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Welcome John!

You should begin at the beginning: open her up and do a visual inspection, you'd be surprised what will jump out at you, even if you're a novice (I assume that you are not actually a novice to electronics, based on the call sign, but even a novice to scopes can still spot some signs of trouble). Next, clean the insides as needed using a static safe brush or compressed air. Finally power it up and have a look at the power rails (as Siggi suggested).

Take pictures. Take notes. People here will be more than willing to assist you with further diagnosis and repair.

You might want to have a look at this document:

Also, download this service manual from TekWiki:

The TekWiki is a source for a great deal of information, both general and specific, about Tek scopes and other instruments. Here is the "reference material" page:
and here is the main page:

Finally, some of the 2400-series scopes can be damaged if they are run for more than a few minutes with the case off. Some of the hybrids really need the forced air cooling, so if you are running it with the case off (to check the power supply rails, for instance) you should direct a fan to be blowing air over the main board with all the heat sinks. I'm not sure that the 2430 is one of the ones that can be damaged that way, but better safe than sorry.

-- Jeff Dutky

I've added a photo of the left interface board of my 7S12 so you can compare.

From the sound of the previous attempts to inform the seller, I doubt that anyone will be successful with any "correction". This is the "Thing that won't go away".

--
Michael Lynch
Dardanelle, AR

Well, it's now listed for (minimum) third time.
Desciption states it's a "dual beam" scope, so I do hope someone can politely correct him on this: don't want it sold and then rejected as "not as described" , do we?
john

Joe:
congratulations, and I hope you enjoy using this wonderful piece of test equipment. I had a very simlar experience with a 575 which I bought "blind" on an auction site a couple of years ago (not Ebay). I've managed to retain the HV electrolytics, but changed all the black jobbies. On my unit, there were quite a few tired valves/tubes: in particular the triodes used as HT regulators. Oh, and the fan bearings were sticky with old green oil, so the fan would not run until things got hot. It took some effort to completely clean the oilite bearings.
John

On Tue, Mar 30, 2021 at 10:02 AM John Morris <k7rld@...> wrote:

Scopes are not my expertise so if anyone has an idea where to start
looking, I'd sure appreciate some guidance.

You'd generally start by looking at the power supplies which may simply
need recapping by now.

Grin!? The 7704A probably isn't recommended, but I've had one on that cart for years.? Just last week I was thinking that my 465 would make more sense on it (and be safer!)

Hi Dave, I didn't realise that. But then I've never worked with 7000 series kit. I don't think it would take my 547:)

Also works for 7704As, well strapped down, of course!

Many years ago, in a former life and former employer, I was using a 5112 Dual Beam Scope that was perfect for my project. The 2 MHz bandwidth was plenty for what we were doing and, while the dual beam wasn't really necessary, it gave us confidence that what we were shown on the screen was actually coincident in time. This scope, however, had a problem. It would occasionally stop showing one half of one of the traces. The EEs with me on this project would "fix" this by removing the affected plugin and SLAMMING it back into place. The shock often cured the problem, but this "solution" annoyed me.

I managed to get the scope manual and noticed that there were 6 identical output transistors which drove the 6 deflection plates, 4 vertical and 2 horizontal. This scope had dual beams, but only one time base. Reading thru the circuit description I could see that each transistor drove its beam over half the screen. So I figured out which transistor seemed like it might be the problem and swapped it to a different location. This was easy because they were in sockets. Sure enough, the next time the problem occurred, it was in that new location, and I found that I could make the problem come and go by tapping that transistor.

The manual gave a Tek part number for that transistor and also a suitable replacement from some Japanese manufacturer. I ordered 2 or 3 of the Jap replacements, so I would have spares. I replaced the bad transistor and taped the spares inside the scope case, in a zip lock bag. A couple months/years later, another of the OE transistors failed and then another. I ordered more spares, and eventually used all of them. As far as I know, the replacements never failed.

So the question is, was this a well known problem with these transistors and were these common to all the 5000 series 2 MHz scopes? The scope was probably 10-15 years old by the time I started replacing transistors, but I'd never run into streaks of failing parts like this before. Sorry, but I don't remember the Tek part number or the Japanese replacement; this was circa 1985-1990.

Other than those problem transistors, I really liked that scope.

Is the fan running? Is there a lot of dust on the heat sink fins?

--
This email has been checked for viruses by Avast antivirus software.

5 of these have now been sold. I'd like to keep 5 for myself, so that leaves 10 still available.

On Fri, Mar 26, 2021 at 09:39 PM, Dave Wise wrote:

You ought to upload the article to TekWiki at w140.com .

Okay, done. Took me awhile to figure out where and how to do this, but I think I (pretty much) managed.

I have a 2430 that PASSES all tests and works fine on both channels using a function generator. After a minimum of 30 mins, sometimes longer, the screen will freeze and no controls will change it. The last curve will be frozen on the screen.
If I turn it off and then back on after waiting 30 secs or so, it will not boot up at all sometimes and sometimes it will go to a horizontal trace but no input will show on the screen.
If I turn it off for several hours and then back on, everything is fine again for another 30 mins or so and sometimes up to several hours. Then the screen with a trace will freeze up again. I can hear the relays clicking as i change the timebase but it changes nothing on the trace. The curve screen position controls change nothing either.
If anyone has seen this before and can point me in the right direction, it would be very much appreciated.

John / K7RLD

I've got a TEK 2430 that seems to work just fine for about 15 mins. Sometimes more. All tests PASS.
I've input a function generator and all different inputs look fine on both channels. Then after 15 mins and sometimes more, I'll look over at it and the screen is still showing a nice looking sine wave, for instance that I've input, but when I go to make a change, the scope is frozen with that image and no other controls seem to make a change.
Relays click when I make some control changes but the screen remains frozen with that sine wave image.
When I turn the scope off and wait 20-30 secs and then turn it back on, it will show the standard horizontal line but will not detect an input.
I can turn the scope completely off and after a few hours it will again come up and work just fine but eventually the same thing happens.
Scopes are not my expertise so if anyone has an idea where to start looking, I'd sure appreciate some guidance.
Thank you. John / K7RLD

For sale: Tektronix Scope-Mobile 200C . Suits many 400 series and 2xxx series instruments.

Good condition.



Best collected but might be possible to dismantle and ship at cost. Location is London N12, UK.

Donation to BECG (registered charity) please:

Hi Joe,

this tale reminds me of my 575, that was sitting together with a 576 for a number of years.... in an attic.

I took down the 576 and it behaved like the proverbial old lady... bad HV transformer, recently a bunch of bad transistors...

Eventually I took a look at the 575. Having the habit of first trying out what happens when rising the variac, thermal cam at hand, well... it worked flawlessly!! Did some realignment, not much was needed. It still has all its original caps, bumble bees, selenium stuff and whatnot that might fail one day. Now its sitting in a (dry) basement, on a shelf connected to the power line where I can switch it on from time to time. So fare no issues.

On the other hand, the old lady... the 576 is sitting on my bench now, in regular use, and the step generator begins acting up (again), doing steps only if well warmed up ;-)
Probably the IC that enables/disables the step counter has an issue...

cheers
Martin

Thierry,

I am glad you are making progress. The schematic shows that when the div. knob is pushed (usual operation), that grounds the 74112 through the 68 ohm resistor (R861) J & K inputs making the Q outputs static as you see. When it is pulled, the 74112 oscillates. The function table shows the states of the inputs and outputs. From the table, this IC appears to be working correct.

See if you have the 400mV pulses at the collector of Q358. This is waveform 7 on <3>. You can pull and reinsert the short coax between J260 and J270. The inner contact could be dirty. The trig. sens. pot may need to be adjusted. The TD bias pots may also need adjusting a bit. There should be a pulse at DA at ,5V d-c.

Now back to the other side of the plug-in on the interface board. Check the waveforms 1, 2, 3 and 5-11 on page <5>. See if you have them there. Also check the transistors there with the number mentioned earlier if you have not already done so. The leakage in these will be from collector to emitter as a diode check. An analogue meter will have the needle vertical on the Rx1 scale. Usually the same number that has a leakage of the 0367 in something, the others likely will be leaky as well. The manual will tell you the Q numbers.

Mark

Hi, everybody.? ?At the risk of TMA (Too Many Acronyms), I ask for a recommendation for a reliable 2-port KVM switch that does VGA video and keyboard and mouse over USB. I've not had issues with the video, but the USB interface is a real PITA!? Just got a new work laptop computer, and I think that was the last straw for my existing Belkin KVM switch.? Now it doesn't work at all, after being flaky with the keyboard and/or mouse for many years.? Why is the USB part so hard to get right?!? ? ? ? ?TIA, Jim Ford?Sent from my Verizon, Samsung Galaxy smartphone

Thanks for the pictures of the various boards. Could we please have a picture of the back showing connectors and especially the label showing options (Like or ) ?