Marshall Origin 50h Static Noise

cgtrman

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A friend came over this AM with test equipment that can check power tube plate voltages and currents. Plate voltages on the power tubes were uneven with 500+v on one and 440V on the other. We replaced them with Mesa EL34s and they were matched with bias set at 40mA w/o touching the bias pot (which we couldn't find!). The "Trim 1" pot was adjusted but we could tell it was not the bias pot - where is the bias pot?

So every preamp tube was swapped out 1 at a time and now the power tubes have been replaced with matched Mesa El34s. The crackling is gone but there is a ton of continuous white noise now! It is under warranty so I have exhausted my options.

This changes nothing about my opinion of this amp - it is either my favorite amp of all time or finishes in the top two!

Thanks again for the great recommendations.
 
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MarshallDog

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A friend came over this AM with test equipment that can check power tube plate voltages and currents. Plate voltages on the power tubes were uneven with 500+v on one and 440V on the other. We replaced them with Mesa EL34s and they were matched with bias set at 40mA w/o touching the bias pot (which we couldn't find!). The "Trim 1" pot was adjusted but we could tell it was not the bias pot - where is the bias pot?

So every preamp tube was swapped out 1 at a time and now the power tubes have been replaced with match Mesa El34s. The crackling is gone but there is a ton of continuous white noise now! It is under warranty so I have exhausted my options.

This changing nothing about my opinion of this amp - it is either my favorite amp of all time or finishes in the top two!

Thanks again for the great recommendations.

Yo Bro...its under warranty! Pack it up as it was stock and take it to a Tech. You have wasted enough time and energy on this. Let Marshall pay for it! Dont lose faith in this amps its a good one just a little bump in the road!
 


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