Need help with a Tektronix 2215A O-Scope problem

It sounds like power supply problems.

"Michael A. Terrell" wrote in news: snipped-for-privacy@earthlink.net:

That is always the first place to check anyways. One must verify the low voltage supplies before anything else.Everything else builds off those LV supplies. A display shrunk in both X and Y axis could be loss of CRT anode voltage,but it would also be dimmer than normal.Focus would naturally be affected.

HV seldom goes such a way of in 2213/2215 scopes to my repair experience. LV supply is more probably the cause.

Go for a service manual ( bama.sbc.edu for download or mirror).

check for bad/dry caps. replace. The fault sympthoms you describe are most often due to one or more LV supply voltages out of range.

hth, Andreas

Hi Jim,

low HV leads to the opposite effect, if the HV goes low, the electron beam gets weaker and it is easyer to deflect, the display expand and is dimmer than normal. In the old TV-Set times with a HV-tube rectifier, which sometimes goes bad, the TV-Set had the "magnifying glass" - effect. If you turn the intensity high, the picture vastly expands. I would expect that the shrunk display comes, as you stated, from the LV-supply. Maybe in the beamfinder-circuit could be something wrong but not very likely.

Jorgen

I doubt that you can tell Jim anything about Tek scopes that he didn't see in the 20 some years he worked for Tektronics at their Orlando repair center.

The "Blooming" on old TV sets was due to the poor regulation. As the HV rectifier tube aged, the voltage drop increased. The starved the CRT of the current it needed during the active display times and distorted the image. The HV returned to normal during the retrace and blanking intervals. The CRT needs a clean, stable second anode supply if you want a crisp, clear image.

"Michael A. Terrell" wrote in news: snipped-for-privacy@earthlink.net:

No,I'm not infallible.I make mistakes like anyone else. although I've never seen a TEK HV multiplier only be low in output V,they usually fail by loading the HV osc,or no V at all.(open)WE never even tried to measure them;if the CRT made a fat spark when shorting the anode lead to GND,then the HV mult works.

If the Anode V is low,the Cathode V is probably also low;then the display spreads out.

Minor peeve;it's TektroniX,no 'C'. ;-)

I never said that you were, but a TV CRT isn't a good comparison to a scope CRT, and I am sure that you have worked on more scopes than most people who pop in here with a question, or an off the wall answer. ;-)

You consistently give good advice and take your time to try and help, which is more than a lot of others will do.

And no 'S' at the end, either ;-)

I know. Give me a break. :) I was posting after getting up sick in the middle of the night. I couldn't get back to sleep and was trying to get caught up on the newsgroups. I just forgot to hit the spell checker. :(

"Michael A. Terrell" wrote in news: snipped-for-privacy@earthlink.net:

I was up all night,too;a couple of thieves tried to break into my Integra at 3:15AM,but the alarm warning triggered(not the full alarm),I looked out a window and saw them shining a flashlight into the car and walking around it,and I went out and chased them off,got a partial description of their car to give to the police.After that,I couldn't fall back asleep.

It's unfortunate that I could not just shoot them.(legally)

Glad to hear you were able to run them off. Not sleeping is a daily thing for me.

Too bad it wasn't parked inside your garage. :(

"Michael A. Terrell" wrote in news: snipped-for-privacy@earthlink.net:

Apartment complex. I dream of having a garage.

I have a four car garage, but its full of tools and old electronics. I have to leave both pickup trucks in the driveway. :(