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Locked Re: New Guy
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Hi Tom,
Yes, those capacitors are still available, but not in the form you have now.? You will have to make them out of single electrolytics of the proper value which is very easy to do. There are many good sources out there and you can go to a search engine to find them. However, before you start playing inside those AC/DC sets, please do several things: Get and use an isolation transformer. Install a polarized or preferably a 3 wire cord set. Spend a few minutes reading the following items of interest and safety: roy.morgan@... To: hallicrafters@... Sent from the Internet (Details) At 08:02 PM 3/6/2005, chandlerh2@... wrote: >i am recapping my SX42 got a cap kit from just radios . i am also going to >replace the power cord with a 3 prong my question is do i hook the ground on >the? plug? right to the chassis.? also does it matter which way i hook >up? the >polarized plug to the transformer. Hallicrafters restorers, Here is my advice on line cords and bypass caps, including how you wife can become a widow with a fuses line cord plug.? For those who don't want to read the rest of this, which material may save your life, I summarize the bypass cap installation here: >RF Bypass caps should be installed as follows: > >One from Line to Neutral, after the fuse. >One from neutral to chassis. Roy's Diatribe on Fused Line Cord Plugs and Line Cords and RF Bypassing powercordsandbypassing.txt From k1LKY Fused Line Cord Plugs: Under no circumstances should you ever use a fused line cord plug, period.? It can kill you in a variety of ways.? The Johnson company put them on Rangers, Valiants, and other equipment.? I have a Heath VHF-1 6- and 2-Meter transmitter with one on it.? These line cords and fused plugs are the first thing to go when I start returning it to serviceable condition. Note that there seem to be two applications for fused line cord plugs: Electric fence energizers and decorative electric holiday candles and light strings.? The electric fence situation is based on long history, and safety may well rely on the idea that the case of the energizer is grounded with a ground rod to make the fence work properly.? The window candles and light strings have no chassis, no switch, no transformer, and very little exposure of energized conductors to people. Some time ago I wrote imaginative but quite serious descriptions of some of the many ways fused line cords can make a widow out of your wife.? I want to re-write that thing and put in back into circulation, but that will have to wait for another day. In summary, however, the way your wife gets to be a widow is as follows: 1) The equipment with the fused line cord plug suffers an internal short such as in a transformer or RFI bypass capacitor, with the short circuit more or less to the chassis. 2) ONE of the line cord plug fuses blows (almost never will both blow unless the fault is a dead short.) 3) You unplug the thing, unhook the "good station ground" wire and antenna, move it to a work bench to figure out what is wrong.? Notice that the ground you *might* have had on the chassis is removed. 4) You plug it back in and haplessly insert the unpolarized plug so the intact fuse puts line voltage on the chassis. 5) You reach for the power switch, the current kills you and your wife becomes a widow. This is a topic sure to generate much traffic on any radio mailing list.? People's attitudes seem to fall into four groups: 1) "Problem?? What problem?? There's no problem here." Duuuhhhh! 2) "Originality forever."? To hell with the fact that it may kill me or someone else, I will use the original fused line cord and my equipment is authentic. 3) "Hmmm..."? I'm glad to know about all this (but I may not DO anything to prevent my death or that of any other hapless and innocent person.) 4) "But of course!"?? Safety in line cords is easy to understand and worth paying attention to.? I'm going to get busy and fix this situation now. Be safe, live long. Do not use fused line cord plugs. Install a three-wire grounded line cord, and make sure your outlets are working right. Line cords and how to install one safely: (in US standard line cords): GREEN is safety ground, and should be tied directly to the chassis. In European (IEC) cords, the safety ground is Green/Yellow. BLACK is "hot" or "line" - it goes directly to the rear of the fuse holder, the terminal farthest from the outside of the fuse holder where the cap is installed.? The terminal on the fuse holder nearer the chassis or panel goes to the switch and should go nowhere else. (See info on bypass caps below.)? If you use an open clip-style fuse holder under the chassis, use either end of it. WHITE is "neutral" and goes UN-fused to the system, e.g. power transformer primary.? Do not put a fuse in both power cord lines. This can lead to a dangerous situation, though it's less likely to be dangerous with a three wire grounded line cord than with the deadly fused two-wire un-polarized line cord plug. On the line cord wall plug, ? - the round, longer pin is green ? - the larger flat pin is neutral ? - the narrower flat pin is line or hot. Note that European color coded line cords have different colors..? Here they are: LINE? ? ? ? ? ? (US) Black? =? (EU)? Brown COMMON?? (US)White? =? (EU)? Blue GROUND? ? (US) Green? ?? (EU)? Green/Yellow. (begin extract from message by Bob Nickels) From: "Robert Nickels" Subject: [Johnson] Fused Plugs ... A good source of replacement 3-wire power cords are those used by computers and peripherals, but most of them use the European color designations?? For years, the colors of individual conductors in cords for use in North America have been black for line, white for neutral, and green for earth (ground). But in order to harmonize worldwide standards,? two major UL equipment standards, UL 1950, Information Technology Equipment, and UL 2601, Medical and Dental Equipment, started several years ago to require the more traditional European conductor color coding: brown for line, light blue for neutral, and a? combination of green and yellow for ground. The color conversion is as follows: LINE? ? ? ? ? ? (US) Black? =? (EU)? Brown COMMON?? (US)White? =? (EU)? Blue GROUND? ? (US) Green? ?? (EU)? Green/Yellow (end extract from message by Bob Nickels) Older HP and other test equipments were equipped with an oval line cord connector and matching cord.? The Belden/Volex 17280 power cords are apparently the normally-connected cord..? There is a version with reversed line and neutral.? In all of them, the offset (center) pin is chassis ground.? When working with these equipments and line cords, do take time to sort out hot from neutral so you retain the safety aspects of the fuse connection. RF Bypass caps should be installed as follows: One from Line to Neutral, after the fuse. One from neutral to chassis. When our boatanchor equipment was made, it was common to use both a two-wire, ungrounded line cord and two bypass caps, one from each side of the line to the chassis.? Do not re-create this situation when you install the three wire grounded line cord.? This causes a danger of fire should the line to chassis cap short but not draw enough current to blow the circuit breaker, and this arrangement also causes the chassis to be at half the line voltage if the safety ground is not present (such as in a two-wire outlet used with an adapter, or in an outlet improperly wired or faulty.) There are currently available "Safety" capacitors meant for line bypass applications. You can tell them from normal caps in the catalogs because they cost about 5 times as much as normal caps.? If you take apart computer power supplies or junk TV sets, you will wind up with one or two from each unit. A reasonable review and discussion of caps used in older radios and line bypassing is at: http://www.justradios.com/safetytips.html ABC's of SAFETY Capacitors for Tube Radios They do fail, however, to discuss the method of installation above.? The authors are in Canada and offer a number of services for old radios, including technical information, and capacitors. Fuses: The topic of fuse installation and choice of fuse type and rating is a complicated one, but here are some points to consider: ? 1) For normal equipment, put one fuse only, in the Hot wire of the line cord as near as practicable to the point where the line cord enters the equipment.? The black, Hot wire of the line cord should run directly to the tip of the fuse holder - see part 2 below for more details. In equipment such as the Valiant transmitters that are made with extensive RFI filtering on all leads exiting the case, you may not want to add a rear chassis skirt mounted fuse holder. In other radios that never did have a fuse, such as the Hallicrafters S-20R, adding a fuse holder would ruin the originality of the set.? In these cases, mount an open fuse clip below the chassis, possibly using an existing screw or transformer mounting bolt. Some military equipment was built with a fuse and possibly a switch section in both wires of the line. This was done? where the equipment was to be used aboard ship or in other places where the power circuits were floated from ground for safety and reliability reasons.? (This situation also applies generally in Sweden and some other European countries.)? If the equipment is in good condition you can leave it as it was built but make sure you have a good three wire grounded line cord and that your outlet grounds are properly connected. Note: the three-terminal MS series, "Amphenol" type connectors used by the military on such equipment as the CV-591 and CV-89 were installed with (at least) two different pin arrangements.. Be very careful that you dope out what you have when working on equipment of this sort. Mis-matching the cord to the equipment could lead to trouble. 2) The Hot or line wire of the power cord goes directly to the rear of the fuse holder, the one farthest from the outside of the fuse holder where the cap is inserted.? The terminal on the fuse holder nearer the chassis or panel goes as directly as possible to the switch. This reduces to the absolute minimum the amount of conductor inside the equipment that is not protected by the fuse.? And it reduces the chance of a shock when you are installing or removing the fuse if the line cord is still energized. 3) The "cold" or neutral side of the line cord should NOT be fused.? The Green, safety ground wire should never be fused.? Also, the safety ground should not pass through any connector other than the line cord connector and should not pass through any printed circuit path.? It should be connected directly to the chassis. 4) Follow manufacturer's specs for the type and rating of the fuse.? Beware of low voltage fuses that may fit the fuse holder you have. Fuses rated at 32 volts may not properly protect you and the equipment in normal line voltage situations.? If you don't know the current rating needed, make a guess at the rating and use smaller and smaller fuses until they blow from time to time.. then increase the fuse current rating a bit. 5) "Inline" type fuse holders can be used under a chassis with no holes to drill or screws needed to hold down an open style fuse holder.? They come in two sorts, apparently. One sort is just like a panel mount fuse holder but has no mounting nut and no external solder connections. Wires enter the cap on one end and the holder body on the other end.? The other sort is rounded and fastens together in the middle. This link shows both types and has them for sale: http://www.members.tripod.com/ralph_graves/littlefuse.htm GFI and Hot Chassis Troubles: The R-390 series of receivers, among others, was built with robust line filters. The arrangement of the capacitors places half the line voltage on the chassis if the chassis is not grounded.? This is NOT because the line filter capacitors are leaking or shorted, it is normal voltage division behavior of the circuit as installed.?? If the chassis is grounded, enough current flows in the safety ground wire to unbalance the two line currents and trip many ground fault interrupter devices.? Old style methods of bypassing both wires of a two-wire line cord to the chassis can do the same things.? Steps to correct these troubles include: 1) Remove the line filters or line bypass capacitors connected in the old style and either leave them out or install bypasses as above. 2) Use an isolation transformer or a "Sola" type constant voltage? transformer (most of which have isolated secondaries).? Note: most "Variacs" or variable voltage transformers do NOT provide any isolation.? Some that do apparently exist but they are rare.? Further, fuses in these things may be in the input wire only and not in the variable voltage output wire.? This can lead to overloading the low voltage turns of your transformer.? Both input hot and output hot should be fused, or at the least only the output wire. 3) Use properly grounded three wire line cords with non-GFI protected power circuits. Outlet Safety Testers: Most home stores and electrical supply houses can sell you a small gadget to test your outlets with.? They have a number of neon lamps that indicate proper functioning or various fault conditions. The cost is less than $10 and is one of the best investments in your safety you can make.? Even "licensed professional electricians" can and have made mistakes wiring up houses, and time and wear can open up safety grounds that were installed properly in the beginning.? You owe it to yourself, your family, and later occupants of your house to buy and use one of these very helpful gadgets. Think safety. Install proper grounded line cords. Live long. (end of diatribe) Roy - Roy Morgan, K1LKY since 1959 - Keep 'em Glowing! 7130 Panorama Drive, Derwood MD 20855 Home: 301-330-8828 Cell 301-928-7794 Work: Voice: 301-975-3254,? Fax: 301-948-6213 roy.morgan@... -- ______________________________________________________________ Hallicrafters mailing list Home: http://mailman.qth.net/mailman/listinfo/hallicrafters Help: http://mailman.qth.net/mmfaq.html Post: mailto:Hallicrafters@... ---- List Administrator: Duane Fischer, W8DBF **for assistance** dfischer@... ---- Hallicrafters Collectors International: http://www.w9wze.org |
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