proper value filters for '66 vibrolux reverb

[Tonegeek]

I am recapping a 66 Vibrolux Reverb. I believe the proper schematic is the AA964. The tube chart says AA864. A search on Vibrolux Reverb displays both but the AA864 is a Bassman schematic. I am concerned about 2 issues:

1) The caps in it now are General Electric 20uF @ 500 volts. I believe these are not the original caps although they look old enough to be. They are gold with blue letters. The schematic calls for 16uF caps. I am wondering if I should put 16uf or 20uf in the amp. The amp sounds really great and i am afraid if I go back with 20uf it will be too stiff as i am sure the old caps have lost some oomph as they are leaking slightly and bulging a bit on one end too. I want to put as close to what was original as possible. Sprague makes both values and I am leaning toward putting the 16uF in and not the 20uf that are there now. Not sure i can trust the schematic though. Anyone seen or remember what is original to that amp? Its also possible Fender had the GE ones on hand and used them, but the solder joints just look a little too new although I suppose they are protected pretty well under the doghouse.



2) Should I go ahead and replace the cathode bypass and bias caps? they are Mallory and appear to not be bulging or leaking. The customer wants to keep the amp as original as possible but also does not want to have to fix it again anytime soon. I hate to mess with an amp that has such great tone. The amp appears to be mostly all original especially if I am wrong about the filter caps.

[selloutrr]

Caps have a pretty big swing in tolorance 16mfd and 20mfd are pretty much the same thing. If you have the ability to test the capacitor you could base the result of the test as your deciding factor. if it's below 16 buy 16 if it's over 16 buy a 20. I would test the other capacitors in question for leakage if they are good no. however I would order replacements and after installing the power caps. I would break the amp in for 48 hours and recheck in the event the new voltage has caused the other capacitors to go bad. if they are still good leave them. though electrolytics are a function not a tone ( debate if you must but generally speaking.)

I've attached a pic of a the filter caps you described they are fender OEM from a 60's blackface bassman.

If you have any doubt and you like the amp now replace it with the values it has. (becareful to meaure the Sprague filter capacitors are physically larger then most other brands! 600V will not fit under can caps)

[selloutrr]

I have a quick sec while the band tunes. Here is a pic of the size of the 600v sprague in relation to the stock caps.

[ampdan]

This is my 1965 Vibrolux reverb. 16uf @ 450
[IMG:640:480]http://i56.tinypic.com/10ft0fc.jpg[/img]

[selloutrr]

they might have switched or ran out of the older mallory in '66 it looks like the card is stamped '66 on the bassman cap board.

I would think it's a stock OEM part. but again either value would work they are basically interchangeable.

how much price difference between values?

[diagrammatiks]

The best thing to do would be to take the cap out and measure it to see what it's actually reading.

[Tonegeek]

@selloutrr - If I can trust AES specs, the 500v Sprague caps will fit but as your picture shows, not the 600v ones. After seeing your pix I am now thinking I have an amp with the original caps.
@ampdan - looks like yours fits with the schemo I have. As Selloutrr pointed out, not a whole lot of difference in the 2 values. I think I will go back with the 20uF ones as that appears to be what was originally in this amp. I think I will change the bias cap too but leave the cathode bypass caps alone for now.
thanks

[selloutrr]

sounds like a plan. I'd buy the cathode bypass caps just to be safe. It would be a bummer to have to wait and pay shipping twice. test them for leakage before and after the filter caps are installed. If they are not leaking after the new parts are in. No need to replace them. Keep them on hand for the next time the amp comes in for service. A few dollars of insurance is usually worth the headache it can prevent. I'd also meter the resistors in the bias section to make sure they are on spec and not drifted. The 100K carbon resistors in the preamp section are also known for drifting and causing artifacts in the tone of Fender amps.

[Jim Mason]

I have a 1965 Vibrolux Reverb designated AA864.
My research indicated that that it is the same schematic
as an AA964 but uses a different speaker manufacturer.

Jim

[Jim Mason]

I have a 1965 Vibrolux Reverb designated AA864.
My research indicated that that it is the same schematic
as an AA964 but uses a different speaker manufacturer.

Jim

[selloutrr]

http://www.speakerrestoration.com/codes.html

[Jim Mason]

I believe they are the same amps but the AA964 uses Jensen C10Q ?speakers and the AA864 uses Oxford 10L5 speakers.
I can't see the manufacturer codes on my speakers because it
is obscured by smoke damage (was in a club that caught on fire,
thats why I got it for $100 in 1969), but I can see the 10L5 stamp
on the magnet structure.


Jim

[Structo]

My schematics show the Vibrolux Reverb AA964 has a GZ34 rectifier while the Bassman AA864 has solid state rectifiers.

I can't find a Vibrolux Reverb AA864.

@ Jim Mason,
Does your 65 Vibrolux AA864 have tube or SS rectifier?

[Jim Mason]

GZ34 rectifier.

Jim

[ampdan]

I believe they are the same amps but the AA964 uses Jensen C10Q ?speakers and the AA864 uses Oxford 10L5 speakers
Jim

My 1965 has the original Jensen C10NS speakers.