cronie

joust, on 21 March 2013 - 09:39 AM, said:

    First , I have a hewlett- Packard 412A analog Vacuum tube  volt ohmmeter which i love and is extremely accurate. I pulled an output transistor from the good channel and it read like the crown manual said it should read. I pulled all eight trans from the bad side and six read identical to the known good transistor.  One of the others read  .4 eb  and it should have read  "large" like the others.The last  transistor read 10ce and should have read "large".like the others. Im not sure what scale I had it on but It  was very sensitive to the touch. For comparative purposes the scale shouldn't matter. Each transistor was measured twice each leg-each polarity.  These 2 transistors may be ok but i would rather have eight that read the same.  Thanks for listening-Im still new to transistors and am trying to learn as i go.   I have new isolators ordered.  Cronie

carlos or joust--is the2n3773 a drop in replacement for th rca 62085 which i have now or do I need to to replace all eight with the same number. Two of the rca 62085 transistor read a little different out of circuit and I would like to replace them. The 2n3773 is readily available. Thanks Cronie

I just had all ten transistors out of the ch2 board.Plus two transistors out of the good side to compare to. They are the mica ones with the tab. I wiil change the isolators.  Channel one would also have distortion on it on startup but would go away after about two minutes. A year later the same happened to ch 2 but would not go away. So far I have swapped the large beer can power cap and retightened the screws to see if it helped- same symptoms. Then I changed the 4 nonpolar timing caps and two other white vertical caps on the main board.  Its funny when i was doing the ohm tests on the transistors i was wondering if the dow compound was conducting. It was smeared on pretty heavy. There is one more large yellow cap on the main board is this the hv cap?  I will replace it also.

just replaced the neg and pos drivers rca3626 with 2n5804s.  The rcas were almost totaly shorted emitter to collector. No more -60 at output.  Original problem still exists. I have crackling distortion at ch 2 speaker terminal - shows up as  about 1 half to one volt dc. I wiggled everthing and tapped on everthing to no avail.  Carlos, you may remember my original problem from a post years ago. any ideas ? cronie    the distortion problem is what I was trying to fix when i was changing caps - my first post. Also, what is the replacement for the rca 61061 predriver and the rca62085 output transistor?  Thanks again Cronie

Well,Igot a 2n4929 from american microsemiconductor thru amazon. I soldered it in but before I powered up I clipped 5 wires connecting the main board to the ch 2 board. The common brown,two feedback wires and the yellow/white striped and purple/white striped.I think this totally separates the boards.  I powered up and still -60 at the speaker terminal. I also have 9 volts dc coming from the yellow/white wire from the main board. I will replace the rca 61061 next and then start pulling output transistors. So much for the "easy" fix.   Something that joust knew all along LOL.  I will look at the neg rail first and maybe bid on a broken dc300a on the bay right now for a parts stash.I think this repair is a little over my head but I will give it the old college try. Thanks for listening   Cronie