Joe Here is a good pix of pins that 'looked' like they were soldered http://pgerhardt.blogspot.com/2009/12/3-500zs-pin-resoldering.html . I also removed the springs from the tube sockets and rebent them to restore the proper tension. The springs took longer than the resoldering but the tubes are still working.
Good luck. Thanks for all the tips on the TR-4 weak RX. I hope to get back to it in a few days. Merry Christmas K3PG Http://pgerhardt.blogspot.com > Message: 1 > Date: Fri, 17 Dec 2010 20:51:20 -0600 > From: Joe Loverti <[email protected]> > To: [email protected] > Subject: [Drakelist] L-7, 3-500Z filament out?? > Message-ID: <[email protected]> > Content-Type: text/plain; charset="us-ascii"; Format="flowed"; > DelSp="yes" > > Hello to All- > > Let me preface this by stating that I am very "green" at > troubleshooting amplifiers, so please bear with me :) > > I've owned and operated a Drake L-7 amplifier for several years > without incident. The other day I noticed my output pwr was diminished > by about 400 watts. I had a look at the back of the RF deck and > noticed the outboard 3-500Z filament was extinguished. After the > sinking feeling set it in, I un-plugged everything and took the cover > off the amp. I pulled the tube that was un-lit and inspected it > visually. I could see no signs of anything cooked, cracked, burnt, et > al. I decided to swap the tube positions and put the good tube in the > outboard socket and put the bad tube in the other socket. I put > everything back together and lit the amp off again. I noticed that > both filaments were now glowing brightly and I was getting full output > again in my dummy load. > > All was OK for a day or so. Then yesterday, I noticed the filament was > out again on the tube that was switched. Only now this tube was in the > other socket. I've read on the web that it's common to the solder on > the filament pins on the 3-500Z to run out due to heat over time. This > causes a bad connection between the filament pins and the tube socket. > I've inspected the pins on the tube and they do not reveal any signs > of solder leaking out of the bottoms whatsoever. They all look > perfectly intact. I also inspected the socket and the "pin grippers" > in the sockets. They look to be in good shape and seem fairly snug. I > cleaned the contacts with a Q-tip and some De-oxit while I was in there. > > Some research on the Web suggested that a check of continuity is > recommended to see if the tube is the culprit and / or if it can be > fixed. I tested the filament pins (1 and 5) on the suspected culprit > 3-500Z and I AM reading continuity. But... the reading jumps around > and isn't stable. I also tested the wires above the pins that lead up > into the envelope of the tube. The readings here are also showing > continuity but, aren't stable. The meter jumps around a lot. I'm > planning on checking the "good" tube tomorrow to see how the readings > compare on it. I did not have time enough to get to it today. > > Does anyone have any other suggestions as to what might be the cause > or if there are other tests I could conduct to help diagnose the > issue? I suppose I could go and buy a new set of bottles for the > amplifier. The tubes that are currently in the amp are most likely the > original Eimac's. They have had a long service life. I think I'd > rather get do some more testing before "throwing tubes" at a problem. > Especially, if there is something else that I may be overlooking due > to inexperience. > > As usual, thanks for your time and assistance going forward! > > Happy Christmas and New Year, > > Joe Loverti Jr. > WS8X _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
