Capacitors?

davode · 2nd September 2006, 03:31 AM

I want to recap my MXP-3036 and need to know some capacitor info. Ive noticed that the channels that sound muddy or have a low volume level have some of the original caps replaced with larger voltage caps, for example, the original cap is a 100uf 16v and it was replaced with a 100uf 35v. The newer replaced caps are also alot smaller in size. Could this be the problem? My other question is what is the best replacement to replace the caps with? I know that a higher temp rating is one thing to do and Nichicon is a good brand, but what else is there to know?? should i replace all caps??(ceramic, mylar, poly film?) oh and the cap im trying to replace are Electrolytic non-polarized and polarized capacitors.

Matt Syson · 3rd September 2006, 07:14 PM

Hi
Capacitors have generally got smaller as manufacturing improves so no big deal there. Changing all electrolytic types is probably a good plan if it is older than say 10 years. You could test and replace those that have started to degrade but it is probably easier and quicker to blitz the lot and you don't have to keep pulling the thing apart. The different makes and types may sound slightly different but all will be better than stuff older than about 15 years. Getting really expensive types is probably both unnecessary and simply makes the unit too expensive to repair.
Matt S

paully · 4th September 2006, 12:47 AM

Quote:

Originally Posted by davode

... the original caps replaced with larger voltage caps, for example, the original cap is a 100uf 16v and it was replaced with a 100uf 35v...

>>>>>>>>>>>>>>>>>>
Slightly higher voltage rating shouldn't make any difference at all.

Paul

AmekGuy · 4th September 2006, 03:48 AM

Quote:

Originally Posted by paully

>>>>>>>>>>>>>>>>>>
Slightly higher voltage rating shouldn't make any difference at all.

Paul

That's correct.

Geoff_T · 4th September 2006, 03:53 AM

Quote:

Originally Posted by paully

>>>>>>>>>>>>>>>>>>
Slightly higher voltage rating shouldn't make any difference at all.

Paul

Hi

With emphasis on the word "slightly". Much higher voltages than necessary in polarised electrolytics are a no no if they can be avoided.

Jim Williams · 4th September 2006, 04:49 PM

Most of those are Panasonic bipolars that are very slow and clogged sounding.
First, measure the offsets off each opamp or hybrid amp stage. Replace the bipolars with polarized caps with the polarity adjusted for the polarity of the dc offsets.

Jim Williams
Audio Upgrades

drtechno · 11th September 2006, 06:28 PM

you can go higher in voltage rating, that much shouldn't do anything. make shure you are replacing with the same type. on power supplies if you replace a polarized electrolytic with a non-polarized (bipolar) the ESR goes up and could cause power supply issues. when ever I build a mic pre I try to stay away from caps in the signal path. as much as possible. When I use caps in the phantom power, I use a low impedence polarized electrolytic with a .1 poly cap tied in parrellel. I know some mic pre's use a 100Uf 25V bipolar in the dc blocking of the phantom and the panasonic su series is a little inductive in nature and you have to hand pick them and/or do the poly parelell trick. If you are using them in a true balanced blocking/coupling input, the tolerance between the two electrolytic must be near the same otherwise you can get phase cancellation/shifts which can effect natual harmonics in the signal.

gevermil · 12th September 2006, 01:37 AM

Well ,, what is the limit on upping caps ?
Say 25v 100uf to say 35v is ok but 50v would be pushing it ?

Jim Williams · 12th September 2006, 04:42 PM

Consider the ratio:

If you have a 220 uf/25v cap hanging on the output of a TL072 opamp and it has 100mv of offset, there's a 250/1 ratio of voltage rating vs voltage applied. That's the same ratio of 1 volt to 250 volts rated. So far, millions of caps are working fine and for many years under these situations.

It's something not to be that concerned with. The quality of the cap is something to be very concerned with.

Jim Williams
Audio Upgrades

Geoff_T · 12th September 2006, 05:03 PM

Quote:

Originally Posted by Jim Williams

Consider the ratio:

If you have a 220 uf/25v cap hanging on the output of a TL072 opamp and it has 100mv of offset, there's a 250/1 ratio of voltage rating vs voltage applied. That's the same ratio of 1 volt to 250 volts rated. So far, millions of caps are working fine and for many years under these situations.

It's something not to be that concerned with. The quality of the cap is something to be very concerned with.

Jim Williams
Audio Upgrades

Hi

Playing Devil's advocate (to prompt more discussion

) I often wonder if the cap failure issue with Neve V series is a combination of the heat in the module and the fact, as you describe above, that the polarised coupling capacitors have no polarising voltage and that the audio can possibly swing + and - 7 volts or so.

Jim Williams · 12th September 2006, 05:36 PM

That's a good possibility. I recall seeing many axial 100uf/4V, yes, 4 volt rated signal caps in the disasterous 8108/8128 consoles. Being in a warm enviroment and 85 degree rated, they would both dry out and get slammed by AC waveforms. Remember, caps are rated for DC voltage, not AC voltage. De-rate about 1/3 of the marked rated voltage for AC operation. So, those 4 volt parts are getting stressed with 2~3 volt signals, not un-common in todays elevated levels for digital. Swing + - 7 volts across one of these and they are not long of this world....

Jim Williams
Audio Upgrades

Geoff_T · 12th September 2006, 05:50 PM

Quote:

Originally Posted by Jim Williams

That's a good possibility. I recall seeing many axial 100uf/4V, yes, 4 volt rated signal caps in the disasterous 8108/8128 consoles. Being in a warm enviroment and 85 degree rated, they would both dry out and get slammed by AC waveforms. Remember, caps are rated for DC voltage, not AC voltage. De-rate about 1/3 of the marked rated voltage for AC operation. So, those 4 volt parts are getting stressed with 2~3 volt signals, not un-common in todays elevated levels for digital. Swing + - 7 volts across one of these and they are not long of this world....

Jim Williams
Audio Upgrades

Hi

Yes, exactly! The +/- 7v swing is exceptional because I chose the VMOS stage swings that can hit +26dBu unbalanced off the +/-25v power rails and I can't recall the value of the coupling cap but suspect it in the region of the 8108/8128 you mention.

Perhaps the SSL servo (no caps) route was a better way to go... or turn the clock back to the good ol' days of 24 volt single rail with a healthy +12v to polarise the capacitors!

drtechno · 12th September 2006, 05:52 PM

Quote:

Originally Posted by gevermil

Well ,, what is the limit on upping caps ?
Say 25v 100uf to say 35v is ok but 50v would be pushing it ?

Depending on where it is in the circuit and what type of cap it is used. Aluminum caps get really poor in quality for signal path use above 63v. In power supplies, if a grossly electrolytic cap is used, say 100uf 400v it might be too leaky causing the dc voltage to decrese and/or dc ripple or cause inrush current to be too high for the semiconductors upstream. Also, the cost factor of a higher voltage cap and physical size make it not practical fo existing board layouts. So, In the repair world, its recommended to go back with componates that the circuit was designed with and leave the design aspects to EE wizards.

Neve8128 · 12th September 2006, 06:39 PM

Most 8108 came by default with 100uf 4v then Neve upgraded to 100uf 10v on the later 8128 series and 82 series.

Quote:

Originally Posted by Jim Williams

That's a good possibility. I recall seeing many axial 100uf/4V, yes, 4 volt rated signal caps in the disasterous 8108/8128 consoles. Being in a warm enviroment and 85 degree rated, they would both dry out and get slammed by AC waveforms. Remember, caps are rated for DC voltage, not AC voltage. De-rate about 1/3 of the marked rated voltage for AC operation. So, those 4 volt parts are getting stressed with 2~3 volt signals, not un-common in todays elevated levels for digital. Swing + - 7 volts across one of these and they are not long of this world....

Jim Williams
Audio Upgrades

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2nd September 2006, 03:31 AM	#1
davode Gear nut Join Date: Jan 2005 Location: new jersey Posts: 98	Capacitors? I want to recap my MXP-3036 and need to know some capacitor info. Ive noticed that the channels that sound muddy or have a low volume level have some of the original caps replaced with larger voltage caps, for example, the original cap is a 100uf 16v and it was replaced with a 100uf 35v. The newer replaced caps are also alot smaller in size. Could this be the problem? My other question is what is the best replacement to replace the caps with? I know that a higher temp rating is one thing to do and Nichicon is a good brand, but what else is there to know?? should i replace all caps??(ceramic, mylar, poly film?) oh and the cap im trying to replace are Electrolytic non-polarized and polarized capacitors.

3rd September 2006, 07:14 PM	#2
Matt Syson Lives for gear Join Date: Sep 2004 Location: UK Posts: 1,507	Hi Capacitors have generally got smaller as manufacturing improves so no big deal there. Changing all electrolytic types is probably a good plan if it is older than say 10 years. You could test and replace those that have started to degrade but it is probably easier and quicker to blitz the lot and you don't have to keep pulling the thing apart. The different makes and types may sound slightly different but all will be better than stuff older than about 15 years. Getting really expensive types is probably both unnecessary and simply makes the unit too expensive to repair. Matt S __________________ Matt S www.mseaudio.co.uk

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4th September 2006, 04:49 PM	#6
Jim Williams Lives for gear Join Date: Feb 2004 Location: beautiful Carlsbad, CA Posts: 4,503	Most of those are Panasonic bipolars that are very slow and clogged sounding. First, measure the offsets off each opamp or hybrid amp stage. Replace the bipolars with polarized caps with the polarity adjusted for the polarity of the dc offsets. Jim Williams Audio Upgrades

11th September 2006, 06:28 PM	#7
drtechno Gear nut Join Date: Aug 2006 Location: Rapid City, SD Posts: 90	you can go higher in voltage rating, that much shouldn't do anything. make shure you are replacing with the same type. on power supplies if you replace a polarized electrolytic with a non-polarized (bipolar) the ESR goes up and could cause power supply issues. when ever I build a mic pre I try to stay away from caps in the signal path. as much as possible. When I use caps in the phantom power, I use a low impedence polarized electrolytic with a .1 poly cap tied in parrellel. I know some mic pre's use a 100Uf 25V bipolar in the dc blocking of the phantom and the panasonic su series is a little inductive in nature and you have to hand pick them and/or do the poly parelell trick. If you are using them in a true balanced blocking/coupling input, the tolerance between the two electrolytic must be near the same otherwise you can get phase cancellation/shifts which can effect natual harmonics in the signal.

12th September 2006, 01:37 AM	#8
gevermil Gear addict Join Date: Jul 2004 Location: chicago Posts: 490	Well ,, what is the limit on upping caps ? Say 25v 100uf to say 35v is ok but 50v would be pushing it ?

12th September 2006, 04:42 PM	#9
Jim Williams Lives for gear Join Date: Feb 2004 Location: beautiful Carlsbad, CA Posts: 4,503	Consider the ratio: If you have a 220 uf/25v cap hanging on the output of a TL072 opamp and it has 100mv of offset, there's a 250/1 ratio of voltage rating vs voltage applied. That's the same ratio of 1 volt to 250 volts rated. So far, millions of caps are working fine and for many years under these situations. It's something not to be that concerned with. The quality of the cap is something to be very concerned with. Jim Williams Audio Upgrades

12th September 2006, 05:36 PM	#11
Jim Williams Lives for gear Join Date: Feb 2004 Location: beautiful Carlsbad, CA Posts: 4,503	That's a good possibility. I recall seeing many axial 100uf/4V, yes, 4 volt rated signal caps in the disasterous 8108/8128 consoles. Being in a warm enviroment and 85 degree rated, they would both dry out and get slammed by AC waveforms. Remember, caps are rated for DC voltage, not AC voltage. De-rate about 1/3 of the marked rated voltage for AC operation. So, those 4 volt parts are getting stressed with 2~3 volt signals, not un-common in todays elevated levels for digital. Swing + - 7 volts across one of these and they are not long of this world.... Jim Williams Audio Upgrades