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 Post subject: OS-8B/U Twist Lock Cap Removal
PostPosted: Jun Wed 13, 2018 9:20 am 
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Location: Hammond, Ind.
I am restoring one of these ex-navy oscilloscopes. The solders on the twist lock cap tabs are quite stubborn and hard to remove. The solders are too heavy to get rid of. Any suggestions on how to remove them? the area is too tight for most conventional tools such as a chisel or a high wattage iron.

Any suggestions are helpful.
Thanks

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 Post subject: Re: OS-8B/U Twist Lock Cap Removal
PostPosted: Jun Wed 13, 2018 3:01 pm 
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Location: Syracuse NY
They are a pain.
If you do not intend to restuff it and reinstall it, my method is to use gas pliers to twist the tab off completely. It takes some practice to grab it and break the solder.
If you have another cap with good tabs, you could restuff that one instead.

Bob

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 Post subject: Re: OS-8B/U Twist Lock Cap Removal
PostPosted: Jun Wed 13, 2018 3:59 pm 
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Pick up a Weller D-550 solder gun. It's high wattage will make short work of the old solder. I keep one around just for that circumstance.

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 Post subject: Re: OS-8B/U Twist Lock Cap Removal
PostPosted: Jun Wed 13, 2018 4:52 pm 
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jimjimmunster wrote:
I am restoring one of these ex-navy oscilloscopes. The solders on the twist lock cap tabs are quite stubborn and hard to remove. The solders are too heavy to get rid of. Any suggestions on how to remove them? the area is too tight for most conventional tools such as a chisel or a high wattage iron.

If you can get to the top of the can with a razor saw, hacksaw blade, or Dremel cutting wheel, then just cut off the top of the can without removing the base from the chassis.

(I've tried using a PVC cable saw -- https://www.generaltools.com/pvc-pipe-cable-saw -- but it loads up after a bit and stops cutting the aluminum. Maybe a real wire saw would work.)

Cut just above the flare where the can is crimped around the base. Then drill holes in the base and install new radial caps from above. If you like, you can remove the guts from the can, clean up the tar with naphtha, and epoxy it back on to the base.

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 Post subject: Re: OS-8B/U Twist Lock Cap Removal
PostPosted: Jun Wed 13, 2018 5:32 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Latham NY
I do this a lot, saves time and looks good. Can gets epoxy inside and put back on.


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 Post subject: Re: OS-8B/U Twist Lock Cap Removal
PostPosted: Jun Wed 13, 2018 7:41 pm 
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The caps are in such a weird spot. The tabs are folded down and soldered. Even if I got the higher wattage gun, how would I pry up the tab? I doubt I will restuff these so I can destroy them. Any other methods welcome.

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 Post subject: Re: OS-8B/U Twist Lock Cap Removal
PostPosted: Jun Wed 13, 2018 9:28 pm 
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I don't understand the destroy them part. The tabs just require a twist to align with the slot they fit into so they can be pulled out. My method leaves all connection below intact, you just drill a small hole next to each terminal to feed the wires from your new caps to solder to the existing terminals. When I'm done you can hardly see any difference from original


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 Post subject: Re: OS-8B/U Twist Lock Cap Removal
PostPosted: Jun Thu 14, 2018 6:05 am 
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Location: Hammond, Ind.
I wish I could use your method, it is just extremely hard to use in this situation. I cant fit any sort of saw in the area. The tabs cant be straightened simply. Two out of the 4 tabs on the two cans are bent level with the chassis and soldered with a very stubborn thick solder. None of my irons can melt it. the other two tabs are twisted and easy straightened. I cant get the soldered and bent tabs off or fit a saw or chisel in. I am thinking a Dremel tool is the best option so far. Maybe it is harder to straighten the soldered tabs since everything is made to military specifications. I am thinking of Dremel tooling or prying them off with a long flathead screwdriver. I don't think there is a non damaging way to remove them.

Thanks

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 Post subject: Re: OS-8B/U Twist Lock Cap Removal
PostPosted: Jun Thu 14, 2018 4:28 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Great Salt Lake Valley
Is it C-134 in the attachment?
If so, you may need to do some more disassembly. Let's face it someone put it in there.


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os8b-man-91707-5207 43.pdf [209.55 KiB]
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 Post subject: Re: OS-8B/U Twist Lock Cap Removal
PostPosted: Jun Thu 14, 2018 9:00 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Monterey California USA
Let me be the troll here and ask "Is this capacitor even in need of replacement?" In military and high-end gear I reform such things and test for ESR, leakage and all that, and they are usually good (but of course not always.) This forum is full of people who will say to replace every electrolyic in any kind of equipment, and while that seems to hold true for old table and consumer radios, very often military and expensive test equipment will still have perfectly good electrolytics. Especially HP, Tek and most military gear. Of course, your mileage may vary.

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Last edited by Geoff Fors on Jun Fri 15, 2018 4:51 am, edited 1 time in total.

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 Post subject: Re: OS-8B/U Twist Lock Cap Removal
PostPosted: Jun Thu 14, 2018 9:23 pm 
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Location: Hammond, Ind.
Yes, the caps are in the C-134 area. This is the power supply circuit, and it is just a major problem. 3 selenium rectifiers which seem good, and these caps. I don't know if the caps are good because i lack proper equipment to test them. I just don't know if it will kill the transformer or the rectifiers if i do turn it on. I replaced all of the other caps and some resistors. The leads to these caps are also way short. I would like to remove the power supply more, but the wires leading too it are too low quality. The caps are Mallory capacitors. They might be newer replacements. The specs are in blue ink on the side of the caps. I cant remove the insulation without breaking the conductor too easily. This is a Hickok 0S-8B/U probably from the fifties, ex navy. I doubt it was used that much. It was stored in good conditions. Are their any easy ways to test capacitors without a leakage tester? My TV-3 tester can measure capacitance but i need to find out how to wire the lead. No one seems to have the 5 pin capacitance lead made for a lot of Hickok's.

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 Post subject: Re: OS-8B/U Twist Lock Cap Removal
PostPosted: Jun Fri 15, 2018 2:55 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Latham NY
Here is another way using a dremel oscillating cutter


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 Post subject: Re: OS-8B/U Twist Lock Cap Removal
PostPosted: Jun Sun 17, 2018 8:45 pm 
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Location: Beaver Falls, PA. USA
+1 on the D-550; there are some jobs where nothing smaller will do.

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 Post subject: Re: OS-8B/U Twist Lock Cap Removal
PostPosted: Jun Sun 17, 2018 10:13 pm 
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Location: N. Palm Bch, Fl.
The military specs for anything the military buys is off the charts. It normally doesn't break. I was in radar maintenance. Spent a year and a half working on mobile radar. We never replaced 1 part while I was there. Once we replace all tubes in the Tx section to see if we could get it over the 300 mile mark. We never did. I will bet that the cap is good. Are there any radio groups or clubs in your area? I'm talking about the people that talk to each other at night. There all over the place and they'd love to talk to you and see what you have. They will have what you need to test the can.

Lou-- I learned how to re-stuff the cans from you. In the past 1 1/2 years I've had 2 with no room and had to unsolder all and pull straight up. Didn't think about the oscillating dremel. It's not in my budget this year anyway.

Good Luck.
Freeman


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