Help Troubleshooting a Tek 453 Scope

[chuck yorba linda]

So I just bought a 453 scope from ebay and of course it has problems. It will not focus and the intensity is running wide open and distorting the signal. (I'm using the internal 1Khz as a input)
I pulled both pots and they tested ok. The focus pot would like to do it's job but is just overwhelmed by the intensity. Traced the signal thru the z amplifier and I get a nice signal out of the output going to the CRT circuit. So that whole piece has me intimidated . My research is talking about problems in the grid control circuit. Any one have experience with this issue?
got the manuals and a couple of DVM's and one of those pocket scopes also a transistor tester. (Chinese knock off)
Thanks,

 

[chuck yorba linda]

Sorry posted this in wrong forum redid over in the right one.

 

[wb8yxi_Ski]

So I just bought a 453 scope from ebay and of course it has problems. It will not focus and the intensity is running wide open and distorting the signal. (I'm using the internal 1Khz as a input)
I pulled both pots and they tested ok. The focus pot would like to do it's job but is just overwhelmed by the intensity. Traced the signal thru the z amplifier and I get a nice signal out of the output going to the CRT circuit. So that whole piece has me intimidated . My research is talking about problems in the grid control circuit. Any one have experience with this issue?
got the manuals and a couple of DVM's and one of those pocket scopes also a transistor tester. (Chinese knock off)
Thanks,

Hi Chuck,
I have had 2 453's and both were fine, but both had some 'quirks". The first one had a low intensity problem and after checking the 8kv and -1950v supplies, both were OK. I tried changing the CRT, by purchasing another 453 on Ebay, and after the switch of the CRT, all was the same and the new scope intensity was still ok. One thing though was that the CRT Grid Bias adjustment R940 did not adjust properly. I was wondering if you had gone thru the HV adjustments and checks? I had a Heathkit HV probe for my VTVM, so I could check my 8kv and -1950v supplies. I have posted a new post for my current 453 and it has a funny problem when using the ALT mode. The unused channel has a weak signal display following the active one. Something wrong in the Switching Multivibrator area I think. The 453 is a nice scope and well worth what I paid, if you don't need a digital. Good l luck Chuck.
wb8yxi_Ski