Blew a fuse.

[thrawn86]

......Literally. Lemme explain.

So since I had some time today, I decided to put in my new power valves. I built a 360 degree 'spit' for my head (partially butchered from something my boys no longer play with ) and stuck it on there. Looky:

Pretty cool, eh? Totally stole the idea from another member

So I get it all set, prepped to bias, and.......NOTHING. No valves are lighting up. It's got juice, panel lights are on, trannies are both humming. I doublecheck; same story. So I start visually cruising around the board for something out of the ordinary, and find the fuse at F4 looks to be shot. It reads T 6.3 E 250V. Never been shot before. Is this the culprit?

Here's a link to the schem. I really don't know if this is what the prob is, since I don't read these well. It's on page 2, in grid E-2, more or less.

http://www.drtube.com/schematics/marshall/dl40-60-02-iss9.pdf

Also, is this a slow blow fuse? And where should I get a new one (if I need to look in a specific store, etc.)? Thanks alot in advance bros.

 

[skeezix]

Nice looking gimbal stand. Little Tykes art easel type-deal, or FP teeter-totter?

Sadly, I have not a DSL. But since it's across one side of the heater filaments, yeah, with it blown, there's no warm glow.

T6.3E 250V, or T6.3A 250V?

First, the 'T' means 'timed,' ie. - 'slo-blo.' T6.3E seems odd to me; dunno bout that...but T6.3A is, of course simply 6.3 amps.

I say any slo-blo 6.3 amp, 250V fuse will work....well, assuming it's the right size of course. Is it the clear glass 5X20mm glass kind? Those are three bucks for a 4-pk at Radio Shack...

 

[clydey]

thrawn86 6.3 amps is a lot of amps
i would remove the new power tubes before i replaced the fuse in case there is a heater in one of the new power tubes shorting.
if it holds then replace the new tubes
hope this helps

 

[Jonathan Wilder]

Blew a fuse

Hey man..fix the damn thing and leave your private life out of it OK pal?

thrawn86 6.3 amps is a lot of amps
i would remove the new power tubes before i replaced the fuse in case there is a heater in one of the new power tubes shorting.
if it holds then replace the new tubes
hope this helps

Well he won't be 100% positive on that unless he replaces the fuse, powers it on without valves installed, then reinstalls the valves, and powers it on again. Fuses blow for no reason every so often. Everytime you power on an amp, the fuse wire will flex due to power up inrush current. Well after so many times of that, the fuse wire just breaks and you end up with a dead fuse.

So that being said -

Replace the fuse

Remove the valves, then power up. If fuse does not blow, replace the valves and power up again.

If fuse does not blow, you're good. If it blows, send those valves back.

However, if with no valves installed it still blows, this points more than likely to an issue in the DC heater supply on the preamp valves.

 

[clydey]

yes, you are right, forgot to say but (took for granted) that he would know if it holds means - on power up if the fuse does not blow
did not want to complicate the matter by bringing up the dc bridge rectifier
but i think we are saying the same here
cheers

 

[thrawn86]

Nice looking gimbal stand. Little Tykes art easel type-deal, or FP teeter-totter?

Sadly, I have not a DSL. But since it's across one side of the heater filaments, yeah, with it blown, there's no warm glow.

T6.3E 250V, or T6.3A 250V?

First, the 'T' means 'timed,' ie. - 'slo-blo.' T6.3E seems odd to me; dunno bout that...but T6.3A is, of course simply 6.3 amps.

I say any slo-blo 6.3 amp, 250V fuse will work....well, assuming it's the right size of course. Is it the clear glass 5X20mm glass kind? Those are three bucks for a 4-pk at Radio Shack...

The stand was a 'bolt-up' board I built out of MDF for my boys to experiment with. It originally had the center going all the way to the top with holes drilled through and screw inserts so they could use nuts and bolts and practice using tools. They loved it for about a month and then it became old hat.

The schem calls for T6.3A. The fuse end has T6.3E stamped into it. I figured the same as you. And I did know that the T stands for a slow blow fuse, but I wanted to check again.

One thing I'm sure of, clydey: It's not the BR. I dealt with that little gem last year.

Wilder, once again, you've outdone yourself.
Thanks guys. When I get some time tomorrow I'll pick up a fuse and go from there.

 

[Adwex]

Nice rotating amp workbench.

6.3 amp fuse?? Isn't that rather specific? I could see 6 or 6.5, but 6.3?

 

[thrawn86]

Nice rotating amp workbench.

6.3 amp fuse?? Isn't that rather specific? I could see 6 or 6.5, but 6.3?

Maybe it is. That's what the schem calls for, and that's the imprint on the fuse.

 

[MajorNut1967]

......Literally. Lemme explain.

So since I had some time today, I decided to put in my new power valves. I built a 360 degree 'spit' for my head (partially butchered from something my boys no longer play with ) and stuck it on there. Looky:

Pretty cool, eh? Totally stole the idea from another member

So I get it all set, prepped to bias, and.......NOTHING. No valves are lighting up. It's got juice, panel lights are on, trannies are both humming. I doublecheck; same story. So I start visually cruising around the board for something out of the ordinary, and find the fuse at F4 looks to be shot. It reads T 6.3 E 250V. Never been shot before. Is this the culprit?

Now thats pretty spiffy Mate!

 

[thrawn86]

Thanks, Maj!

Update:

Got the new fuses from the 'Shack. And yes, they are indeed a 6.3A fuse. Plugged in a fresh one and powered up with no tubes.....no blow. Powered up with my old valves....no blow. Plugged in my new NOS Mullards (can you call something made in the 60's 'new'? ) and powered up...no blow still. So everything is kosher once again in DSL 401 Land. Biased up at around 1.2. Decided to go with that, as it's somewhat cooler than the unmodded recommendation of 1.3 to 1.4. This is also per Marty, since he has a few of these, and NOS valves seem to be happier at hotter values. Besides that, the fan will be running.

Thanks everyone for their input on this.....'specially Wilder.

 

[Jonathan Wilder]

Plugged in a fresh one and powered up with no tubes.....

That's what she said...