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Reforming Caps




 
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W9ZSL
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« on: September 11, 2018, 03:41:54 PM »

I just finished a build of a 600 volt supply. Went by the book on this one. It has a pair of oil capacitors; 4 and 8 mfd in the filter. Rectifier is a 5R4-GY. Rather than plug in and hit full voltage for a smoke test, I decided to use another supply with a solid-state bridge and bring the high voltage up slowly off a Variac with the rectifier out of the socket. The HV from the second supply is clipped onto the tube socket with a test lead. I'm running it at 50 volts right now because I'm curious about those filter caps.  They are rated at 1 KV each. I've reformed polarized electrolytics before and am wondering if it's a good idea to do the same with the oils.  I have a volt meter on the HV output of the supply plus it has its own 50K bleeder. I got a Pacemaker installed back in April and so I've recovered enough from the heart problems to get back into Hamming again. Doc says it's OK if I'm careful not to make like an antenna. Project is a 120 Watt AM/CW rig. Next project, getting the Cataracts taken care of!
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W4EWH
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« Reply #1 on: September 11, 2018, 11:04:49 PM »

Here's a tip: everyone you ask about cataract surgery will say "that's nothing, it's a one-day thing, no problem, you can do it on your lunch hour!"

However, if you ask them when they had theirs done, they'll tell you that they heard it from their uncle/aunt/cousin/whatever, and that their eyes are "fine" or even "perfect" and they never needed work done.

So take it from someone who has had it done: bring a friend, an extra pair of dark glasses, and a lot of patience. Oh, and tell the doctor that you want the good stuff!  Grin

Bill, W4EWH
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W1ITT
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« Reply #2 on: September 12, 2018, 08:24:06 AM »

But, more to the point, oil capacitors don't need to be "re-formed".  There is no electrolytic chemistry to set in action.  The oil is a high voltage insulator from the get-go.
Be aware that HV oil capacitors occasionally show a phantom effect where they recharge themselves.  This is why it's a good idea to short them with a wire across the terminals in storage.  I have a 240 microfarad at 5 kv capacitor that will do the phantom recharge game for days if I don't keep it shorted, or at least leave it in-circuit with a bleeder resistor.
If I make it to NearFest this fall, I'll probably bring that capacitor along.  It makes for great dynamic regulation in the plate voltage supply, but is heavily affected by gravity.  My latest amplifier plate supply "only" uses 60 microfarads.  But, if you have the space, and the strength to horse them around, oil caps are still the cat's meow.
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W9ZSL
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« Reply #3 on: September 12, 2018, 12:25:46 PM »

You bet Bill! Now that the heart is up and running and I'm stronger, the cataracts are next in line. It sure would help if I could see what I'm soldering! I got some pretty funky connections on this thing!
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W9ZSL
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« Reply #4 on: September 12, 2018, 12:28:03 PM »

I wasn't sure if they needed reforming and thanks for the info! I was wondering why some of these things arrived with a pig tail shorting them out.
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W9ZSL
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« Reply #5 on: September 12, 2018, 01:18:08 PM »

Smoke Test today! The iron is Stancor using a PC-8414 Power rated at 1200 VCT, 200 ma with capacitive input filter; 4 and 8 mfd and a Stancor 4.5 Hy @200 ma choke. Got the sketch-o-matic from the 1962 West Coast Handbook. OK, I didn't follow the book completely. It called for a 4 Hy choke. I had a 175 ma @4Hy, so I substituted a C-1411 Stancor 4.5 Hy because it matches the PC-8414 rating. For a bleeder, I used 2 Dale 100K, 50 watters in parallel.   Yeah, there is a big mess of wires on the right side, but I didn't want to shorten them. If the iron is repurposed, who wants to mess with short leads? On the opposite end from the HV, there is a bias supply. I used a pair of Sprague 30 mfd caps in the filter along with a Triad 10Hy choke. The rectifier is a solid-state bridge and I measured -165.8 volts adjustable. The same transformer had a 6.3 volt winding that I will use for pilot lights. The big sliding resistor is for the screen. I'm going to use this with the parallel 807 RF amp from the '57 ARRL handbook.  Next project is the Speech Amp / Driver. Too much fun! REALLY! It's been over 3 years since I've been "in the game" because of the ticker problems.  Why is it that John Denver's "Country Roads" song keeps running through my mind??!?


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WA2SQQ
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« Reply #6 on: September 12, 2018, 03:47:42 PM »

Here's a tip: everyone you ask about cataract surgery will say "that's nothing, it's a one-day thing, no problem, you can do it on your lunch hour!"

However, if you ask them when they had theirs done, they'll tell you that they heard it from their uncle/aunt/cousin/whatever, and that their eyes are "fine" or even "perfect" and they never needed work done.

So take it from someone who has had it done: bring a friend, an extra pair of dark glasses, and a lot of patience. Oh, and tell the doctor that you want the good stuff!  Grin

Bill, W4EWH
I had both eyes done, 3 weeks apart. I requested they numb the eye with drops rather than the "block" injection which requires a very short sedation. Absolutely no sedation, no pain and no annoying eye patch. Regular sun glasses for two days and no heavy lifting for 5 days. I had more discomfort and tension getting my teeth cleaned. A walk in the park - just don't get a doctor who is a dinosaur!
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W4EWH
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« Reply #7 on: September 12, 2018, 09:33:55 PM »

So take it from someone who has had it done: bring a friend, an extra pair of dark glasses, and a lot of patience. Oh, and tell the doctor that you want the good stuff!  Grin
I had both eyes done, 3 weeks apart. I requested they numb the eye with drops rather than the "block" injection which requires a very short sedation. Absolutely no sedation, no pain and no annoying eye patch. Regular sun glasses for two days and no heavy lifting for 5 days. I had more discomfort and tension getting my teeth cleaned. A walk in the park - just don't get a doctor who is a dinosaur!

Glad it turned out OK: I'm not as brave as you, but they used the eye drops on me as well, and it went fine, although I had requested a soporific before the operation: like I said, when it's up to me, I want the good stuff.  Cool

Bill, W4EWH
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Dave K6XYZ
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« Reply #8 on: September 14, 2018, 02:05:06 AM »

Youse guys are scaring the crap outta me with the eye injections and what all.....jeeze....
I'll try to grow another leg so I can get a third knee replacement....gotta be easier than seeing that needle heading towards my eyeball.....yikes!!
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w4bfs
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« Reply #9 on: September 14, 2018, 09:11:11 AM »

.......
I'll try to grow another leg so I can get a third knee replacement........yikes!!

a human tripod ?
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Beefus

O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us.         Robert Burns
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