eden wt 400

[blaise]

start by saying hello to everyone.
ok, i opened eden to fix input jack (acting up when the cable moves)
pretty dirty, no cold solder, no cracked board. just cleaned it.
looking it over, i found what i thought to be a repair, (just don't look right)
follow yellow jumper from swamping R. (those are probably not swamping resistors) not at output stage.
to a, x-istor. does this belong ?
anyone got one, to compare.
p.s. pv still going strong. thanks for that help.

[Mars Amp Repair]

Hello Blaise,
I can't say if that wire is 'supposed' to be there, but if the amp is working properly, I'd just leave it be.
the bigger problem these amps has is the overheating of all those 500ohm 5watt dropping resistors.
Does the yellow wire possibly jump some bad traces under the board? glen

[blaise]

there is some heating issues under one of the 5w resistors or at least the board is dark there. i'll post a pic of bottom.
the yellow jumper is only part of what i was wondering about.
it don't look like that transistor should be there.
their isn't even a drawing on the board for it, like all other components.
plus the way its mounted (not thru board)
i figure signal was weak at that stage so someone boosted it up.
but yes it does work. (i know, then don't fix it).
just curious ?
thanks for the heads up. i've got some heat sinks i could modify,
to possibly soak up some of that overheating issue.
i haven't notice any loud humming out of it, like some others have posted.
in fact i've been very pleased with it.
just full of nicotine, "yucky brown goo" in every orifice!!!
thinking about a filter in front of fan. don't want to overwork it though.

[Robert M. Martinelli]

Hi,
time ago I had to fix one for a fiend of mine , 't was a WT300; I know these amps have a good reputation sound-wise, but they're not up to the price tag they bring ( at least here ) IMHO....dropper resistors are the cheapest way to bring voltage to a desired level, still I would have expected to find something better than that in a high-end amp....or at least to find higher rating resistors to prevent them from overheating and possibly damaging the PCB too.

This is the same system used in way cheaper amps, like the Fender HRD ( and everyone knows about the reliability problems this practice creates ) so it's not a good design practice IMHO ( at least not in the price range Eden amps place themselves ).

I would advise you to replace those resistors with bigger ( power rating ) ones rather than putting heat-sinks on the existing ones.

( I usually throw away droppers and put voltage regulators in their place )

Best regards

Bob

[blaise]

yes, i will double the wattage rating on them. theirs plenty of room for something bigger. (cheap insurance)
any other upgrade suggestions.
I do agree they should not be in the price bracket they are in.
but i got a really good deal on mine. $1000.00 u.s. for the full stack, and being right down the road from montrose, mn. i guess i'm proud to have it.
as long as i can keep it working.
sound is very good, but this is my first hybrid amp.
one thing for sure, i replaced the groove tube it had, with a mesa12ax7. just to
hear difference, terrible idea. the GT really wakes it up.

[Mars Amp Repair]

I've taken to removing the dropping resistors & mounting them with terminal strips as shown in the attached.

I also upped the value of the resistors from 500ohms to 750ohms each.
See attached. Works good...lasts a long time glen

[Robert M. Martinelli]

Originally Posted by blaise

one thing for sure, i replaced the groove tube it had, with a mesa12ax7. just to
hear difference, terrible idea. the GT really wakes it up.

AFAIK Mesa used re-branded Chinese tubes, while GT ( now owned by FMIC ) used re-branded Sovtek tubes.....most people forgets that there are only five valve/tube factories left...two in the Russian Federation, one in China, one in the Czech republic and a last one in the Yugoslavian area, so whatever tube you're buying, it comes from one of these plants ( with the obvious exception of NOS tubes ). Don't know which sound you're after, but, if you like mellower tones I'd try a JJ, for some "raunchy" tones try a Sovtek, and, if you like crystal-clear, punchy highs, I'd go for a NOS Philips Miniwatt or Mullard ( a bit more expensive options, but after all it's just one tube, so it could be worth trying ).

BTW, Glen, now that's what I call bullet-proofing an amp, nice job!

Best regards

Bob

[blaise]

i typed out a whole long reply and it vanished into neverland.
basically said "great idea" will do that.
thanks.
also, to bob. am going with russian, and mullard. like you said "it's only one".
i think i can try a couple options. with out breaking the bank.

[Mars Amp Repair]

Hello,
referring to some of the issues these amps have, has anyone seen any of the newer WT-550's and has Eden remedied this dropping resistor issue in those versions? Thanx, glen

[blaise]

i finally decided to get in here and update everyone on the eden project.
lazy ? (yes)
busy ? (far too)

anyway, the pic is b-4 mounting the resistors to a heat sink.
i decided against changing the values, since i already had these
and theyr'e sit directly in front of the fan.
running nice and cool, wont burn the board anymore.
after that i just wanted to play, so i put it back together. (no pics of heat sink)
thanks glen. great idea !

i did have board issues where it was scorched.
had to jump some traces, replaced a couple resistors.
i finally tracked down a schematic, makes life so much easier.

[Mars Amp Repair]

hello Blaise,
I was wondering, what did you use to mount the dropping resistors on the chassis? I'm supposing since I can't see any terminal strips or anything, that you probably siliconed them there. That correct & did you experience any strong silicone smell when things get hot?

Thanx, glen

[blaise]

no silicone, i used two strips of stainless sheet metal bent into a c shape
one under the resistors to keep them up, and one over, to hold them down.
then they have ears bent over, to bolt it to the chassis floor. i then epoxied a finned aluminum heat sink to the top strip. resistors are just sandwiched in there.

next time i have to take it apart, i'll get pics.
i also drilled a couple extra air holes right under them.

[Mars Amp Repair]

Pretty cool,
You can't even see the mounting from the pic. Looks real clean. Thanx, glen

[blaise]

uh, thats because this pic was taken b-4 the mounting.
but like i said, i will get pics posted next time i take it apart.
which will be soon.

[blaise]

finally opened it back up, just to look it over and
make sure all's well.
so here's what it looks like with resistor mod.

[Mars Amp Repair]

Looks Great! glen

[blaise]

thanks,
i still like yours better.
but i was working with what i had laying around.
it works good, they stay plenty cool .

[Amp Kat]

May also be agood idea to change the filter caps while you're in there as I've seen some go bad from the heat generated. Almost everyone of these I've seen has had a power supply failure as the problem.

[tedmich]

since I don't like adding long leads and drilling into chassis I tend to put in some Caddock thin films; they are TO-126 with ceramic pads, a 15w rating and short lead spacing that works on the board. They stick up enough to get the heat away; a piece of Al can be bolted on if needed too.

They are $3 each though, and only up to 1k.

[blaise]

i tested all p-sup caps they all checked out good
within tolerance and hold charge well.
but i have some quality 220v 6800uF, in the event that i should need them
i found a bunch of them at a local surplus for .25c apiece.
i grabbed 20 of them.
oh and tedmich, i had a couple of those in my parts bin that were unreadable
i always assumed they were a diode, but a quick continuity check proved that wrong, so i measured res. they are 27.5 ohms (strange) musta been some
milspec application or something. but now i know what they are.
this style would have worked nicely in my application.