Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: macula56 on February 17, 2011, 03:32:16 pm

Title: OT screaming at me
Post by: macula56 on February 17, 2011, 03:32:16 pm
I have a modified Bassman that i added a prescence control to a few years ago. i replaced the OT in it today with a Weber tranny with 3 output taps for 2,4, and 8 ohms. i wired the prescence control to the 4 ohm tap and when i flipped the standby switch the amp just screamed at me. a fairly low tone but very loud. if it was a stock tranny i would just flip the wires to fix it but as this has 3 different taps i am at a loss for ideas. how can i get it to stop freaking out? any help appreciated. JMac
Title: Re: OT screaming at me
Post by: DummyLoad on February 17, 2011, 03:37:00 pm
flip the primary leads - usually blue and brown colors. if the feedback ckt. is a copy of the bassman ckt. it should be on 2 ohm tap.
Title: Re: OT screaming at me
Post by: sluckey on February 17, 2011, 03:37:44 pm
Swap the OT primary plate leads.
Title: Re: OT screaming at me
Post by: macula56 on February 17, 2011, 04:38:45 pm
now why didn't I think of that. thankyou gentlemen.
Title: Re: OT screaming at me
Post by: jeff on February 18, 2011, 07:29:04 am
If you already cut the leads to length I think you can just swap the grids.
Title: Re: OT screaming at me
Post by: sluckey on February 18, 2011, 07:59:49 am
Quote
If you already cut the leads to length I think you can just swap the grids.
Yes, that works fine too. And many times is easier to do.
Title: Re: OT screaming at me
Post by: J Rindt on February 20, 2011, 07:05:19 pm
If you already cut the leads to length I think you can just swap the grids.
As a "new guy" to electronics, you cannot believe the smile on my face when I read this kind of stuff.
When the guy said "knowledge is freedom", he was not kidding.
That tid-bit of wisdom is good to know, and as others have said, can make things real easy in an older amp with OT leads already cut to size.
Thank You Gentlemen....for another one.