I keep losing auctions on this unit.
Nice buy.
I bought an S-Parameter last month thinking I was going to win an auction on a broken 3577 unit.
Nope!
I will keep trying.
Like your photos
The thing looks a bit beaten and is full of dust but it seems to work fine at first glance.
Couldn't resist to take it apart a bit. Also the front panel boutons are a bit sticky and I would really like to get them running smooth again.
Also I'm probably going to switch out the CRT with a NewScope-5 LCD.
Interesting links:
-Original fan datasheet (Muffin MD24B2): https://www.jameco.com/Jameco/Products/ProdDS/2215478.pdf
50dBa ! That's one noisey fan! The fan noise and crt are what keeps the 3577A (and 3562A) off my bench. Lovely instruments crippled with noisey fans and hard-to-read crts.
The Achilles heel of the 3577A appears to center around the input relays. That was the major design change between A and B versions, a redesigned front end using different relays.
I probably just install a quiet 12V PC fan with a 24V converter and test with the thermal cam if the 80 CFM are enough without the CRT heating the instrument.
Do you already have some with that issue?
I'm still waiting on Artek to get me the service manual so I have no idea yet what these relays are, but are they replacable at all?
I got one of these for $200 a while back - would not boot. It was the EEPROM's which I replaced with a fresh flash and it booted up. A few days ago the big filter caps on the power supply failed - so I replaced those as well. I have done all the usual tests and it appears to be functioning as expected.
The problem is....I still don't really know how to use it. Joining this thread to learn something.
Glad to hear it was an easy fix. I'm guessing it was the +5V rail caps that went? They have the most ripple current across them.
To me, VNAs are all about transfer functions. So get some devices you want to characterize and experiment. AC coupling is not an option, so be sure to protect inputs from anything with DC.
Isolation and injection transformers are a good place to start, because the 3577A has grounded inputs and output, and at some point you'll want to use a xfmr to isolate the output or insert one in a control loop. Investigate how their mag/phase responses change with load.
Yesterday the postman delivered another boat anchor to my doorstep - A HP3577A VNA with (75Ohm S-Parameter Test Kit).
Snip ...
The error message only flashes on the CRT for a second, but only when you power it up. That means the CRT is not yet displaying anything. I only noticed the message when I pressed the reset button on the processor PCB with re-boots without turning the CRT off. It allowed me to see the startup sequence. Led me right to the end of the rainbow.....
It looks like these can deal with 25VDC on all inputs - not quite as delicate as the HF VNA's and SA's.
That is my first attempt - an isolation transformer for testing control loop response. I am not sure how to set it up, normalize it and just get a scaler measurement of frequency response (as a first test). What is the proper setup to measure the frequency response of an isolation transformer?
I tried a few setups, but they are clearly not correct. The OUT connected to the transformer with the INPUT A in parallel - I normalized that and it is flat. Then I move the INPUT A over to the output of the transformer - but the response looks nothing like what I would expect. I did the same setup on my scope with a signal gen and it is showing that -3db should be 10hz - 6Mhz.
Yesterday the postman delivered another boat anchor to my doorstep - A HP3577A VNA with (75Ohm S-Parameter Test Kit).
Snip ...
Be careful with the 75 N connectors on the S-parameter test set. They will be wrecked if you mate them with 50 N connectors. The center pin is a smaller diameter on the 75 version.
I have both the 35677A 50 and the 35677B 75 test sets.
At lot of the time I use the 3577A for measuring Bode Plots on SMPS without a test set.
Regards,
Jay_Diddy_B
I probably just install a quiet 12V PC fan with a 24V converter and test with the thermal cam if the 80 CFM are enough without the CRT heating the instrument.
I look forward to seeing your results. Since you've been inside the unit, I think you can feel that most of the heat comes off the various PCBs, and it takes some pressure to get air to circulate among them all. I'm doubting if a standard PC fan will be sufficient.
Looking at Delta AFB 120 x 120 x 38 MM SERIES fans (https://www.mouser.ch/datasheet/2/632/AFB120x120x38mm-515857.pdf) the obvious replacement would be the: AFB1224HE. But I probably try the AFB1224ME which has a bit lower pressure (0.25inch) and CFM (~92) but then the noise drop of 12dB to 38dB is worth the risk to me.
I am just in the process of repairing one of those exact CRT modules in my HP 4145B since the NewScope5 is a bit pricy
An excellent workhorse - I use mine quite regularly, mainly for anti-imaging filters. The nice thing about the 4-port model (I hardly ever use the S param set) is it can be used with my LeCroy active probes and the ADPPS power supply. This way I can probe at the output of each filter stage separately, and if something odd is going on quickly track down what is invariably some mistake on my behalf. (The same power supply also allows using the probes with counters and other instruments, just brilliant.)
Doing something about that jet turbine fan would be a huge improvement!
Well I won't put DC on the inputs of mine... all three of my fixer-uppers have input stages issues, and DC is often the culprit... besides, DC shortens the useful life of relay contacts...
: No built-in power splitter. A silly omission.
I am just in the process of repairing one of those exact CRT modules in my HP 4145B since the NewScope5 is a bit pricy
It uses the same switches on the front panel and mine also have an inconsistent feeling. Some are soft and some are clicky. I am guessing that all of them ware supposed to be clicky but the springs got bent enough with use that they don't provide the buckling action anymore. But i prefer the soft feel of the worn out ones. I was guessing if jabbing the spring with a Flathead screwdriver would bend it enough to "break" the clicky action of the switch.
I am just in the process of repairing one of those exact CRT modules in my HP 4145B since the NewScope5 is a bit pricy
It uses the same switches on the front panel and mine also have an inconsistent feeling. Some are soft and some are clicky. I am guessing that all of them ware supposed to be clicky but the springs got bent enough with use that they don't provide the buckling action anymore. But i prefer the soft feel of the worn out ones. I was guessing if jabbing the spring with a Flathead screwdriver would bend it enough to "break" the clicky action of the switch.
Berni, actually the 'soft' ones are those that are working properly. They're the bog-standard leaf spring switches that HP used in skazillions of instruments back in the day. The leaf spring is supposed to have a slight curve in it that lets it bend smoothly, but in older instruments they get sticky and don't want to bend properly, resulting in the feeling you describe.
Below is a link to a YouTube video posted years ago by a guy showing how to remove and reform the springs. I've recently read that the issue can be caused by old lubricant gumming up and preventing the springs from moving properly, and that it can be fixed by flushing the switches with alcohol to clean out the grease rather than taking them apart as shown in the video.
I've flushed a few of them with denatured alcohol and been successful in getting them working again, though some were stubborn and ultimately needed to come apart.
I'd try an alcohol flush first (you may need to hit them two or three times) before going to the trouble of pulling the springs. Easy stuff first, right?
Here is the video link:
http://www.rbarrios.com/projects/HPSWITCH/
Good luck with it.
-Pat
Did you build some AC coupled adaptors? Like you, I would prefer not to test my luck! Addressing this now could save any 3577A owner a lot of trouble.
: No built-in power splitter. A silly omission.
Is it worth buying a commercial splitter for under 200Mhz or is it easy enough to DIY? Searching around for some info - they only seem difficult when the BW goes much beyond 500Mhz.