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geppert

DT25 head dead

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Amp is dead. No AC Power light. Checked line fuse and it is ok, (update, what I checked was NOT the line fuse it was the Tube Protection Fuse, the Line Fuse in the AC socket was blown), no visual sign of damage and continuity. Took chassis out of box, took bottom plate off and pulled out slightly (did not disconnect any plugs). Nothing inside looks burned. No smell. Amp looks fine inside from what I can see. Not sure if there are any other fuses inside I can check on my own? Does it need to come in for repair? Not sure if it falls under the power transformer recall ???

 

Opened support ticket and waiting for reply. Just wonder if the users here have any suggestions other than that?

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Thanks .... will have another look inside today.

 

One would think with a power light failure that it would be the line fuse, but not the case here.

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stumblinman, on 05 Nov 2014 - 09:09 AM, said:

snapback.png

 

There are two fuses on the back of the DT25. One in a round receptacle labeled tube protection, and another directly below the power plug.

 

 

Can somebody tell me EXACTLY where to find the DT25 Tube Fuse? I can't for the life of me see it?

 

1) I know the Line Fuse is ok, (update, not true, the line fuse was blown) visually and continuity check.

2) I know that power is coming into the AC socket appropriately

3) I know the power switch is working (continuity check)

 

I have no power light. The amp is dead as a door nail (technical term). L6 Support Ticket says it has to come in for repair. It is post the "power transformer issue" that previous DT25's were experiencing (i.e.: no recall warranty).

 

I am thinking that the Tube Fuse (if I can find it) will be my last thing to investigate before sending it in? Everything inside the amp chassis looks pristine. No visual evidence of anything burned. It feels like a fuse issue and I am not sure the Tube Fuse would cause the entire amp to go out ... but ....... 

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I don't know about the DT25 but there is a fuse in the DT50 near the Power Tubes on the PCB.

 

Tube%20Fuse%20DT50.JPG?psid=1

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I can't see anything like that on my DT25 circuit board around the tube socket locations (like your pix) or anywhere else?

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there is a fuse built into the power receptacle.  small rectangle just below where the plug goes in.  See pic below.

$_35.JPG

the other fuse is in the round holder right above the power receptacle.

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Radatats ... YOU DA MAN ... although you did say this before, I just didn't get the deal with the power receptacle until I saw your pix .... DUH !!!!

 

... and now that I look again I see the fuse in the tube holder (which I thought was the Line Fuse) CLEARLY says "tube protection" ... I am an idiot.

 

The fuse in the power receptacle was clearly blown. YAY ! Now to find the replacement.

 

The receptacle fuse says T2AL250VP. It is quite small. What indication determines the physical size?  I am assuming this is a 2A/250V slow blow?

 

The Tube Fuse is large, says 375ma/250VP (not sure what the "P" means? and not sure what indicator determines the size?

 

Can you guys enlighten on this??

 

Also, I noticed all 3 tubes have what I would call "heat stress" on their tops ... quite black inside, so I think it's time for replacement?

 

Lastly, in my panic to see things more clearly I pulled two plugs from the bottom plate circuit board, the 3 prong plug can go into one of two sockets marked H15 120/240 and the other H16 100/220. My line voltage here is about 110-117 (Canada) so I am assuming the socket I need go back into is H15??? would one of you know??

 

Radatats ... again thanks ... Brazzy too.

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If you need new tubes, a bias, and a fuse... i'd just take it to the shop... because it's a possibility that the transformer is having issues....

when it happened to my DT50, i replaced the fuse a few times... and there was definitely other issues... ended up being transformer in my case...

 

i believe that the "P" means slow blow.... but it's been a while since i tracked down the fuse... so not 100% certain.

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Here's some info on the fuse:

 

http://www.marshallforum.com/marshall-amps/9265-full-description-fuses.html

 

I had a similar issue a while back and got some replacements from a local Radio Shack:

 

http://www.radioshack.com/2-0a-250v-5x20mm-slow-blow-glass-fuse-4-pack/2701064.html

 

And yes, you should use the H15 connection.  That's what my DT50 is connected to (I'm in the states).

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I'm pretty sure the T means Timed or slow blow, 2amp, 250 Volt Protection.  Radio Shack should be able to replace your fuses with exact match.  As far as tubes, it could well be.  If you know what you are doing its not that hard to change and bias but like Zap says, there may be other issues at this point...

 

http://line6.com/support/topic/3327-dt-50-25-tube-biasing-tips/?do=findComment&comment=21863

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Thanks Zap ... unfortunately I live remote and "taking it to the shop" is a pain in the lollipop, in fact we are still trying to find out where "the shop" is? Line 6's Authorized Service Centre site brought up 2 locations somewhat near me that have been out of business for over 5 years and the 3rd one I called didn't know if they could actually do "out of warranty service" ???? The Canadian distributor is still trying to answer my questions on this deal about service. So "the shop" in my case is a bit of an enigma at this point.

 

I can do my own biasing no problemo. Line 6 Support says my series of DT25 is post the transformer problem (but of course it could be something else with this xformer). I will try the fuse replacement route first, then if it keeps on blowing them I'll send it in. Gotta try some other home remedies first. Sending it out will be both expensive and a loooooong wait I am sure. Good thing I still have my SV MKII 212.

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Sorry I didn't see this earlier. Chances are it was a bad tube that took out your mains fuse. New tubes and a bias should make you right as rain. Second post with this problem within a couple weeks. Weird.

 

Glad you found the other fuse :)

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Mild follow up ....

 

First ... thanks RP for the fuse info, much appreciated, and also the H15 tip (I thought so too).

 

The local dealer has line fuses in stock so will pick them up when I go to town next (I live a bit remote). Also ordered a new set of tubes just in case.

 

This event pretty much solidifies that I'll be keeping my SV MKII 212 for backup. I have always liked that amp. It is really great that you can plug the POD HD in the rear chassis insertion point and it is before the master volume (which isn't the case on the DT amps as the insertion is after the Mstr Vol).

 

Also, this event is now pointing the finger at exactly where my options are for Line 6 out of warranty service .... which I have now found in my area. L&M has a new Service and Wharehouse Centre in Delta, BC but you have to send your amp there via a L&M store, you can't go direct (my understanding anyways) for those of us on the west coast of Canada.

 

Does anyone have an online source for the 375ma / 250A - 30mm slow blow tube fuse?

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Yes I am having a very difficult time finding them also. Still searching online.

 

The actual fuse stamp says  .375ma/250VP

 

Back of amp says TO.375AL / 250V Slow Blow

 

​Since I have a Support Ticket open I have also asked them but not heard back yet (wanna bet they say "ask your certified service centre for them"?)

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I hear ya on the "hard to find". I'm finding that things I used to have an easy time finding years ago are now not so readily accessible. If you buy these things get more than one, lol. :)

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I contacted the vendor and is seems that those fuses on eBay are NOT 375 ma but he is trying to find them so at least someone is on the case.

 

Update: After checking into it further the Vendor confirmed that these were 375mA.

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Excellent Radatas ... thanks.

 

It seems everybody has the line fuses. They are very common and the music store had them in stock (I got 4, still to pick up) .... the Tube Protection Fuse we are discussing of course is another matter.

 

I have sent a detailed email to Mouser (Canada)  including the amp spec for this fuse plus pix of the actual fuse itself so they can confirm exactly what product number it is ... then I order either from them or the eBay guy when we responds back (I sent him the same information as well).

 

I am assuming that this fuse rarely blows or we would have had this discussion before this. It is a bit weird that is has been so difficult finding it but once I do, then all will know. I also asked Line 6 on my Support Ticket where to source this fuse ... waiting for them to reply.

 

.... and Brazzy .... you can be ASSURED that I will order more than one ... lol !~!

 

Last note: ... We no longer have Radio Shack in Canada, they sold out and became "The Source". I called the store in town about this 375mA fuse the guy said "no way, never seen anything under 1amp, try eBay, or Amazon" ... so there you go with that one.

 

Last note really: ... I still don't know why the Line Fuse blew in the first place. I use a high quality AVR. I did order replacement tubes and I can put my EH's back in (which have very little milage) to test when I get the Line Fuses, but somehow I don't think it is a tube related issue? Like Zap said earlier, it could be a "transformer issue". We'll see soon enough.

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.... and Brazzy .... you can be ASSURED that I will order more than one ... lol !~!

 

LOL, Maybe I better get some for my DT50 before I need them, oh wait but if I do that I won't need them, Hahaaa.

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Last note really: ... I still don't know why the Line Fuse blew in the first place. I use a high quality AVR. I did order replacement tubes and I can put my EH's back in (which have very little milage) to test when I get the Line Fuses, but somehow I don't think it is a tube related issue? Like Zap said earlier, it could be a "transformer issue". We'll see soon enough.

 

Nah, my money's on the tubes...

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Nah, my money's on the tubes...

 

Yeah the tubes can get weird. My originals went making me think it was something else like a transformer but then my mechanically oriented brain said wait I better get new tubes, learn how to replace and bias them. 1st rules of mechanicism "Always go back to the Basics" then systematically eliminate things by testing, if able.

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OK ... so your bets lay as follows ...

 

TUBES = 2 

Xformer (or something else) =  none?

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OK ... so your bets lay as follows ...

 

TUBES = 2

Xformer (or something else) = none?

Put me down for tubes. It isn't voltage that blows a fuse.

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OK .... here we go. (Line 6 Tech Support has yet to respond).

 

The actual Tube Protection fuse I have in my DT25 (375mA/250V Slo Blo) is a LittelFuse 0313.375

Mouser Part # 576-0313.375MXP

Manufacturer: LittelFuse

Manufacturer Part Number: 0313.375MXP

 

http://ca.mouser.com/ProductDetail/Littelfuse/0313375MXP/?qs=OJFHm2hVE4H0c833ETykqA==

 

The Bussmann MDL 3/8 is an equivalent.

Mouser Part Number: 504-MDL-3/8

Manufacturer: Eaton

Manufacturer Part Number: BK/MDL-3/8

 

http://ca.mouser.com/ProductDetail/Bussmann-Eaton/BK-MDL-3-8/?qs=KOeOmFnJLTq0cGO5NIGsxA%3D%3D

 

You can do a "comparison" on the Mouser site to see the specs side by side.

 

Now we know. They can both be found on the Bay. Go get em tigers.

 

Whew ......

 

I will update on the status of the amp once I replace the Line Fuse & tubes.

 

... and the current bets on the original problem that blew the Line Fuse are ....

 

Tubes = 3

Xformer = 0 (Zap thought maybe?)

 

BTW ... the tubes are Mesa's. Have been in about 1.5 years. Weekly rehearsals and about 12-16 gigs per year. So not out of line that one or both the power tubes pooched out to take the line fuse? I believe I read here on the forum that these EL84's run very hot in the DT25?

 

Thanks to all for your help and suggestions on this thread.

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UPDATE:

 

Picked up the replacement line fuses. Put one in and put the old tubes back in as I don't have the new ones yet. EVERYTHING WORKS. Had a short rehearsal yesterday and amp was fine. Checked tube bias and it was right on the money. This is not to say it won't happen again and not to say it wasn't something tube related? Need a bit more time with the amp to see if it is stable. Will put new tubes in when they arrive.

 

So, not sure why the original line fuse blew but at least I now know WHERE it is (lol) and I also know where to get the Tube Protection Fuses (ordered 5). I now have a small "spare fuse collection" for my L6 amps. I am very old school, I am used to fuses being located in fuse tubes on amps (similar to the tube protection fuse on the DT25). The line fuse integrated in the AC receptacle was a learning experience (I never thought to look there). Thanks to Radatats for showing the pix of that. I have now received a "modern line fuse location update" in my brain.

 

This discussion saved me from sending the amp in for service, which I might ad, would have been a royal P.I.T.A., expensive, and time consuming. They probably would have replaced the fuse like I did, some short bench testing and then out the door. Wonder what THAT would have cost plus RT shipping etc.? I am going to guess a minimum of a couple hundred with taxes?

 

I will update if anything happens with this amp in the near future. It has been rock solid since 2012 when I bought it. It was also nice to play through my old SV212 MKII again. I still really like that amp (except for the weight). I used a POD HD500 directly into the efx return on the back to bypass the front end. Sounded very sweet. I'll never sell it.

 

Many thanks to all for responding on this thread. You are a great bunch of people here.

 

Like the old saying goes .... "you can learn something new everyday".

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Cool glad you got it going again, although It can still be that power tube. They do weird things inside that glass while they're burning. Jam On!!

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Yes, but I am firm believer also that "sometimes "sh_t" happens for no reason" so hopefully that is the answer in this case, but I suspect you are right and it has some connection with the tubes ... however they will be replaced with new ones soon.

 

I will follow up after a couple band rehearsals with a status report on the amp's health. We'll see where this goes.

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Final Update,

 

Just want to wrap this up. After the Line Fuse was replaced and bias checked/adjusted on the tubes, the amp worked again perfectly and has continued to do so with no stutters. I have no idea why the fuse blew originally but I am thinking it might have been a "tube fart" (technical term) of some sort? At least I now have a complete set of fuses for all my L6 gear and know where to get those darn tube fuses for the DT25.

 

Lastly, this little experience made me get my SV212 MKII out again and I still enjoy that amp. It is a great backup to have and I have no inclination to sell it. However, my back goes into a panic attack every time I have to take it somewhere and "power lift" it up on the tailgate of my truck. My back really prefers the DT25 Head/Cab combination. I have actually tried running the two amps together (I have a A/B-Y switch) .... HUGE sound with 2 x DT25 112 cabs plus the open back 2 x 12 combo. I can be ONE LOUDER than anybody else in the band, which makes me king ... !~!~!~~

 

Thanks to all who responded to this thread.

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Lastly, this little experience made me get my SV212 MKII out again and I still enjoy that amp. It is a great backup to have and I have no inclination to sell it. However, my back goes into a panic attack every time I have to take it somewhere and "power lift" it up on the tailgate of my truck. My back really prefers the DT25 Head/Cab combination. I have actually tried running the two amps together (I have a A/B-Y switch) .... HUGE sound with 2 x DT25 112 cabs plus the open back 2 x 12 combo. I can be ONE LOUDER than anybody else in the band, which makes me king ... !~!~!~~

 

Thanks to all who responded to this thread.

 

Love it!! LOL Happy New Year!!

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Hi All, I recently had a tube go bad in my DT25.  It also blew the tube protection fuse.  I have a new set of EL84's JJ's that I am going to install tonight along with a new fuse.  My question is what is the proper bias voltage specification?  I know how to bias the amp and the safety risk involved, but I've found conflicting information about what the actual specific bias measurement should be.

 

Can anyone weigh in on this?  Thanks!

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Russgoos,

 

You may have a tough time finding those 375ma fuses for the DT 25 Tubes? I listed them a few messages back in this thread (2 manufacturers). I found a source for them on eBay.

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http://line6.com/support/page/kb/_/amplifiers/dt50dt25/dt50dt25-faq-r144

 

direct from the source:

 

Q: What is the Bias Spec on the DT50's EL34 power tubes?

A: 36 mV +/- 1 mV.

 

Q: What is the Bias Spec on the DT25's EL84 power tubes?

A: 25 mV +/- 3 mV.

 

 

Russgoos,

 

You may have a tough time finding those 375ma fuses for the DT 25 Tubes? I listed them a few messages back in this thread (2 manufacturers). I found a source for them on eBay.

 

TheRealZap - thank you for your quick and specific answer!  geppert - I used your link to the Mouser website to order replacement fuses.  Thanks guys!

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Looks like it's my turn to play this game.  I bought my DT25 head & 112 cab last July.  The original tubes didn't make it 90 days.  I replaced them with some JJ's, biased them, and everything was great until last week.  

 

After letting the amp warm up, I flipped the standby switch up and there was a Phhhhht sound and the lights went out.  I checked the fuses and the line fuse was blown.  I picked up some replacements from Radio Shack and put one in tonight.  The amp fired up normally but there was a really soft low hum.  Then I started to get that fried electronics smell and the tube protection fuse blew.  This time the light stayed on and I could see the tubes glowing until I shut it off.  All 3 tubes were glowing although the ECC83S (12AX7) wasn't glowing as brightly as the other two (not sure if it's supposed to or not).

 

So I'm not sure what to do.  Obviously I have to replace the blown fuse.  I'm not sure how to test the tubes to see if they're okay and their appearance is normal.  I guess there are 4 options:

  1. Replace the fuse and try again (probably not the best idea)
  2. Open a support ticket and send it in since it's under warranty
  3. Try to figure out how to test the tubes and see if one of them is the culprit
  4. Replace the fuse and the tubes (there goes another $50)

Any advice?

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Any advice?

 

Open a support ticket and get ready to send it in.

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