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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Oct Mon 14, 2013 5:09 am 
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Dutch Rabbit wrote:
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.
I agree.

If something is (? obviously ?) factory-original, I replace with the same value.

- Leigh

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Oct Mon 14, 2013 7:10 am 
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Leigh wrote:

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


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.

The epitome of that could very well be Packard-Bell, but of course there are always exceptions.
I've noticed in particular with early RCA coat pocket size Transistor sets, it seems that every time they so much as replaced one resistor, they would change the model number by a letter or a digit.
As an example, the 8-BT- 7J, 7LE, 8FE, 8JE, etc. No difference in any of them except a one or two passive component change.

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Oct Mon 14, 2013 3:40 pm 
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The modifications were especially prevalent in the 1946-51 era, due to parts and tube shortages; some changes were never documented by Rider or Sams.

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Oct Tue 15, 2013 12:35 am 
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I was going through all the resistors on a Philco 41-300 chassis measuring them looking for out of tolerance. I compared each one cross referencing the location chart to the parts list and the listed rating of each one. Interestingly I found two that werent on the parts list at all. After thoroughly searching the schematic I found those two resistors. One was listed with no reference number circled next to it like all the rest. It was physically hidden down inside the frequency selector switch. I had to cross the hard to see color code and measure its resistance and found a match on the schematic. The other was listed with a reference number but it had a suffix. It was listed as 78x on the schematic but there is also a #78. But on the parts list there is only listed the #78. Neither part was on the location drawing chart.

I figured that this may have been due to later changes in the schematics during production, but the parts list never was updated to reflect it.


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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Oct Mon 21, 2013 4:16 am 
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One more hint, which was recently brought up in another thread:

Watch out for two-section tubular capacitors! They look just like a standard tubular capacitor, except they have a mounting strap; this is the common for both sections of the capacitor, which is usually connected to chassis ground. They were used by Crosley and Belmont in the 1930s, and they also turn up in the other brands which Belmont made, such as Airline, Freshman, and others; RCA also used them, without the strap, in a few 1940s sets. Don't be confused by these, and replace them with a single capacitor; it's an easy mistake to make, and I have seen it done. Crosley also used some single-section capacitors with the mounting strap, so check the parts list to be sure.

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Oct Mon 21, 2013 10:08 am 
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fordtech wrote:
I figured that this may have been due to later changes in the schematics during production, but the parts list never was updated to reflect it.
That's quite probably true, and a very common situation.

Publishing service documentation was an overhead expense.

All companies want to minimize overhead.

- Leigh

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Jul Sun 27, 2014 3:12 pm 
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Thanks to everyone for all the information and opinions all info is appreciated. I am a "noob" I have not started a repair yet I am gathering repair info and test equipment to start my first project. Bendix 55P2U. Thanks again, Richard


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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Oct Sun 12, 2014 4:22 am 
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I felt it was time to give this useful thread a bump.

Don't use a digital camera to just document before you work on a set. Take plenty of pictures afterwards as well. Doing so really can help if something goes wrong. And the pictures can become a handy reference when working on an identical unit in the future. Also useful when you want to refer to prior work you did without having to re-disassemble a set to find out.

- George

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Oct Thu 16, 2014 4:17 am 
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Another hint: Watch out for open coil and transformer windings! Besides the "green coil disease" which affects 1930-36 Philcos, many radios and theatre/jukebox amplifiers used interstage and driver transformers, and the plate windings are often found open. It's also not uncommon to find open speaker fields, IFs, and output transformer windings as well. A quick ohmmeter check will weed these out. If the break is on the surface, where the wire is connected to a terminal or pigtail lead, the repair is simple; the Philco coils can be rewound without too much trouble. If the break is deep in the winding, you're out of luck.

Although Hammond makes a good line of audio and power transformers, things like IF transformers and coils require a parts hunt; often a parts chassis can be found.

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Nov Sun 06, 2016 7:57 pm 
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Another big hint...Fuses! Although most radios did not have AC line fuses, some did. They are also commonly found in many TV sets, as well as theatre and jukebox amplifiers, auto radios, and ham/communications gear. It's always a good idea to check them for the correct size and type; it's not uncommon to find a piece of equipment "upfused" with one far in excess of its intended rating.

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Nov Mon 07, 2016 1:51 am 
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Tim Tress wrote:
Another big hint...Fuses!

That reminds me of the easiest fix I made, when I worked at a TV-Stereo repair shop. Someone brought in a stereo with separate speakers, with the complaint that one channel stopped working. In checking, I determined that the speaker cabinets had fuses, and one of them was open.

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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Nov Sat 19, 2016 9:16 am 
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BigBandsMan wrote:
Since the Riders are often so hard to read, I stay away from them as much as I can, so I don't have the experience with them that I might have. It seems logical to me, however, that if they failed to update Philco schematics, they wouldn't be too intent on updating others.

:? Larry


Riders definitely has its downside but unfortunately sometimes they are the only schematic available for a particular model period. I own hard copies of the Riders which takes up a lot of room but I like to be able to look at it in hard form. I have found the printing quality isn't bad on the originals. There are a lot of schematics that aren't updated and my first choice is Sams. But as stated for many early models not an option. Sam


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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Dec Fri 23, 2016 8:51 am 
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I'd like to put my $.02 in if I may...when replacing a cap. I clip one lead,then solder the new lead in, then do the other lead, that's the only way for me not to forget which lead goes where..hope this helps. :)


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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Dec Sun 25, 2016 1:13 am 
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As far as taking pictures i have found that if you are working on a radio for a customer they really like to see the before and after pictures. They may not understand any of it but they can see the new parts and clean chassis etc. Really good for public relations. Once the chassis is put back in the cabinet no one can see any of this
Stan Ski


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 Post subject: Re: For the Noob: Wiring Errors and Pitfalls to Avoid
PostPosted: Dec Sun 25, 2016 6:15 pm 
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Before embarking on a chassis restoration, I make a grand sketch on 11 x 17 paper, and sketch in all resistors and capacitors I'll be replacing. Everything is cross checked against the schematic and parts list to make sure all information matches. I even go so far as to modify the schematic on the computer and print it out, to simplify the information and add what is needed for easy cross checking during recapping and making it easy to read.

I do everything I can to eliminate mistakes during recapping.


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