The first was adding a tone control to replace the two position bright-dark switch. A 500k pot is installed and wired just like the switch with the existing wiring. You can widen the switch hole a little with a small file or two, and then use a fender washer to dress up the area and cover the screw holes. Be careful not to scratch the surface of the panel with your file-I did, and I'll probably strip this down and have it electroless nickel plated before long. A trio of vintage chicken head knobs dressed things up a little.
I don't know about you but I don;t like orange pilot lights. I snipped the wires to this eyesore and installed a typical Fender type lamp socket with a red jewel and a #47 bulb. I piggybacked off the wires for the second 12AX7 preamp tube socket which read a nice 6.7 volts. Plate voltage runs about 370 on these amps by the way. At the same time I added a pair of JJ 6V6 power tubes and a Sylvania JAN 12AX7 in the first position.
How's it sound? The tone control gives a little more flexibility and the tube upgrades are useful. Plus Leo would have approved of the red jewel.
Plus you get to see my newly reconstructed shop complete with killer work bench I built Sunday.
My apologies to the ghost of Jean Shepherd-if you spent any time connected to a radio in Jersey youy get the joke.
Great mods!
ReplyDeleteI've done the tone mod and I would love to do the jewel light mod as well. I have purchased the light assembly, jewel and bulb however I don't know which wire from the 2nd 12ax7 to tap into to power it...
Any help with this would be greatly appreciated!
-Paul
Nova Scotia, Canada
The 12AX7 is wired thusly: pins 4 and 5 are connected to each other and pin nine is solo. That's how you get a 12v tube to work in a 6v circuit because the filaments in the 12AX7 are paralleled. So all you have to do is take off of there and run them to the two tabs on your pilot light. It's a good idea to spread them about 90 degrees to each other and then put s dab of superglue on the assembly which will keep those tabs from coming into contact with each other.
ReplyDeleteThis comment has been removed by the author.
ReplyDeleteThanks so much for answering so quickly!
ReplyDeleteAlthough, I'm a bit confused...
Can you give me the color of the wires that I connect to the lugs of the light assembly...
Sorry...I'm a bit of a novice at all this.
Thanks again!
-Paul.
What you need to do is go to a source on the internet and get yourself the pinout of the 12AX7 (how the pins are numbered. Once you see how pins 4 and 5 are connected then it is a matter of identifying pin 9, Then you just tap off them,
ReplyDeleteGot it!
ReplyDeleteAnd this doesn't interfere with the operation of the tube in any way?
Not on my amp it didn't.
ReplyDeletethis is the first i've seen someone install the pilot light so can you add any more detail? When you say piggyback, are you implying just to solder 2 wires from pins 4 and 5 to the pilot light assembly? does any filing need to be done to fight the assembly in place of the stock one?
ReplyDeletethanks!
Well, you can see what the original one looks like-black plastic, definitely el cheapo. You can obtain a new pilot lamp assembly, a bulb and a jewel for a few dollars from Antique Electronic Supply. You don't need to cut or file anything. As far as powering the new old style pilot lamp just run it in parallel with the filament circuit on one of the 12AX7s. (pins 4+5 and 9).
ReplyDeleteThanks! So by run it in parallel it needs to be soldered? I'm just asking as I'd hate to mess up V2 tremelo.
ReplyDeletealso i'm confused as you mention pings 4+5+9 When the pilot light only has 2 wires? I apologize as i'm new to this, but loving the journey :)
Of course you have to solder it. You're just borrowing a little bit off the filament string. The bulb draws 150 ma.
ReplyDeleteYou have noticed that the 12AX7 is a 12v filament and your supply is only 6v. The way it's done is by running the filament supply to pin 9 and pins 4 and 5 paired. That makes it into a 6v tube.
ReplyDeleteok thanks. I'll give it a shot. I know asking if i needed to solder it sounded dumb but you mentioned something about superglue in a previous comment which is why i wanted to check
ReplyDeleteWhat type of light did you between the assembly and V2. I didn't have any luck but want to try again.
ReplyDeletedisregard. I tried 20 guage wire and it worked that time..
ReplyDeleteso glad I came across your site as I love the ability to switch out the jewel light for different colors. Thank you so much!
Thank you very much for these gut shots. Now I know where to reconnect the little black wire from the input board!
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