It is currently Mon Mar 16, 2020 8:25 pm

All times are UTC - 7 hours



Post new topic Reply to topic  [ 7 posts ] 
Author Message
Post subject: parts for biasing super reverb
Posted: Wed Oct 19, 2011 3:51 pm
Offline
Hobbyist
Hobbyist
User avatar

Joined: Sun Jan 09, 2011 12:29 pm
Posts: 81
Location: Charlottsville
My plans are to install a 1 ohm 2 watt resistor from pin 8 to ground as a bias check point. (1972 SR aa270). What is a good comp. to find these? I just located them out on the west coast Velco,at about 90 cents each. Well I will wait and double check the values. 1 ohm 2 watt.


Top
Profile
Fender Play Winter Sale 2020
Post subject: Re: parts for biasing super reverb
Posted: Wed Oct 19, 2011 4:06 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Fri Feb 05, 2010 4:31 am
Posts: 14049
Location: Province de Québec, Canada
1/2 ( half) watts is enough . Buy a precision 1 ohms.

Mouser electronics or Digitech electronics have some


Top
Profile
Post subject: Re: parts for biasing super reverb
Posted: Wed Oct 19, 2011 4:24 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26417
Location: Tombstone Territory
stratele52 wrote:
1/2 ( half) watts is enough . Buy a precision 1 ohms.

Mouser electronics or Digitech electronics have some


+1000

For truly accurate idle-bias adjustments, the resistor must be precisely one ohm. And half-watt dissipation is sufficient for this purpose.

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Post subject: Re: parts for biasing super reverb
Posted: Wed Oct 19, 2011 6:18 pm
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
For these apps, I actually "match" the resistors. Get like ten 1-ohm, 1% tolerance 1/2-watters and match the ones closest to each other with a precise DVM. Keep note of exact resistance. As this number is going to be used to calculate the current draw (Ohm's Law and all that jazz).

1/2-watt is nice as it can act as a fuse is the tube starts to go ballistic and sucking a lot of current. The resistor will pop and save the tube and possibly other $$$ parts.

Matching resistors works nice on those grid-to-ground resistors (usually 220k-ohm in Fenders), for setting up even bias on matched tubes.


Top
Profile
Post subject: Re: parts for biasing super reverb
Posted: Wed Oct 19, 2011 6:32 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26417
Location: Tombstone Territory
BMW2002Ti wrote:
For these apps, I actually "match" the resistors. Get like ten 1-ohm, 1% tolerance 1/2-watters and match the ones closest to each other with a precise DVM. Keep note of exact resistance. As this number is going to be used to calculate the current draw (Ohm's Law and all that jazz).

1/2-watt is nice as it can act as a fuse is the tube starts to go ballistic and sucking a lot of current. The resistor will pop and save the tube and possibly other $$$ parts.

Matching resistors works nice on those grid-to-ground resistors (usually 220k-ohm in Fenders), for setting up even bias on matched tubes.


+1

Same deal for the 470-ohm 1-watt screen resistors. The closer the match, the more even the power-tube performance.

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Post subject: Re: parts for biasing super reverb
Posted: Thu Oct 20, 2011 12:15 am
Offline
Hobbyist
Hobbyist
User avatar

Joined: Sun Jan 09, 2011 12:29 pm
Posts: 81
Location: Charlottsville
Arjay BMW Stratele, Thank You !


Top
Profile
Post subject: Re: parts for biasing super reverb
Posted: Thu Oct 20, 2011 1:00 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26417
Location: Tombstone Territory
Anytime, BT.

Let us know how it goes.

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 7 posts ] 

All times are UTC - 7 hours

Fender Play Winter Sale 2020

Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to: