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HP 8341A sucessfully FIXED!

Tobias Pluess All Messages By This Member #86216 开云体育 Hi all, probably some of you have seen that I had some problems with a 8341A. It was indeed the YTO which failed! But, I was incredibly lucky to fix the YTO. I also did a front panel RF output retrofit on my machine. Some pics of the YTO and stuff can be found on my page, if someone is interested :-) Now I can proceed to my next project, a 5342A frequency counter (hopefully not a blown sampler) and a 8568B spectrum analyzer with blurry focus on the graticule. Best Tobias, HB9FSX
Ed Breya All Messages By This Member #86218 Wow. Nice work, Tobias. Sometimes we learn the most when things seem hopeless. Your reasoning was right that there was nothing to lose by taking a chance on opening the YTO, and you came up with a great alternative to get around the problem. I hope you plan to keep that web-page available - it's a good story and resource with good pix of the YTO innards, for future reference. I'd recommend you also post the images to the photos department here. Ed
Tobias Pluess All Messages By This Member #86223 开云体育 Hi Ed many thanks! Yes, I was really lucky with my YTO. However, I am a bit afraid that the YTO could definitely fail some day and I would like to have a spare, but there's none :-( I even thought whether it would be possible to construct a semiconductor-based, compatible replacement, but this would be a really large and complex project. I have some ideas, though :-) Of course my web page will be kept online. I have several projects I am working on, including a 5342A microwave counter and a 8568B spectrum analyzer, both waiting for repair. I will also present these on my page. I would like to upload my the pics of the YTO, however, I forgot how that works; I probably even have an account here, but I have no idea what credentials I used. This is because posting to the group also works even if you forgot your account details :-) I will try to figure things out and upload the pictures! Best Tobias toggle quoted message Show quoted text -------- Original message -------- From: "edbreya@... [hp_agilent_equipment]" Date: 10/15/17 17:19 (GMT+01:00) To: hp_agilent_equipment@... Subject: [hp_agilent_equipment] Re: HP 8341A sucessfully FIXED! ? Wow. Nice work, Tobias. Sometimes we learn the most when things seem hopeless. Your reasoning was right that there was nothing to lose by taking a chance on opening the YTO, and you came up with a great alternative to get around the problem. I hope you plan to keep that web-page available - it's a good story and resource with good pix of the YTO innards, for future reference. I'd recommend you also post the images to the photos department here. Ed
Adrian Nicol #86228 Hi Tobias, Great job and a great write-up to go with it, thanks for sharing your work. Your story reminded me of something I learned from my first ever boss after I left school (over 50 years ago now - yikes!) he was an electronics engineer in the Radio Astronomy group at Cambridge and whenever we had to fix things that looked like they were 'no user serviceable parts inside' he would pick up a screwdriver, wrench or whatever and say "Well now, it didn't grow like that did it?" and would start taking it apart and more often than not he would fix it! I have followed that approach myself over the years and generally succeeded more often than failed too - and even when I fail I learn something! Congratulations again on that fix! Regards, Adrian On Sunday, October 15, 2017 2:30 PM, "Tobias Pluess tobias.pluess@... [hp_agilent_equipment]" wrote: ? Hi all, probably some of you have seen that I had some problems with a 8341A. It was indeed the YTO which failed! But, I was incredibly lucky to fix the YTO. I also did a front panel RF output retrofit on my machine. Some pics of the YTO and stuff can be found on my page, if someone is interested :-) Now I can proceed to my next project, a 5342A frequency counter (hopefully not a blown sampler) and a 8568B spectrum analyzer with blurry focus on the graticule. Best Tobias, HB9FSX
Tobias Pluess All Messages By This Member #86387 开云体育 Hi, I saw that there was an automated test program which calibrates the attenuator and the ALC using HPIB commands. However, I didn't find that program on the net. Does anyone have a copy of it? Tobias
Tony Goodhew All Messages By This Member #86388 I have the one for the 8340B if that helps. Original files here: ? Unlocked files here: I think I may also have put this in the files section of the forum. TonyG ?
Tobias Pluess All Messages By This Member #86389 开云体育 Hi Tony wow, cool, thanks. These files should work for the 8341A as well I think. I will give it a try ;-) Since I cannot run HP Basic stuff, I will translate the programs to Python which runs nicely with GPIB cards and USB adaptors. I already did that with the calibration program for the HP 4195A. Thanks Tobias toggle quoted message Show quoted text From: hp_agilent_equipment@... [hp_agilent_equipment@...] Sent: Sunday, October 22, 2017 17:07 To: hp_agilent_equipment@... Subject: Re: [hp_agilent_equipment] HP 8341A sucessfully FIXED! ? I have the one for the 8340B if that helps. Original files here: ? Unlocked files here: I think I may also have put this in the files section of the forum. TonyG ?
Lexter Negron All Messages By This Member #86407 You did a great job Tobias. Don't sweat on it breaking. As long as you've documented everything, I'm confident it can be fixed with no problem. It was a really lucky fault though. Had something on the hybrid circuit blown.... that wouldn't have been so good. As for the calibration software, Tony's one drive is great. If you want, there is the raw file in this group as well. I wonder what the path to failure was? You had a blown relay, a bad YTO driver, and of course that shorted feed thru capacitor. The cap was shorted in the first place before you put 1.5 Amps thru it. Heres my theory: ??? on the power supply section surged? > breaks relay but goes to YTO driver > components break on the YTO driver > something on the YTO driver causes that feed thru on the YTO to become shorted. How other components were not affected will be a mystery. Maybe they were? It can be called case closed if you can find the original fault and its pathway. Till then this is good enough. -Lex PS: I can explain what happened when that feed thru cap became 20Kohms before it became a 1 ohm short again. Normally in the AC condition, any incidental AC signal (probably from either the YTO driver or the YTO itself is suppose to pass thru to grounded case from the coil via the feed thru cap which acts as a short for AC. In the DC condition the cap is an open circuit and instead heads to the YTO driver via the wire connection. However since you put high power thru the cap the first time, it turned into a 20Kohm resistor. What this ended up doing was fixing the short to ground for DC but now you have both the DC and some AC signals mixed together going thru the wire of the -40V supply, the coil (has less impedance than 20Kohms), and the YTO driver. That is why you saw the unstable results with the YTO loop. Anyways, that feed thru cap had to be replaced one way or the other since there needs to be a short to ground case for AC but not for DC. DC goes thru the wire.

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