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Type 576 an interesting day
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SoundTech-LG:
Took a 6 mile trip to a "Barn Sale" today as an adventure (you never know). Ad said tools, machinery, electronics. Mostly very old mech parts for farm machinery, linens,pillows, junk, some nice old radios even 30s and 40s. I bought a little Sony am/FM for $5, and an Advent powered sub for $5. I made 2 trips through everything (I thought), then I decided one last trip just to make sure. Well good thing I did, as I saw over in a far corner, in a darkened area, under a cover a caster poking out, and a bit of a blue paint shade that made me startled with joy. Off came the dusty cover, and there it was, a 576 on a cart ! Not sure that cover is a Tek part.
How much? I asked. Oh, let me go get him. Ok. So turns out the guy worked at Fairchild as a Transistor designer 50s, 60s, 70s. Silicon Valley is just down the hill from here. He said he was going to donate the CT to a museum maybe. But then I said what do you want? $50 ok?
Sure! That's great! He said he thinks it works, but wasn't sure when he tried it last. No matter! I'll take it. Well, long story short, is, the Step Generator Offset Mult vernier was pushed inside the chassis. Still intact. The sacrificial plastic mounting ring "CUP" had broken. Probably unobtainium. I'm trying gluing what is left to the panel. Probably won't hold. Powered it up, it has a display, and readout illuminated and working. Then I thought I smelled something hot. Then I thought, maybe just dust on the resistors. Wrong!!! PoP! SMOKE!!! Stink! PWR DOWN right away. Ok, so off come the covers and saw it almost right away an electrolytic on the L.V. Regulator board had released the coiled spring of wrappings out the positive end. A sprague I think. It only said 5  150. Hmmm... 5mfd @150V ? Yep! But no part designations on the board.
No board drawings in the manual. So had to use both the schematic and part list, and other components connected to it to confirm it was C848 I was looking at. Fortunately I had a bag full of 10mfd @ 160V. So it now has a 5mfd @ 320V. Works fine now. Came with cart, manual, adapters, and a hood. No plastic protective enclosure. Probably my best Barn Find ever! ^-^ I'll be offloading my 575 now. No room.
mawyatt:
Nice find!!!

Recall somewhere on here than someone had a broken plastic disc and 3D printed or turned a piece of durable plastic as a replacement.

The old transistor designer must have some interesting stories from back then at Fairchild, wonder if he knew Fullagar, Widlar, Erdi, and all the other famous folks at Fairchild.

Best,
SoundTech-LG:
I may go back today to chat with him.

Got the MULT knob/pot assy. attached with some epoxy, but now also facing having to pick out some of the epoxy, it spilled over a bit onto the knob itself. I may try adding more epoxy now that is stabilized in place. The 3d part would be great! So sure an original piece will never be found. Let me know if you find the lead on it.

Thanks!
SoundTech-LG:
Just a few pics, and yes it was a Sprague cap that popped. Seems better to mark ratings with mfd and volts instead of nothing and DC. Almost forgot I picked up a $3 Weller EC1002 station as well in good shape. Sorry for the photos. The knob glue is pretty damn ugly. Hopefully I find a real part that works.
SoundTech-LG:
Ok, several steps backwards, and a few forward. I failed with the glue. Not to say it is impossible, but difficult. Then I had ideas using polycarbonate clear tubes cut properly and glued together. That requires major disassembly which I really desire to avoid with this 80 pound beast.
Searching youtube I found another fellow with the same problem (7min 35 secs) Then his later video showed it pulled back into the hole (with glue?). I have to search all his videos because there are many, to see if he mentions it again. Attached both video stills.
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