Shahriar, you are an educator and a source of inspiration. Not only do I think that I learnt a lot from your videos, I also find them very entertaining. The best thing, though, is that every single episode of the signal path made me do some additional research about the bits I didn't understand. Simply great.
You spent 1000 dollars for a broken synthesizer just to make a repair video for us? Re-selling it for 3000-7000 wasn't the motivation? I mean, you have the knowledge, and the lab to do it, so buying broken test gear with the goal of fixing it and reselling for a profit seems like a pretty brilliant plan, and if you aren't doing that, you should! You make money, and we get more repair videos, its a win/win!
Truly awesome work there. Excellent video - enjoyed every minute. Thanks for all your hard work putting the video together and sharing your amazing skills. Cheers!!
For what it's worth, there's no need for a screen capture software. The way you film the screen and pan around works great. Might want to increase the brightness just a bit on the screen when filming it. (And adjust the white balance on the camera accordingly).
The failed H1 amplifier looks like a SHF-0189 HFET from Stanford/Sirenza/RFMD. It may be that the (active?) bias network that feeds it has failed and this can cook the SHF-0189. So if you do get a genuine SHF-0189 then check the active bias network is healthy before you fit a new SHF-0189. Or it may die again straight away! :)
Thanks for sharing this Shahriar I got a E4406A a few months ago with a similar problem was scratching my head how I could test the RF section in test in situ.
Cool video, I'm an amateur radio hobbyist and am just getting started with some testing equipment, this exercise was very enlightening. I picked up an E4436B with an UNLEVEL ERR between 250MHz and about 344MHz hopefully this video will help me resolve this. Thanks for the video.
what a hack! (in the good way) Not just to replace a broken part but to be able to completely rip out an amp you knew nothing about and jerry rig something,much less in a piece of high end lab gear, and work perfectly is just.....incredible. Granted you weren't aware of the impedance matching that was already being done but I would have figured you would have done something more on that front instead of just letting it be since you ripped out all the biasing/impedance matching components that were there.
I think it's more to the credit of the amplifier he put in that gain, bias and impedance are all essentially already set internally and it's a DC-12GHz amp. Not bad for a part under $12.
Shahriar are you selling this instrument ? its rather expensive the cheapest price listed was $3,000. Great repair, I think you should help Dave fix hes DSA.
I have a VERY basic knowledge of electronics and most of what you explain goes right over my head. But I watch all your videos. What a clever guy you are, I love your approach to troubleshooting and logical thinking and some of what you say does rub off. Thanks sooooo much for being bothered to make these videos Shahriar. Compulsive viewing.
OMG I love these videos. These are the best engineering videos on the internet. I am an junior electrical engineering student. I wish we would get to do stuff like this in some of our engineering classes. I know this is mostly technician type of work, but you can learn something about design by looking at other designs. Please don't stop making these videos!
Nice repair, great to see your techniques at how to tackle such a problem. Would you ever consider modding out a block section to gain better stats or values, otherwise then stated by the manufacturer?
Great video! Really appreciate what you do for all of our edutainment. That's a large chunk of cash to lay out for doing a video, and you could have lost most of that money, big risk, paid off on many levels. Now take that profit and put it aside for more of the same :)
Greetings from Brazil. Thanks for this really great video! Your channel is the best on electronics. Please keep bringing interesting videos. merry Christmas and happy 2015!
Very interesting and enjoyable practice in repair of a highly complex instrument withVERYminimal documentation! Even more enjoyable was the re-engineering of the OOS stage with modern available components. As an instrumentation repair engineer of many years at the bench and lab I very much like your troubleshooting processes. And all done without module service extenders or a maintenance chassis! Five stars for this project, Thank you for letting me sit in on the procedure!!!!!
We are about the same age, yet you have accomplished so much more. It proves how much it counts in the long run by choosing the right path. And I refer to the signal path, of course. I only have one problem: why so few likes?
Hi, I have the 3GHz version of this unit. From cold it works OK, but once it warms up I get an unlock message. Where would you start looking for this problem? This great video and your repair of this unit has encouraged me to attempt a repair of my unit. Thank you.
I had an E4437B that had a strange problem. Basically half of its frequency range was unlocked. From DC to 250 MHz, the first 125 MHz was OK, from 125.0000001 to 250 MHz it was unlocked. From 250 to 500 MHz it demonstrated the same behavior. And again from 500 MHz to 1 GHz, and again from 1 GHz to 2 GHz, and then again from 2 to 4 GHz. If I'd had access to the detailed service manual so I could figure out the oscillators, fractional-N synthesizers, PIN switching diodes, etc, I would have probably found the bad diode and replaced it.
I was mightily impressed, entertained, and educated. The speed and ease with which you are able to match the board to the block diagram is a great skill to have. Of course, the mod-fix was the best part of the video. I really cannot praise it enough. I also liked the way you got around the limitation of not have an extender board, too.
Erg genoten van de logische stappen die je neemt om tot een besluit voor herstel te komen. Ga door met deze uitleg en je zal er veel volgers bij krijgen. Echt een leermoment. '73 en fijne feestdagen en een gezond 2015. Groet, Henk
Questions, questions... Curious is an extender card is available (and viable) for the output board? The bias supply remained viable despite being stressed through that bad fet. Can you describe the current limiting in this instance? Any thought that perhaps sustained stress on the 8V supply might compromise it in future? Finally, any thoughts on why the amplifier died in the first place? A brilliant repair! I love it when expensive stuff may be restored by replacing a 50 cent part!
I have an E4426B signal generator that is similar to these failure, but in addition to the unlevel error, I also get an Error 513: 1GHz oscillator unlocked failure. I it safe for me to suspect that the problem is in the reference board?
you are wrong about the RF unlevel at different frequencies the signal generator should able to output max level at any frequency CW this means the gain of the amp you replaced is a bit low to can test the max RF output level at any frequency by opening the alc loop regards john davis
Drilling the rivets of the top cover and replacing them with rivet nuts would have been probably easier than soldering coax cables all over the board. Then you could quickly track the signal with a proper active probe instead of loading the circuit with coax cable. Thanks to the rivet nuts the instrument would be much easier to access. BTW I'm a bit disappointed with the recent HP build quality. HP 8662A looks much nicer from the inside.
Unfortunately, not possible. The piece that is on top of the board also bends around and is holding the motherboard extension board up. Perhaps Chuck Norris could scare everything to stay still without any support, but I couldn't.
I have an E4437b with unregulated output. Different symptoms, mine does not indicate "UNLEVEL" so from this video it seems my problem may be in the attenuator. This video has been extremely informative and has given me the courage to attack my generator. Thanks for the excellent presentation and troubleshooting method.
FYI, These units also have a failure mode in the DC bias of the Burst modulator resulting in zero output to the final mixer stage. The simple solution is to rebias using a 20K jumper resistor in the previous stage or to jumper all the burst PIN diodes and defeat the burst. I'll do a small blog with pics soon.
Hi ! Very nice video ! got one of these off ebay with the same error. Would have supected the output amplifier but now I'm prepared to cut a SMA wire in half :-)
Thanks for the great video! I will poke around on a E4433B that shows the same unlevel condition. Interestingly, ours shows no output at all (unlike the ~30 dB down signal yours had), so it's likely not the same issue, but you gave me some interesting pointers on how to probe for the fault. Also, on ours, I can sometimes leave it running for several hours and it starts to work on its own. It's a shame because it's a really nice instrument and it has virtually all the available options installed.
Simply brilliant Shahriar, you are truly gifted in the art of electronics troubleshooting. I watch from start to finish, I sometimes take notes. This is better than fourth year EE lectures. Thank you for the free lessons. Good work young man, very commendable.
Many thanks for yet another super video Shahriar; compulsive post Christmas viewing for me. You take each of us viewers on as supernumerary crew and deliver a table top diagnostic performance to be proud of. It's entertaining and instructional to share your journey. I hope that you get a good price for the sig gen and that your buyer fully appreciates your work.
I watch your video all the time and I must say, your skill in electronic is outstanding dude. I must commend you. I wish I could do what you do but I am just starting out and I can believe your knowledge. Good job
Your videos are inspiring. I can only dream of having access to the range of test gear you have at hand. As for your knowledge and diagnostic prowess, you are in a league of your own. Keep up the good work and keep the videos coming. Karl
TheSignalPathBlog I mean the low frequency LC filters.@23:30 we see 3 rows of L components, I assume that one row corresponds to the one filter. On the block diagram we have 5 low freq. filters.
Toni T800 The diagram has 5 LPFs for 5 different frequencies. The 3 rows are the lower frequency filter stages. The remaining 2 LPFs are the higher frequency filters that are on the top and bottom of the PCB as distributed element filters.
Excellent repair video! Well done you make it look so easy. It helps when you have the toys to fix the toys but also a lot of electronic diagnostic skills.
You need a rack, expensive but you'l clean your lab up, if you can fit one in there. I bought this 48U Dell rack for 750$, it works very well for my workstation environment.
I got a 19 inch audio equipment rack for about £50 I think it was around 12U high. It's not as deep as a server rack, but none of this equipment is as long as a server. We still stuck about 5U of rack servers, 3U of switches and a tower server on its side in it. The racks stuck out the back and only screw in at the front but they were at the bottom and the weight was nicely taken at the back by the frame. My point that I'm getting away from is that if you don't need the depth, audio equipment racks are much cheaper than server racks. The same shallow racks are used for networking switches and telecoms etc. I personally don't see how most of his equipment is very rackable though.
KX36 You can get railed shelves for standard U racks. Most his equipment can be rack mounted other than the oscilloscopes and Rigol power supply. Its good if he wanted to connect all of his equipment to a 10 mhz standard. I have these Dell cable management holders and they make wiring up equipment so easy in racks, they swing so you can pull out equipment on slider rails without having to worry about getting cables caught up. I'm surprised that I don't see them used more. Also things like power management and cooling are easier.
I have an E4432 which uses mostly MMIC amps rather than RF transistors. All my amps are good . My unleveled error goes AWAY for > 250Mhz if I jumper from the burst mod to the final amp input. (Removing the amps input 0.1uf cap to isolate it). PIN diodes check out ok, but I can't get ANY RF at the PIN diode inputs at the final amp stage...I think I may have bad vias or something. Can you help by pointing out which is the precise signal path between the >250Mhz signal (from the burst mod) and the matching PIN diode input and the
ok, traced it to no Burst modulator voltage on the PIN diode modulator, ergo 0% duty cycle. No burst sig coming in on the JP3-6 pin edge connector either.. Jumpering the burst modulator gets things going ok. Any thoughts on how to trace that prob, or should I just direct wire a logic to burst voltage converter to the burst gate BNC /PIN modulator and disconnect JP3-6?
