Quote:
Originally Posted by Electronic M
Most sets have more than two B+ rails (the lower voltage ones are usually derived from the higher ones with a voltage divider). You need a SCHEMATIC to know where to measure and how much voltage should be at such point....Otherwise you are going to just spin your wheels guessing. Until you (or any would be TV restorer for that matter) have at least 10 tube TV restos under your belt it is usually futile to troubleshoot a set WITHOUT a schematic (even with our help), and even those of us seasoned enough to do most work blind sometimes have check a schematic to know how aspects of a given set should be.
Check with libraries in major cities in your region, and libraries at technical colleges/vocational schools....Odds are one of them has a free sam's library, and for the cost of photocopying you can get the service data. There is such a place 15 minutes from my house (they only keep mid 60's and later sam's), and a more complete library in Milwaukee about a mile from my old College.
147V on a 150V rated cap seems high....If that point is at the doubler and there is a resistor or choke between that cap and the circuits loading the B+, which is going open then it would explain that odd measurement and low B+.....If your set uses a doubler it could also signify the other doubler cap failing.
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I actually do have a schematic/sam's for this TV that was provided to me by another member here, bu the schematic is split up between 4 pages and I can't see whether or not there's anything about B+ voltage measurements and what they should be, they have tube pin voltage and resistance readings given but nothing for B+ voltage readings. I tried to upload the copy of the Sams I had for this TV but it was too big for me to upload on here.
I saw something about the boost voltage on the schematic and its coming off of the HV transformer and the Boost Voltage is supposed to be 250 Volts, but I'm not sure if that has anything to do with my TV and its issues or not.
Also the Public Libraries near me threw out anything considered old and obsolete (including service manuals, records, audio tapes, video cassette tapes, etc.) years ago so I don't think it would be possible for me to find any Sam's Photofacts in any of the public libraries near me, plus the library system near me is about 30 years old (with most of the library branches being built in the mid to late 1980s) the only library that's old enough to of been able to of held anything like say Service manuals is the main branch of our public library system which is in town and that library's building was built in the 1920s, and it was the only library in Elkhart, Indiana up until the 1980s when they decided to make a city wide library system that featured several different branch buildings located across Elkhart for each township, and then the original library in town was named the main branch of the Elkhart Public Library, and then all of the sub-branches are named after the township or suburb they are located in (e.g. Jefferson Branch, Dunlap Branch, Osolo Branch, etc. and they were all built in the mid to late 1980s so not even old enough to have a sam's or a rider's service manual archive).
So yeah I kind of have to rely on online sources or other people on here for my service manuals that I don't have if I happen to get a project to work on that happens to be covered in a service manual that I don't own a physical copy of.