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#1
09-30-2010, 08:48 AM
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Progress!
I have a complete RA111 chassis on hand for parts. It uses the same power transformer as the RA112/113. My first Mouser order got cancelled, due to alot of substitutions on their part. Not a problem, though. I will install the transformer and leave out the rectifier for now. Replace the 7-8 electrolytics, and go from there. I've gotten alot of PM's about DuMonts and quality. I look forward to seeing the soft glow of the chassis... minus B+ for right now. The RA111 chassis has a fuse socket mounted on the chassis. It is much newer than the chassis. I will be fusing my set, too. I sure dont want anything like this to happen again. 2010 has been my year of bad power transformers. But, its also been good as I have found replacements for them. I have my friends here at VK, and ARF, to thank for this! More to come, as it happens... 
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#2
10-04-2010, 06:07 PM
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Pulled the old transformer and rectifier tube socket as an assembly today. Found one side of the rectifier tube socket had been very hot at some point and had broken away. Installed in the set, I couldn't see this side of the socket. Thankfully, the doner RA111 has the same transformer/rectifier socket mounting so I reinstalled the transformer using this mount. While in there, I found a single wire that had almost no insulation that was cooked thoroughly. Apparently this wire had a long time working while damaged in this set, as there is rust in several places along its run. Turns out that it runs from the power interlock to the back of the switch.
I attached the new wire to the end of the old one, and gently pulled it through under all the other wiring from the switch back around the side of the rectifier tube socket and up to the interlock. It is working. I'm not applying any B+ anywhere on this set until I get a load of capacitors replaced. I did turn on power thru my variac just to see what it would do. It powers up fine, all tubes are lit, so I left it running this way for a little while just to let the chassis get somewhat warm, and to see if this transformer is OK, which it is. I have to re-solder the transformer filament winding lead after I move some wax caps out of the way. Someone in the past has done some not-so-pretty repairs in the past around this area of the set. I'm fairly sure that this transformer has been replaced before. The one I removed has the same part number as my replacement does. I've found some snipped wires at solder connections with the same colors on them as what the transformer has. I sat here looking at the tubes glowing in the chassis, when... Suddenly, POP! I looked quickly at the chassis while fumbling for the switch on the variac. I watched one of the 2 flat capacitors connected to both sides of the power line to ground slowly open up like a clam. Cut power, and cut it out of the circuit along with the other one. The Riders schematic doesent show these caps, so I will leave these off, unless instructed otherwise. So, here we are. It lights up. All the controls are cleaned except for the tuner itself. It's all ready to run after the cap replacement. Last edited by holmesuser01; 10-04-2010 at 06:13 PM.
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#3
10-04-2010, 06:28 PM
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Some new pictures of the switch wiring, the front of the tuner dial, and some of the transformer with most of its wiring finished, especially on the rectifier socket. You can see the exploded capacitor, and its undamaged, but very warm sister, both since removed.
Also, in the first pic, you can see the routing of the very yellow replacement wire snaking thru the chassis under everything else there. Notice the rust. The wire I removed was thoroughly cooked with very little insulation left. Last edited by holmesuser01; 10-05-2010 at 08:00 AM.
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