1972 super lead 100

[Highroller54]

I hAVE a 1972 super lead 100 and just plu ina new set of tubes and when I go to bias it thenbiasnpot wont go low enough. it runs a 24 watts or about 46 milliamps with then pot turn aslow as it will go need so help guys

Thanks

Highroller 64

 

[Jon Snell]

What output valves are you using now 6550 or EL34?
Schematic?

 

[Highroller54]

im running 6ca7's they have the same 25 watt disapation as el34's but sound different

 

[Highroller54]

they are running at 45 millavolt with the trim pot as l,ow as it will gfo

 

[Highroller54]

does ,anyone knowm how to get a hold of the people at Tubedepot Ill be sending themtubes back two of them redmplated with the bias adjust6ment all then way down. bad tube I stuck my original tubes in and they biased properly.

 

[Marcomel79]

does ,anyone knowm how to get a hold of the people at Tubedepot Ill be sending themtubes back two of them redmplated with the bias adjust6ment all then way down. bad tube I stuck my original tubes in and they biased properly.

Give them a call?

 

[Highroller54]

what number or email is the tube depot cant find anything on therem web pages

 

[playloud]

It's right on their 'contact us' page: https://www.tubedepot.com/pages/contact-us

The symptoms you describe don't necessarily mean the tubes are faulty though. If stock, the bias circuit probably has a 47k resistor and 27k pot in series to ground (so max 74k). If you replace either the 47k resistor (with 56k or 68k) or the pot (with 50k), you'll be quite likely be able to achieve your target bias. It's a bit of a pain, but I've had to do similar with current production tubes in the past (which ran with no issues after that).