Author Topic: .01uF across mains?  (Read 2217 times)

Offline cinnanon

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.01uF across mains?
« on: January 31, 2015, 01:52:34 PM »
Hello all,

This cap was not present on early 200 boards or their schematics. The original is a 150VAC/1400VDC .01uF ceramic cap. Is it necessary for filtering? I bought some of these

http://www.mouser.com/ds/2/427/125l-239774.pdf

and don't know if they will suffice. I'm diving into the realm of amp rebuilding this year and am determined to learn.

Offline pianotuner steveo

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Re: .01uF across mains?
« Reply #1 on: January 31, 2015, 02:29:33 PM »
DO NOT put a cap there. It can short out and cause a fire. There was no reason for this to be there. I used to think replacing it was the best idea, until I learned that it is not needed and potentially dangerous.

1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 200A EP
1980 Wurlitzer 270 Butterfly Grand
2000 Yamaha acoustic piano
2004 Hammond XK3
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
....and a few guitars...

Offline cinnanon

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Re: .01uF across mains?
« Reply #2 on: January 31, 2015, 03:26:06 PM »
Is this considered one of the famous "death caps"?

Offline alenhoff

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Re: .01uF across mains?
« Reply #3 on: January 31, 2015, 05:46:13 PM »
DO NOT put a cap there. It can short out and cause a fire. There was no reason for this to be there. I used to think replacing it was the best idea, until I learned that it is not needed and potentially dangerous.

Let me preface what I'm saying here with this:  I have absolutely no qualifications to give advice on electrical safety. I'm not challenging Steve's statement -- just asking deeper questions.  So, with that caveat:

I've heard that advice, too -- and it sounds like good advice.

But is there more to this?  The caps he's located are safety caps.  My understanding is that they're designed to withstand major surges, and, even if they fail, they're designed to fail safely (i.e. not to catch fire or allow a shock hazard). The original amp designer seemingly placed that cap to filter out AC line interference. Maybe that's useful, maybe it's not.

So, if you replace that cap with a safety-rated cap designed for that purpose, is it electrically safe?  Is it perhaps providing some benefit in reducing line interference?  Or would a "pro" just remove it because even the safety cap might still pose a hazard,or because it provides no benefit anyway?

Alan
1974 Rhodes Mark I Stage 73
1972 Rhodes Silver Sparkletop Piano Bass
1978 Hohner Clavinet D6
1968 Hohner Pianet N II
1966 Wurlitzer 140B
1967 Gibson G101 combo organ
1965 UK Vox Continental
1954 Hammond B2; Leslie 21H; Leslie 31H
1977 Fender Twin Reverb
Vox AD100VT Valvetronix modeling amp
(SEE THE COLLECTION: https://vintagerockkeyboards.wordpress.com/ )

Offline pianotuner steveo

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Re: .01uF across mains?
« Reply #4 on: January 31, 2015, 09:43:54 PM »
Timengr1 can explain it best, I believe...

Are you out there Tim?

Alan, I see what you are saying, I did not realize those caps were that good, but I know from experience that old caps in old Wurlitzer amps in this location should be removed. Usually found in early models like 120, 700, etc.

I got zapped from stray voltage on a 120 that had a bad ceramic cap there.

It was going to ground. Not sure how many volts, though.
« Last Edit: January 31, 2015, 09:49:36 PM by pianotuner steveo »
1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 200A EP
1980 Wurlitzer 270 Butterfly Grand
2000 Yamaha acoustic piano
2004 Hammond XK3
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
....and a few guitars...

Offline The Real MC

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Re: .01uF across mains?
« Reply #5 on: January 31, 2015, 11:21:54 PM »
That was design convention before three-prong outlets became the norm in the 1960s.  Today it is dangerous and definitely not recommended.  I am an EE.

Offline alenhoff

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Re: .01uF across mains?
« Reply #6 on: February 01, 2015, 01:05:48 PM »
Good to know. Thanks for the insight.

Alan
1974 Rhodes Mark I Stage 73
1972 Rhodes Silver Sparkletop Piano Bass
1978 Hohner Clavinet D6
1968 Hohner Pianet N II
1966 Wurlitzer 140B
1967 Gibson G101 combo organ
1965 UK Vox Continental
1954 Hammond B2; Leslie 21H; Leslie 31H
1977 Fender Twin Reverb
Vox AD100VT Valvetronix modeling amp
(SEE THE COLLECTION: https://vintagerockkeyboards.wordpress.com/ )

Offline Stevelazarmusic

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Re: .01uF across mains?
« Reply #7 on: March 01, 2015, 10:21:26 PM »
Does this mean I should remove the old ceramic cap out of my 203 amp?
Wurlitzer 203
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Offline pianotuner steveo

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Re: .01uF across mains?
« Reply #8 on: March 02, 2015, 08:06:52 AM »
If it is across the power wires, then yes. A 203 isn't 3 prong?
1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 200A EP
1980 Wurlitzer 270 Butterfly Grand
2000 Yamaha acoustic piano
2004 Hammond XK3
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
....and a few guitars...

Offline Stevelazarmusic

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Re: .01uF across mains?
« Reply #9 on: March 05, 2015, 02:12:20 AM »
I'll definitely take out that ugly cap, then.  I put in a new 3 prong AC receptacle on mine.  Before I chopped it, I installed it down where the previous one was, and after I chopped it I routed a hole where it is on 200a pianos.  Both jobs were a pain but got rid of a lot of hum with the original power cable. Thanks again!
Wurlitzer 203
1972 Fender Rhodes Suitcase
Moog Slim Phatty
Leslie 2101 mk2

Offline Tim Hodges

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Re: .01uF across mains?
« Reply #10 on: August 22, 2018, 09:14:22 AM »
I came across this thread and thought I might help clear things up.

In this thread there are 2 types of capacitors being mentioned:

  • Across the line capacitors (connects between live and neutral)
  • Line to ground capacitors (connects between neutal and ground) - Older capacitors which aren't safety rated are also known as "Death Caps"

For those of you that have a 0.01UF capacitor on the brown terminal tag strip on the amp rail (most likely if you have a 200 series piano) these are known as X capacitors which connect from the live terminal to the neutral terminal. These are used to filter out electromagnetic interference and radio-frequency interference. Only capacitors specifically marked X1 or X2 can be used to bridge across live and neutral terminals, you cannot use any normal capacitor. In the instance that there is an overvoltage event these X1/X2 capacitors are designed to fail safely (open) exactly like a fuse would when subjected to a high voltage. Any standard capacitor which isn't safety rated has the risk failing short and becoming a fire hazard so it's important to use the correct X1/X2 type, I would suggest that if you have one of these originals ceramic caps installed in your piano that it is replaced with a modern X1 / X2 cap.

If you have a capacitor which spans the neutral to ground then this known as a Line to Ground capacitor. Older versions are not safe and are referred to as Death Caps and should be removed as they have the potential to short and shock people (see pianotuner steveo's post.) Since the US now uses grounded 3 pin power cables these capacitors are no longer required. Some people still use non-polarized two prong power cords, my suggestion is that they convert their pianos to use a 3 pin modern cord to prevent any issues. Their modern equivalent of these line to ground capacitors are now known as Y capacitors, these new caps are safety rated and designed to fail open so that in the event of failure they will not shock the user.

Always best to add that if you're uncertain about any of this it's always best to take your amp to a qualified technician rather than attempting it yourself.

 

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Offline pianotuner steveo

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Re: .01uF across mains?
« Reply #11 on: August 22, 2018, 08:56:45 PM »
I think one of the problems that may have happened with the early models with 2 prong AC cords was since they were not polarized, it was easy to flip them around and have the hot wire on the wrong side of the cap. Just a semi- educated guess...
1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 200A EP
1980 Wurlitzer 270 Butterfly Grand
2000 Yamaha acoustic piano
2004 Hammond XK3
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
....and a few guitars...

Offline Tim Hodges

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Re: .01uF across mains?
« Reply #12 on: August 23, 2018, 02:57:21 AM »
In your case Steveo it sounded like the ceramic line to ground capacitor failed (either from a overvoltage event like a lightning strike or from general fatigue) and shorted which then transferred the negative lead voltage to the the ground (and any metal components subsequently connected to the ground.)

A modern equivalent of that cap (Y1 / Y2 safety rated and made from metallised paper or film) would instead fail open preventing the current from going to ground but as mentioned any 2 prong power cord Wurlitzer for the sake of safety should really be converted to a grounded cable cord.
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Offline pianotuner steveo

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Re: .01uF across mains?
« Reply #13 on: August 23, 2018, 06:02:32 AM »
That's what I figured, but I no longer own that piano. I wish that I did still own it, that was the piano I found sitting on the side of the road waiting for the trash men! It even had the pedal and legs! Mechanically, it was very nice for a 120.

That was years before I knew about the "death cap" situation. I wish I knew it was such an easy fix back then.
1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 200A EP
1980 Wurlitzer 270 Butterfly Grand
2000 Yamaha acoustic piano
2004 Hammond XK3
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
....and a few guitars...

Offline DocWurly (formerly Paleophone)

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Re: .01uF across mains?
« Reply #14 on: September 05, 2018, 01:32:16 PM »
OK, now that we have established that:

*the .01uF capacitors in later 200's (and in all 200A series) are NOT death caps
*they should always be X1 or X2 or Y1 or Y2

My next question is, should they be replaced as a matter of course?  Do these tend to fail as capacitors do, or, as they are ceramic, should it be presumed that they are working even if there's a bit of hum in a Wurly?  (in other words, is the hum more likely to be from another source if that capacitor is present?)

Indeed, they are NOT in most 200 series Wurlitzers of 1970, but they are in full force by late 1971.










Offline DocWurly (formerly Paleophone)

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Re: .01uF across mains?
« Reply #15 on: September 05, 2018, 02:02:46 PM »
I got my questions answered:

*Don't replace them unless they are obviously cracked.  But it's good for them to be there.  They are a safety measure AND they reduce line hum.

*Bumping them up to .047uF is good, given modern wall voltages.  Retrolinear carries a good, safe "X-rated" replacement, and it's affordable.