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#141 | |||||||
master hoarder
Join Date: May 2008
City & State: VA (NoVA)
My Country: U.S.A.
Line Voltage: 120 VAC, 60 Hz
I'm a: Hobbyist Tech
Posts: 10,010
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![]() Quote:
However, the problem with many of the cheap crap brands is that their leakage current can go high once voltage is applied. Well, that can happen to any electrolytic capacitor, really. But it just happens more to the cheap crap brands. Quote:
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However, because these caps are close to the heatsink and are exposed to heat, I'd suggest going with 105C -rated caps. GP 105C caps will probably be fine, but the Panny FR you have should be a nice treat, since those are quite reliable and long life. Quote:
In fact, I suggest getting as many of the caps replaced as possible, especially the ones in the hot areas. All the caps look like no-name cheap brands, and sooner or later they will fail. So probably a good idea to recap the working unit, too. Quote:
Just remember this: capacitors act sort of similar to very tiny tiny batteries in the circuit and as such, they don't like to allow sudden voltage changes across their terminals. So whenever something in the circuit tries to change voltage abruptly, the capacitor will smooth that voltage change into a more gradual one. When you add a resistor in series (in the case of C39, it's resistor R91 and C-E junction of Q2), the change of voltage across the terminals of C39 becomes even slower/"smoother". So this allows the amp to go more slowly between STB, Mute, and Play operation. Quote:
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![]() ![]() In all honesty, though, I don't know why you should care about that. Unless the unit has a clear window with lights inside pretty much begging people to stare... you're just not going to see the insides again. So IMO, you should put whatever cap brand actually does the job reliably rather than focus on the looks. Otherwise, if you want some really cool-looking caps, I have some bright-yellow CapXon KM caps from an Apevia PSU. ![]() Last edited by momaka; 11-14-2020 at 04:51 PM.. |
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#142 |
Badcaps Veteran
Join Date: Apr 2012
City & State: Niš, Serbia
My Country: Serbia
Line Voltage: 220VAC 50Hz
I'm a: Knowledge Seeker
Posts: 262
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![]() Momaka, thank you for this informative post and all the help, especially your patience, really from all of you. I must have asked all sorts of noob questions and thank you for making concrete, clear and wise input on them.
You are absolutely right, changing all the caps would probably be the best step. I was thinking about that when I had issues with my original working unit, but then somebody posted that they replaced all the caps and got weird voltages in some areas, so I was reluctant, especially since I managed to solve the problem. I guess in each build there is a bad cap and it's a lottery which area it's going to appear in. I will need to examine all of the caps on this PCB. Some are quite obstructed by other components and many are glued, all this hiding their ratings. And of course the looks is not an imperative, I'm just so happy we got this thing working again. I will order some other ratings of FR caps if I can find them on Farnell. Hopefully, I will find most of the caps values on those segments from the schematics. I will look tomorrow for some Panasonic 50V1uF caps and order them. Last edited by UserXP; 11-14-2020 at 05:17 PM.. |
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#143 |
Badcaps Veteran
Join Date: Apr 2012
City & State: Niš, Serbia
My Country: Serbia
Line Voltage: 220VAC 50Hz
I'm a: Knowledge Seeker
Posts: 262
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![]() Guys, just an update on this. The problem was definitively the C39 capacitor. I had Panasonic 50V2.2uF FR version, but I wanted to stay within the amplifier's specs. So since you mentioned it can be a general purpose capacitor, I found some Rubycon 50V1uF 105C 5000 hours YXF series capacitors on the local Farnell website and ordered them. I am delighted to say they have arrived and I have installed one today. The amplifier works great now and hopefully this cap will cope well with the heat the amplifier produces. The voltage on the mute pin now hovers around +13.72V in play mode, which is great! Thank you all so much, for identifying the part, and especially you momaka for your thorough and patient step-by-step instructions.
![]() Last edited by UserXP; 11-26-2020 at 09:14 AM.. |
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#144 |
master hoarder
Join Date: May 2008
City & State: VA (NoVA)
My Country: U.S.A.
Line Voltage: 120 VAC, 60 Hz
I'm a: Hobbyist Tech
Posts: 10,010
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![]() No problems!
![]() Rubycon YXF is actually one of the most entry-level low-ESR series, so it is better than regular GP caps. Better yet, it's still rated for long life (5000 hours for 16-100V rated caps in 6.3 mm dia. or smaller... and more for bigger caps), so that's actually a pretty good choice. Should replace the caps now in the good unit too, while you're at it and still remember what the issue is, rather than try to figure it all out again some years down the road. ![]() |
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