Anybody else has one ? I wonder how many there are here...
I actually have two - the second, more functional one, is a Mod 122C with the additional 400V collector voltage option. It at least works, but still needs some going-through.
TWO ?!
Lucky you... and there is a 400V version you say ? Shouldn't have said that, I need to find one now !
Nope... getting hold of one was enough of a miracle, two is less likely than winning the lottery...
Following are some macro photos of the rear of the Base Step Mode switch from my 'working' 575-122C
[..]
Wow, thanks a lot for all these nice shots and explanations ! I appreciate the time and effort !
Sure helped ! I have now diagnosed my switch problem, see pic below. The moving contact for the REPETITIVE position, was damaged. The tip of it suffered metal fatigue and was badly bent... took only a light finger touch to for it to snap/break for good !
Also, the inner contact also in the REPETITIVE position, was badly bent inward, meaning that in the OFF position, it was not making contact as it should.
So for now, I bent the outer contact so that it contact the moving contact, what's left of it I mean, so as to "hard wire" the unit in REPETITIVE mode. Sucks I know, but at least for now it means I can use the instrument and keep working on it to fix it.
Now for a long term repair, not sure how I would go about it ?!
Finding parts for a 575 I won"t even waste my time searching...
With some luck there is the same style of switch in one of my Tek scopes and I can take the switch apart to salvage the particular contact that I need ?!
Or maybe old HP gear had that style of switch as well.. a donor HP might do it...
At least it's good that they can easily be taken apart and "configured" which ever way you want, just take the bits you need to make your favorite "sandwich", and crew it together, done !
Tried cleaning the contacts, they are 100% black, a disaster... but it's beyond hope : I rubbed them with a piece of paper soaked in " Deoxit ", no joy. Not a dent !
The contacts in your pictures look brand new ! To get mine like that, only way is to pull the switch assemblies out of the unit, take the swithc assembly apart and work on every contact individually, with some soft fiber glass pen or something.
So that's what I did at 9AM after I woke up too a quick breakfast and seeing your message.
Then one thing led to another, and another.... in the end it 1PM next day now, and I worked on the 575 non-stop ! Didn't even stop for lunch, no lunch for Vince today. Did have dinner but only a quick 30 minute break, the time to cook some pasta and watch the news, then back on the beast.
In short I discovered many problems, it's clear that the previous owner had two left hands. I sincerely hope he is better at teaching electronics to his student than he is at actually working on stuff !
1) Bat for the STEPS / SEC toggle switch : bent along two axis ! Don't know if I can straighten it... if not, needs to be replaced. That switch is near teh edge of the cabinet so is quite exposed I guess...
2) Chassis : top left cross beam plain missing ! The beam that runs all the way from front to back, connecting the front panel to the back panel. It's just not there ?!
3) Chassis, RHS, lower deck : there is a biiig panel/shield like 20x15cm that's missing ! You can see the 4 screw holes for it, and it's visible in the B&W pics in the service manual. It's got lots of text printed on it, and an access hole for a trimmer cap. It SUCKS BIG TIME !!!
Of course it's not needed for proper operation I suppose, but it's horrible none the less, a big chuck of the instrument is missing, impossible to source of course !
4) Chassis, RHS, bottom deck. There is a triangular reinforcement plate between the rear panel and the deck. 3 mounting screws on the deck side, one is missing.
5) CRT rotation : I always wondered why the traces / curves on the screen where tilted to the left rather than the right as they should... I though hey could be as simple as the CRT needed to be adjusted/ rotated. So looked at the clamping mechanism.... oh my God. Does not look pretty in there, carnage !
The neck of the CRT is flapping in the breeze, unsupported ! Looking at teh exploded view in the manual, and comparing with the CRT on 500 scope... looks like the 575 CRT is missing a huge cylindrical plastic part that's supposed to wrap the neck and fit inside the metal bracket. So, missing part again !
Hopefully I can salvage one from a scope, it's reasonable to believe it's the same part.. .crossing finger !
6) Power cord : previous owner fitted a modern european câble. Practical but
- There is a nasty cut on one of the wires
- He didn't find it useful to connect the fucking EARTH WIRE !!!!
- He soldered the two wires from the cables, straight to the terminals at the back of the original US power socket. Just look at the "quality" of the joints.... it's a wonder it works at all, might catch fire one day, who knows !
7) Was going through each and every switch to soak it in Deoxit and exercise them. When I got to looking at the " x1 / x10 " collector voltage selector switch, see what I found ? Unbelievable... The outer wafer is simply broken big time, a huge chunk of ii parted company ! It's still in there because there wires soldered to that part of the wafer so the wires are keeping it from wondering all around the instrument ! I tried to superglue it back together... somehow it appears to hold up, seems to work.. I can operate the knob, a miracle....
So I need to find a new wafer, with the appropriate configuration... good luck, where the hell am I going to find that ?!
..and of course the problems I had already found initially :
Wrong knob on front panel for the " SERIES RESISTANCE " range switch of the Base Step Generator. Dark grey with a hole in the center rather than black with no hole. I can get the appropriate knob from a scope, no worries.
9) CRT Bezel : one of the 4 mounting studs is missing. Can salvage one from a scope. However I looked at it closely and it's not quick / easy fix ! Seems that there is a retaining nut sandwiched between the front plate and the front of the chassis ! So I need to pull the face plate to get to the bloody nut ! So remove all the knobs, pull all the pots, switches, trimmers bulbs, what have you.... a big job. Of course will need to do it when I restore the instrument, but big job so only going to do it ONCE and only once... so the stud will get replaced toward the end of the restoration, when I put all the pieces together.
So there is quite a bit going on with this poor 575... Previous owner was a butcher !
It will never be complete andnever be showroom, it's just impossible. All I can do is fix it besst I can and make it look as good as possible, and fix all the electrical issues.
I would need a cheap broken donor 575 to get all the parts I need... There is no such thging as dirty cheap broken 575 these days, so I don't count on it.
Hence I will cherish the one I have and just try to make it as good as possible... it's all I can do.
Electrical issues now. Spent all day and night playing with the thing.
I have two main problems :
1) The trace(s) are very unstable, the various traces / steps jump all over the place, see pic.
2) Have some artifact going on at the right tip of the traces / curves, see pic. There is like a "zigzag" / ' S 'shape bit that joins the tips of two consecutive curves. They show only when I run at full speed : 240 Steps / second. At 120 Steps/sec I don't see that problem.
Before I got troubleshooting anything, in case it might be due to a bad contact somewhere, I cleaned all the switches with deoxit, and also cleaned each and every tube socket, and exercised the tubes for a minute in their socket. Took an hour to do, a pain.
Result ? Zero change. So must be an actual electrical issue that needs troubleshooting...
3) If you look at my first pic when I just got the instrument, you can see that there was a problem with the curves : normally you would see a vertical straight line, leaning a bit to the right, where all the curves join, at their left. typical transistor graph... well if you look at my old pics you will see there is NO such vertical line, you only get to see the horizontal part of the curves. I managed to fix that, when I replaced the dead / unlit V132 6AL5 tube. So that's at least some progress.
4) Oh, I notice also some ripple/HF content on the curves... well I say HF but it's not a scope it's in XY mode of course, so I have no idea at what frequency is this ripple.. who knows might just be 50Hz hum from the power supply, though I did check all 3 test points for +100V +300V and -150V and ripple on all of them is very low. So might be coming from some part of the 575 circuitry...
That's it for today with this 575 ! Started at 9AM it's now 2AM next day !
A few piccies and off to bed...
PS: at the very end, before turning it off and calling it done, I tried testing a diode, it looks just beautiful.... I am a simple man
PPS: I attached a pic also of the " CGI " / 3D rendering that the 575 can do ! It looks like a smoke pipe !
These 575 were reallt state of the art, no need for fancy CAd programs and graphics cards ! All done with hollow state !
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