Can anyone provide directions on changing tubes in the CS40?

[Eskimo_Joe]

If possible, it would be great to get a "for dummies" version of how I would change the tubes in the CS40...I would like to take out the EL34's and try out some 6L6's.

Thanks!

[BJF]

Hi,

Yes sure,

You'll need a Digital Voltmeter.
You'll need to set that at 200mV range and use the red probe in the volt socket because you are going to measure a voltage.
However the volatge you are going to measure will directly convert to the total current going through the cathodes of your output tubes.
This means that if you measures say 40mV's you have 40mA's running through the cathode of your output tube and you can measure each output tube individually via the banan connectors at the top of chassis. You will need to remove five screws to remove back cover to access top of amplifierchassis.
When running EL34's recommended static or resting current is about 20mA's. This can be set via a potentiometer that protrudes through the chassis. Next to the potentiometer is also a switch that changes the range of bias voltage to allow operation of say 6L6 tubes.

When you remove your EL34's you'll see a switch to the right as you are sitting at the back of the amp.
Flip that switch, from the position it was in when your EL34's were installed.

Install your 6L6's while amplifer is turne off, now turn amplifier on and let heat up and install the DVM probes set as above and for 6L6's turn the bias potentiometer until you read about 35 -40mA and wait about 10 to 15 minutes to settle.

You might ask why run 6L6's hotter than EL34's?
Well,it's a question of grid space.........

Please ask if anything is unclear before you do anything if all is fine and clear then proceed and have fun
BJ

[analoghog]

Bjorn,

can you use KT66's in the CS40 ?....if so, what voltage should you set the bias for?.....thanks!

[BJF]

Hi,

You can and treat them about the same as 6L6's

Have fun
BJ