Tektronix 585a (tube-based) oscilloscope project

There could be hundreds of opens due to corrosion on the contacts in switches and any plug-in sockets. Have you given all the controls a good workout, and removed and replaced the preamp? Not much else goes wrong with these tube scopes, for the reasons you cited. Of course, you could spend a day or two at an old-timey hardware store checking all those tubes.

It should not be hard to find someone with a manual for that scope. Don't pay some ebay crook 40 bucks for a photocopy.

If you've got no timebase, and no Y deflection either, then you should be looking for a common reason, as these two pieces of circuitry, are pretty much independent from each other. I would suggest starting by checking that the HT supply for the tubes involved, is present. Could be something as simple as an open circuit resistor, or short circuit decoupling cap ( or possibly, both )

Arfa

"Arfa Daily" wrote in news:YArJf.12343$ snipped-for-privacy@newsfe4-gui.ntli.net:

You need a SERVICE manual.

Well,the FIRST check should be all the power supply DC voltages,regulation and ripple.

Just because there's a spot on the CRT does not mean that the PS voltages are what they should be.

--
Jim Yanik
jyanik
at
kua.net

If relevant, I have a repair manual for the 585A my email address on URL below

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

I had some old Tek tube models similar to the one you described. My memories of 'em are fairly vague, but I do remember admiring the internal craftsmanship.

I kinda-sorta remember 2 jumper bars that were mounted within an exposed insulated panel near the back of the cover (an opening in the cover, near the back, visible with the scope cover on).

If my recollection is anywhere near accurate, the jumpers had to do with the beam sweep. The jacks that the bars were inserted into were just panel bananna jacks, and the jumper bars were just bare/uninsulated plated bars with a bananna pin at each end.

I'm not sure that the bars' purpose was, but I seem to think that one of the units wasn't operational, and that I noticed that the bars were missing. Putting a set of bars in place, from another unit restored operation.

Cheers WB .................

zeitguy wrote:

I had one for many years. Amazing device, BUT note:

(1) They're huge, heavy, and draw about 600 watts IIRC. Fine in the winter, unbearable in the summer even with the workshop AC on.

(2)The fan is NOISY. Makes it hard (for me) to concentrate.

(3) There are about 50 tubes in there, each with 7 to nine pins, all corroding away and making poor contact. There are a passel of wafer switches, most of them NOT gold or silver plated, all contacts corroding away. There's lots of redundancy in there, which means a good

10% of those contacts can go open circuit and the scope will still kinda "work", but be totally out of specs.

(4) There's a tunnel diode or three in there which are easily burned out (dont ask) and are very hard to find. Without them you have no sweep and no scope.

(5) Even when it's working at 100%, the triggering is still mighty iffy, at least compared to newer scopes. You can easily spend a minute twiddling the trigger knobs before you get a stable trace. After doing this a few huindred times, the charm wears off and most folks revert to using a quieter, cooler, more portable, better triggering 465 or 475.

(6) Poking around in there can KILL you. There are many high-voltage regulated power supplies.

--
Al that said it's an impressive beast, especially if you're used to a
5MHz heathkit scope.
If you have the time, $$, and patience, by all means go for it.

Here you find help:

You have to became a member of yahoo-groups, but that's an easy task and for free.

Jorgen