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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Mar Wed 13, 2013 2:02 am 
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fifties wrote:
Leigh wrote:
Some people advocate soldering the new lead to the cut-off original lead. I don't do that, nor do I recommend it.

I see nothing wrong with doing it that way, esp if the original seems to be correctly soldered at it's other end, and it's difficult to get to. Very often those leads are simply going to circuit ground and/or the chassis. I've never had a problem with this procedure.
I didn't say there was anything wrong with it.

It just looks "untidy". :D

Back when I was doing repairs 50 years ago we'd encounter this occasionally, from previous repairs.
We always considered it to be "unprofessional".

There are certainly circumstances, particularly in crowded small chassis, where it does simplify the repair effort.

- Leigh

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Mar Wed 13, 2013 5:31 am 
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Leigh wrote:
fifties wrote:
Leigh wrote:
Some people advocate soldering the new lead to the cut-off original lead. I don't do that, nor do I recommend it.

I see nothing wrong with doing it that way, esp if the original seems to be correctly soldered at it's other end, and it's difficult to get to. Very often those leads are simply going to circuit ground and/or the chassis. I've never had a problem with this procedure.
I didn't say there was anything wrong with it.

It just looks "untidy". :D

Back when I was doing repairs 50 years ago we'd encounter this occasionally, from previous repairs.
We always considered it to be "unprofessional".

There are certainly circumstances, particularly in crowded small chassis, where it does simplify the repair effort.

- Leigh

If the wiring was in public view, then of course I would agree to give the extra effort and completely replace a component lead, for appearance purposes.
As we are primarily discussing component connections under the chassis, however, I feel that whatever works the easiest, while not conceding any safety measure, is perfectly fine.

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Mar Wed 13, 2013 3:48 pm 
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Some more tips....

1. Heat rises and solder falls. If soldering to a terminal, it is perfectly OK to tip the chassis on its side before you start in order to keep the molten solder from running down the terminal, and possibly shorting to the chassis.

2. Watch out for those IF transformers! Solder blobs and wire snippings have a tendency to go down the hole in the chassis where the wires from the transformer come out; this can cause a short.

3. Never turn the radio on with the field-coil speaker disconnected! With no load on the power supply, the output voltage from the rectifier may exceed the rating of the input filter capacitor.

4. Check your work! Go over the work that you have done, and check it against the schematic. Pay close attention to capacitor polarity and resistor values; these trip up many novices. Watch out for accidental shorts and missed solder connections.

5. Make a sketch of the wiring before removing a component; this is especially helpful with multi-lead parts like transformers coils, and electrolytic capacitors. Don't trust your memory!

5. Don't try to work when you are tired, stressed, angry, or under any influence of drugs or alcohol. You may make mistakes and even compromise your safety.

I do try to make my wiring at least as good as the factory work, but that is my own preference.

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Mar Fri 15, 2013 3:46 am 
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All of this and more elsewhere could and should be compiled into a nice guide book. We can all work on it.

Sometimes you do need to deal with several parts at once, but keeping track makes it go well. For example, I'm now restoring an AM/FM chassis which has two resistors, a capacitor, and a wire going to one lug on a terminal strip. The resistors had risen high enough in value to need to be replaced, and the capacitor needed to be replaced. Obviously, all three parts need to be done together. The other end of the capacitor goes to ground, so the first step is clipping out that bulky old thing, cutting close to the body. Next, desolder the lug. I like to use desoldering braid, but some others like solder suckers. Then I removed the wires for both resistors from the lug, leaving them atatched at teh other ends. In the case of this radio, one resistor is orange-orange-orange and the other is orange-orange-red, so mixing the up would be VERY easy. To avoid that, I first attached the new capacitor, using the free of the old wire on the chassis ground point (or just solder the new wire to the chassis ground point, which ever is easier in a particular situation). Then I attached the other end of the capacitor and the two new resistors to the lug on the terminals strip and soldered. I then detached the other end of one of the old resistors and soldered in the other end of the new one. Then likewise with the second resistor.

Sometimes you can twist the free end of an old part to the free end of a new part to help keep track when multiple tasks need to be completed together (especially when some parts are under others). Of course, photos are easy to take, and sketches are easy to make. Jumper leads can also be handy, attaching the ends where some part should attach (especially good if you have to stop work, or go get/buy the part.

It is very helpful to have a schematic when you can not read the value of the old part, or somebody has previously replaced the original part and may have used an incorrect value replacement part. I'll be stuck doing that all throughout my Philco 38-690. I'm starting to understand that certain values you see over and over can be used in certain applications when no other information is available, but many others here are very good at understanding what works where and why, so encouraging new or less experienced people to see help in person, by phone, or on a forum is also important.

BigBandsMan wrote:
ONE: ERRORS DUE TO WORKING WITHOUT THE SCHEMATIC.... If the “noob” tries to do without it, wiring errors are foreordained.
Perhaps not. Taking care to keep track of where you are is even more important. My first radio, the one I started with, is one for which no schematic is known to exist. It is a radio, record player, record cutter. The bad 6X5 had killed the power transformer, and all of the other tubes were bad. It works fine now. This web site was quite helpful, as I did not even know AC & DC could be in the same wire at the same time when I started.

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Mar Fri 15, 2013 8:08 pm 
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Just a few more things.

Take plenty of pictures of the "before" layout, and make clarifying notes if needed. Follow original paths with all replacement parts or wiring. It matters!

Never bridge old filter capacitors with new ones. Disconnect, remove, or restuff old filter capacitors.

If it is obvious that some repairs or replacements have obviously been done in the past, do not assume they were done correctly. Follow the schematic.

When replacing components, I like to desolder everything from a terminal or tube socket pin, and get all the new parts or wiring installed before resoldering. Make sure you have a good mechanical connection before doing so. OK to temporarily wrap other end of new part to tail of old one so you can proceed in an orderly fashion. Use heat shrink tubing.

I routinely replace carbon resistors because so many of them are either out of range or become undependable when set warms up. Resistors are cheap enough. Not everyone agrees with this or anything else.

If leads need to be really short, an alligator clip or good old fashioned semiconducter heat sink clips can prevent any overheating, especially on resistors.

Rivited ground connections on terminal strips, tube sockets, etc... can become corroded and unreliable. If you suspect this, brush them off and solder 'em shut to the chassis with a large iron or gun.


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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Mar Fri 15, 2013 8:54 pm 
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codefox wrote:
Rivited ground connections on terminal strips, tube sockets, etc... can become corroded and unreliable. If you suspect this, brush them off and solder 'em shut to the chassis with a large iron or gun.
That, or add at least a partial ground bus.

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Mar Sun 24, 2013 9:45 am 
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Many thanks for all the additional suggestions, guys. Much obliged.

:wink: Larry

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Sep Sun 01, 2013 1:37 pm 
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Bump, for the sake of all the "noobs" who have arrived since this thread was last current...

:wink: Larry

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Sep Sun 01, 2013 8:01 pm 
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Thanks for "bumping" this, Larry.

Great work by you and all who contributed!


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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Sep Mon 09, 2013 4:05 am 
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fifties wrote:
Leigh wrote:

Some people advocate soldering the new lead to the cut-off original lead. I don't do that, nor do I recommend it.

I see nothing wrong with doing it that way, esp if the original seems to be correctly soldered at it's other end, and it's difficult to get to. Very often those leads are simply going to circuit ground and/or the chassis. I've never had a problem with this procedure.


Agreed. There IS nothing wrong with that method. I do always try to desolder the original, clean out all the old solder, and trim and neaten things up a bit. But if it's tough to get at or the solder joint looks clean and solid and I'm going to be doing more disruption than it's worth, I won't hesitate to snip the old one out and solder to the stub. I personally like the method of creating a "pigtail" with the lead of the new component, and slipping it over the stub of the old. It works great and looks neat.

I'd bet every radio I've restored has at least one, and most have several capacitors that are soldered in that way. Again, it's the exception rather than the rule, but I don't hesitate to make that exception where prudent.

Jeff


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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Sep Tue 17, 2013 1:51 pm 
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Beware of previous repair scenarios. Every tech has his own ideas of work arounds to the original design to get the radio working. Some are very different than the schematic and you may have to delete all those "add ons" and depend on the schematic to get it all back to original design. I was installing some resistors in my Philco 41-250 last night that had been reworked by someone decades ago. It had an extra 470k resistor off the push pull tubes not on schematic. If I just popped in another where that was without going by the schematic no telling what kind of issues I may have been trying to resolve post repair.

I didnt read it in this thread so Ill offer also to make sure you get a good hot solder joint. A cold joint can really leave you scratching your head later.


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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Sep Tue 17, 2013 9:58 pm 
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fordtech wrote:
Beware of previous repair scenarios. Every tech has his own ideas of work arounds to the original design to get the radio working. Some are very different than the schematic and you may have to delete all those "add ons" and depend on the schematic to get it all back to original design.

Very good point.

I recently restored a Packard Bell model 48, which amazingly did work when I got it...Sorta. It picked up two local stations, but with heavily distorted audio.

Among the dozen or so -superfluous to the schematic- parts I removed, were two Transistors and a Diode!

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Sep Sat 28, 2013 3:24 pm 
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More tips:

1. Be wary of parts substitution! Many servicemen used whatever replacement parts which were in stock, especially during WWII, and it's not uncommon to find poor substitutes. Watch out for wiring errors on replacement transformers and other parts.

2. Some resistors and capacitors from the 1930s and 1940s may look unfamiliar to those used to present-day components. If you don't know what a part is, check it against the schematic.

3. The early IRC "BT" insulated tubular resistors often used in Philco, Scott, and other makes cause much confusion. They use the same color arrangement as the "dogbone" type, although the third-figure dot is usually replaced by a color band. This type of resistor is easy to spot by its "airbrushed" appearance.

4. Another resistor which confuses newcomers is the Micamold wirewound type, sometimes found in 1935-50 equipment. It closely resembles a mica capacitor, but the body is more slender.

5. Make sure that all of the tubes are correct, and in their proper sockets. A non-technical seller may "fill" an empty socket with any extra tube on hand which will fit.

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Sep Mon 30, 2013 5:42 am 
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in today's world of digital electronics and the convenience of them,

Take Lots of Pictures with your digital camera. take birds eye views of the underside of the chassis, turn on 'macro' and take closeups of every tube socket, every control, and nearly every location of the underside of the chassis. then, go in at an angle, snapping pictures all around the perimeter of the chassis, angling down into it to see all the components, wires, etc.

before every repair/restore, i take 50-75 pics of the underside and a few of the topside of the chassis.

only a couple times in the past years have i had to reference the pics b/c i work from the schematic and such. but when the chassis and the schematic disagree, and/or i became confused, the original unmolested chassis pics saved my hind end and saved it big those couple of instances !

also, there are those momentary laps of memories where a pic is worth a thousand words. the pics can bail you out, and i mean bigtime.

so, on top of everything said here, which is a fantastic writeup (it should be published), take lots of up close, high resolution, macro resolution pictures.

i recommend this to one and all, especially to newcomers in the hobby. snapping 50-75 pics costs you nothing and it just may save the day. they are just another form of reference if needed.

steve

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Sep Mon 30, 2013 12:36 pm 
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Again, all thanks to all who have contributed to this thread. This has turned into a fine primer on wiring and repair technique in general, and I agree that it should be circulated as widely as possible.

Thank you again,

:wink: Larry

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Oct Tue 01, 2013 1:01 am 
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Is there a place for "sticky" posts and a major thread for beginners?

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Oct Mon 14, 2013 12:09 am 
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Here's another big hint... it's not uncommon to see an old set which has been recapped previously; this is especially true of old commercial equipment like theatre/broadcast/jukebox stuff, but applies to radios and TV sets as well. The work may have been done decades ago, and the replacement capacitors themselves may be bad. Obviously newer components, such as "orange drops" are likely to be OK, but beware of any replacements which appear to be very old. Some older replacement capacitors may check OK on leakage, but are now showing internal resistance, which may cause problems in some circuits; when in doubt, it's better to replace them. Of course, any vintage electrolytic capacitor is suspect.

Another good timesaver is to print out a copy of the schematic, and circle each component with a pencil as it is replaced. This can help keep you from losing your place, when you stop working for the day.

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Last edited by Tim Tress on Oct Mon 21, 2013 6:50 pm, edited 1 time in total.

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Oct Mon 14, 2013 2:18 am 
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in addition to the above,

always check the schematic and make sure the correct called for components were used in that old repair. many times, shops used what they had on hand to get the radio out of the shop, as in a 50 mfd first filter off the rectifier which only likes 10-30 mfd.

i've seen some vintage repairs that were not wise repairs.

one can't always guarantee the repairman used the called out parts back in the day.

** all this information should be published somewhere somehow for new persons to the hobby. this thread should always be at the top of the catetory just like the thread Suppliers for tubes, parts, knobs, grill cloth, post which stays on top in the "tubes and parts" category. we experienced ones can continuously add to it.

steve

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Oct Mon 14, 2013 4:41 am 
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Dutch Rabbit wrote:
always check the schematic and make sure the correct called for components were used
one can't always guarantee the repairman used the called out parts back in the day.
Unfortunately that was also true of the factory.

The whole focus of the factory was to ship radios, not to write documentation.

If a production manager told the VP that they had stopped shipping because one component was out of stock, that manager would be standing in an unemployment line. Any part that was close was used.

Beyond that, significant changes in the radio design might have been made for any number of reasons.
A large percentage of these never made it into the documentation, which was an overhead expense.

- Leigh

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Oct Mon 14, 2013 5:07 am 
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Quote:
significant changes in the radio design might have been made for any number of reasons.
A large percentage of these never made it into the documentation


i've seen schematic versus chassis differences. with that said, if the set was untouched, no sign of rework, etc., and the part was different from the schematic, i install the value of what came out of the untouched chassis.

on the other hand, if it was a known reworked/replaced component, i raise some eyebrows and investigate to confirm.

but what if a defective component was replaced with the exact original part value that came out of the chassis but it differed from the schematic back then ?

oh the variables.

steve

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