EF86 channel build

[shadfan4]

Any ideas if this would actually work on an AC15cc1x

Scroll down on the site to the info.

Cheers

Mike

taweber.powweb.com/store/modkits.htm

[Charlie Hall]

Hi Mike,
I think it would work, but you would need to add a HT dropping resistor, usually 22K 2 Watt in a Vox, and a filter capacitor of around 33Mfd to 47Mfd. The 22K resistor would connect to the same point as all the other preamp dropping resistors are connected to, and the filter would connect to the valve side of the 22K and to earth. The filter must be connected in the correct polarity or it could explode, apart from probably not working properly.
The anode resistor in the original Vox and I think also the Heritage models is 220K, not 270K.
You wouldn't really need the drive selection switch if you only want it for the Shadows sound and no matter how it would be set, it doesn't change the drive to the EF86, only the drive to the output. The 250pf cap is the one to use. The switch and all the other caps around it wouldn't be needed.
The 150pf cap on the volume control should be removed in a Vox (ie. not fitted), that part is only used in amps like a Matchless (I think they used 180pf) to get more highs because they didn't use Celestion blues.
I think the original grid 2 (pin 1) resistor in the Vox was 1meg, not 1.5meg. Using 1.5meg would give lower gain and a bit more input headroom, not necessarily what you want if you stick to single coil pickup guitars.
All in all, the kit might be useful if you go for the reduced features version, but you would need a few other parts to complete it, and also, hooking the output up to the phase inverter stage would need to be considered so that its inclusion does not affect the sound of the other channels too much. The output from the volume pot should also have a 0.01 cap in series as it would connect to a point that has a fairly high DC voltage.
Weber tends to offer these kits without much technical information, I think assuming that anyone who fits them would know how to do it.
The original AC15 of 1960 circuit is here:
www.freeinfosociety.com/electronics/schematics/audio/voxac151960.pdf
Look in the top left corner of the diagram for the EF86 section. You could possibly just buy the parts needed from that diagram alone, but the kit is partly attractive as it includes the mounting plate etc.
Amanda might also have some ideas as I am not that familiar with the AC15CC1x.
Finally, if you go for it, be prepared to change the EF86 fairly regularly as new versions of it don't seem to last very long.
Regards,
Charlie

[shadfan4]

Wow, thanks Charlie, I think you given me enough info either to completly bamboozle me, or make me a genius. Time will tell which it's to be.

Cheers Charlie,

Mike.