Fender ‘Custom Vibrolux Reverb, Upgrade service to reduce noise and improve many features of the amp

Fender ‘Custom Vibrolux Reverb, Upgrade service to reduce noise and improve many features of the amp

Credit for this link goes to Marc Moyer

https://www.amprepairparts.com/Custom_Vibrolux_Reverb_Moyer_Mods.pdf

I have successfully performed all the mods on this list for a customer with a Fender ‘Custom Vibrolux Reverb and the amp was fantastic.

If you have this amp and would like top have the mods done for you call Eric at TubeAmpRepairShop.com Tube Amp Repair shop 818 645-1075 and make an appointment to bring your amp in.

Here are some of the details

MOD 1: Eliminate Reverb on Normal Channel.
WHY:
The ‘Lux has Reverb on both channels. In theory, this is a good idea but the negatives outweigh the
positives. Adding Reverb to both channels of the ‘Lux causes a significant amount of hiss. Going to a
common plate load resistor and lowering R23 from 82k to 47k makes the pre-amp run hotter, which to my
ear makes for less headroom. I also suspect some cross talk is going on. Further, the Reverb on the Bright
channel improves by converting the Lux pre-amp back to the Verb. If you like Big Clean Reverb laden tone
with no hiss you must convert the Lux pre-amp back to the Verb.

MOD 2: Fuller Reverb
WHY:
The Reverb on the Lux is much more filtered out then the Verb due to the coupling cap in the recovery
stage. C16 on the Verb is a .0033. On the Lux it is 500pf. This is a significant difference. I highly
recommend replacing C16 on the Lux with a .0033 Silver Mica cap. This makes the Reverb come alive on
the otherwise Reverb challenged Lux.

MOD 3: Shunting cap
WHY:
The Verb has a 100pf-shunting cap across the plates of the 12AX7 Phase Inverter. It is C20. I recommend
placing this 100pf cap in the Lux as it is inaudible and greatly reduces the parasitics that are inherent with
a printed circuit board.
The Verb has a 100pf-shunting cap across the plates of the 12AX7 Phase Inverter. It is C20. I recommend
placing this 100pf cap in the Lux as it is inaudible and greatly reduces the parasitic that are inherent with
a printed circuit board.

 

MOD 4. Add Negative Feedback Loop (NFB):
WHY:
To further reduce the hiss found on the Lux and increase your headroom you must add a NFB loop to the
‘Deluxe.

MOD 5: Remove Surge Protection Diodes
WHY:
While theoretically surge protection diodes are a good idea. However, they tend to cause the amp to blow
fuses when switching out of standby. Further, they seem to drain off some of the high frequencies. I am
talking about the diodes from pin 3 to ground on the 6L6GCs. None of the older Fenders had them and
most of these amps are still going strong 30 or more years later. I recommend removing these Diodes.

The Options
OPTION 1: Install an adjustable Bias
WHY:
Optimize your preferred power tubes rather than relying on the stock fixed bias.