Type 576 an interesting day

[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.

[SoundTech-LG]

OK, so at the beginning of part 7 video it was fixed. Then later on he showed a bit more of what he had done. Glued from inside. Looked like he just removed several pcbas to gain access. I think I can implement my clear tube repair this way too. Maybe try the glue first.

[SoundTech-LG]

Alright, Offset 20 turn plastic mounting cup glued in place after removing Step Generator pcba with switch from front panel. Wiring folded back and out of the way. Piece of cake. I used JB Weld this time, so never to be removed again, and really no need to.
Curing overnight and reassembly tomorrow. This is a really weak part. Tek Mechanical Eng. did not spend much time with it. My lighting sucked sorry about the photos.

[Stray Electron]

  Great find!   And yeah, Tektronix did sell plastic covers for those, a friend of mine has several on his Tektronix toys including one on his 576 and I think one on his 577. 

  But you should go back and talk to the guy and be sure and get any adapters, manuals or any parts or anything else that he has for it or any other Tektronix stuff.  That stuff is getting like GOLD today!

[SoundTech-LG]

Maybe this post is what you were thinking of???

https://www.eevblog.com/forum/testgear/tektronix-576-curve-tracer-adapters/msg4686704/#msg4686704

[SoundTech-LG]

Yes, I got a PILE of Tek adapters with it!!  Still need to inventory. Got the paper manual, cover torn off, plastic binding falling apart.
 The dust cover it had on it was black and had a white tag Made in China. I did save it. It reminded me more of a cheap BBQ cover.  I do now vaguely remember seeing some clear vinyl covers back in the day. Am I wrong?
Thank you! Still a very exciting find...  it's still sinking in.

[SoundTech-LG]

I wasn't really trying to collect these things, they just sort of found ME, My first was the Heathkit IT-1121 mid to late 70s I got it. Then the 575 about 2 years ago, now this. So why do I need 3? I don't.

[SoundTech-LG]

Never ending story, but gets even more interesting...  turns out the CRT is dying quickly and "double peaking". So, first started looking for Rejuvenators. Bought a pile of cr@p and trying to get my money back. Another one on the way. While looking I thought maybe a good crt could be found in another 576. Couple days went by, then bang, one popped up. Here is the interesting part. The front panel did not look quite right. The big screw for the crt bezel was not there, it had what looked like a plastic release button. There was no name plate above the CRT, just the blank spot. The knob lettering appeared different on the panel printing. Here's the big one. I could not quite read the serial number in the photo. So I asked. He said he didn't know where the serial number was. I had to circle it for him in his photo. Then it took him at least a day to finally come back with a THREE digit serial number. Hard to believe, but he took a close up photo, and yep 3 digits. Ready???  Get this...  A01. So, turns out his dad worked at the Beaverton plant. Pretty sure that is a prototype 576 and since it is A ZERO ONE...
likely the first prototype! Betting on low hours on the tube. I am sure there are more bizarre Tektronix stories, but this has to be ONE of them!

[Shock]

FYI, there are power supply transistor and cap end of life issues and separate HV transformer related issue (as best I recall it was a specific part that was corrected). I think all problems can be addressed but you might want to look it up and check earlier than later to prevent damage.

It's quite an iconic piece of gear and they only seem to becoming more expensive. Well worth the time and investment in restoring, in my opinion.

[SoundTech-LG]

Thanks! Yes, EOL caps are an issue. When I turned on the first 576 it blew one in the LV Regulator board. Checked all supplies for voltage and ripple all good at the moment. It has the later black HV Trans. I am sure the Prototype will have a brown bad one. The Proto looks nice and bright in photos. I didn't see the usual burn marks at 0 Horiz and 0 Vert, but they may still be there, who knows. At least it was operated by factory folks who should know how to care for CRTs. I will probably swap the CRTs, if it makes it here in one piece that is. It's one state away, but UPS could drop it any time, any where.

[SoundTech-LG]

Just now received an email replay from Bob Haas at vintageTEK museum...   Here is what he said. Good information when looking at TEK serial numbers in question.

Martin:  You have an early prototype. New product development at Tek typically had 4 phases:  Enn for Engineering, Ann and Bnn phase for production prototypes, and production with Bnnnnnn serial numbers for instruments made in Beaverton. Sometimes there were large changes between A-phase, B-phase and production instruments. It depended on the instrument design.

Bob Haas for vintageTEK