Author Topic: 6825A amplifier fully repaired! end saga, hats off to HP for building it tough  (Read 589 times)

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Offline coppercone2Topic starter

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Ok, I got the ammeter working. I deleted a bunch of crap because it was a wild goose chase based on a bad solder joint on a capacitor and some loose crap

(I almost wrote bad transformer socket! for some reason, wow I am agitated, this does not have a transformer socket on it, I just started imagining words ).

I don't know the exact problem but I think I basically swapped a transistor on one of the PCB now when I measured them all, so the A2 board has all of the power resistors go on fire, but I got it working by overrating the fuse by 300%. At least the transformer voltages are normal, the rectified voltages are normal, hopefully at this point I just need to swap some transistors and maybe it will work. Have not ran it for more then 3 seconds like that.

yep, swapped a transistor. works fine, bit a buzz at full power unfortunately even with all the work, but at least the ammeter works. Problem was mostly a capacitor that via got dissolved making the -45V rail go screwy (everything from oscillation in certain output voltages to the ammeter causing the rails to change. problem was that I replaced a 5 lead cap with a 2 lead cap and one of the vias cracked, at least I think there was a via there, because the screw terminal capacitor has one. 

Maybe it will stop rattling when i replace a few screws but god damn that is a load off my chest, hoorah. buncha crap is still loose. (only at max power).

what a fucking beast though, survived swapped cards in wrong polarity, swapped transistors, a missing power rail and only some resistors got hot when I upped the fuse by 300% to run it on overload for trouble shooting purposes. if it passes after the damages incurred by the insane repair man, its a fine instrument. I wanna see this thing go up against starfish prime lol ;D
« Last Edit: October 04, 2022, 06:49:19 am by coppercone2 »
 

Offline coppercone2Topic starter

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Re: 6825A amplifier /supply current display repair?
« Reply #1 on: October 02, 2022, 09:24:14 pm »


this is the abstraction
« Last Edit: October 02, 2022, 09:26:25 pm by coppercone2 »
 


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