fringedweller

I haven't worked on my DSL 401 before or any other amp, but would like to. Apparently, it could use an ohm selector switch replacement (see my previous thread entitled 'Weird DSL 401 issue. . .' posted 8/24). I have little to no experience fixing electrical equipment, and am worried about shocks. What's the reality here? Are there procedures that can reduce the likelihood to almost zero? What kinds of repairs are most or least dangerous? If the amp is unplugged, is the switch replacement still dangerous? How long should the amp be unplugged before opening it up? The instructions on my multimeter say to wait til the capacitors are drained. Is there actually a way to test if they are drained? Any info appreciated.

ironlung40

you need to take it to a qualified tech. If you are not experienced then don't risk it. However, I used to be in your shoes, but put myself in positions to learn, ie. talked to techs, watched videos, read electrical safety manuals, you name it. I learned how to properly drain the caps, then check for residual voltage to be sure it was safe to work. If you can learn to do that properly you can work on the amp with no cause for concern, but you need to be knowledgeable with a multimeter, and know how to create a disharging tool. the caps will drain slowly off after awhile, but they can hold a charge for quite some time.

You can test the caps for voltage with a multimeter, but if you don't know how to do this then you may be in over your head. Be careful, if you do decide to work on it yourself.

Ironlung40

T-Bird

Hi.

+1 to what Ironlung40 said.

Especially the part about reading about electrical safety and bleeding the caps.

Even with the fear of sounding like a stuck LP, be careful and please don't maim or kill Yourself.

Regards
Sam

MajorNut1967

"What's the skinny on getting shocked?" Well its a shocking experience, you'll be a done Tom Turkey, you'll get Eastern European radio signals in your head!

I can't be nice about this: Don't fuck around with High-Voltage Tube Amps! They can and will kill you or leave severely injured! If you have not been trained or educated in Tube Theory & Safety "DON'T OPEN UP YOUR AMP AND MONKEY AROUND!" take it to a qualified Tech that's it.

I know you guys get tired of hearing this, but no one wants you getting hurt!

__________________
MJN1967 aka BA (Bad Attitude)

fringedweller

Thanks all above, especially ironlung for the well-reasoned advice. The crap has been sufficiently scared out of me, and is laying in a steamy pile on the floor. Nothing like a mid-morning laxative. I don't suppose anyone could recommend someone in Santa Fe, NM. Just a long shot. And yes, I have checked the web and am calling around.

JohnH

Yes, follow the above advice! Just to let you know what you would be up against:

If your problem is indeed that selector switch, which is simple enough theoretically, it is actually quite a tricky repair. It is a six-legged beastie that is mounted and soldered on the edge of the circuit board. You cant get under it to desolder without removing the board, and you cant do that without disconnecting every wire from the board. So apart from care and knowledge of draining caps, there is also considerable further scope for generally stuffing things up!

John

__________________
DSL401
8412 cab
Crate Powerblock
1 x 12 Vintage 30 cab
'76 Shergold Masquerader
'93 Les Paul Studio
'83 Roadstar

fringedweller

Yow! Thanks John. So, if I take this to a tech to fix, seems like I'm looking at an expensive repair. How many hours do you think this will take a tech to fix? Is their an alternative more simple fix?

MartyStrat54

That's why trained amp technician's make the big bucks. If the music store charges 40 to 45 bucks an hour, the tech is making $25 to $30 an hour. Not bad money and you get to work indoors on a safe rubber mat with a grounding strap.

__________________
MARTY

2009 Gibson Explorer-Hell Raising Machine
1989 Fender Strat Plus USA
2008 Fender Tele USA
2004 Schecter Elite w/DiMarzio's

TSL100 with custom 4x12 cab. TSL122 with Man 'O War Speakers.
TSL602 #1 with JBL D123 Speakers and 602 #2 with Altec 417 Speakers. "Oh so sweet my friends."
DSL401 #1 with Red Fang Speaker and 401 #2 with JBL D123 Speaker.

Tubes: Let's just say they are NOS that kick ass.

Tinman

Couldn't have put it better myself. I'm an electrician by trade and I probably wouldn't want to mess with it

fringedweller

So, it's me again, the originator of this thread, just to put a wrap on things. Turns out, after being sufficiently and justifiably scared out of dealing with the switch myself, I found a very cool tech in town, a guy, by the way who has been working on Marshalls since '73, to take the amp to. Turns out, the switch was OK, but three solder points were weak. It was cool to talk to this guy and check out the amp innards. Saw him drain the caps, but still wouldn't do it myself. Anyway, learned a lot, got the tubes checked, bias and output voltage checked. Things look pretty damn good in there. And, a final note to JohnH--you were exactly right about the trickiness of dealing with the switch. As you said, the tech had to disconnect a million wires to turn the board over, so he could check out the solder points and fix them. No way I could have dealt with this on my own. Anyway, thanks to all. The info I got in the forum definitely helped me in diagnosing the problem and getting more out of the experience with the tech. He was kind enough to let me watch the whole procedure, by the way. Later, folks.

sanrico

Hey, I just saw this post. Actually, I used to have an excellent tech in Santa Fe. I lived there for 10 years. Jeez...I can't remember his name, but they use him through Candyman there. Randy at Candyman can tell you. He lives near Saint Francis in a neighborhood just north of Siringo. Sorry I can't remember his name. He works out of his house and is very helpful and knowledgable.

I'll bet it's the same fella you took the amp to. How many can there possibly be in Santa fe?

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fringedweller

Thanks ,sanrico, pretty amazing to get the reply. I am aware of the person you're referring to, I think. I didn't take the amp to him, but went with another person I found through High Desert Guitars, a local shop. The tech I went with was excellent and I was totally happy with him.

sanrico

That's great! Can you let me know (PM if you want) the tech you used? I am just about to have a mod done and would like a second opinion.

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MartyStrat54

Although a Marshall amp isn't as stout as an electric chair, it still puts out more voltage than necessary to kill or dismember someone's body.

Earl Conrad Bramblett executed on the 9th of April 2003 in Virginia. Initial burst of 1800 volts for 30 seconds, followed by 240 volts for 60 seconds.

Daryl Holton executed on the 12th of September 2007 in Tennessee. 1750 for 20 seconds, followed by a second shock of the same voltage for 15 seconds.

It is very important to keep the current under 6 amps or the body will cook.

Under 6 amps at 240 volt? Yeah a Marshall can do that no problem.

__________________
MARTY

2009 Gibson Explorer-Hell Raising Machine
1989 Fender Strat Plus USA
2008 Fender Tele USA
2004 Schecter Elite w/DiMarzio's

TSL100 with custom 4x12 cab. TSL122 with Man 'O War Speakers.
TSL602 #1 with JBL D123 Speakers and 602 #2 with Altec 417 Speakers. "Oh so sweet my friends."
DSL401 #1 with Red Fang Speaker and 401 #2 with JBL D123 Speaker.

Tubes: Let's just say they are NOS that kick ass.