#1
I have an original Fender Blues Deluxe from '93 that has been giving me some problems for quite a while now. After asking around and posting on many forums, nobody could give me a good suggestion. All I heard was "check your grounds" and "check the solder joints." All of that stuff was perfect. So, just the other day, I found my answer in physics class of all places. There is a bad capacitor somewhere. Does anybody know 1) how many capacitors are in this thing and which ones are most likely to be bad and 2) is there somewhere I can just get a kit that comes with a full set of capacitors so I don't have to order each one individually?
#2
I think it'll be your flux capacitor
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#4
Its a buzzing sound that gets worse as I turn it up. Which is consistent with a capacitor having a path through the dielectric.
#5
Your description of the problem getting worse as the amp is turned up tells me the issue is before the preamplifier circuit. A buzz or a hum can come from a couple of different places. A bad capacitor in the power supply section can also cause a hum, since it allows unfiltered DC to pass. A bad capacitor in the preamp section could also cause a problem, which would get louder as you crank the knob. Since you describe it as more of a buzzing noise, I'd recommend looking for a loose or missing ground - most likely at the input jack of the amp. Is this a tube amp or solid state?
#6
Yep, there are at least 40 some odd caps, I think, so if anyone knows which ones are the most likely to need replacing, that would make things much easier.
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#7
Does it buzz when you don't have a guitar plugged in?
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#8
Quote by KG6_Steven
Your description of the problem getting worse as the amp is turned up tells me the issue is before the preamplifier circuit. A buzz or a hum can come from a couple of different places. A bad capacitor in the power supply section can also cause a hum, since it allows unfiltered DC to pass. A bad capacitor in the preamp section could also cause a problem, which would get louder as you crank the knob. Since you describe it as more of a buzzing noise, I'd recommend looking for a loose or missing ground - most likely at the input jack of the amp. Is this a tube amp or solid state?


It's not a loose ground, and it's a tube amp.
Feel free to call me Kyle.

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#9
It only buzzes when I play with the volume above about 4. And, it is a tube amp, KG6. I'm not sure if you read my first post or not but all the grounds are good, that is not the problem.
#10
Since it's a tube amp, there are two possibilities. The first is it's being caused by a tube, especially if the tubes are several years old and have seen a lot of use. The other is that the power supply filter caps have been dried out from the heat generated by the tubes. An amplifier produced back in '93 is probably a good candidate for a capacitor job. If you know electronics, are familiar with soldering and fixing things, then it's fairly easy to do it yourself. If you don't know one end of the soldering iron from the other, this is no time to experiment on your amp. Keep in mind these tube amps use high voltages to operate and the caps will store these voltages, especially if they don't have bleeder resistors, or the bleeders are open. Best bet is to refer this job to a qualified amp technician.
#11
The tubes are all brand new. My friend (the threadstarter) and I are perfectly capable of changing caps, he's just curious if there's a way to figure out which ones to replace to keep from replacing 40+ caps.
Feel free to call me Kyle.

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Just so you know, I read everything you type in a Mike Rowe from Dirty Jobs voice.

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I mean in Kyle's case, it is in the best interest of mankind that he impregnate anything that looks at him funny...
#12
^Maybe start with the big filter caps? I don't know much but something tells me that a smaller cap going bad wouldn't cause as big of a problem as the larger filters going bad.
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#13
Yeah, you could be right.
Feel free to call me Kyle.

Quote by ibz_bucket
Just so you know, I read everything you type in a Mike Rowe from Dirty Jobs voice.

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I mean in Kyle's case, it is in the best interest of mankind that he impregnate anything that looks at him funny...
#14
Quote by Kevin Saale
^Maybe start with the big filter caps? I don't know much but something tells me that a smaller cap going bad wouldn't cause as big of a problem as the larger filters going bad.


That is what I think, but I don't want to have to go through there changing them all out. And, I don't have a real good way of checking them at all.
#15
Yeah, i'd check the filter caps.

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#16
Maybe change one, test and if you still got hum change the next one. Maybe if you get lucky you'll only change 2 or 3. I don't know any way of checking caps so that might be your only option.
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#17
I'm not a big fan of shotgunning a repair job. Shotgunning refers to the replacement of several components to hopefully replace the bad one. If I was working on your amp, I'd use the schematic, along with a signal injector and oscilloscope to find the source of the buzz. I would concentrate on the preamp section, since this is where the error is going to be found.
I don't know how many caps are in the preamp, but there can't be too many. Without the proper tools and test equipment, it makes these jobs more difficult. I don't know if Fender sells a kit, but armed with the schematic, you could easily go to Mouser.com and order the parts you need. The chances are pretty good that your schematic may not match what you have sitting on the floor in front of you. I've seen that happen plenty of times. The manufacturer makes an improvement in their product, only to leave it out of the schematic.
Again, I would focus only on the caps between the input jack and the preamp stage with the volume control - that's where you'll find your problem.
#18
Quote by Kevin Saale
Maybe change one, test and if you still got hum change the next one. Maybe if you get lucky you'll only change 2 or 3. I don't know any way of checking caps so that might be your only option.


I could get an ESR meter but I don't know anybody that has one. One of my professors may, I haven't asked yet but, I've never used one and don't know exactly what to do if I get one.
#19
Quote by Kevin Saale
Maybe change one, test and if you still got hum change the next one. Maybe if you get lucky you'll only change 2 or 3. I don't know any way of checking caps so that might be your only option.



There are several different component testers out there that will test caps for value, ESR and leakage, but the price for the casual home hobbyist is too high. Sencore used to make a nice one - an LC-102 tester. I think they've since replaced it with something else, but even the old ones are just too darned expensive.
#20
^So pretty much what you're saying is that unless the ts can get a hold of a tester then "shotgunning" as you called it is the best choice?
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#21
Quote by KG6_Steven
There are several different component testers out there that will test caps for value, ESR and leakage, but the price for the casual home hobbyist is too high. Sencore used to make a nice one - an LC-102 tester. I think they've since replaced it with something else, but even the old ones are just too darned expensive.


I'm sure we can acquire some sort of tester. I'm definitely not planning on buying one but, we are in school for electrical engineering so I'm sure somebody could let us borrow one.
#22
or you can hang out wt colin. buy him a beer or something.

Jenneh

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#23
Yeah, if he was nearby, we'd have had this problem worked out a long time ago.
Feel free to call me Kyle.

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#24
sorry, i would have helped more than a bump, but i cant think of anything that might help. good luck tho
Jenneh

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#25
Feel free to call me Kyle.

Quote by ibz_bucket
Just so you know, I read everything you type in a Mike Rowe from Dirty Jobs voice.

Quote by tubetime86
I mean in Kyle's case, it is in the best interest of mankind that he impregnate anything that looks at him funny...