feeding pin 7. The anode pin 6 is not connected to anything. Which is either a schematic error or something I need to learn more about. Does anything change the sound or noise when you wiggle the tube around when the amp is on?

[pdf64]

Does the gain control affect the noise?
Regarding V5 pin6, I think it’s reasonable to assume a drawing error, and that it actually connects to R8.

[Sea Chief]

Does the gain control affect the noise?
Regarding V5 pin6, I think it’s reasonable to assume a drawing error, and that it actually connects to R8.

Hi pdf.. gain, erm are we talking MV or the 'volume' in the preamp section-?

(the MV turns the !GRRR! up & down.. more than 2 & its ridiculously loud).

SC

[Sea Chief]

pdf64 the noise is nil wiith both the preamp Volume, & MV both at zero. So it -does- then become affected by the preamp volume, but not incrimentally like with the MV.

IE turn preamp vol to 3, & the GRRR is similarly loud to when it's turned to vol 10. It just changes slightly in sound, that's all.

This time (all knobs not changed since this gremlin started) I hear a pulsing to the GRRR noise.

Wiggled v1 whilst amp on.. nothing changes.

Thanks. SC

[Sea Chief]

Schematic again here https://el34world.com/charts/Schemat...x_ac1596pa.pdf

DrGonz78 can I narrow it down to such a degree, that it can only be ascociated with a relatively few components on "the input side"?

Is the input side (I assume the input jacks included primarily) basically everything up to but not onwards from V1?

--

In general do noise issues like this get louder the further back they are in the 'gain' chain-? IE this being loudest Ive ever known, is this volume due to it being within the area of the 1st tube?

Thanks, SC

[pdf64]

The earlier in the signal path that the problem is, then the more gain will be available to amplify it.
I can’t make out from your description of the symptoms whether any guitar signal is getting through?
If not, is there continuity between the shield of the input jack to 0V common of the amp circuit?

[Sea Chief]

The earlier in the signal path that the problem is, then the more gain will be available to amplify it.
I can’t make out from your description of the symptoms whether any guitar signal is getting through?
If not, is there continuity between the shield of the input jack to 0V common of the amp circuit?

Hi pdf.

No not when the GRRR happens, no guitar signal. With guitar unplugged (GRRR happens with or without gtr pluged in): yes continuity between both input jacks' shields & chassis gnd (I assume same as circuit 0v).. in fact all 4 jack terminals similarly show continuity to chassis gnd.

Thanks SC

[pdf64]

Hi pdf.

No not when the GRRR happens, no guitar signal. With guitar unplugged (GRRR happens with or without gtr pluged in): yes continuity between both input jacks' shields & chassis gnd (I assume same as circuit 0v).. in fact all 4 jack terminals similarly show continuity to chassis gnd.

Thanks SC

Ok, so is there continuity between an 0V common node on the circuit board, eg the bottom of the input stage’s cathode resistor, and the chassis?