eden wt 400 power board

[carlos1955]

Hi

need some help fixing a eden wt400 power board....it had a humming sound really loud when the power board was plug and all of the amp stopped working... so I change a new nte59 since one of them was missing and I had a resistance (0.47) that was not working anymore so I plugged it back and the hummm is still there and the new resistance was hot like hell.... I check all of the caps on the board but they all seem to work... any clue anybody?? should I change both nte59 and the nte58 to ? could it be the problem ? the only thing I didn't check was the zener diode since I don't have the tool to check !!

I posted pics with was has been made on it as far as it go's

so in red is the resistor than was broken that is know heating up

and in green is the nte that was missing

[52 Bill]

... any clue anybody??

Yes, there are two transistors missing from the board. See the two silpads in between the two power transistors? Two TO-220 sized transistors mount to the heat sink right there.

Find a copy of the schematic and find out what else is missing.

[carlos1955]

ahhhhh thanks 52 bill

I tough something was missing there but I can't find the schematic do you know where I could get it ?? or what value transistors go there ???

[J M Fahey]

Here:


1) Build and use a bulb lamp limiter, or you'll keep burning expensive components
2) disconnect that speaker *now* or you'll kill ot
3) get a reputable supplier (Mouser, Digikey, etc.) and buy original parts as shown in the schematic.
NTE are expensive and often not an exact replacement.

[Jazz P Bass]

DigiKey has the correct output transistors & drivers:
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Make sure you check the big cement resistors.
They may go open in a failure.

[carlos1955]

ok so i've reworked the bord and again still that humm and when it's plug-in everything on the amp stop including the fan.... I noticed the 2 wires (in the picture) are these supposed to be there ?? I changed the 2 nte59....but I didn't changed the 58 could it be this ?? i'm new to this so sorry for all the question but I would really like to fix it without going to my tech !

[Enzo]

DO NOT CONNECT A SPEAKER UNTIL YOU KNOW THE AMP IS NOT MAKING DC VOLTAGE. You will destroy your speaker.

[Jazz P Bass]

You need to take a few basic voltage measurements so you know what the amp is trying to do.
Base of the drivers & output transistors is a good place to start.
And are the power supply rails up to snuff?
They should be the same voltage (opposite polarity) & free of Vac ripple.

[52 Bill]

I'm missing something here, do you have the correct schematic for this amp? Exactly what model number is it? If you contact Eden, they normally will send you the correct schematics.

The schematic that JM posted doesn't look like the same amp, too many output transistors and the wrong types.

[oc disorder]

52 Bill ~ following this from a distance I thought that too until I saw the underside photo in post #6 with some "low slung" transistors !

carlos1955 I'm not sure if it's a good idea to not take this to a competent tech.

The wires you are referring to go to a thermal switch that activates a mute circuit when the transistors get too hot !
It is shown in the bottom left hand corner of the schematic Juan provided.

I'm more concerned (although I stand to be corrected) that the output transistors are in the wrong positions. (photo 2 post #6)

The 2SA1494 (PNP 200v 17A) you have replaced with a 2SA1216 (PNP 180v 17A) which is probably within the ball park
but as the schematic shows both bases are connected to the emitter of TIP32 and I would have thought they
would both have to be mounted to the left side of the board top and bottom !

Likewise the 2SC3858 or 2SC 2992 (comp to 2SA1216) bases should both be connected to the emitter of TIP 31
on the right side of the board. (Left and right refers to your 2nd photo in post 6.)

The emitter of a TIP transistor is the right pin facing the front of the transistor and the base of the 2SA/2SC Sanken's
is the left pin facing the front of the transistor.

So again from the diagram both the bases and the collectors of the Sanken's of the same numbered transistors
should be connected together.

From the photo I cannot see how this can be so !

[52 Bill]

52 Bill ~ following this from a distance I thought that too until I saw the underside photo in post #6 with some "low slung" transistors !

Yes, what threw me was the fact that the output transistors on the top side of the board were both the same types.

[carlos1955]

oc, thanks for your explanation and I think i'm gonna follow your advise and go see my tech...I'm maybe too newbie for this...gonna stick to basic's and keep on learning....tough that with all the guitar's I worked on and pedal I could tackle this one but might be more than I can chew...you guy's are great you really know your stuff thanks for your help and explanation

[carlos1955]

Ok guy's being hard headed I went back to recheck everything and took the time to read oc's explanation and made all the change's to the amp....now i've got sound and it's alive !!!!!!!!!!! the only thing is there is distortion in the sound.... it's not the bass or the cab and not the tube i've cleaned all the jacks and the knobs to including the fx loop in the back... any tough's ?

[52 Bill]

... any tough's ?

Crossover distortion? Did you bias the amp after you replaced the parts?

[carlos1955]

Y'a I did but I think there's a transistor that,s shot on the power board could it be that ?