Thank you guys! A friend of mine did it !!! He replaced the bias caps under my clever supervision !!!! Thank you Garey, without your help I would certainly have had the polarity of the caps wrongly connected !!!! And thanks to Gary, I liked very much your technique with the hot glue gun and we followed your picture, it was very clear and we did a neat work !!!!
I finally tuned up the T-4XB, which now delivers about 110 W, not too bad as a starting point! 73 CUL, Frank IZ2OOS 2010/1/28 <[email protected]>: > Be sure to discharge the old capacitors before working on the power supply. > Here is a link to some good information on the AC-3 and AC-4 power > supplies. > http://www.wb4hfn.com/DRAKE/DrakeArticles/TechTips/PowerSupplyTroubleshooting.htm > > Al, n7ioh > > > On Jan 27, 2010, at 9:18 PM, Garey Barrell wrote: > >> Frank - >> >> The 200V caps would be ok. Later versions of the AC-4 used 40 uF >> capacitors for C5, so if you can find bigger ones it would be better. >> >> You must disconnect ALL wiring from the old can type capacitor. Best is >> to mount an insulated terminal (tag) strip near the can, soldered to the >> chassis, and move all the wiring there. You can leave the old can in place >> for appearance, but NO connections to its terminals. >> >> NO, the two Negative (-) leads are connected internally and to the outer >> can. This is why the can has a cardboard tube over it to insulate the -100 >> VDC on it. The two terminals "big" in the "center" are the Positive (+) >> leads of C5 A and B. Both (-) leads of the new caps, the "free" end of R5, >> one "blue" transformer lead are all connected together with a "green" wire >> going to Pin 9 of the connector. >> >> Once your repair is completed, I would strongly suggest testing the supply >> without connecting to the transmitter. This can be done by unplugging the >> supply, inserting a piece of bus wire to connect Pins 1 and 2 of the >> connector together. Put a piece of tape or other insulation over the bare >> wire to prevent accidental contact. When the supply is plugged back in, it >> will be _ON_ so beware of exposed HIGH voltage under the chassis and on >> the connector pins. >> >> You should see the following voltages, referenced to the chassis. >> >> Pin 10 (orange wire) should be 740 VDC. CAREFUL !! >> >> Pin 11 (yellow) should be 300 VDC. CAREFUL !! >> >> Pin 9 (green) should be adjustable with the BIAS control from about -50 to >> -100 VDC CAREFUL !! >> >> These voltages are with the supply wired for 120 VAC. Yours is probably >> wired (or switched) for 240 VAC and these voltages may vary roughly +/- 10%. >> >> Be SURE and check the fuse. It should be a 5 Amp Slow Blow for 120 VAC >> and 3 Amp Slow Blow for 240 VAC. >> >> 73, Garey - K4OAH >> Glen Allen, VA >> >> Drake 2-B, 4-B, C-Line& TR-4/C Service Supplement CDs >> <www.k4oah.com> >> >> >> iz oos wrote: >>> >>> Hi Folks, >>> >>> I have 2 spare 400V 22microF and 2 spare 200V 22microF. The former are >>> quite bigger than the latter ones but both types could be soldered >>> underneath the old big can as there is enough space. I would like to >>> make things as simple as possible and mechanically durable. How would >>> you suggest to place these newer capacitors exactly? Would you clip >>> off all the three leads of the old can? Pictures would be greatly >>> appreciated!!! >>> >>> The old can as far as I see contains both caps inside; viewing from >>> the bottom one lead is the positive side of C5a, the lead in the >>> center of the can is the ground and the third lead is the negative >>> side C5b, thus, the connection between the negative sides of C5a and >>> C5b cannot be seen as they are connected inside the can, am I wrong? >>> >>> TU and 73, >>> >>> Frank IZ2OOS >>> >>> >> >> _______________________________________________ >> Drakelist mailing list >> [email protected] >> http://mailman.zerobeat.net/mailman/listinfo/drakelist > > > _______________________________________________ > Drakelist mailing list > [email protected] > http://mailman.zerobeat.net/mailman/listinfo/drakelist > _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
