VOX ac 30

[Valvehead]

working on a Vox AC 30 . this is a 2x12 combo , ss rectifier , 4-el84 , has vibrato . maybe a 70's model ?

Some of the scems ive found are very blurry , or just for the tube rect model .

SO--- i have a burnt resisitor inside and cant tell what it is

looks to be a 10 watt , its blue and round/skinny , and looks original . its mounted near the power tube section. Its mounted alone on a terminal strip.

if youve ever worked on a 5150--it looks exactly like that big blue guy.

So---- anyone know the value of it ??

[Jazz P Bass]

It would be nice if you told us what it attaches to.

If it's the cathode resistor, that is 50 ohms/ 5 watts.

[Enzo]

It is mounted alone on a strip? Fine. follow the wires from either end until they connect to something. Then tell us what that is.


I'd be betting Jazz P is right.

[drewl]

Right if a cathode resistor it will have an electrolytic cap across it, or if it's used as a choke it will be connected to the first high voltage node.

[Valvehead]

its not the cathode resisitor .

one end goes to the bridge rect.

the other to a 50uf can cap (filter) and the center tap of OT .

i still cant find a clear schematic for this--or i wouldnt have posted

[pdf64]

See http://schems.com/manu/vox/ac301986.pdf
Maybe 22 ohms 10 watts, sag resistor?

[g1]

Is it completely open or does it still measure some resistance?
You recognized the size and type being the same as one in a 5150, from that you should be at least able to figure out the wattage.

[drewl]

Yup, cheap way instead of a choke.
Wow, don't think I've ever seen the schem of the 80's AC30's.

[Valvehead]

hard to find drewl !

Interesting.... it looks like on that scem that r76 / r77 are in place of what i have. they are 390 ohm - 2 watt.

so the resistor in my amp is at least a 5 or 10 watt. it measures 50 ohm out of circuit--but its definately burnt

i will attach a pic

[g1]

R76/R77 are between the OT center tap and the screen supply.
You have described R78 off the bridge as pdf64 mentioned. It is 22 ohm 10watt. Your measurement backs that up, if it reads 50 ohm, it could never have been more than that as resistors do not decrease when burnt. So it would have had to be 50ohms or less.
The 22ohm 10watt makes sense.

[Valvehead]

ok--i see it.

i might have a 22/10w here