I am reviving an interest in electronics I had in my youth, my day job is a race car engineer, and I need to get a better grasp of electronics as cars and engine become ever more complex in their management and control strategies. I have bought a bit of basic test gear, as well as stuff I have had for a long time. I now have a working Philips PM3380B analogue / digital scope, a 150 meg USB scope, some basic voltage measurement gear and a basic signal gen. I also have acquired through the ubiquitous Ebay a half dead Tek 475 scope to play with. it cost not a lot and was a surprise win on a bid I put in and forgot about. The abridged story is below:
Right, I picked the 475 up this evening and have had a word with the seller and a quick look inside it. It was stored under far from ideal conditions for some years in an old building undergoing restoration. It has slight signs of this damp on one board, some of the metal canned transistors have the very first signs of green verdigris / corrosion on their cases, very very minor, mind you. One of the vertical side boards has very minor corrosion on some of the ground foil near a vent on the case, but the tracks still appear fine, it's very localised and would clean off I am sure. When the scope was purchased five years ago it worked fine save for the second channel losing the display if turned up to what he described as 2 megs?? Below this ?? it worked fine, and channel one worked fine in all respects. After coming out of storage and being put in a warm dry environment the problems were apparent with which it was sold.
It will focus quite well, in the centre of the pot. The dot almost appears to be two very short lines one above the other though, hard to say. Intensity needs to be in the last tenth of clockwise rotation to get any display to show. Horizontal control needs to be fully clockwise to bring the dot to the centre of the screen, a 1/4 or so turn anti clockwise and the dot is off the left of the screen. Beam finder creates a very bright bigger dot, with a lot of illumination on the phosphor around this dot.
The vertical control fully clockwise has the dot off the top of the screen, fully anti clock has it a maximum of a 1/4 of the way down. Fiddling with the control will make the display occasionally flash below the vertical half way point instantaneously, as if noise in the pot is doing it.
Randomly probing a few of the voltage test points which have their expected voltages shown on the main board give sensible readings, what the ripple is like I have no idea. There's a point marked "5 V unreg" on the main board, this is showing 62.9 volts. Others are within 0.01 volts of the stamped values on a reasonable hand held DMM, referenced to ground tags on the main board.
Fan works, three or so of the panel switch plastics are broken, Bezel of main front panel has some corrosion, fascia is so so, but perfectly legible and usable. Would you recommend I attempt more diagnostics, or is the above enough to condemn it as a source of spares only? Thanks. I can post photos. I would like to fix it as it would be my first attempt at fixing anything electrical of any complexity, and very different from working on new automotive engine and chassis control systems.
I don't NEED this to work, it won't change my life it it's a white elephant, but I know I'd get a buzz if someone were willing to treat me like a normal Joe passenger who ends up in the cockpit of a plane when the pilot has a seizure and needs talking into landing the thing, however inelegantly ;) All I have are a 150 meg dual channel USB scope, a PM3380B 100 meg dual channel Fluke analogue / digital scope, a bench and a hand DVM, a signal gen that goes only to 1 meg. I have some soldering gear anyone with a true interest in PCB work would probably laugh at, but I don't mind buying a cheap fairly basic soldering un-soldering station, I have fancied something better for years. If I blow it up (further...) I will be annoyed, but would put it down to experience.
