WT800C Meltdown

#21
Hopping onto this thread with a slight tangent - I posted a year or two ago about getting a WT800 fixed and hit a dead end. Is there a certified Eden tech anywhere in the USA? Depending on the cost I would love to get this thing working and not just serving as a brick.

EDIT - I've emailed Eden and will report back.
 
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#23
Thanks for the input everyone. We won't be throwing the amp in a dumpster or some kind of heavy metal shredder. If anyone has any ideas on why all power transistors in that circuit failed let me know. I'm leaning towards user error.
 
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#24
DrEvil said:
Thanks for the input everyone. We won't be throwing the amp in a dumpster or some kind of heavy metal shredder. If anyone has any ideas on why all power transistors in that circuit failed let me know. I'm leaning towards user error.
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That’s the whole point of forensic analysis. EVERYTHING else is a wild ass guess.

Sometimes, the damage precludes a definite cause.
 
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#26
DrEvil said:
Our bass player has a WT800C amp that he said he thought was running hot. We pulled the cover off to observe as he played it. A few minutes in, there was some pretty spectacular arcing between R27A and the speakon output (on the low out power amp side). Before this lighting show I noticed there was no heat being produced on that side. It seems that the power transistors were not operational beforehand. Checking them afterwards shows shorts between all legs. There are also several spots of heat damage on the board resulting in broken traces. Not sure if all of that is a result of the arcing. What I'm thinking of doing is replacing all burnt components and anything connected to any of the burnt up spots on the board, and bridging the traces with wire.

What I'm wondering is:
can anyone say what might have caused this? Maybe the amp has been run in bi amp and bridged mode at the same time in the past and some components finally failed. Or running bi amp with no load on that side? Or is it possibly an inherent problem with the amp?
Is it possible to get a new circuit board? Eden only deals with authorized service centers for parts like this. Meaning they won't help consumers working on Eden amps. How about recommendations for someone who can make a copy of the board?

Is there any issue using different types of solder together? I've been using Kester 63/37 rosin core. In removing a couple resistors from this board I found that my normal temp setting will barely melt the solder. Using different materials gets me thinking about galvanic reactions, corrosion, and overall bond compatibility.
Many thanks!
View attachment 4983969 View attachment 4983970
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the-office-ouch (1).gif


:)
 
#29
agedhorse said:
That’s the whole point of forensic analysis. EVERYTHING else is a wild ass guess.

Sometimes, the damage precludes a definite cause.
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I get it. Diagnosis and analysis and already knowing everything about an amp is the best way. For me, getting help with an unfolding case study from someone very familiar with the amp/condition would be a great way to build experience. Doesn't look like that's going to happen here.
 
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#31
DrEvil said:
I get it. Diagnosis and analysis and already knowing everything about an amp is the best way. For me, getting help with an unfolding case study from someone very familiar with the amp/condition would be a great way to build experience. Doesn't look like that's going to happen here.
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Already did this, you just haven't understood.

The bast way is for the person understanding the amp to understand how it works. There is no cookie cutter repair approach, the damage is different in most failures. My experience with this amp is that upon failure there can be a lot of collateral damage, but it's a bit like "which came first, the chicken or the egg?"
 
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#32
agedhorse said:
Already did this, you just haven't understood.

The bast way is for the person understanding the amp to understand how it works. There is no cookie cutter repair approach, the damage is different in most failures. My experience with this amp is that upon failure there can be a lot of collateral damage, but it's a bit like "which came first, the chicken or the egg?"
Click to expand...
 
#33
You can still get the parts you need to fix that power amp.

If you are qualified and ambitious enough to perform the rebuild...

I have found that it's most efficient to depopulate the entire board, test all components to see what got fried (to get a sense of what could have went wrong), repair/bridge any damaged traces and then reassemble the power amp with new replacement parts purchased from reputable suppliers (Mouser, Digikey, Newark, etc.). Since most of the parts are cheap, you are best off just rebuilding the amp with new parts instead of reusing anything and risk frying your expensive new power transistors. Get yourself some ChipQuik, flux, a really good desoldering pump and desoldering braid to minimize the risk of damaging pads and traces with your soldering iron while removing the old parts.

Digikey still has authentic 2SC3856's in stock.

https://www.digikey.ca/en/products/detail/sanken/2SC3856/3661813

For the 2SA1492, the only supplier with Sanken verified parts is chip1stop.com in japan:

Online Sales Check Stock ｜Sanken Electric

https://www.chip1stop.com/USA/en/vi...6&classLv=3&keyword=2sa1492&partSameFlg=false

You can find a copy of the schematic on Electrotanya:

Elektrotanya for electronics experts

Economically, this is probably not the best option, but if you really are dead set on fixing the amp....good luck!
 
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#34
I understood what you've said completely. The definition of help can be subjective I guess. Kind of like the difference between parsimony and wild ass guess. Oh well, good day.
 
#36
SNCpre said:
You can still get the parts you need to fix that power amp.

If you are qualified and ambitious enough to perform the rebuild...

I have found that it's most efficient to depopulate the entire board, test all components to see what got fried (to get a sense of what could have went wrong), repair/bridge any damaged traces and then reassemble the power amp with new replacement parts purchased from reputable suppliers (Mouser, Digikey, Newark, etc.). Since most of the parts are cheap, you are best off just rebuilding the amp with new parts instead of reusing anything and risk frying your expensive new power transistors. Get yourself some ChipQuik, flux, a really good desoldering pump and desoldering braid to minimize the risk of burning up the board with your soldering iron while removing the old parts.

Digikey still has authentic 2SC3856's in stock.

https://www.digikey.ca/en/products/detail/sanken/2SC3856/3661813

For the 2SA1492, the only supplier with Sanken verified parts is chip1stop.com in japan:

Online Sales Check Stock ｜Sanken Electric

https://www.chip1stop.com/USA/en/vi...6&classLv=3&keyword=2sa1492&partSameFlg=false

You can find a copy of the schematic on Electrotanya:

Elektrotanya for electronics experts

Good luck!
Click to expand...
Thank you! This is what I was planning on after seeing if an Eden service center is available to price an install with a new board. I figure components are cheap, why risk having something fail in a month or a year due to the damage here. Thanks for the links. I usually shop Mouser, Digikey, Mojotone, Amplified Parts or similar. I don't risk putting cheap ebay and amazon parts in an amp. Turns out it not going to matter now. Guy requested a return on reverb (purchased 2 weeks ago) and the seller accepted. He's being very cool about this situation. But thanks for the help anyway.
 
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#37
SNCpre said:
You can still get the parts you need to fix that power amp.

If you are qualified and ambitious enough to perform the rebuild...

I have found that it's most efficient to depopulate the entire board, test all components to see what got fried (to get a sense of what could have went wrong), repair/bridge any damaged traces and then reassemble the power amp with new replacement parts purchased from reputable suppliers (Mouser, Digikey, Newark, etc.). Since most of the parts are cheap, you are best off just rebuilding the amp with new parts instead of reusing anything and risk frying your expensive new power transistors. Get yourself some ChipQuik, flux, a really good desoldering pump and desoldering braid to minimize the risk of burning up the board with your soldering iron while removing the old parts.

Digikey still has authentic 2SC3856's in stock.

https://www.digikey.ca/en/products/detail/sanken/2SC3856/3661813

For the 2SA1492, the only supplier with Sanken verified parts is chip1stop.com in japan:

Online Sales Check Stock ｜Sanken Electric

https://www.chip1stop.com/USA/en/vi...6&classLv=3&keyword=2sa1492&partSameFlg=false

You can find a copy of the schematic on Electrotanya:

Elektrotanya for electronics experts

Good luck!
Click to expand...
Thank you! This is what I was planning on after seeing if an Eden service center is available to price an install with a new board. I figure components are cheap, why risk having something fail in a month or a year due to the damage here. Thanks for the links. I usually shop Mouser, Digikey, Mojotone, Amplified Parts or similar. I don't risk putting cheap ebay and amazon parts in an amp. Turns out it not going to matter now. Guy requested a return on reverb (purchased 2 weeks ago) and the seller accepted. He's being very cool about this situation. But thanks for the help
 
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#40
DrEvil said:
Ha that's funny! But take a look at the circuit. There's no magic there. I offered 3 ideas for a cause and asked for input and keep being told 'You must learn the amp Daniel-son' lol.
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And your question was:

"What I'm wondering is:
can anyone say what might have caused this?"

And the main answer was, it could be several things, without doing the forensics, who knows.

At least that's what I got from the discussion.

:)
 
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