SEX C4S Question

Shreekant, Im in San Diego, USA. I bet those v Caps sound nice in the Sex. I went with Mundorf SO and Jupiter copper foil. V Caps are going in my nest kit. Probably the Mainline. Didn't mean to hijack your tread, but are problems  seem to be the same, so I think it will work out. Ordered sone LED'S from BH this morning and will install them in the Sex even though the ones in there are lit. Running out of ideas. Not happy about a hot C4S.
 
Just a bit of re-assurance here - we are looking at some possible approaches to resolving this issue. Had some good discussion at (and after) the club meeting on Saturday. Stay tuned!
 
I was able to get my left channel working by resoldering the MJE5731A, Played great for an hour or two and then the right channel quit.  Definitely a paranormal event!
 
proud indian said:
Looks like we will have  to live with a stock of led's, considering that we are unable to come up with a solution.

Shreekant
My problem seems to have been a bad solder job on the the center lug of the transistor. The lug is  to the heat sink and takes bit of solder heat to get the lug soldered right. Since I fixed it I have had no problem with the amp. Why the resistor leads are burnt a bit I dont know. I live in the high desert and the temps in the summer get bit warm. Since you are in an air conditioned space thats not your problem. My LED's are not a problem. Hope you get it figured out.
 
High room temperature cannot fry a resistor.  I have never heard or experienced  it. A friend of mine feels it could be a bad tube and I have changed it. So far no problem.

Shreekant
 
proud indian said:
High room temperature cannot fry a resistor.
That's absolutely not true.  If your room is 20C above what would be considered "room temperature", everything in your amp is going to run that much warmer.  This will be especially rough on electrolytic capacitors, but a resistor that's case temperature is 100C at an average room temperature will now be that much warmer in a hot room.
 
There are more than a 1000 views and still I havent got a solution to this problem,  unless I am to assume that the temperature is the sole cause. Need some reassurance.

Shreekant
 
I have nudged the guys again to come up with a suggestion for this. I do wonder about the overall condition of the tinning on the pads on the PC board. It seems oxidized. Did you wipe the board with some sort of solvent, perhaps? The condition of the pads makes me wonder if there is a conductivity issue between the resistor leads and the pads they are soldered to. The resistor bodies don't look cooked as much as the solder joints do. You might just try reflowing those resistor connections.
 
I think temperature is only part of the cause for failure, seems that everything works after you have re-soldered in a part.  What kind of solder do you use?  Are you adding flux?  Something seems common to all your solder joints oxidizing and if the boards are all common the unknown is the solder material you use.  I'll share your board pics with some of the guys at work, they do a lot of inspect and review of this type stuff.
 
I have soldered it more than 4 to 5 times as that is the number of led's that I have changed. Every time the led is changed, I check the joints and reheat them.
As of now, it is playing fine, and will continue to do so for a few months.. I have changed tubes.
To answer your question solder..... yes it has flux. I cant remember the type of solder, as I bought it off ebay. I thimk it was wbt.. it has a mix of silver if I recall right.
The amp is placed on isoblocks, on a maple wood slab, so it has more ventilation then with just the feet.


Shreekant
 
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