Vox AC-10 repair/mods

iron layout

OPT response,  open sec, 1 k, 10 k, 100k and 1 meg

back to reality,  :-X

check it out, Orange tube tester> 

limited types

What caps should I replace on the ac-10?

Ive taken some voltage measurements on a few bits and the vox seems to be about right, considering its 50 years old next year!.
Ive changed a few caps which should have been 25uf and were 31-32uf, changed them for some 22uf.
couple of the 47nf i've changed as they had gone over 50nf.
have taken out the ECF82 as it wasnt doing anything apart form lighting up, made no difference if it was in or out, the normal channel didnt work, have ordered a new ECF82 as i dont have anything to replace it.
Hopefully when the new tube arrives it will just be a case of putting it in and away we go!!

crack open the old lytics and see how dry they are, if no juice, i would replace all of them,

ever seen one of these?

what a junk pile, then the owner tells me they used it on floyd albums, wtf?

Never seen one of them, used to have an old WEM mixer off the pink floyd ummer gumma album! also a load of crap!!

the electrolytics your on about, i have gone through them and ive spotted 7 of them.
Ive changed the 25uf ones to 22uf but what voltages should i get for the others?

C2 - 25uf / 25v (electrolytic)
C3 - 25uf / 25v (electrolytic)
C6A - 16uf / ? (electrolytic)*
C6B - 16uf / ? (electrolytic)*
C10A - 8uf / ? (electrolytic)*
C10B - 8uf / ? (electrolytic)*
C21 - 50uf / ? (electrolytic)

also ive measured the dual caps (*) and they dont seem to be to far out, the 16uf measure 16uf and 15uf, the 8uf ones measure 10uf, still replace them as they are nearly 50 years old?

also what voltage would i need for C21? its a 50uf but would 47uf be the closest modern equivalent?

I cant seem to find any of those dual capacitors like it has in it, dont know the name of them!!
I could still do it with normal ones just would have to probably glue them in or resuse the case of the old one and pot them in it?

Bit more searching and ive found them, dual capacitors, gonna get them and a 47uf / 450v for C21, probably doesnt need to be 450v but it'll be sods law if i dont get it!!

im also building an effects loops and wondered where i could fit it within the ac-10? its going to be for the other two amps im building as well, the JTM45 and the BE-50, so would be good to testit on this vox

Have ordered all the dual caps for the vox.
Thinking about making a fresh turret board for it so I can clean it all up.

I have made a start on the turret board for the fender champ, I have the tubes, output txf, i have a mains txf from a line 6 spider which i need to check but it did work for the champ before.
Need to build a little cabinet for it as well as a chassis to house everything.
If I can get these two builds and repairs done I can then concentrate on the jtm 45 and then the BE-50.

im also building an effects loops and wondered where i could fit it within the ac-10?

Click to expand...

Take it or leave it - but if you have a 1962 vox AC-10 get it restored as close to stock as you can and don't add any mods. It's a awesome piece of history.  You can build a clone with all the mods you want and pay for ten times over with what you could sell the AC-10 for. Would go for a few grand I expect

I own a 1964 AC30, which I have worked on a little bit from time to time.

In Vox amps, the 25/25 caps are typically for cathode bypass (gain), these might do with replacing (can get rid of hiss). If you are not familiar with valves, follow the circuitry up to the valve pins and learn what the pin numbers represent for a given valve. Be very careful with the turret boards as they are very fragile in these old amps. I would, if possible, leave all of the polyester caps alone, even if reading a little high. Most likely all of the carbon comp resistors are reading +20% but I would probably leave them to. Guitar amps are pretty tolerate when it comes to component values. Replacing valves is a good idea (you are doing this). If it were my amp, I would leave all of the audio circuitry resistors and capacitors well alone and keep it original as possible. As a previous poster alluded to, it may depend on whether it matters to you to maintain the amp in original form.

Good luck and please let us know what it sounds like when you get it going. I built an AC15-type head that was based on my three favourite Vox channels (Normal channel (with a variable tone cap mod a bit like some Matchless amps), Top Boost and EF86 with bright switch). Even this is too loud for me now.  As I get older I tend to play amps with lower & lower wattage (Champ is my current favourite). I'm thinking of using building a little (Vox-styled) push pull amp with EL91s next!

I had to replace the 220k going to pin 1 of ecf82, the resistor didnt work at all so no wonder the ecf82 wasnt working!!
Normal channel now works and sounds pretty good.
I replaced the 16uf + 16uf and the hum is much reduced, will also replace the 8uf + 8uf.
The 50uf 25v c21 I replaced for a 63uf 63v.
The vibrato channel works but no vibrato?

I hear what you say about keeping it original but if a part has broken it will have to be replaced.
I just want to enjoy this amp and have no desire to sell or put it into a original enclosure.

I will investigate the voltages and resistors in the vibrato oscillator and see if I can find what's wrong.