vox berkeley super reverb

[Zephedone]

I got a vox berkeley super reverb from a friend and he wants to spruce it up and go over the electronics . Did a little cleaning of the head cab as I had to pull the guts . First thing I notice is the power supply voltages are way too high . The rectifier tube (6ca4) tested good on my tester and I even swapped it out with another known good rectifier tube . The power tranny secondary voltages measure 284-0-284 vac . That is real close to the schematic showing 280-0-280 vac . At the first node of the filter supply I get 356 vdc where it should be closer to 270 vdc . The following voltages are also all high as well . I should say that the circuit was loaded with all of the tubes installed as well as a speaker connected . I have had high voltage problems with a champ before and replacing a bad tube was all that was required to fix that problem . Could this problem be in the 40+ year old filter caps which need to be replaced as a rule of thumb anyways ? I did not hear this amp play as I was told by my buddy that he had played it a day or two prior to me picking it up . I guess I should hook it up and have a listen though .

[rp]

365V is high but not so out of whack to be an indication of a fault. ~340V is pretty normal for old EL84 amps in 2013. I don't recall what the voltage drop is for a 6CA4, or what the schematic recommends but it could be high wall voltage, or a unhappy combination btwn those specific output tubes and the bias resistor. If they are drawing low current the plate voltage will go up. Together w/ a high wall voltage and I could see 365V. If the cap can was very bad it would hum, sound farty or motorboat. If slightly bad it'd be dark and soft and woofy.

I owned one of these and they are great, and sure look freaking snazzy in the living room. Great speakers if orig, they were ceramic bulldogs 10s Rola IIRC. Inside it's a Thomas organ PTP rats nest but I was able to cleanly remove and replace the can in mine. I got lucky and CE had a 1" can very close to the right values so it was a flawless repair, but that was 15 years ago. Maybe they still offer it. I think I changed the bias resistor to something higher wattage and higher R to get it running right. Anyway the amp came to life. I hated it at first, lost the mellow easy sweatness, but I quickly got used to it. Put some real Mullards in it.

BTW that red & green stndby / power indicator uses one normal and one REALLY weird bulb, I found them at mouser years ago.

[Structo]

Love to see a picture of the amp.

I have a Vox 2x 12 extension cab that I use now with 2x EV 12L's.

I think it came from a Berkeley.

[Zephedone]

Thanks rp
The wall voltage was just under 120 vac as I was running my tests . I had an old Silvertone that had a similar problem and it was caused by a bad output (6v6) tube . On that amp the voltages were way too high and swapping out the bad tube fixed it . I will try a different set of el84 tubes and see what happens . I do believe all of the tubes tested good though . Structo , I will post some pics of the amp . Be warned it is ugly . Sat on a porch down here in Florida . It's hard to find anything in excellent shape due to the humidity and poor storage practices .

[Zephedone]

A few pics ...

[rp]

Ouch! You really went and plugged that thing in? Might want to turn it upside down first and let the water and baby alligators run out.

But heck, looks like it's all there at least.

[Zephedone]

I always spray everything I work on with Baby Gator B-Gone before I open it up . Can't be too safe here in FLA ...
I did a little checking of values of the resisters per the schematic . Everything is close enough for a 40+ yr old amp . Almost everything . On V7-b which is the second half of a 12ax7 the plate resister is supposed to be 220k but measures in at over 800k and actually has the color codes of a 470k resister . This triode is in the trem circuit and the rest of it's resisters are within specs . The cathode resister for the el84s measured in at 132 ohms . I did find some issues with the filter supply not matching the schematic mostly having to do with the reverb section 12au7 not being fed by the right node .

[Zephedone]

A few more pics of the clean up while I wait for electrolytics . The old particle board is swollen and falling apart . Looks like it will be in for some surgery .
I tried everything on the tolex to shine it up after a soap and water scrubbing . Turtle wax , Pledge , Murphys oil ...

[Leo_Gnardo]

All too often I find at least one bad pot in a Berserkly or AC15 - and they don't respond to cleaner. Drifty resistors & failed small electrolytics, par for the course in any old amp. Yes, rat nest wiring & chassis not really meant to be taken apart, lotta sharp edges. BUT when you get 'em workin' right, what a glorious tone, and not awful loud either.

[Structo]

Wow, that thing is in pretty bad shape.

I like the oval back on the cab.

[Zephedone]

A little more progress . I hope to get to the electronics upgrade and the grillcloth + trim this week .

[Reeltarded]

Really fantastic work. What a mess to start with. I feel that pain here too. Everything turns to rust.

NOTE: GOJO ORIGINAL AND A SCRUB BRUSH.

[Zephedone]

Hello Reel...
Are you getting any snow ? NOTE: GOJO ORIGINAL AND A SCRUB BRUSH.
What's the GOJO good for ? I have'nt used any since I rebuilt my last straight six ford motor 10 years ago .

[Gibsonman63]

cleaning Tolex.

[Reeltarded]

Yeah! And guitars, straps.. yuck yuck buildup on metal that you son't want to resurface.

Everything! Takes off everything but the originality. If you can get to a vintage guitar before the weather does it will look pretty much the same 40 years later except for play wear. No crazing. Lanolin. It's sheeply magic.