You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an alternative browser.
You should upgrade or use an alternative browser.
tell me about tubes
- Thread starter kdwiz57
- Start date
I would google , bias tweaker amp but it is simple !
Careful so as not to touch the amp chassis bottom where capacitors can zap you.
I set my rebel 20-30 amps on the end with the transformer supported by a stack of books so I can access the component section.
Make it stable and find the test points , red & black contacts for the Multimeter set too 200 millivolt range DC and touch nothing else.
Run on standby till warm and go off standby to read MV and my 6v6 tubes side say (set to 40 MV) on the circuit board and same for el84 tubes.
I do not trust sino power tubes for long , when ordering power tubes ask for high IP tubes matched and those will not red plate and turn completely red and short out.
Do not be tempted to order early breakup power tubes from sellers , hi IP rated tubes are better an stronger and are more hardy.
I caught 3 tubes in 3 years red plating in the early stage of voltage runaway on the plates and saved the amp.
Egnater transformers are running the tubes hard to start with.
Tip- bias late at night when the line voltage is highest not when the heat of the day and all AC everywhere are full on !
Do not attempt to measure and voltages in amp only the bias test point carefully and adjust the tiny trim pot to the millivolt at or below where recommended for the amp !
My plates are running very high voltages and the bias drifted up twice and and a low IP rated tube was the third failure !
Caution and thoughtful setup before you proceed is paramount !
You need a set of miniature screw drivers , I needed flat head not Phillips !
Surgical gloves are cheap and I would use those for sure.
Careful so as not to touch the amp chassis bottom where capacitors can zap you.
I set my rebel 20-30 amps on the end with the transformer supported by a stack of books so I can access the component section.
Make it stable and find the test points , red & black contacts for the Multimeter set too 200 millivolt range DC and touch nothing else.
Run on standby till warm and go off standby to read MV and my 6v6 tubes side say (set to 40 MV) on the circuit board and same for el84 tubes.
I do not trust sino power tubes for long , when ordering power tubes ask for high IP tubes matched and those will not red plate and turn completely red and short out.
Do not be tempted to order early breakup power tubes from sellers , hi IP rated tubes are better an stronger and are more hardy.
I caught 3 tubes in 3 years red plating in the early stage of voltage runaway on the plates and saved the amp.
Egnater transformers are running the tubes hard to start with.
Tip- bias late at night when the line voltage is highest not when the heat of the day and all AC everywhere are full on !
Do not attempt to measure and voltages in amp only the bias test point carefully and adjust the tiny trim pot to the millivolt at or below where recommended for the amp !
My plates are running very high voltages and the bias drifted up twice and and a low IP rated tube was the third failure !
Caution and thoughtful setup before you proceed is paramount !
You need a set of miniature screw drivers , I needed flat head not Phillips !
Surgical gloves are cheap and I would use those for sure.