| Zenith J880R | |
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nomo reoil Beginning Member
Join date : 2020-02-15
| Subject: Re: Zenith J880R February 20th 2020, 5:22 am | |
| No, "it worked" meaning the schematic posted. Am ordering parts today. |
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Cliff Jones Site Administrator
Join date : 2010-11-22
| Subject: Re: Zenith J880R February 19th 2020, 6:41 pm | |
| So is the radio running now? _________________ I'm a Science Thinker, Radio Tinkerer, and all around good guy. Just ask Me!
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nomo reoil Beginning Member
Join date : 2020-02-15
| Subject: Re: Zenith J880R February 19th 2020, 6:32 pm | |
| It worked. R12 is 1 Megaohm. |
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Cliff Jones Site Administrator
Join date : 2010-11-22
| Subject: Re: Zenith J880R February 19th 2020, 6:15 pm | |
| [You must be registered and logged in to see this image.]My first attempt at inserting a schematic, hope this helps. Heres the location of that resistor. (Yellow Highlite) So look at the value. That should be it. you need to measure the white component to find out if it a cap or resistor and then replace it. So What are you going to do? _________________ I'm a Science Thinker, Radio Tinkerer, and all around good guy. Just ask Me!
Last edited by Cliff Jones on February 19th 2020, 6:40 pm; edited 1 time in total |
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nomo reoil Beginning Member
Join date : 2020-02-15
| Subject: Re: Zenith J880R February 19th 2020, 6:00 pm | |
| Thanks. I have been studying the schematic and parts list. The original pic I attached is on top of the chassis, left rear corner (viewed from the front) next to T1A and T1B. Looking at the parts list, I see the resistor values run from 39 ohm to 10 Megaohm. |
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Cliff Jones Site Administrator
Join date : 2010-11-22
| Subject: Re: Zenith J880R February 19th 2020, 4:39 pm | |
| Click on this link for a 4 page schematic and parts list. This should be the first priority. In order to be on the same page. Also setup a convention of the chassis picture top end the left side and right side then bottom. Then make a grid system of 4 to 8 sections and write those along the edges like a map grid. Number and letter (Numbers across the top of the schematic and letters on the side) Read the list and look at the approximate location of the part on the provided list. On a separate piece of paper do the same in this order Group like parts (All capacitors & the Value of each along with the Part ID such as C-1, C12 etc.) Then on the list mark along side of each part the Grid location. You also need to trace the wire connections from part to part or what parts have a common wired connection. Then mark on the actual schematic each wire trace you have identified. Use colored highlighter pens or pencils. Can you download the provided link? Here is the Link Below that you should download and save AS a PDF file to your desktop for easy retrieval.: I have done the same on my computer for reference. [You must be registered and logged in to see this link.] _________________ I'm a Science Thinker, Radio Tinkerer, and all around good guy. Just ask Me!
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Cliff Jones Site Administrator
Join date : 2010-11-22
| Subject: Re: Zenith J880R February 19th 2020, 4:35 pm | |
| Relating to the picture you submitted Where is the photo location from on the chassis. there is a parts identification on the picture of the chassis included in the schematic. (PS I did find All 3 1Megohm resistors in the schematic) MY PDF copy isn't as clear as the one on the web. You cannot change the resistors willy-nilly or you could make things worse. Stick with the printed values. _________________ I'm a Science Thinker, Radio Tinkerer, and all around good guy. Just ask Me!
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nomo reoil Beginning Member
Join date : 2020-02-15
| Subject: Re: Zenith J880R February 19th 2020, 9:11 am | |
| Understood. From the responses I've received and my own reading of the schematics I still have not determined the correct replacement. It is in the antenna circuit so is not high voltage. (right?) I do not have the parts list in front of me to see all resistor values used in this set. just wondering,If lowest to highest values are not that far apart, will the highest value cause negative consequences? |
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Cliff Jones Site Administrator
Join date : 2010-11-22
| Subject: Re: Zenith J880R February 19th 2020, 8:31 am | |
| An an exact replacement would be preferable of course, but within the tolerance, if you have a resistor that falls within the tolerance range (when measured) would also be acceptable. This has to do with design for signal strength to audio gain to prevent overload of any of the stages in the line. Wattage has to be considered if its connected to high voltage. _________________ I'm a Science Thinker, Radio Tinkerer, and all around good guy. Just ask Me!
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nomo reoil Beginning Member
Join date : 2020-02-15
| Subject: Re: Zenith J880R February 19th 2020, 5:29 am | |
| Would it be acceptable to install the highest value resistor, listed on the parts list, in the antenna circuit without adverse effects? Thanks |
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Rod Clay Technician
Join date : 2018-08-01
| Subject: Re: Zenith J880R February 16th 2020, 1:42 pm | |
| Yes. I have also noticed that some wire wound resistors like that (Sand Ohm, Cement, etc.) age with corroded copper or copper clad leads. 73, Roderick WB6FBF |
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Cliff Jones Site Administrator
Join date : 2010-11-22
| Subject: Re: Zenith J880R February 16th 2020, 12:42 pm | |
| R12 is 1Mohm 1/2watt 20% but as a 4 bander its 1 MΩ ±0.05% (3 used?) I can only find one in the schematic.It is located on the schematic below second IF Tube 12BA6 as a group connection
c5 is .05Mfd. 200v (2 used) c8 is 110Mmfd. Ceramic 500v (3 used) R10 47Kohms 1/2w 20%
the rest are very hard to read on the schematic and some designations don't match the parts list. The corroded leads could be acid core solder. _________________ I'm a Science Thinker, Radio Tinkerer, and all around good guy. Just ask Me!
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FrankB Moderator
Join date : 2010-11-22
| Subject: Re: Zenith J880R February 15th 2020, 10:30 pm | |
| The white component is a resistor. For some reason, that style often ended up with corroded leads. I have even had NOS ones leads corrode that way. Likely some sort of mfg. screw up, or impure or contaminated copper. |
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nomo reoil Beginning Member
Join date : 2020-02-15
| Subject: Re: Zenith J880R February 15th 2020, 8:50 pm | |
| Brown black green silver. 1000k ohms 10% res Thanks Nomo |
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Cliff Jones Site Administrator
Join date : 2010-11-22
| Subject: Re: Zenith J880R February 15th 2020, 7:06 pm | |
| It looks like its part of the antenna circuit. The white component looks like its a capacitor. What is the value of the resistor in the back of the picture? Do you have a schematic? If not its in Riders Vol. 23-PDF page counter 1111 or looking at riders paging system its 23-19. You might find a clearer photo of the schematic if you have the actual Riders book. Sometime looking at similar Models may help. [You must be registered and logged in to see this image.] _________________ I'm a Science Thinker, Radio Tinkerer, and all around good guy. Just ask Me!
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nomo reoil Beginning Member
Join date : 2020-02-15
| Subject: Zenith J880R February 15th 2020, 2:54 pm | |
| Just starting on a Zenith Cobramatic console. While trying to read a cap, another component broke off. The leads are copper and quite brittle and corroded. The piece has no markings and I am still learning schematics. Hoping someone can ID the piece. Chassis # 52551. Pic is top left rear of the chassis. Can take more pics if needed. [You must be registered and logged in to see this link.]Thanks Nomo |
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