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Sprague FQ-425 oil filled cap specs




 
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Author Topic: Sprague FQ-425 oil filled cap specs  (Read 615 times)
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KD6VXI
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« on: February 25, 2018, 05:24:35 PM »

Got a cap here I can't figure out.

Photo flash cap from 'back in the day'.  Google, came up empty.

Looked for a Sprague catalog, again, empty.

Anyone know what it is?  Can't read the voltage reading.   Cap tester shows 27 uF.

Came out of a 4-1000 I'm parting out, with 12 volts in it showed 550 out, full wave CT choke input power supply, if that helps.

Pic attached, sorry for the dim photo.

--Shane
KD6VXI


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W2PFY
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« Reply #1 on: February 26, 2018, 02:06:37 PM »

It's most likely a 25 mf cap. I have a number of that type but not your number and they are all 25 uf.
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KD6VXI
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« Reply #2 on: February 26, 2018, 05:28:11 PM »

Yeah, I'm comfortable with the 25 uF rating.  It's the voltage rating, I've no idea about.

My hi pot starts at 8kv, iirc.  Not much good here.

--Shane
KD6VXI
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KA2DZT
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« Reply #3 on: February 26, 2018, 06:42:04 PM »

Most likely not FQ but PQ-425,  the number tells you what it is.  25ufd 4000volt PEAK, 200W/sec.  Photo flash oil caps are not designed for heavy duty power supply service.  Sprague catalog indicates not to exceed the max peak voltage.

Sprague "CR" series caps are designed for xmtr power supply service.
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W2PFY
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« Reply #4 on: February 27, 2018, 03:10:08 PM »

For awhile I had one of my 25uf caps in parallel with the capacitors in my BC-610D for a few months and it never showed any signs of heating. Cool as a cucumber as they say.
It was running at 2100 vdc on fone & 2600 vdc CW. It really helped the regulation but the bleeder was not sufficient and the bleed off time was too long causing me some kind of problem that at the moment, I can't remember?   Shocked Shocked Shocked
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KD6VXI
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« Reply #5 on: February 27, 2018, 08:42:01 PM »

Well, I'll take it as a 4kv cap, seems about right to me.

Thanks everyone for the sanity check.  Cap looks good in the esr meter, etc.  Now I know what it's good for voltage-wise.

I totally understand the photo flash vs real caps.  This will end up in a 2 to 3 kv supply.

--Shane
KD6VXI
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