Zenith 7H820Z

edteach wrote:

So I have in the kit the EC to replace the three but need the 80uf 150v. I think this one from Mouser is the one I need. Here are the Specs is this correct? Thanks.
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Manufacturer:

Vishay

Product Category:

Aluminum Electrolytic Capacitors - Axial Leaded

RoHS:

N

Product:

General Purpose Electrolytic Capacitors

Termination Style:

Axial

Capacitance:

80 uF

Voltage Rating DC:

150 VDC

Tolerance:

20 %

Minimum Operating Temperature:

- 20 C

Maximum Operating Temperature:

+ 85 C

Diameter:

15.875 mm

Length:

44.45 mm

Series:

TVA ATOM

Brand:

Vishay / Sprague

Product Type:

Electrolytic Capacitor

That looks right. you always want near the capacitance, but no lower in voltage rating. Even higher in voltage rating can be used.

OK so my marking by color saved me. LOL I found the markings. When I removed the leads there is an almost covered part of the fiber board that has a small cut out that was covered by the leads. I was looking for some kind of impression or mark but its a cut out and not real visible.  So I put the three 47 Uf caps in the can and will put in the 80 underneath. That way I can get the can epoxied back in place and installed. I twisted all the grounds together and have one ground wire coming out the middle to hook to the chassis. [You must be registered and logged in to see this image.]

So I have in the kit the EC to replace the three but need the 80uf 150v. I think this one from Mouser is the one I need. Here are the Specs is this correct? Thanks.
[You must be registered and logged in to see this image.]

Manufacturer: Product Category: RoHS: Product: Termination Style: Capacitance: Voltage Rating DC: Tolerance: Minimum Operating Temperature: Maximum Operating Temperature: Diameter: Length: Series: Brand: Product Type:

Vishay
Aluminum Electrolytic Capacitors - Axial Leaded
N
General Purpose Electrolytic Capacitors
Axial
80 uF
150 VDC
20 %
- 20 C
+ 85 C
15.875 mm
44.45 mm
TVA ATOM
Vishay / Sprague
Electrolytic Capacitor

19&41 wrote:

I believe Cliff had posted some pages from a service folder.  I think he may have taken them down.  You may need a tube layout if he has one for it.  It will aid greatly in interpreting the schematic to where the tube connections are.  You will have to trace each wire that was attached to the capacitor in order to determine which is which.  It's ground should be the can and it's connection to the chassis.

I will see what I can find but there is more than one wire going to two of them. One wire goes to the little tranformer? in the middle of the underside of the chassis. What I will do is trace it down and take picrtures of where it goes and maybe you guys can help that way?

I believe Cliff had posted some pages from a service folder.  I think he may have taken them down.  You may need a tube layout if he has one for it.  It will aid greatly in interpreting the schematic to where the tube connections are.  You will have to trace each wire that was attached to the capacitor in order to determine which is which.  It's ground should be the can and it's connection to the chassis.

I painted the connections and the bottom of the tube and then cut them off and removed the can. I could find no marks anywhere. So I am hoping someone could help me figure out how to trace these down. Thanks for the help .[You must be registered and logged in to see this image.]

The tabs will sometimes have solder obscuring the shapes.  Sometimes the ends of them will have the shape.  If all else fails, you will just have to trace the wiring, comparing it to the schematic and seeing where each are connected.

19&41 wrote:

If there are no shapes impressed in the base, check the tabs themselves, they sometimes carry the identifying shapes.

Nothing on the base under the chassis. I looked best I can at the pegs and could see nothing that looks like the marks indicated or any numbers. The top tube has this though but that does not tell me much. I was wondering if I should cut the case open from the top pull the tube case and seewhat is there maybe the marks are inside.
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If there are no shapes impressed in the base, check the tabs themselves, they sometimes carry the identifying shapes.

19&41 wrote:

Before you even get to the point of testing the unit, remember that it is a hot chassis radio and should be assumed to have mains potential on it when plugged in, not just when switched on.

Thanks. My plug in is polar specific. I will plug it in and test the chassis with a multi meter. Good to know. Now on to the electrolytic. The side of my can has half moon, square and triangle to the masurements of the cap. But there is no such marks on the bottom where the wires go in. How do you figure out what connector goes to what cap?[You must be registered and logged in to see this image.]

Before you even get to the point of testing the unit, remember that it is a hot chassis radio and should be assumed to have mains potential on it when plugged in, not just when switched on.

Looks like you got them all.

I used this coding chart to do all the caps. And this is a photo of the finished job. Did I miss any caps? If I did not miss any the electrolytic is next. [You must be registered and logged in to see this image.]

The value seems correct.  The voltage is low compared to the caps in the parts list.  I can't see any caps of that exact value in the parts list either, though they may have used a close value type.  Here is the parts list.




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So I am trying to learn how to read the color striped caps. I read this one and this is what I came up with. [You must be registered and logged in to see this image.]

Red text is not as easy to read I will try yellow seems to be eaiser to see. [You must be registered and logged in to see this image.]

I will do one at a time and blow up the text on the photo. Thanks [You must be registered and logged in to see this image.]

Cliff Jones wrote:

edteach: I sent an Email with an attachment(s) of Sam's Dial Stringing Guides

got it thanks. So the dial string is repaired. I found a code for the electrolitic caps but there is no such code on the bottom of my ECap only the four connections. Is there another way to figure out which is witch C26  7 8 and 9? [You must be registered and logged in to see this image.]

edteach: I sent an Email with an attachment(s) of Sam's Dial Stringing Guides

That 3 legged cap is C21.  It is a shield grounded .1uf cap.  I have not had the experience of replacing one.  That model of radio is a bit fussy about any alterations to it's wiring.  Maybe someone can chime in on properly replacing it.  The lead on the end with the band on it should be the shield ground.

19&41 wrote:

The 47 uf caps should cover the 40 uf caps in your unit.  For the 80uf, i try to find a single cap of nearly the same capacitance but no lower voltage rating.  It's difficult to make out the detail and your notations in the picture.  I do see it has a old solid state rectifier mounted behind the speaker.  If I were restoring the unit, I would consider replacing it.  There should be tutorials on selecting a replacement for it.  I suggest the tutorials because they can be repeated or stopped as you work, making it easier to learn.  When replacing the wiring try to replace with the same type wire (stranded or solid) the same gauge and try to cut it to the same length and routed in the same manner.  Try to take a close up of the 3 wire cap you have mentioned.

 A few more pictures. [You must be registered and logged in to see this image.]

19&41 wrote:

The 47 uf caps should cover the 40 uf caps in your unit.  For the 80uf, i try to find a single cap of nearly the same capacitance but no lower voltage rating.  It's difficult to make out the detail and your notations in the picture.  I do see it has a old solid state rectifier mounted behind the speaker.  If I were restoring the unit, I would consider replacing it.  There should be tutorials on selecting a replacement for it.  I suggest the tutorials because they can be repeated or stopped as you work, making it easier to learn.  When replacing the wiring try to replace with the same type wire (stranded or solid) the same gauge and try to cut it to the same length and routed in the same manner.  Try to take a close up of the 3 wire cap you have mentioned.

Here are some pictures of the three[You must be registered and logged in to see this image.]

The 47 uf caps should cover the 40 uf caps in your unit.  For the 80uf, i try to find a single cap of nearly the same capacitance but no lower voltage rating.  It's difficult to make out the detail and your notations in the picture.  I do see it has a old solid state rectifier mounted behind the speaker.  If I were restoring the unit, I would consider replacing it.  There should be tutorials on selecting a replacement for it.  I suggest the tutorials because they can be repeated or stopped as you work, making it easier to learn.  When replacing the wiring try to replace with the same type wire (stranded or solid) the same gauge and try to cut it to the same length and routed in the same manner.  Try to take a close up of the 3 wire cap you have mentioned.

19&41 wrote:

Here are some tutorials on reading tube era schematics.  There should also be examples of capacitor coding on Bing.  Even when you have the color codes, the colors on the component can be difficult to identify.  That's where the schematic and component layouts can be of benefit.

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Thanks. I am watching the videos on reading a and the symbols for caps, resistors ect to read a schymatic. But that looks like its gong to be a bit of time. While I am doing that I am fixing what is obvious. Wires that have the insoulation brittle and broken. Also I did a arrow point and questions to show what I am doing and what I have questions on. So the electrolitic caps in the can I need I am told are C26 80uf 150v,C27 and c28 40uf 150v, c29 40uf 25v. My question is I bought a cap kit from Sals caps. It has three types of electrolytic they are 22uf 160v 33uf 160v 47uf 160v my question is will any of these work to replace the ones for this radio? Also the paper three wire cap in the picture has a .02 400 on it. Is the three wire something special all I have in the kit are two wire. Thanks for any help. This is going to be a learning curve for me to lean as I go. The forum degrades the picture so here is the full size link [You must be registered and logged in to see this link.][You must be registered and logged in to see this image.]

Here are some tutorials on reading tube era schematics.  There should also be examples of capacitor coding on Bing.  Even when you have the color codes, the colors on the component can be difficult to identify.  That's where the schematic and component layouts can be of benefit.

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I have a schematic of the Zenith but not sure how to read it. I also don't know how to read the color code of the old caps.

If you are going to need servicing information, I would suggest getting one of these DVD-ROM libraries.  They contain most of the schematics, alignment guides, parts lists, component layouts and dial stringing diagrams in high resolution printable format.  I have and recommend it.  Good luck.


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So I am new to the forum.I bought a vintage Zenith and its in really good condition.I took the cabinate off and there are some issues with it like the tuner to knob cord is broken.I ordered a new cord. I need a cord diagram.I solder so its not an issue there. But I don't read skamatics much. I know the capacitors need to be replaced and the electrolitic also. I don't want to put them in the same sliver tube and there is room in the chassis. But if anyone has or can use my picture to do a diagram with arrows to help me locate what needs to be replaced that would help greatly. I don't know how to read the color coded values on these caps either. So any guidance would be appreciated.

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