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Hey all,
I've got a Musicman 130 amp that makes some noise. When I turn it on it will make crackling noises and sounds distorted while played for a while -- maybe a couple of minutes? The noise fades away and it eventually sounds fine, but it takes a lot longer than a normal tube warm up. A minor annoyance, but it has got me wondering what is going on. A tube going bad, or something else about to give out?
I haven't been in a big hurry to take it to a tech since the noise fades away, but I wouldn't mind knowing what was going on. I haven't messed with the tubes at all yet . . . theories?
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11-16-2017 11:16 AM
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I'm going to take a wild guess and suggest it is on the solid state front end and a component going south. A capacitor has possibilities here but that doesn't mean something else isn't going out of spec. I have a old Ovation preamp with a similar issue and like you have put off dealing with it and just let it warm up. It is starting to get worse so time to dive in!
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A couple of years ago I replaced all of the PS caps and some tubes, but my 210HD has been doing that for years it's not worth cracking it open and spending time with it unless it gets worse. It seems like every time I went to debug it, the noise went away, it's tough to find a ghost.
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It's always easier to let the ghosts find you.
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That group of amps Leo came up with sure are something. Around here the 130 is considered to "Out Twin a Twin". I've got a Andy Fuchs ODS modded HD130, what a beast !!!!
Life's short man, don't shorten it even more by diagnosing and "fixing" your amp. Let a qualified pro take care of it once and for all... That's something I'd never mess around with, electricity.
Big
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Originally Posted by BigMikeinNJ
In one case (a Boogie Mark III) the amp regularly lost about 40% power after running it for forty minutes. The first tech i brought it to could find nothing wrong but charged 50 francs anyway. After the second tech had fixed it for the ridiculous amount of 400 francs it run fine for an hour and then stopped working completely. I was lucky he agreed to fix it again for no additional charge. After that the amp was fine, but it had cost me a lot of nerves.
Another amp i sent in for repair (cost 160 francs just for overseas shipping & return) came back with the same problem (obviously caused from shipping), this one i luckily could fix myself. After that i feel that a successful self-repair can bring much joy. It doesn't necessarily shorten one's life ;-).
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Well, you have to learn about the big voltages present in tube power section caps first and how to drain them because they can kill you which puts a personal spin on the ghosting angle. I do agree that learning how to do this sort of thing is worth the effort because amp techs seem harder to find than guitar techs. Tube guys who understand basic class A circuits are plentiful but don't often work on solid state or more complex tube amps, at least with good results. Hybrid amps like Musicmans need understanding of both tube and solid state circuitry.
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"Sometimes even a qualified experienced pro can't fix it. I've had my share of experiences of that"
I've been working on amps since the 60's and that's very true to a point where a tech sees diminishing returns, because no honest tech can justify chasing shadows while on the clock a client is paying for.
I am NOT advocating a tyro run a chassis opened up while hot but sometimes a non conductive probe touching about the amp innards with a signal applied is the only way to find a ghost.
Every thing possible that could be tightened, solder reflowed etc. I did. One day it'll manifest itself and I can exorcise it properly, till then it works :-)
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If replacement tubes do not fix the problem, consider selling the amp and getting something with available factory service. Old amps are for collectors or those that understand the schematic.
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You need someone with a scope and tone generator to isolate where this is coming from. Because it always happens shouldn't be that difficult to find. You could give the op amps a spray with some cooler and might get lucky and find a bad one.
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+1 skiboyny
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I am going to suggest you have a look at this modded HD130, this is one that Andy Fuchs did his total restoration on. It's like a new amp, the work Fuchs does is amazing... I am not affiliated with the seller but I know how much I love my Fuchs modded HD130...
Fuchs ODS MusicMan HD-130 Conversion Guitar Amplifier | eBay
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Musicman amps have some particular issues; I know, I've had a few. The unconventional hybrid design can cause problems; one vulnerable point is the channel switching relay, if the amp has one - some don't. Most of them operate on VERY high tube voltages, up to 700v, so quality tube replacements can be an issue. The 130 above runs at 700v, it's there on the schematic. Because of this high voltage, the tubes are biased very cold, and any drift in this bias ( which is generated in the solid state circuitry) can easily make the amp sound harsh and crackly - and is impossible to adjust without technical knowledge and the right tools.
In other words, these are not user friendly, user-adjustable amps. When they work well, they are great, built like tanks, but when they don't, they are a complete PITA. Shame.
The RD50 series are great for jazz, compact and very loud, but really difficult to keep running properly. I gave up with mine, ripped out all the solid state circuitry, and rewired it as an all-tube deluxe.
There used to be a MM amps resource on the net with some good maintenance tips, maybe it's still there.
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Just wonder where you end up gigging with a 130 watt tube amp?
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Originally Posted by jads57
Ironically, I'm a pretty quiet player.
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Originally Posted by BigMikeinNJ
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Originally Posted by Longways to Go
just be aware that removing 2 of the 4 power tubes changes the ohm rating that the speaker is matched to...
here's good article about removing tubes..from the good folks at premier guitar
Ask Amp Man: Removing Output Tubes to Reduce Power | Premier Guitar
also the musicman 130 used 6ca7 tubes..the now hard to find usa version (similar) of the el-34...
cheers
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I ran an SF Bassman 100 for years on two 6L6s. I yanked the interior tubes for better heat dissipation, and swapped them out regularly with the other pair in order to keep the quartet (NOS Sylvanias) decently-matched. Ran it into a 4x10 cab loaded with Celestions with no issues. I seem to remember it was a 4-ohm load the cab gave.
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Originally Posted by icr
I've owned 3 amps that have had the ODS mod run on them: two Music Man HDs (a 75 and my current 130) and a silver face Princeton reverb. My understaning is they rip out all the wiring, sockets and caps and rebuild the amp and make it an ODS by adding the ODS circuit board. So my Princeton Reverb ODS was still a Princeton Reverb, except the previous owner had Ken install a 25 watt Mercury Magnetics transformer and a Cannibis Rex 12 inch speaker - it all went into a really nice maple/mahogany custom cabinet that would accommodate that speaker. It had all the latest SLS, ODS, half power mods. Ken is always coming up with something new.
The Music Mans are still Music Man amps, he just makes them totally freaking new inside and adds the ODS circuit board and mods. The 130 has the 4 EL84 tubes in it, I run it on the original half power switch into 1 12 Celestion. And I run it at a very low volume and it's still incredibly loud...
I finally broke down and bought a Fuchs ODS 20. When I left Jersey I sold my modded Princeton to a guy from the moving company who did the moving estimate. He saw the Fuchs amp on my description and practically flew over with his strat to try it out. I had always played it at low volumes with the Jazz and Fat switches on and got a great tone out of it. He really cranked the amp up and was doing some David Gilmore shit that blew me away, I never knew it could do that stuff so well.
I think the Fuchs modded amps are remarkably pick dynamic amps, very much like my Sebago Sound Texas Flood, yeah sure you can crank her and get all that wild shit with it, but if you want subtle pick dynamic rich tone a Fuchs modded amp isn't a bad option. If you have not tried one please go check it out, just supposing what it sounds like, well you don't know.
Big
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Originally Posted by BigMikeinNJ
Maybe the output tube sockets are saved and the output jacks on the back.
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ICR,
Ill repost that sellers ad link again, have a look see at his many detailed photos. He doesn't show the guts inside the chassis but it'll give you an idea of what Andy Fuchs does, I remember taking my first MM ODS to a guitar broker to sell when one of my cats needed an operation. He did his usual looking around online to get an idea what his wholesale offer should be to me and meanwhile the guy who shared the building space with him, an amp tech that did repairs and sales, had a real thorough look at the inside. This guy never said squat the many times I was in there browsing or selling gear. BUT that day he told Bob, buy this amp, it's really killer...
If you are ever in my area you should reach out, stop by and try out the amp or some of my other gear, stay for a bite to eat... Sound like a plan ??
Big
Fuchs ODS MusicMan HD-130 Conversion Guitar Amplifier | eBay
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130w out of four EL-84s? Am I missing something?
Perhaps you meant EL-34s?
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Originally Posted by Thumpalumpacus
YOU ARE CORRECT SIR...
Sleep is highly over rated...
So 4 EL84s would power a damn radio station right ??Last edited by BigMikeinNJ; 11-18-2017 at 07:06 PM.
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Andy Fuchs does good work. I don't have any of his amps, but I can say good things about his VERBRATOR (functions like a Dumbleator) which I use on my amps with Overdrive Special circuits.
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