Help!! MkIIB

[Harry the Horder]

I can't seem to get a clean sound on my amp it is ok until I play my bottom strings and then distorts or sounds dirty. I have changed the valves and checked the speaker. Is it a caps job next? and what does LDR stand for?
I've just pulled it apart to get more details.
It is a mkIIb circa 1980 fitted with Altec spkr.Hardwood/Wicker.
Readings I'm getting in 60watt mode plate voltage=452v
in 100watt mode plate voltage=444v
The output valves fitted are 6L6GC (Mesa) 40 AR Yellow
The Bias Readings from Left to Right looking into back of Amp are
V1= -23-9 V2= -26-7 V3= -28-0 V4= -22-4 using Bias tool and VOM.
Any Ideas would be more than welcome I read somewhere that the Bias should be between -48 to -50 in that case it is way of or is it?
Not bad for a first posting Heh! Happy New Year to all.
Harry the Horder.

 

[LesCarr]

Definitely Caps, once the get this old they should be replaced. I had a tech do mine and the sound tightened up.
New grove tube 6L6GE's or KT66's (if they fit) are my next improvement.

 

[Harry the Horder]

Thanks for the advice I intend to go right through it anyway I only use it at Home but want it sounding good for when my AC30 goes down.
Harry the Horder.yes its me again.

 

[RussB]

How are you setting the amp controls?

Your current reading aren't "negative" unless you have your DVM plugged in backwards. What you're reading is current draw...

I don't understand this,

V1= -23-9 V2= -26-7 V3= -28-0 V4= -22-4

What is -23-9? What does that signify?

And them power tubes should be run NOWHERE near 48 to 50mA of current draw! Mid 20's are just about perfect in a MKII

 

[Harry the Horder]

:lol: HI.All.
Thanks but I think I got there in the end thanks to boogiebabies Help!see "mkIIb plate voltage." The figures I refer to in V1.etc. are from the use of a: Bias Tool and b: Plate Voltage Tool I expressed the Bias figure in negative volts hence -23-9 That is the negative DC Voltage reading I recieved from my Bias Tool and VOM .as you know Bias is the Negative voltage applied to push the valve in to a certain range of operation and not having much info. Just a Mesa Repair guide I wished to check if I had my Amp correctly Biased to eliminate Bias settings as a possible source of distortion :? anyway we have got their in the end and Ive learnt a lot more about Mesa Boogies.This is a great site.and thank you for your input.
Harry the Horder