My first new build AC15

[plook]

Fired it up tonight after checking all connections and for a moment it sounded ok and then started to get a nasty distortion and low volume. Not had time to check voltages but something is not right. There is also a bad hum when the guitar jack is pulled from the amp and one channel is much lower than the other. This may take a while.

Anyone got a voltage chart for the 1961 AC15?

[plook]

I'd really appreciate it if you'd take a look at my voltages and let me know what you think. I can't find anything to compare against.

One channel is low volume, lots of hum but i think that is lead dress, Vib/Trem not working, but shouldn't be too hard to fix.

Update:
Hum solved. Needed an artificial centre tap for the filaments. Just two problems left:

1. No vib/trem
2. Very low output on Ch1

Which wires need to be shielded in the AC15?

[plook]

Coming along nicely.

[martin manning]

Got a link to a schematic? It's hard to tell exactly what looks off without that, but I can see that the control grids (g1) on the EL84's are not at zero volts, which they should be when cathode biased. Maybe leaky coupling caps? Some of the plate voltages in the earlier stages look very low as well.

[plook]

Here is the schematic.

Interesting that you should mention that about leaking coupling caps. I've decided to take out the NOS caps, I think it's asking for trouble unless they are properly tested - which I don't do other than of a capacitance test.

There is 324volts leaving the rectifier.

I'll do another voltage test once I have replaced the caps and also more accurate resistors.

One thing I have noticed, I can't get the cathode resistor voltage lower than 17 volts at the moment no matter if I change the values up or down. A thorough check on the boards I'd the starting place though.

[martin manning]

Should be the same as this?
http://www.voxamps.com/downloads/circuits/ac151960.jpg

[plook]

Tell you the truth, the one I'm working from is the 1961 version from Stephen's book.

[martin manning]

The one you posted isn't very readable if I download and save, but not too bad viewed in a browser window. Do you have something close to the 315V supply voltages in all of the places it is shown on the schematic?

[plook]

I'll have to come back on that. I find all of the schematics hard to make out voltages on. The circuit boards are out at the moment but I'll do some voltage tests for those key places when it's back together.

[TNblueshawk]

Hey Plook, whatever came of your troubleshooting? Hopefully it all worked out.

[lego4040]

That is incredible plook, you really went for the clone look. These voxs have lots of parts Ive found out on my build. Next one is a minimal parts build

[sluckey]

There is a very clear schematic in this pdf...

[beasleybodyshop]

Great looking build, that whole 3 dimensional thing looks intimidating to me

[lego4040]

Jump over to Hoffmans world and checkout Legos ac15 build. Three of us got the amp going