Dsl5c Sudden Death - Power Issue

myonlybliss

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Hey Guys,

A couple weeks back I came home from work excited to plug my LP in and jam. Turned on the amp, red power button lit up, but no noise or sound from the amp....NADA!!!

So, I peaked around the back and sure enough, my fears were confirmed when I saw that NONE of the tubes were glowing. Checked the Mains Fuse, it was fine. Replaced it, still nothing.

Channel Light: Upon further inspection, I noticed that the channel light is also not getting power. No matter how I switch it - clean/dirty, full power in the back, half power, FX Loop plugged in, Not plugged in the issue is the same.

What do you think is bad? Obviously the amp gets Power, but the power stops between the Power Button and the first Tube! Any Help or Advice would be appreciated!

Thanks,
Brandon
 

Gunner64

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Does this amp have a fuse in the filiment supply for the tubes? If so check that. It would be inside the amplifier on the pcb. I' m not an expert on this model but I do know of some Marshalls that get the voltage for the channel switching from the filiment supply. Filiment Fuse blows, no power to the filiments of the tubes (no glow) or channel switching circuit, including the led. I don't know if this is your issue as like I said I'm no expert on your amp model.
 

myonlybliss

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Hey Gents - First & Foremost, Thanks for your responses!

Gunner64: I was late to the punch, but I do remember seeing pictures (I think of Micky's) DSL5 opened up with three (3) inside fuses.

mickydg5: I don't have a schematic, so I'm not sure how to identify FS1, unless it's labeled on the board?

Micky: I know you've taken yours apart. For a complete electronics novice, is it pretty easy/simple to open the amp up and look at the fuses? (hopefully it won't void the Warranty)?
 

Micky

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Yeah, the fuses are generally labeled, although the writing is sometimes small.
The mains fuse is T500mA.
FS1 is T2AE250V and protects the 12V circuit. (possibly tube heaters?)
FS2 is T2AE250V also and protects the bias circuitry
FS3 is T250mAE250V and protects the hi-voltage circuitry

It is fairly easy to pull the chassis, but you need to remember safety first. Always follow safety procedures such as unplugging the amp and letting it rest for a while to discharge the circuits before working on it. If you are unsure, unfamiliar or uncomfortable working on a tube amp, please take it to a qualified tech.

If the fuses are not soldered to the board, it is best to remove them and test them with a DMM to insure their state. Testing while in place can yield varying results, as they is sometimes no visual indicator they are blown.

Fuses blow for a reason, and if you replace a fuse and it blows again there is a high probability there is a deeper problem, such as a bad tube or other component.

Be safe.
 

Gunner64

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The fuses are just clipped into holders on the board. Pretty easy change once the amps out of the cabinet. As mentioned and as I have found fs1 is the one, and like has also been mentioned it is labeled on the board..the fuse is more likely than not blown, as both circuits connected to it do not function..the heaters and the channel switching.
 

myonlybliss

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Yeah, the fuses are generally labeled, although the writing is sometimes small.
The mains fuse is T500mA.
FS1 is T2AE250V and protects the 12V circuit. (possibly tube heaters?)
FS2 is T2AE250V also and protects the bias circuitry
FS3 is T250mAE250V and protects the hi-voltage circuitry

It is fairly easy to pull the chassis, but you need to remember safety first. Always follow safety procedures such as unplugging the amp and letting it rest for a while to discharge the circuits before working on it. If you are unsure, unfamiliar or uncomfortable working on a tube amp, please take it to a qualified tech.

If the fuses are not soldered to the board, it is best to remove them and test them with a DMM to insure their state. Testing while in place can yield varying results, as they is sometimes no visual indicator they are blown.

Fuses blow for a reason, and if you replace a fuse and it blows again there is a high probability there is a deeper problem, such as a bad tube or other component.

Be safe.

Thanks - big help! Does my description of the amp's problem (tubes not lighting, no sound, channel LED not working but power button IS working) sound to you like a fuse is the likely culprit?

As tube-amp repair is VERY expensive and I've barely had this amp 1 year, I think I will give it a try myself!
 

myonlybliss

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The fuses are just clipped into holders on the board. Pretty easy change once the amps out of the cabinet. As mentioned and as I have found fs1 is the one, and like has also been mentioned it is labeled on the board..the fuse is more likely than not blown.

Thanks Gunner64 - A blown fuse would be my best case scenario! Although, it's a little concerning HOW I blew a fuse on a ~1 year old amp with not an extreme amount of usage. Guess we'll cross that bridge IF/WHEN.....
 

Gunner64

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Like was mentioned if you replace it and it goes again, then you have another issue. I have had a heater fuse go just from flexing at start up. After i replaced it i watched it the next time i powered the amp up and it went from kinda limp to straight out, so it is possible that just flexing made it go. My slx did this and it had no other issues..keep your fingers crossed.
 

myonlybliss

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UPDATE: Last night I opened up the amp. I saw three fuses and you guys were dead-on. There was a fuse FS1 that looked a little dark but not blown.

I took the Mains spare fuse (which is good) and replaced FS1 (slightly different part numbers but same size). Mains Fuse = T500mAE250V and FS1 Fuse = T2AE250V. So, the Mains Fuse SHOULD have worked.

But it didn't..... Power button still lights up red but channel light does not, no sound, no tube glow.

What NEXT?
 

Micky

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They are different part numbers because they are different current ratings.
Mains is 1/2 amp, FS1 is 2 amp. Both are rated 250V.
Is the power switch in the back stuck in the middle?

Chances are you blew the fuse again.
 

myonlybliss

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They are different part numbers because they are different current ratings.
Mains is 1/2 amp, FS1 is 2 amp. Both are rated 250V.
Is the power switch in the back stuck in the middle?

Chances are you blew the fuse again.

The mains fuse should've worked, right? Being a lower amperage means it would blow "easier" but would still close the circuit....

Are you referring to the Full/Low Power Button? I have engaged (back and forth) that button several times while powered to see if anything changed, and nothing.

These pics show the amp open - fuse FS1 is visible.

amp2.jpg amp1.jpg
 

mickeydg5

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The mains fuse should've worked, right? Being a lower amperage means it would blow "easier" but would still close the circuit....

Are you referring to the Full/Low Power Button? I have engaged (back and forth) that button several times while powered to see if anything changed, and nothing.

These pics show the amp open - fuse FS1 is visible.

View attachment 43796 View attachment 43794
NO.

The MAINS fuse is a 250mA fuse which equates to 0.25A fuse.
The other fuses require 2A fuses which equates to 2000mA.

Fuses are set/specified for designed jobs. The 250mA could not handle the 2A specified draw so it blows right off the bat. It is too small, too weak.

The "T" on the fuse indicates time delay or slow blow.
 

Gunner64

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The guys are right..get the proper fuse dude. You need the 2amp slow blow in fs1. You cant half ass it. Its a 2amp for a reason.
 

myonlybliss

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UPDATE:

Replaced the fuses and still nothing.... :ohno:

Any suggestions on next step to make this DSL5C sing again?
 

Micky

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Have you swapped out the tubes for your known good spare set?
 

myonlybliss

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Have you swapped out the tubes for your known good spare set?

My first tube amp.... So, I don't have a spare set of tubes.

Do you think the tubes are the likely culprit? It seems like a power issue, as the LED Channel doesn't light up. All four tubes not lighting up either - wouldn't it be improbable that all four would have gone bad?
 

Micky

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Tubes may have a fault and are possibly blowing the fuse in that circuit.
The 12V circuit feeds all the channel switching circuitry as well as the tube heaters.
If that goes out, the LED's go blank.

Pull all the tubes out and fire it up with a good fuse to see if the channel selector lights up.
Then you know it may be the tubes...
 


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