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 Post subject: Zenith 6G501M portable
PostPosted: Apr Tue 07, 2020 1:51 pm 
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I'm working on my second radio project. This is a Zenith AC/DC portable.
http://www.nostalgiaair.org/pagesbymode ... 025125.pdf
According to the schematic there are 5 electrolytic capacitors, I've located 2 double electrolytics mounted on paper tubes.
Are there 4 or 5 electrolytic caps? Where would you mount the new electrolytics; in the paper tubes?
Thanks
Steve

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 Post subject: Re: Zenith 6G501M portable
PostPosted: Apr Tue 07, 2020 2:52 pm 
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It appears that there are five electrolytic caps: three in one multicap and two in the other. The multicaps can be disconnected from the circuit and five discrete axial-leaded caps wired in underneath the chassis.


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 Post subject: Re: Zenith 6G501M portable
PostPosted: Apr Tue 07, 2020 7:11 pm 
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STYMIED!
There are 2 double caps on this radio. #22-1026 is a double 40mfd and 20mfd.
#22-1081 is a double 40mfd and 20mfd. These are riveted to the chassis and appear to be original.
The schematic shows #22-1159 as the triple cap which I think is 20mfd, 40mfd and 40mfd.
Any help is appreciated.
Steve

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 Post subject: Re: Zenith 6G501M portable
PostPosted: Apr Tue 07, 2020 9:13 pm 
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Are you sure of the model number? chassis number? There were many of these Zenith universals that only used 3 electrolytics.

DM


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 Post subject: Re: Zenith 6G501M portable
PostPosted: Apr Tue 07, 2020 11:20 pm 
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I wouldn't worry about it to much. Maybe they ran out of the 3 cans when yours came down the line so they used what was available to keep the line moving. The missing one may be the 40 C12 connected to3Q5 pin 7. The filaments already have 3 electrolytics attached. It doesn't need another IMO.
Just run through the schematic and see which one is missing. You could add number 5 under the chassis or stuff it in a can,

Freeman


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 Post subject: Re: Zenith 6G501M portable
PostPosted: Apr Wed 08, 2020 8:34 pm 
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I may be incompetent, but I don't know what I'm doing. The 3Q5 pin 7 is connected to a 20mfd capacitor zenith # 22-1069 under the chassis. One end is marked + so I'm thinking it is an electrolytic. I tried to disassemble a double electrolytic tube on a spare 6G601 chassis I have but they seem to be filled with tar so I guess I'll have to mount new electrolytics underneath. How do I determine which end is positive?
I'm in over my head on this one. Probably should have done another easy one, but I'm detrmined!!
Thanks for any help
Steve


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 Post subject: Re: Zenith 6G501M portable
PostPosted: Apr Wed 08, 2020 11:26 pm 
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Yes. You want the positive (+) side to pin 7. The negative side may have a metal plate and that goes to B-. Does it look like it is an original part the factory installed? Are we talking about just one cap with two leads?
So there’s your missing cap and Zenith must have had a real bad day because the schematic calls for a 40u. NBD as a 20 is fine.
You shouldn’t have trouble restoring this, as it’s just a nice AA5-6 radio.
Take pictures, make a diary (take notes) as you go along, and compare everything you do with the schematic. Then move along to the next part you want to replace. It’s easier finding a mistake now, then at the end when the radio doesn’t work and you have to go over the whole chassis to find your screw up.

Been there, done that.
Freeman


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 Post subject: Re: Zenith 6G501M portable
PostPosted: Apr Thu 09, 2020 1:58 am 
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I will be watching this thread as I am working on one of these too! I changed the electro's and the hum is gone but now the radio is fairly silent and I cannot seem to figure out where to go next.


Todd


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 Post subject: Re: Zenith 6G501M portable
PostPosted: Apr Fri 10, 2020 2:21 pm 
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It looks like this has not been worked on for many decades, if ever. All the parts are Zenith. I'm trying to figure out what goes where. My latest confusion is caused by the yellow battery plug wire. In the schematic it shows it going to the ac/dc switch and on to the on/off volume knob. In this radio, it is connected straight to one of the double capacitors, and stops there.
Any help is appreciated.
Thanks
Steve


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 Post subject: Re: Zenith 6G501M portable
PostPosted: Apr Fri 10, 2020 3:07 pm 
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That yellow wire is connected to a tie point on the capacitor can. Right next to it are a couple more wires(see marked up photo) that are also electrically tied to the same point. There may be others. This is commonly done on a lot of radios.

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 Post subject: Re: Zenith 6G501M portable
PostPosted: Apr Fri 10, 2020 5:24 pm 
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So it really is not part of the electrolytic capacitor circuit, just using the can as a connector!? In that case it does flow to the ac/dc switch and then to the on-off volume knob.
The schematic does not indicate positive and negative symbols for the electrolytic caps, and it doesn't use the I( symbol to indicate +/-. How do I determine how to hook up the electrolytics?
Thanks
Steve

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 Post subject: Re: Zenith 6G501M portable
PostPosted: Apr Fri 10, 2020 11:34 pm 
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I found the schematic a little confusing when I first restored a TO, So I color coded it.
Green is ground ( B-) return path.
Red is B+ and the Blue is the beginning of your filament string which you follow through the ins and outs of the remaining tube filaments. This ends with pin 8 of the 1LA6 which is B-.
The inside pins on the electrolytic cans are + voltages and the outside edge pins are generally B-.
Most of the electrolytics now have a - sign pointing to the negative side ( B- ).
I'm not sure what level you are at in restoring radios, so I am just trying to make it somewhat simple to understand.
Attachment:
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Hope this helps.
Freeman


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 Post subject: Re: Zenith 6G501M portable
PostPosted: Apr Sat 11, 2020 4:24 am 
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All of the electrolytic minus - terminals connects to the B-. In Freeman's post the - terminal of all electrolytics connect to the green B- line. As you have already noticed the B- is the can and tabs of the old electrolytics. Any wire connected to the can tabs is connected to B-. On radios having two multi section capacitors the can is B- on both of them and they are connected together in some fashion. A simple ohmmeter test will verify this. The can is insulated from the chassis, the chassis is not B-.

I typically restuff the old cap cans after first removing the old guts. This usually requires removal of the can, cutting it open near the base and removing the guts with heat, usually a hair dryer or small butane torch. This helps to tidy up beneath the chassis on these radios with tight spaces. Most of the Zenith caps have a black cardboard tube over the aluminum can, this can be removed with a little heat to loosen the tar that secures it. The nice thing is that the cardboard covers the surgery scars. I use aluminum tape to re-secure the top of the can to the base and as I said the cardboard covers the repair.

Reading schematics and then trying to follow point to point wiring in a radio takes a little time to understand the method to the madness, any convenient point is utilized. You will find that unused terminals on tube sockets are regularly used to tie wires that are not part of the tube circuit. You will also find components connected to a tubes terminals that are difficult to locate in the schematic because they are not placed on the schematic near the tube but are part of the circuit nonetheless.

It will do you well to verify all of the components (resistors and capacitors) in the radio, to the schematic. This will help you to figure out how the radio is wired. This radio has rubber coated wire that is very prone to get hard, brittle and crack. You may need to replace some of the wiring if the insulation breaks off and leaves the wire exposed. Take care to disturb the hardened rubber insulation as little as possible.

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 Post subject: Re: Zenith 6G501M portable
PostPosted: Apr Sat 11, 2020 5:38 am 
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On most Zeniths if you look at the outside of the cap can on the side you will see the capacitance followed by the voltage then a symbol such as a triangle, square, and a rounded top square. Look under the chassis inside the plastic V that has the terminals in it . If it has three on the outside of the can it will have the very small symbols by the cap terminals on the outside of each terminal. Some could be surrounding the terminal. Most of the time they are hard to see and you will have to maybe bend back the cap terminal. that terminal is the positive and the outside lugs are the B- or negative terminals. You cut the wire off of the inside terminals and connect the positive side of the replacement cap to that wire. The negative side of the terminal will be soldered to one of the outside lugs. I hope this helps. Tom


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 Post subject: Re: Zenith 6G501M portable
PostPosted: Apr Sat 11, 2020 11:26 am 
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Thank you for the replies. My understanding of radios is very limited. I'm trying to learn as I go.
The colorized schematic is very helpful and the description of these capacitors is very helpful.
I'll be taking my time to make sure it is all put together correctly.
Have a nice day
Steve

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 Post subject: Re: Zenith 6G501M portable
PostPosted: Apr Sun 12, 2020 4:44 pm 
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OK, thanks for the education! The original double electrolytic capacitors are marked on the paper tube with rating; a square for 4Omfd and triangle for 2Omfd. The bottom has corresponding triangle and square. I would never have noticed that without your help. Pictures for people like me. On the 6G6O1, the triplecap is marked on the paper tube, but I don't see any markings on the bottom.


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 Post subject: Re: Zenith 6G501M portable
PostPosted: Apr Sun 12, 2020 10:48 pm 
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Your problem with the second cap with the missing symbols is because they ran out of triples that day and the girl put a double in which didn’t have symbols on it, but she did have a black cover and through it over the can. Not all cans have them on the bottom.
This is where the schematic comes into play. You have 2 knows. ( The can with the symbols ) Pick one terminal and follow the wire and mark where it goes. Compare it with the schematic and place the symbol on that cap. Do the same with #2. You said there is an electrolytic under the chassis by itself. Do the same thing with that cap. Mark the schematic as known somehow. Now only 2 left and do the same thing here. Write it down like. Blue wire is 40u and red wire is 20u. Now you know where all your electrolitics are under the chassis.

I take pictures with my camera. A lot of pictures. I’ve done a lot of TO’s and I still take pictures. Print out the underside of the chassis and write, were each cap terminal is and the C number of that cap.
When ready, remove the wire from one terminal and attach it to the correct new cap. The positive wires must be removed from the cans, but you can use the original B- that is attached to the cans edge lugs.

Hope I didn’t confuse you.
Freeman


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 Post subject: Re: Zenith 6G501M portable
PostPosted: Apr Tue 14, 2020 2:04 pm 
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These 2 resistors got me scratching my head. They go from 1LH4 pins 1 & 8 to the volume control. Both are yellow, brown, and red.
How much resistance should they have?
Thanks
Steve


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 Post subject: Re: Zenith 6G501M portable
PostPosted: Apr Tue 14, 2020 2:28 pm 
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Looks like yellow-violet-red which is 4.7K.

Steve D


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 Post subject: Re: Zenith 6G501M portable
PostPosted: Apr Tue 14, 2020 10:20 pm 
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Thanks! I was confused on the color, but also because these both show exactly 7.5K ohms. These are also the only resistors in the radio which tested bad.
Thanks
Steve

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