zero

help...u67
« on: January 02, 2012, 11:23:32 AM »
hello all,
Happy new year!

I´m having trouble doing myself a repair on my u67.
i need to replace the electrolytic output coupling capacitor c9, the on in there is 0.5 uf 350v but i dont´t seem to find one anywere.
i allready posted on the blackmaket regarding this, Axel was kind enough to give me an idea of a substitute(evox/rifa) but it does not fit in there.

does anyone has experience with recaping u67´s?
Wich one is the best modern substitute?

thank you

all the best,
Pedro


Marcocet

Re: help...u67
« Reply #1 on: January 02, 2012, 02:08:56 PM »
Nichicon .47u is prob the way to go. I don't know who makes .5u electrolytics anymore, and NOS seems like madness with something that dries out over time. But some people love to go that way, so who knows.

pucho812

Re: help...u67
« Reply #2 on: January 02, 2012, 03:01:50 PM »
.47 is the way to go, it's tolerance will most like cover your needed value with ease
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

Skylar

Re: help...u67
« Reply #3 on: January 02, 2012, 03:29:06 PM »
I would try to fit a 0.47uF film cap (polypropylene preferably) in there if possible.

WIMA MKP4 series might work, but I don't know how much space you have to work with. Photos please.

Also, stick with 250V since size is a concern.

MagnetoSound

Re: help...u67
« Reply #4 on: January 02, 2012, 05:24:56 PM »

I would go with the MKT1813 polyester, 470nF 250v. From personal experience, these sound great in a U67. I still have it in mine. It is the exact same size as the original cap.

The Vishay/BC Philips-style 021ASM 1uF is a good electro. Get the highest voltage that fits.

There is no reason not to use 1uF if you prefer.

Dan

I don't think people realize what an embarrassment of riches this place is   -  Paul Gold

zero

Re: help...u67
« Reply #5 on: January 02, 2012, 06:00:31 PM »
Hi good people,

First of all, thank you for the help!!!

you are getting to all my doubts, polarized, or not, 0.5uf or 1uf, voltage......

on the vintageking schem. c9 is 1uf 450v:
http://www.vintageking.com/site/files/images/u67.gif

on the rest is 0.5 250v:
http://danalexanderaudio.com/Micpics/Neumann/U67Schematic.jpg

there is were my doubts began.

my first toughts were to put polypropylene or polyester in there but since my knowledge limits my decisions, i screamed for help.

i made a mod on a acm1200 with ERO mkt coupling and funkenwerk trany and i like the result very much, but i would like to bring my u67 back to the original sound.

so, for the info by Skylar and Dan, not using electrolytics is ok, my doubt came from the schematics of the u67 c9 is polarised and for ex. on the u47 it´s not,  my Flea u47clone has PIO.

Dan, did you notice a diference when you changed to polyester? the same?better?

here are some photos:
http://photobucket.com/u67_inside

Thank you all for the help! much appreciated!

Pedro



« Last Edit: January 02, 2012, 06:13:12 PM by zero »

MagnetoSound

Re: help...u67
« Reply #6 on: January 03, 2012, 01:00:45 AM »
Dan, did you notice a diference when you changed to polyester? the same?better?

I noticed a slight extension in the top end, a little more air. Subjective preference, not necessarily scientifically arrived at.

(Do make sure that you keep the original cap of course, to replace if you sell the mic.)

Dan

I don't think people realize what an embarrassment of riches this place is   -  Paul Gold

EEMO1

Re: help...u67
« Reply #7 on: January 03, 2012, 04:13:41 AM »

 side question...


 i've noticed that some mics have electrolytic coupling cap. any reason for that AND can you substitute it for polyester or something (not polarized)?

MagnetoSound

Re: help...u67
« Reply #8 on: January 03, 2012, 06:30:20 AM »

Back in the day, electrolytics were chosen as they were able to offer smaller physical size at the required capacitance value and voltage rating. PIO tended to be much larger.

Modern film caps can now achieve the same physical size, and without being susceptible to the aging effects that electrolytics are renowned for. The differences in sound are subjective and a matter of preference.

Dan

I don't think people realize what an embarrassment of riches this place is   -  Paul Gold

zero

Re: help...u67
« Reply #9 on: January 03, 2012, 07:11:31 AM »
Dan, did you notice a diference when you changed to polyester? the same?better?

I noticed a slight extension in the top end, a little more air. Subjective preference, not necessarily scientifically arrived at.

(Do make sure that you keep the original cap of course, to replace if you sell the mic.)

Hummm, i like that!!

Mybe that´s a parts of KH´s mod to open up the mic without removing the filters, or not!

It´s not easy to find a electrolytic that fiits in there, do you think that a lower voltage Philips/bc is safe having 210v in there?
And what do you think about polyprop. as Skylar sugested?

Skylar, have you tried it on this mic?

Sorry for all this questions and indecision.

thank you.

Best regards,
Pedro

« Last Edit: January 03, 2012, 07:14:41 AM by zero »


MagnetoSound

Re: help...u67
« Reply #10 on: January 03, 2012, 08:56:04 AM »
It´s not easy to find a electrolytic that fiits in there, do you think that a lower voltage Philips/bc is safe having 210v in there?
And what do you think about polyprop. as Skylar sugested?

Ah, good point. I forgot the 021ASM are only good for 100v. IIRC, the B+ ramps slowly enough to be safe while the cathode heats, but you would have to be careful not to power it up without the tube. If you can find a 250v that fits, all the better.

I certainly wouldn't advise against polypropylene, but they tend to be larger than polyester due to their higher voltage rating.

Dan

I don't think people realize what an embarrassment of riches this place is   -  Paul Gold

zero

Re: help...u67
« Reply #11 on: January 03, 2012, 05:02:55 PM »
yes, size is a problem!

i´m gonna try the MKT1813.

i sincerely thank you all for the great help!!

I´ll post the results.

Best regards,
Pedro

EEMO1

Re: help...u67
« Reply #12 on: January 04, 2012, 04:04:58 AM »

Back in the day, electrolytics were chosen as they were able to offer smaller physical size at the required capacitance value and voltage rating. PIO tended to be much larger.

Modern film caps can now achieve the same physical size, and without being susceptible to the aging effects that electrolytics are renowned for. The differences in sound are subjective and a matter of preference.

 so like a u87, no reason that it is electrolytic... thanks for the info!

eynkel

Re: help...u67
« Reply #13 on: May 05, 2012, 10:36:24 AM »
Hi there, I am brand knew here, and I need some help too about my U67
I tried to repair it myself, but it apears to be more difficult than I thougt !

First of all I had a problem the the Capsule : too old and stored in a wet place ! One side worked but the other one had no Hi freq !
I changed it for the moment with a crap Chinese one, in order to fix the other problem, witch is :

A kind of white noise with quick fade in and slow fade out most of the time after receiving a signal, but sometimes with no reason appears on the output.

It is realy frustrating because the sound is marvellous (except that white noise pollution !!)

Any Idea ?


Thanks ;-)


 

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