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FDP Forum / Miscellaneous and Non-Fender Topics / Marshall Head Goes Down

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5Strats
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Edmond/OKC

GospelBilly!
May 13th, 2019 09:32 AM   Edit   Profile  

My Marshall DLS100 head died on me at band practice on Saturday. I've never had a tube amp go down before in my very long history.

The pilot light works and the tubes that I can see through the back panel are lit.

Is it a fuse or power tube issue?

ps - I drove home to get my JCM800 50-watt head to finish practice. It sure sounded different from the DLS100H.

Leftee
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VA

May 13th, 2019 09:38 AM   Edit   Profile  

It's hard to say. If it was a fuse, there's a reason why it went.

It's gonna need a trip to the doctor.

BrentD
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Michigan

May 13th, 2019 11:12 AM   Edit   Profile  

If you're willing to safely pull the chassis you can sometimes get an idea. I bought a 6100 from a guy that had no output but all the tubes we're lighting up. A bad tube fried some fuses and resistors and you could see her sitting cooked on the board.

5Strats
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Edmond/OKC

GospelBilly!
May 13th, 2019 11:55 AM   Edit   Profile  

I'm taking it the repair shop this afternoon.

The fuses are not accessible without removing the back panel. By contrast, the fuses are on the back panel of my JCM800.

Peegoo
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Planet Peegoo

Rhythm & Lewd Guitarist
May 13th, 2019 12:07 PM   Edit   Profile  

It's probably the HT fuse. Even when the HT fuse blows, the amp still powers up and the tubes all get heater power (they glow).

If you're having a tech look at the amp, ask them to show you how to replace the HT fuse.

And buy several spares. Wrap them in a little piece of paper and tape them to the back of the amp with gaffer tape.

Leftee
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VA

May 13th, 2019 02:05 PM   Edit   Profile  

And since you play it frequently, it might be due for new power tubes? I don’t know how old the tubes are. For a gigging amp that sees weekly rehearsal 6 months to a year on a set of tunes is prudent. YMMV

(This message was last edited by Leftee at 04:16 PM, May 13th, 2019)

ejm

usa

May 13th, 2019 11:38 PM   Edit   Profile  

And don't forget: If the fuse blew, it did it for a reason.
Hopefully you can find out what that reason is.
Determine if it makes sense.
Then take steps to fix the problem.

Otherwise, the fuse is going to go again.

I believe that there is a schematic in the database at the TubeStore.
However, for the life of me I can't figure out where most of the connections go.


5Strats
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Edmond/OKC

GospelBilly!
May 14th, 2019 05:38 AM   Edit   Profile  

Our singer was adjusting the PA mixer and there was a loud pop through the PA speaker.

My DSL head went down simultaneously with the loud pop. Was there any connection between the two?

Peegoo
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Planet Peegoo

Rhythm & Lewd Guitarist
May 14th, 2019 09:51 AM   Edit   Profile  

Yeah...probably a voltage spike.

OR something inside your amp let the magic smoke out and that caused a spike in the voltage, making a popping sound through the PA speakers.

Electrons are just like water: they speed along as flow allows, and as soon as a "valve" (switch) opens, that creates a transient/millisecond voltage spike in the line. It can pop fuses.

This is the reason why many tube amps need 'slo-blo' fuses to properly operate; voltage spikes are commonly created in tube circuits, and standard AGC 'quick' fuses will not handle these transients. Slo-blo type fuses can tolerate several milliseconds of over-voltage/over-current conditions before they pop.

Modern electronics are quite sensitive to voltage and current, unlike older circuits. That's why many modern amps have two or more fuses in them, e.g., a slo fuse on the AC input to the power supply and a quick fuse on the PC board to protect the more sensitive components.

You can differentiate between a quick and slo fuse by the conductor type. Quick fuses have a straight wire or metal ribbon through the center. A slo-blo fuse has a conductor wire coiled around a ceramic or glass fiber filament.

More info here.

(This message was last edited by Peegoo at 07:57 PM, May 14th, 2019)

5Strats
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Edmond/OKC

GospelBilly!
May 15th, 2019 05:25 AM   Edit   Profile  

Wow Peegoo, I told our singer I thought it was caused by his messing around with he mixer, but he said that couldn't be the case. Voltage spike!

QUESTION: Can I protect this from happening again (including at a gig) by using a surge protector power box?

willie

Too Near Atlanta GA

Amp Tech Emeritus
May 15th, 2019 08:33 AM   Edit   Profile  

DSL100H has a 1 amp HT fuse...and, oddly, a 500ma bias fuse (something I have a difficult time rationalizing the purpose or need of).

Peegoo's hypothesis is wise and likely quite factual.A voltage surge, as well as a number of other fairly innocuous conditions, can blow an HT fuse. Output tube deficiencies and bias issues are also a common cause.

I will say this as a, now retired, one time Marshall service tech, the JCM 800 50 watt is a far more reliable amp platform over time than any of the newer issued Marshall tube based amps. Many of the amps that followed the JCM 800 sounded great, but lack the basic bones of the JCM 800 and earlier models that made Marshall the name brand it is today. That said, they had to keep up with the times and various price points like all the other manufacturers. I am in no way bad mouthing the DSL series or any of the amps designed and produced after the JCM 800...just an observation from a number of years of experience.

w

RDR
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I tried to think

but nothing happened!
May 15th, 2019 08:58 AM   Edit   Profile  

Hmm, wonder how the Marshall Origin series will hold up. Thinking about snagging a 50 watt head.

5Strats
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Edmond/OKC

GospelBilly!
May 15th, 2019 09:52 AM   Edit   Profile  

RDR - I bought a Marshall Origin 50 online and just tried it out. It's very LOUD and very classic Marshall. Even with the gain on full, the amp is fairly clean.

The Origin 50 will be my backup head for gigs (it weighs around 27 lbs and is smaller than my DSL100 and JCM800 heads).

AND . . . the Origin 50 head costs "only" $650.

Peegoo
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Planet Peegoo

Rhythm & Lewd Guitarist
May 15th, 2019 10:32 AM   Edit   Profile  

There's a pretty good comparo of a 20-watt and a 100-watt Marshall here (link). Lee and Rob do a pretty good job of discussing the differences in speed, headroom, and sponginess or "squish."

The one thing this does not communicate is the 'feel' of the amp in the room. Close-mic'ing any amp captures the sound of the speaker only; it does not present the sense of air moving in a room. Even with each amp blasting through a 4x12, the difference in room feel is quite noticeable due to the bigger amp's speaker damping power.

One of their better vids.

BrentD
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Michigan

May 15th, 2019 12:45 PM   Edit   Profile  

^ Great link, especially when they pull out the Strat and start talking about the attack. The extra oomph and percussive attack is what you get out of more watts and SS rectifiers.

I didn't experience this until I felt a JTM45 squish when I wanted it to thwack.

5Strats
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Edmond/OKC

GospelBilly!
May 15th, 2019 04:58 PM   Edit   Profile  

"extra oomph"!

RDR
Contributing Member
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I tried to think

but nothing happened!
May 15th, 2019 05:40 PM   Edit   Profile  

5Strats, do you use a pedal for extra dirt?

5Strats
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Edmond/OKC

GospelBilly!
May 16th, 2019 06:25 AM   Edit   Profile  

RDR - Yes, most of my OD comes from a Tone Monk Seed of Life pedal. I also use a TC Electronic Spark to boost my solos.

Roly
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Whitehorse Canada

I don't get out much
May 16th, 2019 09:43 PM   Edit   Profile  

Jon Bessent told me that the last good Marshall amp was the JCM800.
He said, and I quote..."everything newer are horrible distortion machines."

cheers

5Strats
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Edmond/OKC

GospelBilly!
May 17th, 2019 06:21 AM   Edit   Profile  

Roly - The newer Marshall heads sound great if you run them with the gain set fairly low.

I agree that the high gain sounds aren't good. That said, I don't like the high gain sounds on Orange amps either.

Next 20 Messages  

FDP Forum / Miscellaneous and Non-Fender Topics / Marshall Head Goes Down




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