HP 437 power meter - Page 1
Forum section: electronics / repair

author: Nemo1956
author_rank: Contributor
timestamp: July 06, 2017, 01:51:13 am
content: Can anyone help me out. I have one of these units and now when I need to use it it goes tits up on me the next day i used it. It was working fine the day before.It will see the power sensor but when I put it onto the 50MHz ref signal it will not read anything. I have looked at the ref output and that is fine. I have put the sensor onto my signal generator with no reading at all just seeing noise.I have also put my sensor onto others units and it works fine. I have even out the sensor from these other bit of kit on to it still the same but they all work.Does anyone have a schematic for these so I can find the fault.Thanks.Paul.

author: alm
author_rank: Super Contributor
timestamp: July 06, 2017, 02:34:51 am
content: Lookhere. I believe the two ZIP files contain JPEG images of all the schematics, and the PDF contain the normal sized pages.If it turns out to be BER, then at least you are somewhat lucky. The power meters usually go for much less than sensors that have not been blown.

author: Nemo1956
author_rank: Contributor
timestamp: July 06, 2017, 09:51:32 am
content: Wonderful Thanks very much. I will let you know what I find.BRPaul

author: texaspyro
author_rank: Super Contributor
timestamp: July 10, 2017, 03:00:02 am
content: FYI, about half the (50+) "dead" power sensors I have seen were due to broken wires in the connector! A few others had one or more of those tiny gold wires in the sensor head broken. They can sometimes be fixed by re-soldering but that may affect the accuracy... HP supposedly used magic solder excreted by virgin unicorns on the second winter solstice in September.

author: alm
author_rank: Super Contributor
timestamp: July 10, 2017, 03:57:43 am
content: Funny, traditional wisdom is that the sensors are pretty much always unrepairable because usually the thermistor/diode is blown by excessive power. Sounds like your experiences are quite different from that.

author: texaspyro
author_rank: Super Contributor
timestamp: July 10, 2017, 02:43:28 pm
content: Quote from: alm on July 10, 2017, 03:57:43 amYes, if the thermistor / diodes are blown the unit is trash. But before tossing it check the cable wiring and those tiny gold wires. You might luck out. I was rather surprised about the cable wiring issues.

author: Nemo1956
author_rank: Contributor
timestamp: July 11, 2017, 02:37:46 am
content: I have put all my sensors onto a second unit at the office and that all seem to work fine but not in my unit. It will see the sensor head and will read it but when connected to a sig gen it wont read anything just noise.I can seem to locate where the problem is.

author: Nemo1956
author_rank: Contributor
timestamp: July 19, 2017, 06:42:31 am
content: I have tried to test my head unit on my machine in the office again but now it will not work. The normal sensor head is working so I toke this one home and tried it there and it works. So I have come to the conclusion that my sensor head is not working so the unit will be scraped as I can't buy a replacement. Just to expensive for me.So that's the end of that bit of test equipment. More on the junk pile.Thanks to you all for your kind help.Paul