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 Post subject: Substitute for .05 mfd 1600v tubular capacitor?
PostPosted: Apr Mon 09, 2012 5:55 am 
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Joined: Jan Sun 22, 2012 8:14 am
Posts: 86
Hello,

I was able to get an old 6 meter Gonset Communicator working this weekend. However, a tubular capacitor connected between the plates of the 6X4 rectifiers and ground appears to be in bad shape, it gets hot and appears to be leaking wax. It is .05 mfd 1600v. These does not appear to be a common value in today's market, only ones I saw were $10 each.

Any suggestions for a cheap substitute? And is this component even necessary? I have seen several schematics of 6X4 power supplies without any such capacitor.

73, Bill NZ5N


Last edited by nz5n on Apr Mon 09, 2012 6:36 am, edited 1 time in total.

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 Post subject: Re: Substitute for .05 mfd 1600v tubular capacitor?
PostPosted: Apr Mon 09, 2012 6:26 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 2276
Location: Seattle WA US
.05mfd/1600v is only $2.19 at
http://www.justradios.com

I've been very satisfied with them as a supplier.
--Chuck


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 Post subject: Re: Substitute for .05 mfd 1600v tubular capacitor?
PostPosted: Apr Mon 09, 2012 11:49 am 
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Joined: Oct Sun 15, 2006 12:57 pm
Posts: 3558
justradios.com 1600V-.047 Disc will be fine and its only 99 cents.


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 Post subject: Re: Substitute for .05 mfd 1600v tubular capacitor?
PostPosted: Apr Mon 09, 2012 12:05 pm 
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Joined: Jul Mon 26, 2010 8:30 pm
Posts: 8517
Location: Annapolis, MD
nz5n wrote:
And is this component even necessary? I have seen several schematics of 6X4 power supplies without any such capacitor.

Two truisms come to mind:
1. (At least most of the time) there is a reason for every part in a device, circuit, etc.
2. "If it works, it's OK"

without a good reason, I'd try to keep it the way it was originally designed

_________________
"It's always something". --Gilda Radner
My name is Mark, and I have a radio problem


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 Post subject: Re: Substitute for .05 mfd 1600v tubular capacitor?
PostPosted: Apr Mon 09, 2012 2:41 pm 
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Joined: Mar Fri 14, 2008 1:40 pm
Posts: 8797
Location: SE USA
Since the Gonset was touted as a fixed or portable rig I gather that they knew it might tend to be operated from a generator at times. That cap would be for taming the spikes and transients often seen in generator operation. Good thing to have.

I've encountered a few pre-war European table radios that also had this cap on the secondary. Usually blown and clipped out. Being on the secondary AC voltage is pretty tough service and slight leakage will create heat - then it leaks more - and creates more heat, etc. A good modern cap should be much more reliable.

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 Post subject: Re: Substitute for .05 mfd 1600v tubular capacitor?
PostPosted: Apr Mon 09, 2012 2:47 pm 
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Joined: Jan Sun 22, 2012 8:14 am
Posts: 86
Thanks, folks. I was advised on another forum that this is the arc capacitor for the vibrator, and since this unit came with a missing vibrator and I don't intend to use it mobile I can just cut it out for now. Jack, doubt I'll ever use it with a generator but that's good to know.

For 99 cents it's worth replacing with my next order from Just Radios, which has a $15 minimum plus $6 shipping.

73, Bill NZ5N


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 Post subject: Re: Substitute for .05 mfd 1600v tubular capacitor?
PostPosted: Apr Mon 09, 2012 5:03 pm 
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Joined: Jan Fri 13, 2012 6:52 pm
Posts: 231
Location: Grays Harbor, Washington
Well, for what it's worth, The Gonset had a built in Vibrator/chopper and it used the same
transformer to create HV, just like the old car radios years ago. The cap does not bypass to ground but rather goes between the plates of the two 6X4's and provides the same hash reduction and reduces the arc on the vibrator points. If you never intend to use the vibrator you don't need it but I'd take the advice earlier in the post and replace it.
That capacitor going bad often took out the transformer or, in the case of the old tube car
radios the OZ4 tube associated with the power supply. It was standard practice to replace that cap when you changed the vibrator or rectifier as most all the old car radio power supplies using OZ4's had them.

Pete


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 Post subject: Re: Substitute for .05 mfd 1600v tubular capacitor?
PostPosted: Apr Mon 09, 2012 5:52 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1385
Location: Eagan, Minnesota, USA
AES has .05 mfd 1600 volt orange drops. I bought a few not too long ago, and they weren't that much. Ask for USPS shipping to save cost.


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 Post subject: Re: Substitute for .05 mfd 1600v tubular capacitor?
PostPosted: Apr Mon 09, 2012 6:25 pm 
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Joined: Jan Sun 22, 2012 8:14 am
Posts: 86
Pete, on my unit this cap does go to ground. I'm still looking for a schematic of the 6 meter version, but I do have schematics for the 2 meter version of the Comm I and Comm II. The cap is between the plates as you describe it on the Comm I schematic (although the value there is .015uf), but it goes to ground on the Comm II schematic (with a value of .05uf). My 6 meter unit is a Comm I, but perhaps a prior owner substituted a Comm II power supply, or perhaps the 6 meter version was always different.

A replacement vibrator would cost more than what I paid for the entire radio, but can't hurt to replace the cap just in case.

73, Bill NZ5N


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 Post subject: Re: Substitute for .05 mfd 1600v tubular capacitor?
PostPosted: Apr Mon 09, 2012 6:29 pm 
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Joined: Jun Sun 19, 2011 2:31 pm
Posts: 1499
Mouser has them in a variety of styles, use USPS instead of default UPS shipping to save money on small orders and there is no minimum order. A Cornell Dublier brand .047@3,000 volts is $2.55 in single item quantity.

Other than a few vintage style can caps I buy all of my passive components from Mouser. Orders placed in the morning ship out by afternoon.

Rodger WQ9E


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 Post subject: Re: Substitute for .05 mfd 1600v tubular capacitor?
PostPosted: Apr Mon 09, 2012 6:38 pm 
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Joined: Oct Sat 20, 2007 3:36 am
Posts: 14393
Location: Southern NH, 03076
+1 on Mouser. Great service and same day shipping. Ive yet to see ANY benefit to using Justradios.

Carl


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 Post subject: Re: Substitute for .05 mfd 1600v tubular capacitor?
PostPosted: Apr Mon 09, 2012 10:38 pm 
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Joined: Nov Tue 15, 2011 11:19 pm
Posts: 243
Quote:
Mouser has them in a variety of styles, use USPS instead of default UPS shipping to save money on small orders and there is no minimum order. A Cornell Dublier brand .047@3,000 volts is $2.55 in single item quantity.


Amen. They also have a 1600V version. If you specify USPS First Class in the "Special instructions box" at checkout, you will pay about $3 shipping.

Justradios is great, except for 2 major things. One is they have a $15 minimum order, with shipping, it is about $22 minimum. Second thing is that they are in Canada, so you might have to wait 7-10 days.


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 Post subject: Re: Substitute for .05 mfd 1600v tubular capacitor?
PostPosted: Apr Tue 10, 2012 1:36 am 
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Joined: Oct Sat 20, 2007 3:36 am
Posts: 14393
Location: Southern NH, 03076
And third, their general purpose caps are no name Chinese and several have reported problems with the electrolytics but many just keep on falling all over themselves with praise :o :roll:

With Mouser I have the Nichicon or other major brand axial lead caps in hand and the radio repaired before the order is even looked at in Canada and I often pay less.

Carl


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 Post subject: Re: Substitute for .05 mfd 1600v tubular capacitor?
PostPosted: Apr Tue 10, 2012 2:07 am 
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Joined: Nov Tue 15, 2011 11:19 pm
Posts: 243
I order all my electrolytics from Mouser, usually Xicon, Nichicon, or Panasonic. Most of my polypropylene cap I also order from Mouser. I did order from Justradios a few times for Orange Dips and tubular. But never Electrolytics.

Digikey is also pretty good.


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 Post subject: Re: Substitute for .05 mfd 1600v tubular capacitor?
PostPosted: Apr Wed 11, 2012 3:06 am 
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Joined: Feb Sat 04, 2012 11:51 pm
Posts: 22
Location: Myrtle Beach, SC
That cap is know as a buffer cap. Was used to kill the spikes from the power supply used in a mobile
operation. It is NOT needed for AC only. If you look at some of the older radios like the Johnson or
simular, the schematics show the buffer only in the DC units. The AC only units it is omitted.

The vibrator makers stated right on the vibrator that the warranty would be void unless you changed the
buffer cap.

Leave it out unless you'll use it mobile.

Clayton N4EV

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If it ain't broke, fix it 'til it is.


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 Post subject: Re: Substitute for .05 mfd 1600v tubular capacitor?
PostPosted: Apr Wed 11, 2012 6:54 am 
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Joined: May Wed 06, 2009 7:01 pm
Posts: 572
Quote:
Post subject: Re: Substitute for .05 mfd 1600v tubular capacitor?
I'm still looking for a schematic of the 6 meter version, but I do have schematics for the 2 meter version of the Comm I and Comm II. ...
73, Bill NZ5N


Send me a PM if you still need the 3049 schematic and parts list.

-- Rich


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 Post subject: Re: Substitute for .05 mfd 1600v tubular capacitor?
PostPosted: Apr Sat 14, 2012 5:43 am 
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Joined: Jul Sat 23, 2011 9:33 pm
Posts: 496
Location: Mississippi Gulf coast
There was an old modification I remember where transistors were used to build a plug-in circuit that replaced the vibrator. I don't remember if it was in the 50s or 60s but -- if you ever do try it, make sure the correct buffer cap is in place. It resonates the transformer winding when used switching and the transformer may arc internally without it.
Then the cheaper fully transistorized power supplies came out.
They were better and smaller, so the old vibrator supplies went into the circular file.
Pat

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Pat W5THT
Unhappy tubes blush while unhappy power FETs scatter plastic


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