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Old 18th Jan 2021, 4:16 pm   #1
OldTechFan96
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Default How To Do a Neat Job With a Point to Point Chassis?

Hello,

I am wondering what advice members have to give when it comes to doing a neat job replacing components on a 'point to point' chassis?

I would like to make the chassis work I do neat and close to original as possible.

Any ideas appreciated!
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Old 18th Jan 2021, 4:38 pm   #2
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Default Re: How To Do a Neat Job With a Point to Point Chassis?

Bear in mind before you start that modern through-hole components will typically have been designed with pcb use in mind, so will be physically smaller themselves and will also have significantly shorter leads than their vintage equivalents. If the chassis you're working on has the connection points a long way apart then you may struggle to find modern components capable of bridging the gaps.

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Old 18th Jan 2021, 4:47 pm   #3
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Default Re: How To Do a Neat Job With a Point to Point Chassis?

For a start :-

1. High resolution photos, include detailed high-res photos too.
2. Ensure any replacement parts have legs long enough to reach between the 'points'.
3. If '2' cannot be met, ensure any joins are long enough, and ideally hidden. As an example, an axial cap with legs too short, solder on new longer legs right up to the body, and position the new part so the over-lapped join has the smaller (original) legs facing away from you.
4. Only disturb 'what's required' to be disturbed.
5. Work with the general layout and not the schematic layout. It's not always possible or advisable to start at the front end of a set working you way towards the final output stage, which would otherwise be a logical approach.

Just some ideas

Good luck,

Mark
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Old 18th Jan 2021, 5:10 pm   #4
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Default Re: How To Do a Neat Job With a Point to Point Chassis?

One issue I find when doing this is that modern components are smaller - look at an old 1940s 1-Watt carbon-composition resistor and compare it to a modern carbon-film/cracked-carbon part of the same power-dissipation.

I regularly use 2-Watt carbon-films to replace the generic 1-Watt carbon-composition ones - it's possible to do similar 'uprating for greater physical size' when replacing waxies by modern MKT capacitors, or with electrolytics in applications like cathode-bypasses.

If you need to 'extend' a leadout the soldered joint where the extension is done can be discreetly covered by a bit of heatshrink sleeving.
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Old 18th Jan 2021, 5:44 pm   #5
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Default Re: How To Do a Neat Job With a Point to Point Chassis?

Hello OTF96(Christian name ?), when you say 'point to point' do you mean the higledy-piggledy layout of components & interconnecting wiring which some radio manufacturers chose to use underneath a chassis - out of sight?
In my book, for a full rewire or replacement of a number of duff components, there is nothing wrong with carefully fitting a paxolin tag strip or two or insulated pillars. Nor can I see why one shouldn't do some neat lacing & looming if possible.
Wouldn't depreciate the value of a bog standard domestic radio from the 40's, 50's & 60's, I reckon. However, much rarer sets from the 20's & 30's need a lot of thought regarding rewiring. Old paxolin &/or bakelite encapsulated components can be carefully "re-stuffed" with modern components. Also modern versions of cloth covered or enamelled/varnished wire can be obtained.
My pet hate with old radios is the use of un-used valve holder tags being used for circuitry terminations. One can always find room for a wee tag strip or tag pillar.

Regards, David
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Old 18th Jan 2021, 6:16 pm   #6
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Default Re: How To Do a Neat Job With a Point to Point Chassis?

Hi OldTechFan,


Here is an example from a quite common Dansette. (That was my first attempt at cable-wrapping so plenty of room for improvement!). It's neater than what was there before.

Some tips.

*Really clean that solder bit all the time and use a good flux.

*It is quite OK (IMO, others could disagree but it's really your personal aesthetics) to snip out just the body of a resistor and solder the replacement onto the existing remains of the leads. I haven't done this here, but I do it quite a lot and if your soldering is clean and on-point, it looks good.

*Conversely, if you have to undo quite thick leads that were tightly wire-wrapped, you will need to do it patiently and in pieces. If the tag-strip is old and fragile, it could fail if you apply too much heat, either in one go or in several goes.

*Try to gauge the bends in any leads before you solder. You don't need the strict right-angles that you see sometimes, unless they are a hallmark of that era and you are trying to preserve originality in a rare or unusual set.

*Make heater-wire replacements into nice tight twisted pairs, as shown. Same with any AC carrying wires.
Don't, though, just pair any old wires together.

*Use decent wire. Avoid PVC covered. It's nasty to solder as it melts easily and my personal view is that it looks poor in situ. You have a range of other options - have a search on what others recommend.

(P.S - do use grommets for through-chassis wiring. I haven't here as I am using very burly Teflon-covered wire which is also strain-relieved).

Do you have any examples of recent attempts?

Cheers
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Old 18th Jan 2021, 6:55 pm   #7
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Default Re: How To Do a Neat Job With a Point to Point Chassis?

Very interesting thread, neatness is something I struggle with too.

What I find hardest is placement of the new electrolytics (when not restuffing). Sometimes I get lucky and find an unused tab on a tag strip, or I try to add in a tag strip of my own, but I'm never completely satisfied with the aesthetics. Any tips?

Apologies to the OP, don't want to hijack your thread

Thanks
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Old 18th Jan 2021, 8:25 pm   #8
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Default Re: How To Do a Neat Job With a Point to Point Chassis?

Removing individual components that are on tags/posts with multiple components wire wrapped and soldered on the same posts/tags is what I dread the most
There's not much info on how to properly do that on here or places like youtube.

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Old 18th Jan 2021, 8:37 pm   #9
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Default Re: How To Do a Neat Job With a Point to Point Chassis?

A good solder sucker, a pair of small fine-nosed pliers, something like a small jeweller's screwdriver to lever the end of the wire up and a bench magnifier with a bright light so you can really see what you're doing make unwrapping wires from tags so much easier.

Cheers,

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Old 18th Jan 2021, 8:46 pm   #10
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Default Re: How To Do a Neat Job With a Point to Point Chassis?

I think it's a good idea to try and make the new part conform to the component layout photograph on the service sheet, that way if you need to do any remedial work in the future, you can still use the original layout.
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Old 18th Jan 2021, 8:52 pm   #11
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Default Re: How To Do a Neat Job With a Point to Point Chassis?

Sometimes "tidying up" wires and components compared to how they were laid out originally can lead to an oscillator you don't want or kill an oscillator you do want.

Lawrence.
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Old 18th Jan 2021, 8:58 pm   #12
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Default Re: How To Do a Neat Job With a Point to Point Chassis?

Yes. Replacing bare wires with screened lead 'to cut down noise pickup' can bite you that way.

Cheers,

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Old 18th Jan 2021, 9:20 pm   #13
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Default Re: How To Do a Neat Job With a Point to Point Chassis?

In the case where several component-leads are threaded-through-tag-holes-and-wrapped-over-before-soldering, rather than wrestling one component's leads out of the hole and risking damaging other components/wiring in the process, I will happily snip the leads off the compomnent-to-be-replaced as close to the component as possible, then fit the replacement to the old 'tails'.

A neat way to do this is to make up little coils of a few turns of tinned copper wire, with the hole-through-the-middle just big enough to take the tail and the lead from the new component. The little coils can then be soldered.

The result is electrically good, and cosmetically-acceptable. The same wire-coils method was actually used in production by some manufacturers as a way to join multiple component-leads together without using a tagstrip.
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Old 18th Jan 2021, 10:19 pm   #14
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Default Re: How To Do a Neat Job With a Point to Point Chassis?

Quote:
Originally Posted by G6Tanuki View Post
The same wire-coils method was actually used in production by some manufacturers as a way to join multiple component-leads together without using a tagstrip.
Notably Philips. I always thought it was such a neat way of joining multiple wires together I use the method myself.
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Old 19th Jan 2021, 10:16 am   #15
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Default Re: How To Do a Neat Job With a Point to Point Chassis?

Quote:
Originally Posted by mark2collection View Post
5. Work with the general layout and not the schematic layout. It's not always possible or advisable to start at the front end of a set working you way towards the final output stage, which would otherwise be a logical approach. Mark
I don't think that's ever advisable or logical. I start with the PSU and then work from the speaker back towards the aerial socket. That way you can do testing as you go along rather than having to change all the faulty components first. It's easy to test the PSU and audio stages. IF and RF stages are more complex and harder to test.
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Old 19th Jan 2021, 10:46 am   #16
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Default Re: How To Do a Neat Job With a Point to Point Chassis?

I have found it difficult to source suitable turret boards.
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Old 19th Jan 2021, 11:11 am   #17
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Default Re: How To Do a Neat Job With a Point to Point Chassis?

Turret boards are not a problem, simply make your own. Turret pins are readily available, unlike the older style of tags.
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Old 19th Jan 2021, 11:59 am   #18
David Simpson
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Default Re: How To Do a Neat Job With a Point to Point Chassis?

Al's picture in post 6 shows some very neat lacing, well done. Regarding re-location of components & more neat runs of wiring causing PO in domestic sets - I don't think that designers or factory bench staff considered that as a reason for choosing higgledy - piggledy wiring. For donkey's years, military, marine & commercial radio equipment has used looming & lacing and multi-tagboard layouts of components without encountering circuitry PO problems. Cheapness of construction is all it is, domestic radio-wise.
Graham's testing & fault-finding method is what I've mostly used for years, when it comes to dealing with a "new to the bench" set of unknown serviceability.
In many old sets, the component leads & the wiring are of much greater cross-sectional area than is warranted for the actual current incurred. SWG sizes equivalent to 1mm sq. or even 1.5mm sq.(5 to 10 heffing amps, eh ?), when only a few 10's or even not much more than 100mA is flowing. This harks back to sets from the 1920's when hard-drawn copper wiring was "self-supporting" in runs between component's screw-terminals. (no multi-strand Rubber or PVC insulated wiring back then, in many cases).

Regards, David
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Old 19th Jan 2021, 12:11 pm   #19
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Default Re: How To Do a Neat Job With a Point to Point Chassis?

Quote:
Originally Posted by David Simpson View Post
Regarding re-location of components & more neat runs of wiring causing PO in domestic sets - I don't think that designers or factory bench staff considered that as a reason for choosing higgledy - piggledy wiring.
Philips for one, gave instructions in some of their radio receiver service manuals as to the specific placing/orientation of some components.

Lawrence.
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Old 19th Jan 2021, 12:58 pm   #20
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Default Re: How To Do a Neat Job With a Point to Point Chassis?

Quote:
Originally Posted by David Simpson View Post
Al's picture in post 6 shows some very neat lacing, well done.
Thank you, David! Much appreciated :thumbsup

Quote:
Originally Posted by David Simpson View Post

In many old sets, the component leads & the wiring are of much greater cross-sectional area than is warranted for the actual current incurred. SWG sizes equivalent to 1mm sq. or even 1.5mm sq.(5 to 10 heffing amps, eh ?),

Absolutely right. And a related problem is when really thick passive component leads are tightly wrapped around valve-holder pins, turrets and tag-boards. It's enough to tether a small elephant.

It can cause carnage for a novice trying to unpick it, soldering iron in one hand, pliers in the other. Pulled out valve pins, melted insulation, the smell of burning vinyl chloride... I well remember my journey with all this when I was starting out. Unless someone is ambidextrous, it's a problem - both hands are needed for precision.

Of course, we all learn ways around this but it is an art in itself to dissect what's already there at least causing no harm.

On production cost dictating layouts -- yes. One effect is that the quality of wiring looms in some domestic equipment from the 50's and 60s's in particular seems poor and a better standard can be reached than original factory gate. This seems remarkable at first, but I've seen it over again. It can manifest as poor soldering on OG circuit boards, unnecessarily shoddy and loose cabling where it is actually causing hum pick-up, badly routed heater wires etc. Of course, nobody ever put the under side of a chassis under the same scrutiny as we do when we are restoring something - but it took me a while to believe what I was seeing.

Of course there are stand-out examples of consistent build excellence - Hacker to name just one.

One of the first sets I ever saw, David, was just such a model with hard-drawn bare copper wire as you are describing. I just missed out on an opportunity to pick up a simple two-valve model a few years ago. Something really solid about these.
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