Fender Custom Vibrolux (blonde '95) Tremolo Issue

Sharky77

I bought this amp a week ago and everything works great apart from the bias trem which I really want to use. The guy said it was working fine when he bought it, then he didn't play it for a couple of months and when he went to sell the amp it wasn't working.

I tried replacing the tube with one I knew was good but that didn't change anything. I checked the footswitch and sure enough one of the wires that solders onto the TRS jack end had come off. Great! Simple fix I thought... Soldered it back on but it still doesn't work. The reverb footswitch functions perfectly and has a second cable soldered to ground. The white cable on top for the tremolo is what I'm working with. All I can think is that the trem is actually an issue with the inside of the amp but thought I'd check here first if anyone knows of anything stupid I've done. I

t's a huge expense to drive it to my tech and then leave it there and it's gonna be at least £50 bench fee + whatever else. I can upload a picture of the inside of the plug when I get home. Any help would be hugely appreciated! Here is the amp - 

ICBM

It's odd that it's not the valve, if it was working but now isn't. The footswitch turns the tremolo off rather than on, so it should work with the footswitch unplugged.

It's possible that if the valve failed it could have blown its cathode resistor, since the second half of the valve is a cathode follower, and Russian-made 12AX7s are quite prone to failure in this configuration.

Being biased too hot also reduces the effectiveness of the tremolo, although not to nothing from memory. (And would have to have been deliberately modified, since it's not adjustable as stock.)

Hopefully it's not a wire come off - the flying leads from the PCB to the valve sockets are very fragile on these.


Your Strat is lacking tone by the way - a third of the bridge screws are missing .

MichaelAT

Beautiful amp, beautiful Strat!
Might not be related at all, but I had a similar issue with the bias tremolo of my '63 VVRI. Turned out a resistor was dead. Seems Fender didn't do a good job with their PCBs (and components) back then - the VVRI was around that time as well.

Here is a thread about it, but it won't help you much if you are not ready to work inside an amp:
Fender Vibroverb RI: Tremolo no worky | The Gear Page

ICBM

MichaelAT said:

Might not be related at all, but I had a similar issue with the bias tremolo of my '63 VVRI. Turned out a resistor was dead. Seems Fender didn't do a good job with their PCBs (and components) back then - the VVRI was around that time as well.

The Custom Vibrolux is a modified Vibroverb reissue, and uses the same PCB.

The PCBs are actually fine, it's the component choice which is the problem - if it's R55 or R64 which has gone it's only a 1/2W resistor, so if the valve shorts one of them will fail.

Fender used undersized resistors on several models around this time, including the '59 Bassman reissue which is notorious for blowing the plate resistors if you fit a 12AY7 in V1 - which you should be able to, since it's the original 50s spec.

Sharky77

@ICBM thanks so much for your input. I'd read about the bias being too hot but as you rightly pointed out it hadn't been changed and the power tubes weren't redplating or noticeably too hot like they were faulty. In fact the amp sounds incredible apart from the trem.

Ahh yes the infamous extra mid scoop you get from removing the inner screws from the bridge. I should make a YouTube video 'SECRET Strat Tone Trick only the Pros do'

I actually just realised on NYE that I had all the parts to build a strat sat in my parts cupboard (including a stunning set of Lollar Blondes). Maple neck, single ply guard, 3 tone burst -  late '58/early '59 replica? Alas, I didn't realise until the final moments, I was missing 2 screws. It was this moment that I discovered the SSTT.

Anyway, amp is booked in for Friday - I've managed to tie it in with driving to a studio day so it's not too much of a detour.

Sharky77

@MichaelAT huge thank you aswell - it's booked in for Friday and I will send my tech that link. After reading it I think it will be one of the things mentioned. Really helpful! 

soma1975

Fuck me that Strat is stunning looking. 

Sharky77

Thanks @soma1975 ;

57Deluxe

...do you live in a Tree House??

Sharky77

Yeah! Loading in and out from gigs is a little tricky but apart from that it's great