Marshall SC20H weird problem! I am getting desperate so please help...

southbound suarez

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I have my Excel spreadsheet for what tubes live where in which amps.
Great Idea, I am nowhere as neat and organized as all this but I wish I was!
I spend alot of time tube rolling and as someone else had already mentioned. Tubes by nature are inconsistent and vary from brand to brand and lot to lot. One tube may sound nasty in one amp but might work well in another. This is especially true of microphonics tubes. Some microphonic tubes might work ok in a different amp.... A spreadsheet and inventory would be nice. Especially at finding trends between certain tubes and how they may behave.
Regarding new production tubes....
I have been having great luck and very pleased with much of the whole line of the Reissued TungSol sold by New Sensor... I don't understand how a company that produces one third of all production tubes for so many different labels can make a brand of tubes that behaves differently than another brand of tubes made at the same production facility. These reissue brands are they or are they not just simply labels silk-screened onto the same tube? Is a reissue Mullard or reissue Tung Sol or Genelex simply just a Sovtek in different drag? I don't know but the Tung Sol reissues have been excellent and affordable alternative to the Old Stock " test like new" vintage tubes I used in the past. Even these Test as new supposed NOS tubes have a large reject rate regardless of how they test on the Hickok ,,, due to the fact that in reality most NOS are indeed used tubes or were factory seconds and rejects... Used tubes are just that.... Well I'm used! I like used tubes but I have to wade thru many of them because they all have little noises and artifacts that make for hiss or static and crackle. When you get thru the static crackle and fizz from used old vintage tubes , you will enjoy super tone, but with these reissue tubes such as the Tung Sol it gets me half way there with way less hassle. New Amps Tung Sol , old amp maybe old tubes with a set of TungSol in reserve. Far more toneful than JJ but perhaps not as robust....
So far knock on wood not a bad TungSol in over 25 amps across my bench!
 

Jethro Rocker

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Great Idea, I am nowhere as neat and organized as all this but I wish I was!
I spend alot of time tube rolling and as someone else had already mentioned. Tubes by nature are inconsistent and vary from brand to brand and lot to lot. One tube may sound nasty in one amp but might work well in another. This is especially true of microphonics tubes. Some microphonic tubes might work ok in a different amp.... A spreadsheet and inventory would be nice. Especially at finding trends between certain tubes and how they may behave.
Regarding new production tubes....
I have been having great luck and very pleased with much of the whole line of the Reissued TungSol sold by New Sensor... I don't understand how a company that produces one third of all production tubes for so many different labels can make a brand of tubes that behaves differently than another brand of tubes made at the same production facility. These reissue brands are they or are they not just simply labels silk-screened onto the same tube? Is a reissue Mullard or reissue Tung Sol or Genelex simply just a Sovtek in different drag? I don't know but the Tung Sol reissues have been excellent and affordable alternative to the Old Stock " test like new" vintage tubes I used in the past. Even these Test as new supposed NOS tubes have a large reject rate regardless of how they test on the Hickok ,,, due to the fact that in reality most NOS are indeed used tubes or were factory seconds and rejects... Used tubes are just that.... Well I'm used! I like used tubes but I have to wade thru many of them because they all have little noises and artifacts that make for hiss or static and crackle. When you get thru the static crackle and fizz from used old vintage tubes , you will enjoy super tone, but with these reissue tubes such as the Tung Sol it gets me half way there with way less hassle. New Amps Tung Sol , old amp maybe old tubes with a set of TungSol in reserve. Far more toneful than JJ but perhaps not as robust....
So far knock on wood not a bad TungSol in over 25 amps across my bench!
I have a plethora of old tubes, some the label has disappeared so I have to keep track of what is where.
Tung sols, I have had 3 crap out very early in PI slots. So no more TS for me in that spot. Seems like they can't handle the voltage. Long smooth plate EIs or Raytheon Black plates are nice in there.
 

Dean Swindell

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Hello guys! Here I come again with another streak of bad luck...

So...I've just got a new SC20H...plugged it regularly from the 8-ohm speaker output to an 8-ohm speaker cab by using a high-grade speaker cable. The thing does not make a sound! I put preamp at the half and then slowly started raising the volume. No sound was coming out of the amp until I really struck the chords very strong and then some weird distorted buzzy sounds of loud volume start to come out...no normal tones. The same is if I do the low input or high input, except when it is on high input this bad sound is much more distorted (again), and on the low input is more towards the cleanish sound.

What is really crazy about it, I noticed that when I go to switch the amp off on the power button, by not transitioning from standby but going straight off from say high mode... then those chords that I've just played are heard and start to sound normal - this happens only when I hold the power switch in between ON and OFF...kinda stuck in the middle. I noticed this because the sound started to appear normal for the blitz of a second when I was shutting the amp down. And when it got shut down on the off switch it still rang a bit of those chords but seemed to me it was a normal sound there. Now does any of you know what a hell is this and what this means?

I've never encountered this problem before.

Also if I might add, no weird smell, flames, or whatever occurred. Tubes seem to glow normally, amp powers up normally.

I have an Origin 50 that normally works with this same cabinet and the same cable connection, just tested it after this.

This is my 2nd faulty Marshall in the row and I honestly can't believe it...I am really desperate and afraid I am going to have to return this one as well.
If you just got it, and after you've tried another speaker cord, take it back. If not, take it to a shop. Hopefully you can get it replaced.
 

jazzdj

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Man ... I have seen more complaints about these SC20H on this forum ... I wouldn't touch or buy one with YOUR 10 foot poll and check book. Why are you guys buying this crap?

I am so glad I still have my '81 JCM800 50W 2x12 Lead Series combo that has never had a day of problems since i bought it new.
 


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