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DT25 sudden increase hum then pop no sound

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I have owned my DT25 for a few years now, and it has only seen light rehearsal use and the odd gig here and there. I haven't used my DT25 in a few months due to the lockdown and no rehearsals allowed. I went to try it out on Friday. I switched the power on, with the standby OFF, and noticed that it had a louder mains hum than I remembered, I let it warm up for a minute or so, then flipped the standby switch on, immediately the mains hum increased in volume almost as if someone was rolling the volume up to maximum, ten there was a slight whistle and crackle, followed by a pop or phut, and then no sound.  This happened in a few seconds.   All the lights were still on, the topology lights swapped when I moved the switches but no sound whatsoever. Switching it off and on made no difference.  Just lights but no sound.  I tested using both guitar directly in and HELIX LT via L6 LINK.  No sound.

 

I checked the fuse that is mounted on the back of the chassis and it looks intact BUT there looks like there are black marks on part of it and a tiny black burn mark dot on the glass.  I think its blown.

 

I suspect that some part has failed and the fuse has blown protecting the amp, so I don't think simply replacing the fuse is a good idea.  I think it needs to go in to an authorized repair centre to be checked out and very likely repaired.

 

Just wanted to check on here if anyone else has had a similar problem and if so, what it turned out to be?  And could it be repaired?   Thanks.

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Should be one panel fuse.

When was the last time the tubes were changed out?

Are they the specified factory tubes?

 

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42 minutes ago, psarkissian said:

Should be one panel fuse.

When was the last time the tubes were changed out?

Are they the specified factory tubes?

 

There is just the one fuse on the back panel on the left hand side. It looks intact except for the black marks at one end and the black scorch mark on the glass.

Can't remember exactly when I had the tubes replaced but I believe they were the factory specified tubes.  I am a hobby player so it doesn't get a great deal of use.

I have taken it back to the repair shop that did the tube replacement for me last time and they are going to take a look at it for me.

 

The tubes all looked OK after the problem - they were glowing as usual and didn't seem to have blown. In fact all the lights were on and working and responding to the switches - just no sound.

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Fuse is done.

The lights mean that the main board is good.

Can't tell a tube by it's looks. Good that it's going to get looked at.

Make sure the repair shop is Line 6 authorized. Most techs aren't familiar with the quirks in these.

The only techs I call give advice to are the L6 authorized ones. They have access to service docs

support and me, others don't. There is a post bias test to be done, and only L6 authorized have access to that document.

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20 minutes ago, psarkissian said:

Fuse is done.

The lights mean that the main board is good.

Can't tell a tube by it's looks. Good that it's going to get looked at.

Make sure the repair shop is Line 6 authorized. Most techs aren't familiar with the quirks in these.

The only techs I call give advice to are the L6 authorized ones. They have access to service docs

support and me, others don't. There is a post bias test to be done, and only L6 authorized have access to that document.

 

Thanks psarkissian.

 

Do you have a list of UK Line 6 authorized service centers that you could send me or point me at?

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E&M in Milton Keynes, near Blechley and Oxfordshire.

 

Mark Wright Music isn't officially authorized as far as I'm aware, but he was my opposite number

at Line 6 Rugby, when we had a location there. He knows this stuff as well as I do.

 

https://line6.com/find/service_center/

 

... would have the current list.

 

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Thanks for the information psarkissian.

 

Unfortunately, I don't live near either of those recommendations, and my local repair shop are not on your list so I guess they are not authorized Line 6 repairers.

 

They changed over the tubes for me last time, so reading between the lines, there is a possibility that they did not perform the tube swap and biasing exactly to Line 6 specs and that may have contributed to the failure that I have just experienced.  So, I guess there is also a possibility that they may be able to get things up and running BUT if they haven't done all the Line 6 specific processes that perhaps my DT25 could fail again.   Is that correct?

 

Or is there a good chance that all will be OK?   

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Mark Wright is in Northampton and knows this amp series really well.

 

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15 hours ago, psarkissian said:

You're near Glasgow?

 

 

No - I am about an hour east of London  

 

Northampton is probably at least 90 to 100 minute drive from me.  It's about the same distance as Milton Keynes.

 

I can look Mark Wright Music up on Google.

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:)

Great. Was going to drop that in there too, but figure FB was quicker.

Had a problem trying to link to his website though.

 

Cheers.

 

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10 hours ago, psarkissian said:

https://www.facebook.com/MarkWrightMusicdotcom/

 

A bit of drive. Milton Keynes is a smidge closer. Have a friend and colleague, a Professor Emeritus

at Uni of Essex in Colchester. Runs the Audio Research Lab (ARL) there. A top flight guy.

 

 

True.  That's interesting - what a small world.  Colchester is about an hours drive from me too.      :)

 

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Quick update.  Just got my DT25 back from repairers. They say they fitted a new matched pair of EH EL84s, biased in and soaked as per service manual. They left it on without issue for a day.  They didn't see any other procedures in the service manual that were relevant to fitting new tubes.

 

Am I good to go - or do I need to get the amp checked out by an authorized Line 6 service center?

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On 7/7/2020 at 11:11 PM, psarkissian said:

:)

Great. Was going to drop that in there too, but figure FB was quicker.

Had a problem trying to link to his website though.

 

Cheers.

 

 I messaged Mark on both FB and LinkedIn but he didn't reply to either message.   :(

 

 

Quick update.  Just got my DT25 back from repairers. They say they fitted a new matched pair of EH EL84s, biased in and soaked as per service manual. They left it on without issue for a day.  They didn't see any other procedures in the service manual that were relevant to fitting new tubes.

 

Am I good to go - or do I need to get the amp checked out by an authorized Line 6 service center?

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" They didn't see any other procedures in the service manual that were relevant to fitting new tubes. " ---

Bias and Burn-In documents for DT series isn't posted in the service manual. They can get it from me on request

or the Service Forum (for authorized techs). Letting cook for a day is good. Getting the procedure done is better,

as there are signal levels to check at the different topologies and output level checks.

 

You can have them do the checks if you like. It is better as it leaves little or nothing to chance.

Authorized techs are always good, they have access to the service manuals, service tips and me.

 

 

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53 minutes ago, psarkissian said:

" They didn't see any other procedures in the service manual that were relevant to fitting new tubes. " ---

Bias and Burn-In documents for DT series isn't posted in the service manual. They can get it from me on request

or the Service Forum (for authorized techs). Letting cook for a day is good. Getting the procedure done is better,

as there are signal levels to check at the different topologies and output level checks.

 

You can have them do the checks if you like. It is better as it leaves little or nothing to chance.

Authorized techs are always good, they have access to the service manuals, service tips and me.

 

 

Thank you psarkissian - how can they contact you?  You can email me the details privately if you prefer or communicate via my Line 6 account.   Thank you.

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Authorized service centers have a channel to me if they need to consult me.

Goes with being an authorized service center.

 

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3 hours ago, psarkissian said:

Authorized service centers have a channel to me if they need to consult me.

Goes with being an authorized service center.

 

Sorry - I got confused - in your earlier post you said "they can get it from me on request"  - so I thought that meant that my repairers could contact you directly and ask for the procedure details?

 

The local repairers are not the official authorized repairers in the UK.  I thought you knew that from my earlier posts. 

They told me they got the manufacturers service manual and followed the bias and burn in process from that but they didn't see any other relevant procedures to perform other than what would be done initial factory build. They said it was 80 pages worth of manual.  Anyway - do I need to now take it to an authorized repairer to get the final "procedure" performed OR am I ok just with the tubes changed to a matched EH pair, biased and burnt in?

 

Many thanks.

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I'd feel better if it were done by an authorized one who knows our product.

 

Don't know where they got their manual from, that number of pages doesn't sound right.

 

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