How to bias a Carlsbro 100..

[Ostelarsen]

Hi someone (I Hope).

I recently brought my old Carlsbro 100W guitar amp up from the cellar, because I wan't to get it up and running again. I have have not much knowledge about electronics (yet) but I want to learn how to change the tubes/measure and bias the thing. I have found what apears to be a diagram over the sucker, and I've opened it up. I had another amp in the basement (a super Bass 100, whitch I've a couple of years ago used for guitar). That amp is pretty sick but I think the tubes in it is ok and not that old, so I have put them in the Carlsbro 100w. Now comes the golden quistions:
1. How do I find the bias knob? I have a suspicion that it is the one on the second picture with the yellow arrow but how can I be sure?   

2. The tubes is Tesla EL34 (or compatible at least), they've got the number "513" on the back side (the old ones said something like 523). What does that mean and can I use that information to something useful acording to the bias?

I have a standard volt/ampere-meter.

hope someone can help!

[J M Fahey]

Not quite "solid state", but we´ll try to help our "old technology" friend.   If that preset pot reads 10K and is connected by track or wire to the  diode that lives on the upper right part of your picture ... yes. Try to get around -39 Volts on the negative side of the electrolytic that lives on its right, which should read 47 uF. Having a generator and scope would be better, but those -39 are a pretty standard value for EL34´s. Don´t touch anything else, be *very* careful with the 400+ volts you´ll find everywhere inside that chassis, specially since I don´t see the 150K 1W equalizing/discharging resistors that should exist in parallel with every big blue 68 uF high voltage capacitor. Please post your results here.