Sandbagger
Administrator/The Boss
Posts: 6,247
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Post by Sandbagger on May 15, 2017 14:13:51 GMT -5
Damn nice lookin Pioneer! Well Dave, it looks like both of us ended up with nice radios this week-end..and MonkeyMan bringing the 'tunes! Ironically, a reasonably priced tuner or receiver is what I was hoping to find at the radio show, and in a roundabout way I guess I did. I had 10 minutes to kill so I gave the Washington a quick look at. It's not the AM regulator, as I first suspected. Looks like the relay is the culprit. The contacts are pretty dirty, so I'll give it the $20 cleaning and see where that gets me. Also looks like the radio's an old enough version that I may have to do the final bias mod. I'll know more when I check each part value. Fun time!
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Sandbagger
Administrator/The Boss
Posts: 6,247
|
Post by Sandbagger on May 19, 2017 8:00:11 GMT -5
It cleaned up rather nicely... Ok, I guess it's time for a status update on this little gem I picked up from Monkey. At first I thought that the AM transmit issue was the AM regulator. Turns out, I was wrong, it was the relay. The contacts were really dirty and a little pitted, so I cleaned the crap out of it and it still didn't help. So I was trying to align the middle contact so it would make contact sooner and I ended up snapping the plastic that holds the contacts (brittle with age). No problem, a little super glue and that was fixed. The next day I found that NONE of the contacts would work. Testing with the ohm meter had me scratching my head. I cleaned the contacts again, and I was still not seeing any reliable connection. Then it occurred to me that the fumes from the super glue might have left a residue on the contact surfaces, so I cleaned the contacts with a dab of acetone and a re-polish and that fixed it. Now the relay is working again for the time being. With the transmit issues taken care of, I turned my attention to the stuck meter. As is usual with these situations, a little loosening of the meter bearing screw freed it up nicely, so now that's working. So on to receiver alignment..... Uh-oh. The receiver was pretty weak, needing 10 uV input to be heard. My first thought was the front end transistor, but that was ok. The culprit turned out to be the 3SK45 mixer(FET 1). Fortunately I had another, and that brought the sensitivity back to .3uV. There's still an issue with the meter reading. Setting it for 50uV=S9, it drops off rapidly (not the expected 6db/S-unit) when signal is reduced, which tells me there is an issue with the AGC, or something still a little weak in the receiver chain. But all in all, it's working now. Managed to debut it in the last 1/2 hour of last Wednesday's Roundup. I plan to work over the modulation sections and increase audio bandwidth a little bit (or a lot). One of the segments is burned out in the channel display, so I'll see about replacing that too
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