Modda en JVM(med hur ställa bias)...
<b>.. det ska nog jag göra med min..
sprang på en tråd på nätet(bilden nedan får bli ev steg två).
en så kallad C83 mod.. ska tydligen göra underverk med stärkaren..
återstår att se.. nån mer som läst/hört nåt om denna mod?</b>
<i>"Removing C83 on the board will be the solution for what you are after. Just snap it off of the pcb and both gain and treble response are lowered while retaining the bite and not getting muddy. I also think that the gain control will be more usable in all its range and those modes more dynamic"
Clipping it will reduce the high end and have a usable gain range in OD1 & OD2 Orange and Red modes. Given range will be far more usable and the top end fizzle (prone to feedback) is gone
Response from longtime Gear Page lurker MRMOJORISIN, a high end gear owner that I've actually bought some stuff from and feel he know's whats up:
"Clipped mine this afternoon. The man wasn't lying. Eliminating a 5 cent cap from this amp took it from very good to great. It "feels" like an old Marshall now..."
and to answer "where the hell is C83 and is it marked" (from same lurker)
"Yes it is and its really easy to find. Front edge, left side of the board near where the input jack comes in. While you have chassis out, bias the damn amp right (about 42 ma). It will be an entirely different (better) beast after this 10 minute surgery.""]
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Här kommer en DIY för att ställa BIAS i en JVM.. om nån nu behöver veta det[;)]
<font size="1">OK, take off the back grille with the 4 screws and lie the amp on it's face.
Undo the 4 bolts underneath the amp holding the chassis in place. Then put the headcase on it's side, grab the top transformer and carefully slide the chassis out of the amp.
Be careful to not touch anything inside the amp and to have one hand in your pocket if possible when working on it.
I leant the amp against my filing cabinet for easy access
Here are the bias pots, one per pair of tubes, adjust using a precision screwdriver
And the contact points. Middle is ground, outer pairs are for each pair of tubes and match to the pots.
Turn Masters to 0, add a speaker load (for safety), and plug in the power lead. Turn the amp on and leave in standby for a few minutes.
Measure teh bias by probing the centre and left terminals of the connector with a Multimeter on the 200mV setting. Stock you should have a value of around 60mV = 60mA = 30mA per tube. I pushed my bias up to 35mA per tube = 70mV reading. Some people go as high as 40mA which is an 80mV reading
Change the bias with small increments on the pot and allow to settle. Ditto on the right side of the tubes.
It's worth turning up the masters a little to give it a play. Remember to zero them if you're going to adjust bias again.
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