I started this in another thread but I decided to open a new one since it really is a little OT from the other thread.
I have a Plinius Jarrah phono preamp that needs at least its PS caps replaced. I do not have the schematic for this preamp so I am limiting my changes to match as closely as possible to the original parts.
The input to the preamp is 90 VAC, which appears to be split to +45 VAC / -45 VAC across the LM317/LM337 regulators. The main caps, which are showing evidence of bulging and leakage, are Cosonic 1000uF, 63 Volt radial electrolytics. The part number is no longer listed on the Cosonic website (no surprise, the PCB was made in 2006). I've contacted Cosonic but they have not replied with what the equivalent cap might be.
Since I've never heard of Cosonic before I figured I'd replace these with caps that have had known good reputations. I searched for one for one matching caps in value, rating, and physical size (it is space limited) and came up with these options:
Nichicon PW 2200uF
Rubycon ZLH 2200uF
United Chemicon KZE 1000uF
Nichicon PW 1000uF
Panasonic FC 1000uF
and just for kicks a Kemet ESY 1000uF
I know I can try any of these and they all should work, but of course one of the questions is how will each affect the sound? Hard to tell without knowing what the rest of the circuit looks like around the cap - but I'd be interested in hearing recommendations for which to try first.
The next thin is all of these new caps have very low ESR, which in one way is good, but for these older 317/337 designs I hear can be a problem in causing HF resonance. I'd really love to get my hands on a schematic so I could see if Plinius added a bypass cap or some resistance to the circuit to help with resonance - but that would assume the original Cosonic also had low ESR. Would I be safe, not knowing what's around these caps, to even add something like a Vishay 1837 in 0.01uF or 0.1uF assuming it will always be "the good thing to do"?
I have a Plinius Jarrah phono preamp that needs at least its PS caps replaced. I do not have the schematic for this preamp so I am limiting my changes to match as closely as possible to the original parts.
The input to the preamp is 90 VAC, which appears to be split to +45 VAC / -45 VAC across the LM317/LM337 regulators. The main caps, which are showing evidence of bulging and leakage, are Cosonic 1000uF, 63 Volt radial electrolytics. The part number is no longer listed on the Cosonic website (no surprise, the PCB was made in 2006). I've contacted Cosonic but they have not replied with what the equivalent cap might be.
Since I've never heard of Cosonic before I figured I'd replace these with caps that have had known good reputations. I searched for one for one matching caps in value, rating, and physical size (it is space limited) and came up with these options:
Nichicon PW 2200uF
Rubycon ZLH 2200uF
United Chemicon KZE 1000uF
Nichicon PW 1000uF
Panasonic FC 1000uF
and just for kicks a Kemet ESY 1000uF
I know I can try any of these and they all should work, but of course one of the questions is how will each affect the sound? Hard to tell without knowing what the rest of the circuit looks like around the cap - but I'd be interested in hearing recommendations for which to try first.
The next thin is all of these new caps have very low ESR, which in one way is good, but for these older 317/337 designs I hear can be a problem in causing HF resonance. I'd really love to get my hands on a schematic so I could see if Plinius added a bypass cap or some resistance to the circuit to help with resonance - but that would assume the original Cosonic also had low ESR. Would I be safe, not knowing what's around these caps, to even add something like a Vishay 1837 in 0.01uF or 0.1uF assuming it will always be "the good thing to do"?
Adding a bypass can make resonance problems worse, not better, especially if the main cap has low ESR. Bypasses are often 'a bad thing to do'.
Rayma, the original caps are rated 63V and the thing has been running almost 24/7 for 12 years. Never had a problem until the last few months when I noticed that one finally started leaking. I think the regulator output is something like 40 volts (I measured it a long time ago). Derated at 80% the 63V 'lytics seem like they're rated okay.
@DF96 and @BigE, I really wish I could get my hands on the schematic. I will skip the consideration of adding the bypass. I'll go just replacing the cap. Would there be any harm in going to a 2200uF part?
@DF96 and @BigE, I really wish I could get my hands on the schematic. I will skip the consideration of adding the bypass. I'll go just replacing the cap. Would there be any harm in going to a 2200uF part?
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