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Old 27th Jun 2013, 12:19 pm   #20
davidgem1406
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Join Date: Feb 2011
Location: Sheerness, Kent, UK.
Posts: 936
Default Re: Tektronix 465B Scope - Some problems.

Hi John,

I have not done as you suggest as yet, I am concentration on the power supplies for the moment but will try to do that later today.

What is collimation referring to? the definition for this, from a web search, is referring to the alignment of optical devices.

Yes the screening is in place.

Hello Al,

Yes those parts are missing from the copy I have as well, load of junk as far as all the diagrams go. I have another copy on CD coming.

The variation in trace brightness is not actually happening, it is the camera shutter speed, trace speed and the light causing it. It is even more pronounced in the pictures that accompany this post as there was more artificial light.


I now have the result of the checks made on the power supply outputs.

First I did manage to make a basic ESR check on the 5000uf capacitor using information found from a net search. This used a signal generator and a scope to view the output.
The result was that the 5000uf capacitor looks to be good. I have however a new 6800uf cap on it's way, this may or may not fit.
I did look to see if an original was available from QService but they are nil stock.

-8V rail with a 4400uf capacitor used was showing 100Hz @ 50mV looking like the bridge rectifier has partly failed, this is also very hot. (Image_a Top trace, the lower trace is just 100Hz from a signal generator for comparison)

+15V supply shows 2mV with HF (Image_b top trace) The bridge rectifier is also very hot.

+5V supply shows 2mV also with HF (Image_b) Again the bridge rectifier is very hot.

+110V supply shows 15mV @ 100Hz sawtooth with about 2mV of HF (Image_c)

+55V rail 3mV mixed with HF, looks like a mixture of 50Hz and 100Hz. (Image_d)

It now looks like a major strip down to replace some of the bridge rectifiers, at the very least the one for the -8V supply.

Ignore the variations in the trace brightness in the images, it is not really happening. It is the result of the trace speed, camera shutter and light.

Dave.
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