n72 problem (r49 dead)

[mrniss]

i had good luck the first time with two N72s... the one module stopped working after about 4 months (then was lost in the mail getting to SCA for repair, but that's another story)

i powered up N72 #3 just completed, was adjusting the collector voltage and R49 torched. i had something like 23.5 volts showing when this happened, but i think the resistor was already at the bottom.

now what?

[tpryan]

Are you sure that you first turned R39 fully counter-clockwise before applying power? Is it possible the module was shorting against the chassis divider? Are you confident that all of your solder joints are good and the component leads are trimmed properly?

[brett10000]

Hey this just happened to me ,

any luck with getting yours to work ?

Brett

[Volume11]

This just happened to me as well, awesome. Have you tried to replace R49? I'll give it a try and report back in a couple days. For the record, this was a working module that I added to the newer style chassis. I can't see where it possibly could've shorted out to the chassis.

I know it may cost more money, but it will cause less headaches... maybe you should have these chassis powder coated or painted, like the originals? Just an idea. A little sanding of the edges won't hurt anybody, to get the ground throughout the entire thing. I'm going to run some electrical tape on both sides of the inserts.

[Volume11]

Just to give anyone, and everyone, a heads up that has this problem, or who may be trying to avoid this problem. I realized that its the underside of the module, where the heat-sink from Q6 grounds out to the chassis. All four of mine where doing this! I easily fixed this by just bending the heat-sink in towards the module a little. Then I placed a couple strips of electrical tape on the chassis itself. I just placed the tape where the heat-sink was grounding out, to avoid covering up too much of the ventilation holes. Worked like a charm.