I thought it was well known by now that 2 types of calibrator units exist. Regrettably I only have a CSA803 and CSA803A, hence the slower type. See also https://groups.io/g/TekScopes/message/155394?p=

#photo-notice

Hi Max, I'm really too color blind for to read resistor values correctly. Since I measured 500R and at that time also didn't recognize RT43 as an NTC resistor I checked that R44 for having 500R colors

Hi Max, Now I made a mistake in reading "XB" in the parts list: R43T/R44 were introduced long ago in stead of removed. The .5 k replacement resistor I mentioned must be a new version NTR. The resistan

Hi Max, I think you are mistaken here. R40 (RT40 in the parts list) is the small cap-like component just right-above the label R40 and left above C10 in the PCB-layout and in the photo at Tekwiki. Jus

Hi John, works fine here with Firefox. In such cases I click Photos at the website and set "Sort by created" arrow down, i.e. new to old. It will be one of the first albums. Albert

Stephan, that's just short for "old messages at the Tekscopes website". A lot of information and hints there. You also should know about Tekwiki , w140.com/tekwiki/wiki/Main_Page . Albert

You are right Ed. I overlooked that the negative supply at R72 would also be missing. I don't remember that I have seen such a protection with an active component (so not counting clamping diodes and

Hi Ed, When -12 V is lost, U30B will not conduct and the base of Q72 will have the proper voltage for comparator operation, like in period 2. Hence I think the TD current will not get higher than Ip.

Thanks for the replies so far. The common thread is protection of the TD in case of other failures. I was thinking along the same lines, but also thought that one single other failure could do no harm

Hi all, A recent topic (ending at message #168946) about S-52 repair brought up the mysterious role of Q32. During normal S-52 operation Q32 will never conduct . Anyone an idea? Some kind of protectio

Hi Max, That must be a relief! I think the protective function of Q32 is needed immediately after switching the scope to on, when the power supply lines come up (perhaps one after the other). Just a g

Hi Max, For comparison I added a photo of the waveform at timing pin E to your album. Because of both the "+15V" effect and the temperature effect also Q32 might be suspect. As far as I can see Q32 se

Hi Max, At the more negative level Pin E resets the output to true zero in periods 3-6 and 9, by switching the pair Q86/Q88 such that Q86 conducts and Q88 is off. Pin E is the only Timer board output

Hi Max, I think the extra 3.9 ohm helps a tiny bit (makes the snap-off current to the TD somewhat stronger) but in my opinion its not the problem. Since at 15.5 V I suspected a wrong state of Q86/Q88

Hi Max, Those pictures helped me a lot to understand what you previously said in words! Just for comparison I added an annotated picture to your album (and somewhat destroyed the order). You said R90

Hi Max, Any progress? Today I used an S-52 on an extender, case removed, and then thought of your problem. I read your first post once more: The 1N3130 is a 50mA/25pF TD, while the original one is 50m

Hello Thomas, Often a simple Google search for the part number brings you further, for instance 465(A) for the first transformer. A lot of info can be found at Tekwiki, http://w140.com/tekwiki/wiki/Re

Hi Max, A few thoughts. I don't see how one of these resistors being open can be the cause for no pulse at higher (+15V) supply voltage while there is no problem at lower supply voltage. In my opinion

Gentlemen, Comparison is dangerous, it depends on the measurement range (measurement voltage) of the DMM. I tested 3 7S11s with 4 DMMs. Measured with the same DMM all 3 resistances at the 15DC pin are

I found that knowing the part number 352-0100-00 and "holder" didn't help when searching for a replacement. In some instruments the trimpots are mounted on a "stand-off" but that search term also gave