Tektronix 475 Oscilloscope Repair Ep# 1 - powers on but no trace.
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- Опубликовано: 28 авг 2024
- We found a transport damaged Tektronix 475 for cheap, the seller stated that it was working before he sent it to the original buyer.
Apparently he tried to repair it, but obviously gave up at some point and decided to sell it as it is.
On first inspection, we found some damaged pot/switch in the timing circuit and a -8V supply short, but that was not all,... following was quite a lengthy investigation on some mysterious collection of faults. At the end, it turned out to be something rather simple, causing all the confusion and the strange behavior of the circuitry around the channel combiner circuitry.
It is also rather unlikely that it was in fully working condition before the transport damage happened as we found a power supply capacitor which was completely dead. Probably would still have displayed a trace, but the scope won't be really usable with that amount of hum on the supply..
On powering up after a brief safety inspection, the scope heavily distorted the camera audio (the sequence is only about 20 seconds to show what happened) . This was either something wildly oscillating, or a hefty dose of X-rays. No trace was visible, only a brief dot in the center, confirming the CRT is most likely working and sweep does not work at all.
The scope is already back in working condition, so please follow us over few episodes on the bumpy journey to success.
Part 2 is here
• Tektronix 475 Repair E...
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You slipped one by me! :)
Sorry, upload time wasn't really favoring you time zone ....:-) ...hope you well.
I have a Tektronix 545B oscilloscope 1965 vintage
Can you advise please the trace fades to nothing about 10 mins after switch on
.otherwise all in very good condition
I'd suspect power supplies at first, so check voltages and go from there
It COULD be CRT cathode emission. Check the P.S, especially the electrolytics, first. If the CRT is on its last legs, a TV CRT "rejuvenater" might extend its life.
Was it typically damaged by the post office ?
I don't know as i've bought it from the guy who initially sold it to someone else. This is were the damage happened, but i suspect it was Hermes (now Evri) ....:-)
Hermes. Phah!!!
Is it actually possible for an old scope to emit that many X rays???
If things go wrong electrically, these could emit a fair amount of x-rays, essentially any CRT produces x-rays, the higher the anode voltage, the more
@@dynoguy ive recently got my hands onto an old crt scope and now im concerned 😅😅. Its having some troubles but im getting a reading . Is there any way to tell besides a radiation meter if its harmfully emitting?
well, ..people were staring at CRT TVs and PC monitors for several decades (me included) and not many were concerned. So if you really concerned about x-rays coming off an old scope CRT, i'd suggest to buy an new one with an LCD screen and you are most probably safe.