Marshall anomally

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anemochore
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Marshall anomally

Post by anemochore »

I've got this early '74 50 watt MkII
Turns out 150k resisters were used stock instead of the spec 100k resisters. Thoughts?
My amp tech figures they were out of 100k's that week or someone was color blind

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Dr Tony Balls
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Re: Marshall anomally

Post by Dr Tony Balls »

Its probably fine, and not much i'd worry about. I dont think its worth modding it just to get the right plate resistors. The only place where it would be of potential concern is the plates on the phase inverter. You can see them in your pic in the upper right corner, partially obscured by the twisted brown and green wires. Those values should be (L-R) 82K and 100K. It looks like the one on the right is 100K, but hard to tell, and I cant read the red one. If those are too far apart from one another you'll have an unbalanced phase inverter which wouldnt be good.
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waveclipper
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Re: Marshall anomally

Post by waveclipper »

Yes, a few less volts on the plate for a slightly 'browner' & more compressed sound I guess. Shouldn't do any harm and you could always try piggy-backing 300K resistors across them if you were curious about hearing the 100K toanz.
If it sounds good my vote would be to leave it alone too. Loads of lovely mustard in there :badlove:
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Re: Marshall anomally

Post by anemochore »

Great advice Gents The ones at the phase inverter were swapped out. it is a 100 K but those were the only ones. He thinks a number of them are making it sound a bit more bright and aggressive. For certain when comparing to his '75. Dude has a great ear. Stlll good sounding but I had finally taken it to him because I thought it was too bright. Even rolling all the treble back. I also brought it over to have the master volume mod removed. Those green and brown wires that you see. I'll mention the 300 K jumper. Then he can just play around. He loves doing that.
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redeyeflight
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Re: Marshall anomally

Post by redeyeflight »

Hmmm...sounds like my kind of Marshall then!! Usually i find then to be pretty dark sounding amps, but im super used to fenders.
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jerms
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Re: Marshall anomally

Post by jerms »

Even channel 2 is bright? That should be dark... Channel 1 is the bright channel on my 50 watter... It's unsuable unless you jump channels and just add a dash of channel 1 to give channel 2 some edge....
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Re: Marshall anomally

Post by anemochore »

jerms wrote:Even channel 2 is bright? That should be dark... Channel 1 is the bright channel on my 50 watter... It's unsuable unless you jump channels and just add a dash of channel 1 to give channel 2 some edge....
Yeah 2 is full on massive bass. I like to open up 1 to get volume then jump and roll in 2 to give it bottom. 2 may even have more bass than others. Brent described why and suggested maybe adding a different value component but I forget what that was. I like what it adds to the treble channel so for now we'll leave it.
redeyeflight wrote:Hmmm...sounds like my kind of Marshall then!! Usually i find then to be pretty dark sounding amps, but im super used to fenders.
It's just been a bit spikey to my ears lately. especially when not going full out. Set just before breakup. Dime channel 1 and it sounds great but I'd still like to roll off the top a bit. Actually I like how his sounded better when we were A-B-ing them. He's promised they'll sound identical.
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Nerd
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Re: Marshall anomally

Post by Nerd »

150k bias splitter resistors ware common in US spec Marshalls that ware shipped 6550 power valves
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anemochore
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Re: Marshall anomally

Post by anemochore »

Nerd wrote:150k bias splitter resistors ware common in US spec Marshalls that ware shipped 6550 power valves
Yes, a few years back I had EL34's installed. I'm guessing that would be why the 150 was changed to 100 at the phase inverter. ?
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Nerd
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Re: Marshall anomally

Post by Nerd »

anemochore wrote:
Nerd wrote:150k bias splitter resistors ware common in US spec Marshalls that ware shipped 6550 power valves
Yes, a few years back I had EL34's installed. I'm guessing that would be why the 150 was changed to 100 at the phase inverter. ?
As far as I can see you still have 150k PI splitters in. Can you mark which resistors you talking about as I think we are talking about two different things. Also, picture of the whole main board would help, though.
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