pin-diagram vs schematic

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pin-diagram vs schematic

Post by DancingBear on Mon Feb 18, 2013 1:04 pm

I'm working on a Zenith 547S chassis. I'm about ready to wrap it up after a five socket swap and am checking my work. I was trying to figure out wtf a PDF file is and how to get it on here but failed. Still trying but I think this can be answered without a schematic.

On the 7B4 pin-out diagram they label one of the pins IS (fuzzy), I believe it is a suppressor grid and lists the connection as having 0 volts. Every other connector in the diagram that is labeled on the pin-out has a wire connected but this one doesn't. I've checked my notes and the pix I took beforehand but it took me awhile. The schematic doesn't show the connection or even the element.

So, whilst I'm trying to figure out PDF files, the question I have is about whether the two diagrams can conflict like that for no reason? Why did they label it and put a voltage there, even though it could indicate nothing? Would it be wise to connect it to ground to at least achieve the 0 volt point? That idea scares me with all the odd ground practices I've noticed since trying to re-educate myself.

I chased this awhile but shouldn't have. I really need to figure out how to get one piece of a PDF schematic on here. I'm sure the info is there but in the meantime I thought I'd ask.

Tony
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Re: pin-diagram vs schematic

Post by Dr. Radio on Mon Feb 18, 2013 10:58 pm

I'm not sure what a 547S is....is that a chassis # or a shorthand version of a model #?

A direct link would help, even if it's a link to the PDF file to review.
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Re: pin-diagram vs schematic

Post by DancingBear on Tue Feb 19, 2013 11:54 am

I appreciate the response. Weird question and I'm not sure I asked it correctly. I have answered it by looking around at a few other schematics. I see a few other instances of this but not many. In my case it was only brought into question after I changed all the sockets and then verified wiring. In my experience it is always worth looking into if someone took time to label it, and in this case apply a bias to it even if only on the socket-voltage chart.

I need to sit down and figure out how to do the transfer of info like pix and schematic diagram onto the site. I have accomplished the task before but, as with most computer functions, I have no idea how it got done. I'm at that 'event horizon' in life where the intelligence of the computer is eclipsing what is in my head. But we argue...
Tony
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Re: pin-diagram vs schematic

Post by jtauser on Fri Feb 22, 2013 3:17 am

If you post the serial number of the chassis I can look it up in my Zenith service literature and determine the model number.

Joe T.
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Re: pin-diagram vs schematic

Post by DancingBear on Sat Feb 23, 2013 4:34 pm

I had to replace five of the sockets. The phenolic-composite material decided to deconstruct after I recapped. They were in need of a good cleaning anyways and may have prompted the swap regardless. 75 years was too much.

I was able to get things going again without too much of a hassle. The odd wiring point on the schematic was confusing me. My question is from a purely speculative angle. I'm now used to modern schematics mixed with PLC crap so am just trying to re-educate myself. Each generation adds and subtracts from the patterns.
Tony
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Re: pin-diagram vs schematic

Post by GaryRabbitt on Sun Mar 17, 2013 9:44 pm

Perhaps you damaged the tube wafer by trying to remove the wires on the lugs? They don't like heat. Recapping, you can usually leave a small stub to connect your replacement cap to.
Sorry you had to replace those, I have replaced one or 2 on different chassis, but not 5.
As for the PDF file it's an Adobe format, you can install the Adobe Reader.
Once you can view the files such as on Nostalgiaair, you can save then to your system. Then you can copy just a portion of one diagram, (copy) then paste in MS Paint, save as a regular image (jpg).
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Re: pin-diagram vs schematic

Post by DancingBear on Sun Mar 17, 2013 11:49 pm

I appreciate the help. This is my first radio after a long time away from this facet of "repair" and have learned the hard way that restoration bears little resemblance to repair as I understood it. I think I boasted of my soldering skills at one point and figured I would have little problem going down onto the socket lugs to rebuild circuitry as I was trained to do.

One socket was broken beforehand but I think I could have fixed that without much of a problem if I'd looked closer.

My problem now is the transformer. It was OK when I first got it going again but now there is fresh "oil" oozing out and my secondary voltage keeps climbing.

This stuff can be real humbling.

Tonym
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Re: pin-diagram vs schematic

Post by GaryRabbitt on Mon Mar 18, 2013 12:32 am

Hi,
Yes, I learned the hard way too a long time ago. I thought it would look nice to remove the old part from the lugs, (that had other components on it too) and then install the new. The heat however took it's toll on that phoenelic stuff and made it very brittle, then the lug came out! So, I can feel your pain in installing 5 sockets, that surely wasn't any fun. But, you did learn something I hope.
The same will be true if you ever have to replace rubber wiring on an IF transformer. It goes up insnde of the can to the terminal with hair thin wires. While we can install shrink tubing up into the can on some leads, sometimes you may want to add a whole new wire.
I have the can out of the chassis, and the cover off. I snip the lead about 1 inch or so before it connects to the lug inside.
Now, solder your new wire to that stub, add shrink tubing to cover the joint. That way, you never have to melt the solder right on the lug and possibly disturb or break that hair wire that goes to the coils.
OK, that sounds bad that your trans is oozing, very bad.
If you pull the tubes, then apply power to the trans. Does it still get hot or sizzle? It shouldn't. If it doesn't, the trans might be fine. Add the tubes, except the rectifier, apply power.
Does the trans start to heat up? If not, good. You probably have a high load on the transformer HV, is is the 6X5 tube rectifier?
(I have never heard of a 547S chassis)what are we working on?
I don't see if you have replaced any capacitors yet. Your filter caps, ones with the large values, might be shorting, causing your trans to heat. Don't go and replace every cap at this time.
Obviously you have something that is either miswired when you replaced those sockets, or your filter caps have not been changed, or are miswired.
The tube you mentioned, 7B4 that's a Loktal with the special socket. Did you have to replace those? There is a way to properly remove those tubes, you can't just pry them up.
If there is a Zero voltage reading on a socket pin, you don't want to add in a wire to ground it. There may be a reason it is not grounded. Remember, some unused socket pins are only "tie points" and might not connect to the tube's elements.
Personally, if the set were mine, I'd have the correct schematic in front of me (using Adobe PDF reader ) then starting with the AC plug, trace every wire that you resoldered. Mark it off on the diagram with a yellow highlighter to verify it's 100% correct.
It might get confusing I know.You should be able to do it though.. I have had to go over someone else's work more than once to find where they made a mistake, or more then one mistake.
PLease get back to us with the set you're working on. Or, at least post a link to a photo of the same set. Did I mention Adobe PDF reader Smile Good luck!


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tnx

Post by DancingBear on Mon Mar 18, 2013 1:23 pm

Thanks, Gary. All good points.

I apologize for stating the weird chassis number. I have five radios and I refer to them through a number I found on the schematic. After looking I now discover why people have been confused. I was using model #. The set is a huge tombstone Zenith model 7s547 chassis 7A02. I may have another 7A02 chassis later this week as my friend claims to have one in his barn.

The transformer is definitely bad. I'm not sure it ever got real hot for me but when the high voltage secondary went up I noticed the fresh seepage. The winding R has increased from 385 to 440 ohms. Primary about the same. I am also getting leakage between the primary and secondary.

I am pretty sure it isn't wired incorrectly but 'pretty sure' is all I can go on that. I'll admit to being thrown by a few details during the recapping/resistor swaps but I kept good notes as I proceeded and referred to the Macro-pictures taken when I opened it up. BUTÖand a big one, I have good days and I have bad days. I try to work only on the good ones but I may not be the best judge of the parameters.

I read Wildcatís downsizing thread and can relate to a lot of what he and contributors have offered. I quit silently a few times over the last months but never went through with it because I really need the mental exercise this stuff gives. I was bedridden for a long time and incapable of doing anything except write. I had some success there but tired of it and wanted to quit pain medís and be more active again. I did both.

I figure Iíll be in a wheelchair before long so getting set up and running with confidence is important to me. I love complex problems but, as anyone who has done it knows, it takes thinking on several levels. Iíll never get my brain back to where it was twenty years ago but I now have days where things are rosy and my logic isÖlogical. Other times it seems I have a bird in my head.

Itís nice to have help. I welcome any and thank you for the offer.

TonyM
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Re: pin-diagram vs schematic

Post by GaryRabbitt on Mon Mar 25, 2013 2:11 am

Hi Tony. When you are measuring the transformer leads for resistance, do you have the trans isolated from the rest of the circuit ? If it's still connected, that might throw a reading off.
I'd pull the tubes, then apply power to the trans. If it is a bad trans, you'll hear the sizzle, possibly see smoke.
But if it sits there and does not get hot/ had the correct voltages coming out, the issue might not be the trans.
The trans could be wired in wrong too, if it's a replacement. Shouldn't take long to verify the wiring in the power supply section.
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Re: pin-diagram vs schematic

Post by DancingBear on Mon Mar 25, 2013 11:48 am

Thanks, Gary. I isolated it before checking and then I pulled it. There isn't a lot of tar coming from the hole on the bottom but there was fresh every time I ran it up with a load connected. It's a metal-enclosed can-type xfrmr that looks like that big black rock the Muslims circle in Mecca. that I'm guessing the turns-ratio has been altered with a few internal shorts. The filament voltage was up around the 7.9 VAC region (under load).

I've shopped around but have yet to find a replacement. I put in some queries so maybe today I'll get a positive response. I work with a "picker" who finds things for me and he said he had another 7A02 chassis but he's on the road until later this week. I'm still looking because there is no guarantee that one will work

Oregon is having wonderful spring weather.

TonyM
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Re: pin-diagram vs schematic

Post by GaryRabbitt on Sat Mar 30, 2013 3:47 am

Hi Tony,
You might try the ARF classified column. I think I know the transformer you are talking about. I have a 6A02 Zenith that used an enclosed transformer. Before I bought the set, 6X5 tube had shorted and took my trans out. Was yours like the style in the photo below?


If so, I was able to pull the old trans out of the box, then install a standard type inside.




There should be a number on the transformer case side.
When I did my set, one of the guys on the "other forum" had specs for that part number.
I bought the transformer from RadioDaze IIRC.
I know I had a guy send me one trans, NOS but it was slightly larger and would not fit on the chassis. Perhaps that trans would have fit your set. That is, if you use the same type. I could put you in touch if need be.
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Re: pin-diagram vs schematic

Post by DancingBear on Sat Mar 30, 2013 12:45 pm

Gary-
This was extremely helpful and answered several ??? I had. Thank you so much.
TonyM
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Re: pin-diagram vs schematic

Post by DancingBear on Sat Mar 30, 2013 12:50 pm

I should mention the one pictured is the same type as mine. I was going to ask today if anyone had ever taken one apart.
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