Author Topic: Got some questions about the scheme..(cornish tb83 and tb83 extra)  (Read 246 times)

dave5152

Greetings~ :)
Recently I started building pete cornish tb 83 and found some interesting information on this forum

https://www.diystompboxes.com/smfforum/index.php?PHPSESSID=875c9mko913fjkjk0kuld16ha1&topic=112790.40

On this forum, the guy who posted the scheme said he replaced r11(6k8) with a 10k pot and added a 'wiper' to the C6...

What does it mean to add a wiper to a cap??

Best regards



iainpunk

Re: Got some questions about the scheme..(cornish tb83 and tb83 extra)
« Reply #1 on: January 18, 2021, 11:22:48 AM »
welcome to the forum

what i gather from it is wired as a variable resistor, with the wiper and one end of the pot connected together with the Collector and C6
it essentially means wiring the pot as a bias control, basically making it a variable resistance to dial in the perfect dc voltage on the transistor, so you can get the perfect tone, instead of hoping that the resistor you put in there is perfect.

cheers, Iain
half man - half snail - 6 feet to scale - Snail man's - not frail - He's been - to jail
snail man [x11]
snail man is fuccing real

dave5152

Re: Got some questions about the scheme..(cornish tb83 and tb83 extra)
« Reply #2 on: January 18, 2021, 12:00:09 PM »
I see....Thanks alot!

Then, should i have to ground the third leg of the pot?

iainpunk

Re: Got some questions about the scheme..(cornish tb83 and tb83 extra)
« Reply #3 on: January 18, 2021, 02:43:18 PM »
no, this


cheers, Iain
half man - half snail - 6 feet to scale - Snail man's - not frail - He's been - to jail
snail man [x11]
snail man is fuccing real

antonis

Re: Got some questions about the scheme..(cornish tb83 and tb83 extra)
« Reply #4 on: January 18, 2021, 02:59:12 PM »
Why not this..??



To let the bias unaffected while setting gain..
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

iainpunk

Re: Got some questions about the scheme..(cornish tb83 and tb83 extra)
« Reply #5 on: January 18, 2021, 04:59:33 PM »
Why not this..??



To let the bias unaffected while setting gain..
in a treble booster, the bias makes a substantial difference in tone, i'm not totally sure why it makes such a HUGE difference, but it does.

cheers
half man - half snail - 6 feet to scale - Snail man's - not frail - He's been - to jail
snail man [x11]
snail man is fuccing real