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Old 19th Dec 2011, 8:54 pm   #1
2E1CIH Mike
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Default Accepted restoration methods

Hello,

Could anybody please tell me what is considered the "done thing" regarding disconnecting wiring, and component (ie mainly caps) removal?

I seem to recall reading (but can't remember where) that most receivers have mechanical joints prior to soldering in the factory. My Marconi CR300 seems to have this type, and they are problematic to "undo," especially if they are in confined/awkward to get at places.

I also recall reading that it is acceptable to snip the wires and then to make tiny coils (where possible) on the replacement capacitor leads which slip over the snipped stubs which are left.....then soldered.

I would be grateful for guidance with this.

Thanks......Mike
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Old 19th Dec 2011, 9:20 pm   #2
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Default Re: Accepted restoration methods

Depends on how dedicated you are....components wrapped through and round tag strips, valve base tags etc can be removed with a decent iron in conjunction with a sharp pointed tool, good snipe nosed pliers and a decent set of fine sharp cutters, some times if access is real tight then I do a simple lay on joint, if done properly it will be ok. I normally test that kind of joint by giving it a good wiggle with snipe nosed pliers once soldered and allowed to cool.

A lot is down to personal technique and preference and perceverence, some times it's a case of the o'sodits!

Lawrence.

Last edited by ms660; 19th Dec 2011 at 9:31 pm.
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Old 19th Dec 2011, 9:25 pm   #3
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Default Re: Accepted restoration methods

OK thanks Lawrence. I'm happy to persevere where possible, but reluctant to disconnect many wires to gain access to some caps in tricky places. I think these few may be in the "o'sodits" catagory.
Cheers....Mike
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Old 19th Dec 2011, 9:50 pm   #4
Andy Day
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Default Re: Accepted restoration methods

Hi there.

I trained as a wireman at GEC at the Grove in Stanmore in the early '60s. This was on state of the art - at the time - military kit. We were taught that all joints should be a firm mechanical joint first. Multi strand wire was stripped, twirled wth no crossing of strands, tinned and wrapped 270 deg around terminal posts, then soldered quickly with no shrink back of the insulation. If that happened it would be rejected by inspection who examined EACH joint and gave it a small dab of ink to indicate a pass. Component leads were given the same 270 deg treatment, often the GA (General Assembly Drawing) would call for the component lead to be sleeved and likewise no burning or shrinkage of the sleeving was tolerated. Component leads at valve bases (which at this time were only seen on training pieces) had to go through the hole and round 180 deg before soldering. Heater leads had to be twisted at a certain number of twists per inch - But I can't remember how many!

The coils of wire refered to are called Jenkins springs, and were only used for terminating multiple braids of screened leads, with a single pvc insulated lead going to a termination. They may have been used in a service environment but I have no experience of that.


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Old 19th Dec 2011, 9:58 pm   #5
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Default Re: Accepted restoration methods

I tend to do both - one problem with aged tagstrips is that of brittleness - they can break easily, this is a real pain in the proverbial!

A nice stainless dentists pick is ideal for this work, sadly mine went walkies yonks ago, so I tend to snip the connections after desoldering, in an attempt to release the mechanical joint.

HTH
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Old 19th Dec 2011, 10:21 pm   #6
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Default Re: Accepted restoration methods

Another tip that has helped me many times is if after sucking the solder you can expose a small hollow loop in the turn then i have used a plasterboard screw to help enlarge the hole so that it is big enough to get your snips along side. Plasterboard scews make really good screw wedges as the thread point is very tapered and the tips are like needles, you only need the smallest of gap to get it started, in fact for that particular job I have more or less abandoned the use of a standard pointed tool, using this method also reduces the chances of anything breaking as hardly any pressure has to be applied if using the correct posidrive bit, also if you want to re stuff wax capacitors they are really good for inards abstraction if you have an awkward one to do, screw it in for about an inch or more then pull, also good for parting part desoldered wire loops etc quite often they will part the joint open, they are also excellent wood screws for indoor use if you pre drill and countersink the piece to be fixed.

Hope this is of some use

Lawrence.

Last edited by ms660; 19th Dec 2011 at 10:23 pm. Reason: addition
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Old 20th Dec 2011, 7:13 pm   #7
David Simpson
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Default Re: Accepted restoration methods

Ref - re-soldering wires to tags & valve bases. Remember this - prior to WW2 there wasn't good old 60/40 flux-cored solder on a handy reel. Just lead, gas heated & copper bitted soldering irons, and Bakers Flux. If not done carefully - a recipe for dry joints. Also, in most domestic radios - wiring ran unsuported between the components. When called up for war-work or military service, most radio guys kept to their pre-war soldering methods. However, from WW2 & into the 50's & 60's, the services & their suppliers(Marconi, AVO, Wayne-Kerr,Hartleys, etc) ran wiring in well supported looms, and this silly method of wrapping wiring around & around tags etc was redundant.
A single "tight U" bending of the wire's tinned end was what the RAF was teaching in 1961 when I joined, &/or a single poke through a tag's wee hole(guess the Navy used that method also). When I became an Instructor in 1970, and tought soldering to many apprentices, this frugal method was used, solderingwise. Plus several methods of looming, lacing & so on.
To apply enough solder to cover a silly wrapped connection, will require a lot of heat from one's soldering iron, and hence frequent suseptability to shrinkage of the wire's insulation - not acceptable.

Regards, David
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Old 20th Dec 2011, 7:29 pm   #8
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Default Re: Accepted restoration methods

I was taught to wrap the wire around the joint to make a good mechanical joint first, our teacher many years ago was an ex - Navy engineer and I believe they call this the "Philips wrap".
We where also taught to tin the wire first and never to melt the solder then carry it to the joint - we had to always allow melt the solder and flux on the joint to allow it to clean the joint. This method has stuck with me ever since probably because we had such a strict teacher at college!
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Old 20th Dec 2011, 7:35 pm   #9
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Default Re: Accepted restoration methods

Good quality medical tweezers are an essential part of my toolkit.
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Old 20th Dec 2011, 7:37 pm   #10
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Interesting, I have always wondered if the wraping of component wires around tags etc made a better joint or just stopped the components falling out on an assembly line prior to soldering up. Having said that the wrapping method was always taught to me when doing City and Guilds but it kind of went out the window when printed circuit boards took over. Many TV manufacturers used wire wrap to terminal posts on these boards but relied on the mechanical wrap with no solder, because of my C&G training I always viewed these connections with suspicion but in my experience the technique turned out to be very reliable.

Lawrencce
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Old 20th Dec 2011, 8:53 pm   #11
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Default Re: Accepted restoration methods

When valve radios were built it was probably assumed that they would have a life of about twenty years, maybe being repaired two or three times during their life time. Each repair would probably have meant replacing one or two wire ended components. Ease of replacing components was not a factor being considered, so wrapping leads round tags wasn't a problem. Now fifty years later we're replacing large numbers of components in a set and regard wrapped wires as a curse.

If wires must be wrapped one turn is enough, but I've encountered some original wires wrapped round a tag two or three times. If there is more than one component terminated on the tag..... Tags with 'V' shaped notches in the sides will hold wires firmly in place prior to soldering, but some modern tags don't seem to have them.

Whoever thought of putting holes or slots in tags and especially in valveholder pins, has a lot to answer for in my opinion. Extracting the wire is very difficult, even if a solder sucker is used, and and I often resort to cutting the wire into small bits using small sharp cutters.

If terminating a wire through a hole in a tag, don't double it back on itself like an umbrella handle. Instead dog leg it. It will be much easier to remove if/when the need arises.

I have to admit that, where access is difficult, I sometimes resort to cutting off the wires close to old components. I then bend them at right angles and wrap the wires of the new component round them. One turn only of course.
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Old 20th Dec 2011, 9:03 pm   #12
2E1CIH Mike
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Default Re: Accepted restoration methods

Many thanks to you all.

My question seems to have caused some interesting comments. You all obviously have a wealth of experience which I feel fortunate to be able to access. I'll invest in some plasterboard screws, decent tweezers, and perhaps a dentist's probe.

I think David raises a good point regarding the extra heat required for substantial mechanical joints.

Anyway, I'll see how things go, and will reflect on all your sound advice.

Thanks again.......Mike
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Old 20th Dec 2011, 9:44 pm   #13
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Default Re: Accepted restoration methods

Talking of medical tweezers etc- For some time now I've used a pair of lockable foreceps, and some angled tweezers which I scrounged off the local vet. Also, just recently replaced some 40 odd year old worn-out pliers & snips, with some from a company called "Zutter" - designed for snipping & forming wires for flower arrangement. But they are ideal. Especially for the sort of work being disscussed in this thread.
Whilst on a dental slant - Us RAF Instructors at Cosford used to go out to various stations, from time to time, to check on the progress of recently qualified electronics apprentices. Being close to home, I chose RAF Sealand,(a 3rd Line Radio MU), near Chester. Some guys there, who were delving into encapsulated components & larger chips, had aquired lovely sets of dentistry tools from Liverpool Dental School, and were doing a marvelous job. (Aquired - as in officially purchased. Not off the back of a lorry, as one might expect when a scouser mentions Liverpool).

Regards, David
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Old 21st Dec 2011, 10:33 am   #14
2E1CIH Mike
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Default Re: Accepted restoration methods

Thanks for the tips re equipment David. My neice is a vet, so I will give her a ring.
Interesting you talking about being an instructor. I started life teaching engineering to YTS trainees at North Manchester (my home town) College. We also used to monitor trainees in the work place.
I now work for the MOD at Bassingbourn Barracks (nr Royston). But, soon to take voluntary early release (yippeee!) as the barracks is closing as part of the defence cuts. I must add, I have never been in the forces.
I hope nobody decides to invade us after reducing our army down by about 20%. The North Korean Army (to name just one) already stands at 10 times bigger.
Sorry.....should keep to the subject at hand (for sanity).
Best wishes.....Mike
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Old 21st Dec 2011, 12:08 pm   #15
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Default Re: Accepted restoration methods

I too remember being told to get a good mechanical joint before soldering and it stood me in good stead when I ran out of solder on field calls way back in the 70s.

David GM8JET
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Old 21st Dec 2011, 9:29 pm   #16
2E1CIH Mike
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Default Re: Accepted restoration methods

OK. Thanks to all again.
Regards....Mike
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Old 29th Dec 2011, 4:54 pm   #17
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Default Re: Accepted restoration methods

Dental picks are a wonderful asset when it comes to unsoldering joints.

Having grown up in the 60's and spending a lot of time hunched over radio chassis I was taught that a secure joint was absolutely necessary prior to soldering. Solder itself, is not a good conductor and the electrical integrity of the joint came from a good mechanical contact, soldering was used only to maintain that stability.

My experiences are similar to the other posters and any re-capping (capacitor replacement) I do is done by snipping out the old component but leaving the leads. I carefully wind a few coils in the end of the new components and slip it over the snipped end, crimp it with pliers and solder it. This also provides some flexibility in locating the new component. Typically the old components used heavier gauge lead wire than the new components so it is relatively easy to make the "floating connection" and the heavier lead provides addition support to the connection.

Trying to unsolder and remove leads, especially where there are multiple connections on a single lug can be extremely frustrating and could cause ancillary damage due to overheating or mechanical disruption. More than once I have damaged a tube (valve) socket by too much movement on a connection which ultimately caused it to break off! Remember much of that equipment was only designed to be soldered once!!

Kinds regards,
David
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Old 30th Dec 2011, 1:57 pm   #18
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Default Re: Accepted restoration methods

"Solder itself, is not a good conductor" - Really?
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Old 30th Dec 2011, 3:07 pm   #19
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Default Re: Accepted restoration methods

During my apprenticeship training I was taught to consider solder as a insulator, which clearly it isn't. They just wanted to impress on us the need to wrap joints well.

Of course there's no wrapping on most PCBs.
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Old 30th Dec 2011, 4:08 pm   #20
Brian R Pateman
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Default Re: Accepted restoration methods

The secret with solder joints, like any other jointing method, is to make a good mechanical joint.

If you just have a couple of wires or component leads in close proximity and drop a blob of solder on them you are going to have problems in the future.
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