Tektronix 2213 low intensity

[NorfolkDaveUK]

Hi all ,
     First post here so go easy on me haha (they all say that right )

Ok I just bought a tek 2213 from ebay and it all appears to work except that the intensity of the beam is very low. Almost to the point you can`t see it . I got it as a project to repair so I knew this when i bought it so wasn`t ripped off or anything , knowing nothing about how scopes work (other than to avoid the HT) , can someone give me a pointer in the right direction please .

Many thanks

[tkamiya]

A very first thing you must do is to check power supply voltages.  If I remember correctly, right by power supply, there are a row of what look like resisters.  They are usually white.  Along them, there are voltage specifications screen printed.  Check those.  I think the highest voltage there is 130 volts.

Then, check the intensity potentiometer and focus potentiometer.  Make sure they go full range.

[NorfolkDaveUK]

Thats great , thanks for your help .

I will do that and report my findings .

Thank you .

[NorfolkDaveUK]

Voltages are all correct , pots go full range ,

The intensity is very weak , when you increase it using the pot the beam goes out of focus but doesn`t get any brighter . I have noticed under the power supply housing there are some very suspect looking caps (malory caps , why they used those I have no idea) , so I think I`ll replace them and then see how it looks .

[David Hess]

The early 2213/2215 had a design mistake producing a high CRT heater voltage which lead to low CRT operating life.  There was a change notice to fix this so maybe yours is one of these or it just has a lot of operating hours.

Before blaming the CRT, make sure to run your test at a low sweep speed of 1ms/div, automatic triggering, no x10 horizontal magnification (1), and with the trigger holdoff control set to minimum.  High sweep speeds at low repetition rates can cause a dim trace.

(1) Check that the trace length is about 10.5 divisions by using the horizontal position control.

[particleman]

I agree with David. I  replaced a CRT in a 2215 a while back. Dim trace almost non existent at higher speeds. Ended up finding  a used CRT from a 2230. Needed to change the PDA connection but it's nice and bright now. Good luck.

[NorfolkDaveUK]

Just thought I would report in ,

I replaced all the 870uf 10v malory caps with 1000uf 40v panasonics and its almost as good as it was new now (well ...kinda...lol ) . I have a few more caps to replace in the power supply but I don`t have anything close (I`m running out and need to restock just been so busy) , but happy as Larry so far , its made a massive difference just replacing those so I`ll now go ahead and replace the whole lot once they get here .

Thanks for your suggestions everyone , if you have one of these , ditch those mallory caps , I`m not sure why they used them along side good quality ones ? ? They didn`t need to used those old ones (70`s caps they are) along side the 80`s ones ...bit weird . Anyway its now very useable at least , the beam is a bit "thick" so it definitely needs calibrating once I get the caps in and wot not I`ll have a go at that but I dont want to make it worse !

[David Hess]

So it was the capacitors after all?  I guess that comes down to having to measure the AC component also.

There was nothing wrong with the Mallory capacitors.  Just like all aluminum electrolytic capacitors, they wear out with age and these oscilloscopes are old.