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Eden WT400 heating problem. Help!

Nenor

Nenor

Feb 9, 2003
1,313
738
#1
I've noticed lately that my WT400 head seems to be over heating more then usual. After working for a few minuets, even at low volume, the upper part of the head (right near the on/off switch and the vent) gets really warm.
I took a look inside and noticed burning signs on the circuit board around two little white blocks (photo attached). These two blocks get very hot.
The amp works fine.
I wonder if this is normal. The amp is from 1993.

I have tried to contact Eden through their customer service a few weeks ago but with no reply.

I'll appreciate any help/suggestion.
 
#4
The white blocks are resistors. Normally when they go bad they go open. Meaning what ever they are connected to will stop working. Very seldom do they just burn up especially the ceramic ones. Pull the board out and see what they are connected to. If it is your fan, you may have a few shorted windings in the fan motor. That will overheat the resistors like that. Once you find your problem (if you can) replace the resistors with new ones. My experience tells me when they overheat like that they go out of spec.

Also check that diode that the right most resistor runs into. Go on google and get a data sheet for it (use the numbers on the diode) De solder it and check it. It has been stressed just as much as those resistors have.
(Diode looks like it has a metal "tab" on it. Says D something next to it.
 
#5
Thanks for your notes.
Fan is fine. I actually used the amp in a recording session a few weeks ago in which it was switched on during a long session, maybe 8 hours. The fan went on and off automatically (which surprisingly didn't really go into the mics...)

Bassmodder, thanks for the detailed explanation! I will take a close look at all your comments. Do you have any idea where can I get those components online, if I need to?
 
#6
As has been stated above the blocks are power resistors. It is quite normal for them to get hot. Notice how they are mounted above the PCB to allow for cooling. If the fan is running freely check if the cooling tunnel is in any way clogged with dust and vacuum it out if it is. By your last post I would think that the amp is fine, vacuum it out any way and put it back together. Make sure all inlets and outlets are clean and clear.

Paul
 
#7
Update:

Thanks Paul for your input.

I did some additional search and found I'm not the only Eden user to encounter this problem.
Apparently these resistors do get very hot during operation. After a few years of use, depending on actual working time, the resistors solder joints melt, causing loss of power to the circuit. This result in all kinds of malfunctioning.
I took the circuit board off and went over the joints resoldering them. Now, all preamp knobs suddenly perform as new - no crunching sounds or any other knob-age-symptoms that did exist before this operation.

here are two links about that:first + [Invalid or Expired Link Removed]

Thanks again for the help. I hope my problem ends here, this one anyway :D
 
#9
nenor said:
Thanks for your notes.
Fan is fine. I actually used the amp in a recording session a few weeks ago in which it was switched on during a long session, maybe 8 hours. The fan went on and off automatically (which surprisingly didn't really go into the mics...)

Bassmodder, thanks for the detailed explanation! I will take a close look at all your comments. Do you have any idea where can I get those components online, if I need to?
Click to expand...

I would try a local electronics store first. They look like 5 watters which are pretty common. Other than that maybe try your local hobby shop (they are used for the speed controller on electric R/C cars) or ebay. I get alot of chips and transistors from there because I don't have to buy 5000 of them at a time.
Makes my life easier when theres only two or three bowen.

Glad to hear you got it working.

Makes me wonder if you can not simply replace them resistors and JB weld the replacements to the chassis and run some solid core heat rated wire over to the board. Let the chassis absorb the heat instead of the board. I would do this if it were my amp.
 
#10
bassmodder said:
I would try a local electronics store first. They look like 5 watters which are pretty common. Other than that maybe try your local hobby shop (they are used for the speed controller on electric R/C cars) or ebay. I get alot of chips and transistors from there because I don't have to buy 5000 of them at a time.
Makes my life easier when theres only two or three bowen.

Glad to hear you got it working.

Makes me wonder if you can not simply replace them resistors and JB weld the replacements to the chassis and run some solid core heat rated wire over to the board. Let the chassis absorb the heat instead of the board. I would do this if it were my amp.
Click to expand...

Indeed, these are 1K Ohm 5 Watt resistors.
Your idea of removing the resistors away from the board is interesting but a little too much for me. I'll try first to get some new resistors to replace and see what happens.

Generally I'm not enthusiastic of bringing it to the Eden dealer here. There is only one in my country and they practically suck you out of cash while I don't trust them to be honest.

I'll check the fan direction. Why is it important, it's the same amount of air moving from side to side, no?
 
#12
bassmodder said:
Ok, sounds like a plan. Will probably run you about 5 US dollars for the new resistors if you feel like replacing them yourself. The joy of fixing it your self.
Click to expand...

Ya' sure, I really like to do what I can by myself. I'm not depending on this amp right now so I'm in no hurry too. I just hope I can find these resistors here, otherwise I'll have to order online from... somewhere.
 
#13
Those power resistors are responsible for dropping ~76V from the main power rails down to ~15V for the preamp section. They have to dissipate the extra power as heat. It is common in the older Eden amplifiers for the solder joints underneath these resistors to become intermittent and cause popping through the speakers as the power to the preamp circuit is interrupted.

It is sometimes necessary to either resolder or replace these power resistors as the amplifier gets older. I've replaced the 5W power resistors in my WT-500 with 10W versions in order to reduce the problem in the future. True, the 10W resistors still need to dissipate the same amount of energy, however, they do it over a larger area.
 
#17
JMH3 said:
If I were in your shoes and ended up needing professional help, I'd locate a good amp repair shop and bypass Eden.
Click to expand...

Good advise. I have dealt with their service center on three different heads - each of which was a huge pain and on two occasions, the product was not fully repaired. :hmm: Well, they said it was...but it wasn't functioning as it did when new. I sold off their products after that.
 
#18
12bass said:
Those power resistors are responsible for dropping ~76V from the main power rails down to ~15V for the preamp section. They have to dissipate the extra power as heat. It is common in the older Eden amplifiers for the solder joints underneath these resistors to become intermittent and cause popping through the speakers as the power to the preamp circuit is interrupted.

It is sometimes necessary to either resolder or replace these power resistors as the amplifier gets older. I've replaced the 5W power resistors in my WT-500 with 10W versions in order to reduce the problem in the future. True, the 10W resistors still need to dissipate the same amount of energy, however, they do it over a larger area.
Click to expand...

Thanks 12bass,
Can you elaborate a little on the different resistors you used? Is it also 1k ohm? If these work better why did they chose to use 5W to begin with?

I'm still not sure if my resistors operate on a normal temperature. They get very hot, very quickly - 20 seconds after switching the amp on I can't touch them.
 
#19
As I said previously, those resistors have to drop the voltage from the main amplifier level of ~76V to ~15V for the preamp. Doing so means that they have to dissipate the difference as a couple of watts of heat. So, yes, they do get hot.

I used 10W rather than 5W rated power resistors - the resistance remains the same. The 10W resistors still dissipate the same amount of energy, just over a larger area. Using a larger resistor with more surface area makes them a run a little cooler and should lead to less trouble with bad solder joints in the future.
 

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