Point-to-point wiring

[ozmoid]

I am working on a p-to-p wired amp, and I have developed a new appreciation for what the techs are going through working on this stuff! My Grommes was originally assembled 'dry' by folding all the wires over the contacts, then gang soldered. Some of the 'clumps' of component leads and wire took quite a bit of solder to put together - I have used 3 feet of desoldering braid for just a handful of components!! I have to unbend the leads while the solder is molten on any parts I need to re-use. There is not an 1/8" of wasted wire or component lead anywhere, so cutting is NOT an option for anything that needs to be saved.

More power to you pros, what would we do without you?

Finally getting a real education,
Todd

 

[soundmotor]

I would get a spring plunger-type desolderer. They don't cost very much and they are more effective than braid on masses of solder. You also want an iron with enough wattage. I think my Weller is 800W and it gets the solder to a completely liquid point. Braid is handy but a PITA to use on lots of connections. Last things you need are a solder "spudge" and a set of small bentnose pliers. The spudge is like a pick tool. On one end you have a point and the other the point is slotted. It has a wooden handle usually and the whole tool is about the size of a pencil. After you've vacuumed off as much solder as you can with the plunger, you keep the connection heated and use the spudge to unwind the wires from the connection with the slotted end. The tool is made from aluminum so solder won't stick to it. The plier are useful to apply more "English" when needed.

If the gear is just too much of a mess I'll try to take everything out en masse. If the sockets are mounted from the bottom you can usually do this. I will only unsolder things like the transformers and power supply connections then I will take out all of the socket mounting screws and pull all the guts out in one step. It is easier to unsolder when you can turn it over and get at the side that was next to the chassis.

 

[ozmoid]

Actually, it's not a mess, it's a very neat job. The masses of solder are occurring where lots of wires attach at a single point (by "lots" I mean three or more) and all those wire loops are filled, making a big dollop of solder. I'm used to PCB soldering, where everything is either surface attached or pinned thru the board with just a speck of solder. I can see how the P-to-P technique makes assembly easier (I did the same thing putting it all back), but it makes disassembly a little more labor intensive. Thanks for the tip on the pick, I'll look for one!

 

[mhardy6647]

umm... I am lazy and I usually make "pigtails" from the cut leads of old components.
There's a nominal risk of forming an antenna for RFI, but I haven't had any noise/hash problems. E.g., the Marantz 8B I "restored" was so dead quiet, it was impressive.

EDIT: Adapting the little Hexfreds into the HV power supply was a little tricky!

Before:

After:

 

[ozmoid]

Mr. Hardy, that is a very neat and clean looking job there! The Grommes is a touch more crowded than that.

 

[mhardy6647]

Gotcha! Like a Pioneer SX-34/Allied 333, mebbie? :-(

(this was "before"; I don't have an "after" of this 333)

 

[Clmrt]

Damn firewalls. No seeum pics.

 

[skippy_ps]

Nice pics Hardy and nice work too.

I usually use an Xacto knife with a #11 blade to get in under the bent over leads and pry them up enough so that I can grab it with some small modeling pliers. This works pretty good on samll diameter wire but not so hot on larger stuff. Four letter words directed at the recalcitrant connections doesn't seem to help much.

Murray

 

[rickon66]

soundmotor - I may be wrong, but an 800 watt soldering iron sounds like too much for most audio type soldering. I use 40 watts for most jobs, but it may be too small. Is it better to use more wattage? I may need to upgrade.

 

[mhardy6647]

The photos are in Photobucket. Cut 'n' paste the links when you get to a friendlier network

Every solder-slinger ows it to him/herself to get at least one pair of hemostats. I keep about 4 of em hanging on pegboard at my bench. Great tools for holding and adjusting.

 

[Redboy]

Every solder-slinger ows it to him/herself to get at least one pair of hemostats. I keep about 4 of em hanging on pegboard at my bench. Great tools for holding and adjusting.

Dang, why didn't I think of using one of those?! And I've got one, too!

I've been slowly recapping a Pilot integrated. Much slower process than I anticipated due to those little wrapped leads. ozmoid, the solder spudge (love that term!) is key. That and the minipliers. I was working with regular needlenose pliers for awhile - don't go there! Come to think of it, the spring-type solder sucker is a lovely device, too...

 

[blue_lateral]

What Soundmotor said.

I would only add that you can help a lot by adding a little new solder to the joint to get things flowing, before you hit it with the solder sucker. I reccommend the big blue and yellow "soldapullt" by Edsyn if you can find it. Edsyn also makes more modern smaller soldapullt's for modern circuit board work. For point to point (or big old through-hole circuit borads from the 50's and 60's) you want the big one.

Sears has a 3 piece set of 2 kinds of needle nose pliers and a 1 small dikes that are extremely handy for working on point-to-point. They're cheap, too. They have hideous bronze and black handles.

I dont think I have ever resorted to 800 watts for anything except soldering directly to the chassis, but nearly always the best policy is to get in, get it hot fast, get done and get out. I wont argue with the 800 watts, though I use a Weller temperature-controlled station. It's probably more like 40 or 50 watts.

I use Mhardy's method usually if I'm working around unobtainable parts, like wafer switches, and it looks like the old leads wont come out easily. By the way, there is no good reason I can think of to wrap the leads around the terminal like they used to do. Just stick them through the holes and solder them. The next guy will thank you.

John

 

[soundmotor]

^^^

Everyone should question my 800W iron.

That is only useful if you are trying to melt copper, steel, & perhaps the table underneath.

Weeeeeeeeeeeeeeeeeeee!

My Weller is a 60W station rather than a handheld, direct plug-in.

I am going back to bed now.

 

[Clmrt]

My soldering iron is Class-A.

 

[Bob E.]

By the way, there is no good reason I can think of to wrap the leads around the terminal like they used to do. Just stick them through the holes and solder them. The next guy will thank you.

Well, you really do want a good mechanical connection established either by crimping or wrapping...not only is the electrical connection better, the sturdiness of the joint is much improved and you also avoid cold solder joints. Solder is a much poorer conductor of electricity than a good mechanically-established joint.

--Bob

 

[blue_lateral]

Well, you really do want a good mechanical connection established either by crimping or wrapping...not only is the electrical connection better, the sturdiness of the joint is much improved and you also avoid cold solder joints. Solder is a much poorer conductor of electricity than a good mechanically-established joint.

--Bob

I'll admit that I still do it sometimes, but..... several months ago I recapped an old Tektronix scope from the mid 50's. Tek equipment from that era is probably the highest quality tube-based equipment ever made, period. There wasn't a wrapped connection in it anywhere.

It was really nice, because some of the caps were on rotary switches, in really, really inaccessible places. I just heated them up, hit it with the solder sucker, heated again and pulled the old parts out. I put the new ones in the same way they were originally. Things look as nice in there now as they ever did, and it was easy.

There is a persistent story about Howard Vollum, founder of Tektronix. He was an electronics enginneer or tech of some kind in the military during WWII. The U.S. military required wires to be wrapped at that time, I believe two wraps on everything. Howard apparently felt very strongly that this was a bad idea. After the war, at Tektronix, he insisted that it not be done. There was some contention with the military about this, because Tek scopes were not "mil spec". Based on his experience during the war, Howard felt that if there was a bad solder joint, you wanted it to fall off so you could find it, rather than poke around for two days looking for it, possibly while under attack. There was also less chance of breaking stuff while doing repairs. He held his ground, and eventually the military saw it his way, or at the very least bought a bunch of Tektronix oscilloscopes.

I rebuilt an old shortwave set recently, and because of it's military origins (sort of) I wrapped all the wires... almost. I just laid the wires through on the most fragile parts, like the wafer switches and the coil forms.

I had the coil stacks out of it three times before it was done. Nothing broken. I'm sure glad I didn't wrap those wires.

John

 

[skippy_ps]

This is an interesting thread expecially the thoughts on wrapping/not wrapping. I guess it makes common sense to wrap some, like 1 90 degree bend or bend back around but I've wondered how much difference it actually makes regarding conductivity and not really worrying too much about the security. If that makes any sense.

Murray

 

[ozmoid]

WOW, you guys have really got something going with this thread! Excellent! I had only intended to make a little statement of discovery, because I had never done anything like this before, and those of you who have experience take little things like the wrapped leads for granted. Thanks for all the posts and info, I'm really impressed!

Sears has a 3 piece set of 2 kinds of needle nose pliers and a 1 small dikes that are extremely handy for working on point-to-point. They're cheap, too. They have hideous bronze and black handles.

And THIS is also one of the things I like about AK: Members urging other members to buy hideous tools! I'm gonna go find a set!

 

[Bob E.]

According to the 1969 Radio Amateur's Handbook, resistivity of metals is calculated by measuring across a cube one centimeter on a side. The following table compares various metals against copper (thus copper is shown as "1", not one ohm, just the base against which other metals are compared).

Aluminum (pure)..........1.6
Brass....................3.7 - 4.9
Cadmium....................4.4
Chromium...................1.8
Copper (hard-drawn)....1.03
Copper (annealed).......1.00
Gold..........................1.4
Iron (pure).................5.68
Lead.........................12.8
Nickel.........................5.1
Phosphor Bronze......2.8 - 5.4
Silver.........................0.94
Steel.....................7.6 - 12.7
Tin.............................6.7
Zinc...........................3.4

I've talked to engineers at my shop over the years, and I have gleaned that the lowest resistance electrical connection is a gas-tight interface where the contact and wire have been mechanically deformed into each other, as in a wire-wrap connection like the phone company used to use, or an insulation-displacement contact that bites into the wire. Solder, being an alloy of lead and tin would appear to be anywhere from 6 to 12 times as much resistance as copper. Don't know if it is enough to make a difference at the frequencies and currents we deal with, but there must have been a reason they took the extra effort to wrap the wires in point-to-point days!

--Bob

 

[blue_lateral]

Your point is well taken. There will always be some solder in the current path, but there will probably be less solder in the current path in a wrapped connection.

John