Blank oscilloscope screen

[amateur_24]

I've just get myself a 2nd hand oscilloscope to play with. It's an tektronix 2215a.
However when I switch it on, the monitor doesn't appear to light up even after 5 minutes warm up time. Should the backlight not be on? I tried turning the intensity left and right but no difference. It switches on though.

No signal not even a flat line. any ideas

 

[Grossel]

If you doesn't have a repair manual, then look at the print card nearby the crt and look after bad soldering points. That's a start anyway.

 

[cr0sh]

First - are you familiar with how to use a scope? I am not saying this to be rude, but rather so we know what your level of expertise is on these instruments; they don't tend to be "intuitive" unless you have played with one in the past. If you are familiar, then are you sure you have everything in the "default" positions, and you have tried hooking up one of the probes to the built in test signal, and pressed the "beam locater" button? If the beam locator button gives you nothing, then there's probably a big issue. Maybe if you can also post a pic of the front of the scope and controls, so we can see what your settings are...

I would also be wondering if the Z input (beam intensity - back of the scope) wasn't somehow damaged in the past; I don't know what the fail mode of this part is, but I do know that it is fairly easy to blow... Also - have you found the manual for it; I have a 2213, which is close to the 2215...

 

[tunod]

I believe your scope service manual is available for download on this site, have a look Oscilloscopes Tektronix : Service Manual free download,schematics,datasheets,eeprom bins,pcb,repair info for test equipment and electronics

 

[gootee]

While they are great scopes, many of the Tek 2200-series suffer from a tendency for the power supply to fail.

Luckily, they are usually easy to repair.

But first, you have to know how to stay SAFE when working on live high-voltage circuits! The following assumes that you can.

You will probably want and need a service manual for your scope, which contains all of the schematics and troubleshooting information.

After you figure out how to remove the case, first check the power supply voltages, which include +100, +30, +8.6, -8.6, and +5.

If any of them are off by more than 3% or so (I forget what the actual spec is, but some of yours will be way off if the power supply is down), then the first thing I would do is to find the discussions that are already on the web, where people went through diagnosing and repairing these power supplies in great detail. I have collected some of the better threads into text files that I can email you (PM me if you want them). But it is probably against the rules to post them here. You can find them yourself, though, as follows:

Find the TekScopes group, at yahoogroups.com and search its message archives for this exact title:
Tex 2213A - Power Supply Problems

Yes I know it says 2213A. But the power supply is identical in the 2215A, as it also is in the 2235, and probably others (except for the non-A 2213 and 2215, which didn't have the 43V pre-regulator circuitry).

Also go to Google Groups and search the sci.electronics.repair group for this title:
Tek 2235 problem

Both groups also have other threads that deal with these power supplies. And after you get into the actual diagnosis of your scope, those groups have people who can be very helpful, including some ex-Tektronix technicians and engineers. (But remember to be polite, and always search before asking.)

If the power supply rails are NOT the problem, the first thing I'd check (besides "pilot error") is the wires that connect to the CRT tube (the single wires that connect to pins on the sides of the tube, not the ones going to the socket in the rear). Some of them had a habit of coming off the (deflection) pins, which kept the beam off the screen.

After that, there are lots of other reasons why you might get no display. But they are mostly pretty easy to diagnose and repair, in the 2200-series scopes.

Good luck,

Tom

 

[bryan]

I have a pdf of the 2215 service and operation maunuls. Unfortunately they are 32mb in size. perhaps I can host it somewhere for you to download.

 

[amateur_24]

to be honest it's my first time and I have no idea. However I thought even if you don't have anything connected it should still show a flat line on the screen.
It doesn't even light up, never mind display a flat line. At least that's what the picture of the scope suggested.

 

[gootee]

Yes. It should have a flat line. Did the photo on ebay show the line, or any type of display? Have you contacted the seller?

If you do eventually open it up, the easiest thing to check is the wires that connect to pins on the side of the CRT tube. They sometimes come off, especially in shipping, and would cause the symtoms you have described.

 

[amateur_24]

thanks for confirming this for me. I was thinking it was me being an amateur.
The photo did show the scope showing two flat lines as it's got 2 channels without scopes. That's why I thought it's supposed to have one line at least. I'm reluctant to open it because I don't want to end up in A&E. Also he may blame it on me as there's warranty stickers on the screw holes but the warranty has passed since it was last serviced in 2003.
I'm not qualified to work with high voltage circuitry and am afraid to do so. Thanks for everyone's help anyway. I'm waiting for the seller to respond. If not I'll just have to report him to ebay.




Just out of curiosity why do they come off? I've never heard of/ experienced such issues with pc components

 

[Mikebits]

Yes. It should have a flat line. Did the photo on ebay show the line, or any type of display? Have you contacted the seller?

If you do eventually open it up, the easiest thing to check is the wires that connect to pins on the side of the CRT tube. They sometimes come off, especially in shipping, and would cause the symtoms you have described.

Not necessarily, if the trigger mode is set to external trigger or single sweep you will not see a trace. If the vertical position knob is cranked to an extreme position, you will not see a trace. This may seem obvious but turn up the intensity knob and as was already suggested, try the beam finder button. Your best bet is to eliminate operator error first.

 

[amateur_24]

Not necessarily, if the trigger mode is set to external trigger or single sweep you will not see a trace. If the vertical position knob is cranked to an extreme position, you will not see a trace. This may seem obvious but turn up the intensity knob and as was already suggested, try the beam finder button. Your best bet is to eliminate operator error first.

How should I have setup the scope then?

To be honest there's only one switch am not sure about. What should the swp sep switch do?

There's an auto and a normal mode in the trigger section. It's toggle switch hence it's one or the other.
I pressed the reset switch which allows me to deselect both modes.

It's a tektronix 2215A