212Mavguy Posted July 11, 2013 Share Posted July 11, 2013 My Marsh Overlord is a decently done clone of Dumble #124 completed as a 50 watter with one or two extra bells and whistles built in. Shortly after I got it, I had the chassis out and had adjusted a part which in Dumble-ese is called the FET trimmer. I was also adjusting the PI trimmer during the same sesh, and by far more attention was spent on that. Must not have verified FET input operation after buttoning back in the head cab...a couple months later when I decided to use it, there was what sounded like a bad tube noise coming out of that input, it started to happen after about 30 seconds and would not go away despite tube rolling. So I shrugged my shoulders and assumed that a solder joint had not been happy as the result of shipping. I used the normal input and used the amp for lots of very happy hours over a year long period. Then while having a cup of coffee this morning I remembered the thread about the dirty pot making the same kind of noise as a type of tube malfunction, so I got the Philips head out and decabbed the chassis. Went to that trimmer pot and moved it back and forth a bunch of times, it had a sticky spot where it had been previously adjusted to. So I moved it to a different spot, and plugged in... No noise, even after 10-15 minutes. Cranked it up to 3 on the master volume, FET input is a good deal hotter than the normal, originally designed to amplify low output piezo equipped acoustics back in the 80's when original was bench birthed. While I was strumming some Fender bassman-ish sounding rumble grind a tube tremolo pedal fell of its perch across the room onto the carpeted floor. Still no misbehavior in the Marsh. Recabbed, plugged in, Still all good. Now I have a whole new amp to play with. And this one will flay folks' faces off anytime I want, as well as dish up some soft serve ice cream single notes, The FET serves up a nice "Stones" clean, but that's about as clean as it gets. The mean, well it's aggressive to say the least. The amp's palette of tones from the normal input was already huge in variety...the FET input adds Solid State OD pedal kind of distortion to both channels. Fun! Link to comment Share on other sites More sharing options...
DetroitBlues Posted July 12, 2013 Share Posted July 12, 2013 I don't know what is more incredible... The fact you have an amp like that or the fact you had an amp like that and never played it for months???? WOW! Good advice though, that you for sharing! Link to comment Share on other sites More sharing options...
Hfan Posted July 12, 2013 Share Posted July 12, 2013 My Marsh Overlord is a decently done clone of Dumble #124 completed as a 50 watter with one or two extra bells and whistles built in. Shortly after I got it, I had the chassis out and had adjusted a part which in Dumble-ese is called the FET trimmer. I was also adjusting the PI trimmer during the same sesh, and by far more attention was spent on that. Must not have verified FET input operation after buttoning back in the head cab...a couple months later when I decided to use it, there was what sounded like a bad tube noise coming out of that input, it started to happen after about 30 seconds and would not go away despite tube rolling. So I shrugged my shoulders and assumed that a solder joint had not been happy as the result of shipping. I used the normal input and used the amp for lots of very happy hours over a year long period. Then while having a cup of coffee this morning I remembered the thread about the dirty pot making the same kind of noise as a type of tube malfunction, so I got the Philips head out and decabbed the chassis. Went to that trimmer pot and moved it back and forth a bunch of times, it had a sticky spot where it had been previously adjusted to. So I moved it to a different spot, and plugged in... No noise, even after 10-15 minutes. Cranked it up to 3 on the master volume, FET input is a good deal hotter than the normal, originally designed to amplify low output piezo equipped acoustics back in the 80's when original was bench birthed. While I was strumming some Fender bassman-ish sounding rumble grind a tube tremolo pedal fell of its perch across the room onto the carpeted floor. Still no misbehavior in the Marsh. Recabbed, plugged in, Still all good. Now I have a whole new amp to play with. And this one will flay folks' faces off anytime I want, as well as dish up some soft serve ice cream single notes, The FET serves up a nice "Stones" clean, but that's about as clean as it gets. The mean, well it's aggressive to say the least. The amp's palette of tones from the normal input was already huge in variety...the FET input adds Solid State OD pedal kind of distortion to both channels. Fun! Isn't that a great feeling? Nothing like fixing something that has been bugging you for some time. For me it's like pulling a thorn out of my foot, instant gratification. Sounds like an awesome amp. I don't know the terminology, FET? From 1980s tech school field effect transistor? They actually still use these things? I had an easy fix too this week, my Blues Jr blew it's power fuse. I need this for my late night playing, great low volume house amp. Pictured ripping the thing apart and trying to figure it out. Quick google search, typical power tube symptom. Found the fuses at the Home Depot, no tubes installed, no blown fuse, installed tubes, fuse blows, done. Had an old set around, quick re bias and done, relieved.. Got some EL84 recommendations from KBP, thanks Brian. Link to comment Share on other sites More sharing options...
bolero Posted July 13, 2013 Share Posted July 13, 2013 nice...always good when you find an easy, quick fix for someting that has been nagging you forever...now to figure out how to do that with our mother in-laws Link to comment Share on other sites More sharing options...
H Posted July 13, 2013 Share Posted July 13, 2013 nice...always good when you find an easy, quick fix for someting that has been nagging you forever...now to figure out how to do that with our mother in-laws It's called divorce Link to comment Share on other sites More sharing options...
SouthpawGuy Posted July 13, 2013 Share Posted July 13, 2013 It's called divorce On form today H Link to comment Share on other sites More sharing options...
212Mavguy Posted July 14, 2013 Author Share Posted July 14, 2013 Well I took it to the gig and plugged it in and that Field Effect Transistor (YEP!) input had almost no signal passing through it. So I played the gig as I always have, through the normal input. After getting the amp home decabbed , shot that little part with some lubricated pot cleaner (Jiffy Bath) and turned it back and forth a few times, let it dry. plugged in and everything ok again. Don't think I'll have any more problems with it. Going to play an outdoor gig with it today, will see how it goes. It had sat unplayed because I had left it at my mom's house for another musician to purchase, but he didn't pull the trigger. She lives 800 miles away. Link to comment Share on other sites More sharing options...
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