general conversion questions for Allied Knight

[dmartn149]

Hi. I got an Allied Knight PA/record player at a garage sale. It has 4 6sc7 and 2 6l6 tubes. The schem. looks alot like a tweed Pro (5c5) but with an extra gain stage. I'm going to convert it into a guitar head. I've worked on a couple of tube amps before (with the generous help from members of this forum), but I'm learning as I go, so please excuse any stupid questions I may ask. I do know how to drain the caps, and how deadly these amps can be even when unplugged.

So here are my questions. Guitar amps have jacks that ground when not used, while this amps mic inputs are open when not in use. Should I use grounding input jacks or not, or does it matter? Also I've seen adapters to use 12ax7 in 6sc7 sockets. Is there any other mods required with these, or are they "plug n play"?

Thanks, Dan

[loudthud]

Grounded jacks will eliminate some hum when nothing is plugged in. The also change the sensitivity when you use input #2.

A 12AX7 has more gain than a 6SC7 so circuits may not bias perfectly, but they should pass a signal. Consider one of the Fender amps that use octal preamp tubes.

[dmartn149]

Thanks. I guess I'll get grounding jacks and stick with the 6sc7s until I find a good reason to switch.
It looks like it's going to be a really easy project to just get it ready for guitar use. It has 2 channels though, so I'm toying with ideas to make the second channel different from the first. Maybe a high gain channel with a master vol. It has an extra volume pot that went to the phono pickup.
Anyway, thanks for the advice

[dmartn149]

Here is a schem. of the amp I'm converting. Does it have a "death cap"? if so, which one is it?
Also I am adding a fuse. I was initially going to put it in the lead going to the power switch. but then I thought it should go in the lead just above that, marked 130v Which would be better? or is the same either way?
One last thing (for now) I have 3A fuses on hand is that okay?
Thanks

[loudthud]

Your picture is 160x120 pixels, too small to see any detail.

A "Death cap" will be from one side of the power line to the chassis on old equipment sold in the US. Usually a .01uF to .05uF. Just remove it.

INSTRUCTIONS FOR USA ONLY: The line cord should be connected as follows. The ground wire, usually green with a yellow stripe, should connect to the chassis. Use a spade lug to a screw, nut and lock washer that does not hold anything else. The neutral side of the line cord, usually white, should go to one of the power transformer wires. It may also go to one side of a 120V pilot light if the amp has one. The Hot side of the line, usually black, should first go to the fuse, then from the other side of the fuse to the power switch. The other side of the power switch connects to the power transformer and to a 120V pilot light if so equiped.

IMPORTANAT SAFETY INFO: Look closely at the fuse holder. Some types have a center spring loaded terminal and the other terminal comes out of the side. You should connect the line cord to the center terminal and the power switch to the side terminal. That way you can not come in contact with the hot side of the power line when you are changing the fuse.

[dmartn149]

Sorry about that small picture. I found the cap based on your instructions. A .02 just after the power switch, going to ground.
Thanks for your help, Loudthud. I almost have the conversion done, still waiting on new electrolytic caps though.

[dmartn149]

WOW this amp really rocks! Nice clean sound, stays pretty clean all the way up, not that loud. I put a tube screamer in front, and then it really roars, plenty loud too. Just played through it a couple minutes. It's not really done yet. Still waiting for caps, and I need to do something with the hole that the power chord goes through, and the hole in the top that the record player went through. I'm really encouraged and surprised with the sound though.
Thanks again for your help Loudthud.