GSG 6A3 Build - Questions.

2nd harmonics for the masses

Re: GSG 6A3 Build - Questions.

Postby Vapour » Tue Apr 21, 2015 8:29 am

Ok, embarrassed :$ , found C10 was in backwards...doh. I guess that explains the excessive current, overheated resistor R18. But the low heater voltages?
Vapour
 
Posts: 13
Joined: Sun Nov 30, 2014 4:17 pm

Re: GSG 6A3 Build - Questions.

Postby TomMcNally » Tue Apr 21, 2015 8:52 am

Glad you found the problem. I've built 20 or more get*set*go's and never actually measured any voltages. They just work!
I'm not sure why there are AC readings on the voltage chart for the filaments, since they are DC. If the amp WORKS, I'd put
the meter away and enjoy listening.

... tom
User avatar
TomMcNally
Darling du Jour
 
Posts: 2729
Joined: Sat Nov 19, 2005 2:19 pm
Location: Northfield, NJ

Re: GSG 6A3 Build - Questions.

Postby Vapour » Tue May 19, 2015 6:02 pm

Finishing up on this amp, & been testing the heater circuit. It's a little high as tested, so just a question or two.
AC heaters measure 6.7Vac.
So I need to add resistance to the Ac heater inputs, how much though? Came across the formula: R = Vactual - Vdesired/2 x Ih .
Heater current for the rectifier + 6A3 gives R = 6.7-6.3/2x(1.2+1.0) = 0.1Ω
For the 6SL7 + 6A3 gives R = 6.7-6.3/2x(0.3+1.0) = 0.15Ω.
If I'm doing this correctly, would a 0R12 resistor be a good compromise?

Edit (a week later): added a 0R15 resistor each side & voltages now good. Thanks for all your help.
Vapour
 
Posts: 13
Joined: Sun Nov 30, 2014 4:17 pm

Previous

Return to get*set*go

Who is online

Users browsing this forum: No registered users and 1 guest

cron