Quote Originally Posted by Ali Tait View Post
Did you try swapping the pairs of valves round at all? i.e. miz and match to see if you could get better readings? You really don't need to worry too much about matching each channel exactly,as long as each channel is within the spec.As for buying matched valves,IMHO even getting a set of perfectly matched valves would be a total waste of time,as within a couple of months,they would drift anyway,and the readings would be nothing like when they were new.Near enough really is good enough!
If you would like to have the amp checked out,may I suggest contacting Nick Gorham on Audio Talk.I'm sure he'd be happy to take a look at it for you,and maybe you could have some nice coupling caps fitted at the same time.There's not much Nick doesn't know about valve amps,and he does repairs for some commercial companies,so you can rest assured the amp would be returned in perfect working order.

Hi ali

Yes I did swap the tubes around.

On the first adjustment period I heard after about 40 mins of being on, some crackling from the left channel...I checked the readings right side okay left not(this is where the valve went)I tried adjusting again and figured I would swap the two middle valves round as the third one measured closer to the first on the left and the second on the left measured more like the fourth one. I thought this might help me get things a bit closer.

I did this but while the right side was okay after readjusting and stayed so the left didn't. After being on for about 20 mins the crackling came back on the left side and I rechecked the bias. The second valve position second valve in series to the first (left channel) was rocketing from 40 to 58 and climbing. I figured the blown valve must have caused a problem...so I switched it off rather than risk another wrecked valve. I rang my engineer and he agreed that either a fault had caused the first valve to go or it going caused a problem.

I am sure your recommended engineer would be very good but with the luck I am having at present it would probably end up smashed in transit. To be honest I can't afford it anyway...money is running out and valves and Mikes radio etc I can't really afford to spend anymore money this way. I will take the amp to Rodney hes a great guy and I can discuss the caps with him for the future.

Hi Nick

The Gloves were purely for extra electrical (maybe not thick enough) safety....cotton gloves are more suitable for changing valves. I am not to anal about this but maybe I should be. Your right about some issues arising out of light bulbs halogen etc and projector bulbs. The I-Max projector bulb is changed by guys in bomb proof suits...no dust, no dirt, no grease from finger prints. These bulbs are so big that if one blew or was dropped when changing the people doing it could be killed.


Regards D S D L