Polam Help PLEASE>

[jockman]

Hello,

Just got my pair of Polams from the sarge, put them in my amp, and they glow VERY red and are rediculously hot.
I have put a few pics up here http://myweb.tiscali.co.uk/jonroberts/valves.html

BUT the actual pics do not show the red glow to well, you can see a bit, I put a pic of the Teslas that were in also, and as you may see, they are perfect.
Could anyone tell me why this may be.
I have sent a mail to sarge.

Jon

[kd]

A few questions:
1.Which amp is this?
2. What size is the cathode resistor?
3.what size screen resistors are you using?
4.Are the plates glowing red?

Ken

[jockman]

Hi Kd, you will have to forgive my ignorance in these matters, my amp details are here http://myweb.tiscali.co.uk/jonroberts/

When you ask if the plates are glowing red, what are the plates? ( )

[kd]

Sorry, I assumed you were talking about an 18 watt amp. Since I don't have any experience with a Park I'll just step out of the way and let someone who has more experience take a shot at it. If the plates are glowing, then don't use the tubes until the problem is fixed, you'll ruin your tubes. I would think at the least your going to have to up the size of your cathode resistor in order to run these tubes safely. I put a link below to the anatomy of a vacuum tube so you can see what the plates and other parts are.
http://en.wikipedia.org/wiki/Vacuum_tube

Ken

[rjgtr]

The Park is very similar to the Marshall 18 watt. There's a thread with the schematics around here somewhere.

I would suspect that the plate voltages are probably too high for the Polams. You could replace the Bias resistor with a higher value to get things in line. Do you know which model the amp is?

[jockman]

The Park is very similar to the Marshall 18 watt. There's a thread with the schematics around here somewhere.

I would suspect that the plate voltages are probably too high for the Polams. You could replace the Bias resistor with a higher value to get things in line. Do you know which model the amp is?

I was lead to beleive the Polams could cope with high voltages, and it raises the question of why the Teslas don't display the same symtoms.

Jon

[kd]

Different tubes have different tolerances to plate voltage. What kind of plate voltage are you running? See what sarge says about the problem.

Ken