I collected this probe power supply waiting for use in one day. Recently I have more time at home and thus opens up if any thing need maintain inside. It ends up i recalculate the supply voltages to within spec after cleaning. There is no line filter capacitor inside and thus no risk of leaking due to aging of RIFA capacitors!
June 24, 2021
hp 1143A Probe Power supply inside photos and calibration
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75 Ohm termination to 50 Ohm
I have 6 pcs 75 ohm terminator for TV measurement use. As I can see there is a screw to open up and thus I try to do it and found there is a 75 ohm resistors (carbon composition or metal film) inside, I changed all of them to 50 ohms as today there is no more need for 75 ohm termination any more!
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hp 3478A 5.5 digits DMM repair
In fact it is not a repair but try to open up to see if any thing need replacement after over 25 years of use! Very worry about the power leakage!
- The Y Capacitor is using RIFA PME271 again! This is a poor reliability filter capacitors (well know to me!) used in many equipment which will cause line voltage leakage to the ground point of the equipment! You can see the body is crack and swell a bit after used some times! My experience is that I brought replacement 5 years ago and put into my Lecroy Scope but is failed again (in fact the scope is idling most of the time) when I power up the scope early this year!
- The 3V lithium battery inside the two meters I have is still very healthy above 3V! Very surprise to know that but the battery size is BIG.
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NI PXI-6221 DAQ Analogy Output Repair
Acquire that from eBay but the analogy output two channels is not working! Quick check on the power supply capacitors found that the one near the DACs is not connected to +Vcc. After trace through the path, it goes to the inductor L3. Checked one plated through hole is OPEN near C83 (as seen dented at the bottom). After discussion with the seller, I want to repair it myself and he agreed. So putting a jumper wire as shown, the card is working again. Another bonus is that the Seller refunded me US$25 and thus I am buying this card at 20% discount!
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July 23, 2017
hp 5334A Frequency Counter 100MHz
Pick up this in junk yard for a low price and found inside all corrosive due to battery leakage! After I do a cleaning and washing on the main PCB and replace all 6 pcs 100uF 15V cap with new Panasonic FC capacitors, the set can work as it is. Gone through performance check and all ok, self diagnostic also all OK, frequency can measure up to 105 MHz and level down to 35mVpp which is a bit better than spec. Date code of part is mostly at year 1986, this this is a 30 years old hp equipment and is still working fine! Made in USA.
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