Bottlehead Forum
Bottlehead Kits => S.E.X. Kit => Topic started by: proud indian on March 20, 2017, 03:59:18 AM
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I was going to post my c4s problem amd saw this thread.
Well, my c4s is eating led's. Every six months or so one channel led will go bust and that channel will stop working. I ordered a set from BH and got 4 of them. Now I am down to one. I have changed tubes.
On the rear of the board, where a " jumper" Wire is, there is a discolouration.
Any suggestions. If it matters, I am on 240v.
Shreekant
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Can you post a photo of your SEX PCB?
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Ok. Will do that later this week.
Thanks,
Shreekant
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Hopt I got it right.
Shreekant
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What's your line voltage? What voltage is your power transformer rated for? Are the 8.2K resistors in place?
Those resistors are charred because there's too much B+ across them. Having used many of that exact resistor across the exact voltage that's supposed to be present in the kit, that amount of discoloration is almost certainly an indicator of too much available voltage.
-PB
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Do you mean my voltage at the wall outlet...... if so, it is 240v, which is the transformer I requested for. The 8.2k are in place.
Shreekant
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Checked the voltage, they are bang on. No problem there.
Shreekant
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I have the same problem. Running 125 v. The left channel went out about three weeks ago and I have been unable to find the cause. Only my resistors on the B side are blackened.
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As you can see both 150 resistors are fried. Only the 499 on the b side is blackened(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwww.pbase.com%2Fmordicai%2Fimage%2F165195657&hash=e75d51b5ec31df2a2343632b9cb5bb82565caa57)
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http://www.pbase.com/mordicai/image/165195657
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Can some knowledgeable people suggest something?
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My sex has been down for three weeks. So far unable to find the problem, and seem to be losing the incentive to try. My voltage at OA is 66; OB 56. Don't know if thats excessive or not. Of course thats with 125 line voltage. When yu loose a channel does it first click on and off for a while, or just quit allot once?
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I'm looking into a possible issue - more later, if it pans out.
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I get a popping sound and then the channel goes dead. If I turn it on again after some time, like a day or so then it plays normally for about 20 mts and again the popping sound and a dead channel. After afew time it finally dies.
I flip it over, change the led and I am good to go again. This lasts for about six months.
I have put in a servo stablizer to ensure a proper 240v.....just in case voltage was a problem.
Shreekant
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That is exactly how my Sex acts!!! On, then pop off, then on, then pop off and no more on. The difference is that all my LED's are lit up and when I take to the work bench, flip it over, hook up power, a source and some phones it plays just great except to a brief pop now and then. I'm wearing out a chopstick looking for the offending gremlin.
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We are going to discuss this when we all get together later today. It's bit of a conundrum since these amps were packed a few years apart and we don't have any other, similar cases to add to the knowledge base.
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Thanks for the effort Doc.
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How do the resistors measure?
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The resistors are right on. 150, 151.......499, 499. Everything else looks bright and shiny. Not quite sure how to measure the other two sets of resistors.
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I am travelling, hence unable to check. But I do remember that all the valus matched what was given in the manual.
Shreekant
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Mordicai, which country do you live in, since you mentioned 125v.
Shreekant
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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.
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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!
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Thanks for the heads up Paul
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Thanks Paul.
Shreekant
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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!
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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
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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.
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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
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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.
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Like I said earlier, my dedicated music room is air conditioned and is set at 26°C. So that would be my room temperature.
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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
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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.
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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.
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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