Find great deals for HP a Spectrum Analyzer Display Mainframe W/ HP b Pattern Generator. Shop with confidence on eBay!. Find great deals for Hewlett Packard HP a Display With b Optical Spectrum Analyzer. Shop with confidence on eBay!. Software and documentation supplied. This service guide is part of an Option OB3 package which includes: HP A Service Guide. HP A Component.
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This board is a latter revision than the ones that appear on the np but there are not many changes. You really need to know what you are doing before probing and testing a thing like this live. I could see 07004a power LED flash briefly upon turn-on and then I used a thin teflon tube and a copper wire to recreate the four turns that form the secondary and guess what, it worked!!
Hewlett Packard HP 70004a Display With 70950b Optical Spectrum Analyzer
High voltage, big and the troubleshooting will need to be done live. No surpise, the secondary jacket was burned and touching the primary in one spot:. Can you tell one from the other? The supply operates a high switching frequency and many parts of the circuit are shorted at DC, so I could not find this until I took both transformers out.
There is no way to check one of the blocks 7004a the power supply alone, you have to give it power and hope for the best.
I built this “adapter” thing as a temporary solution, you too know what that means: The block diagram was invaluable, this switching power supplies are complex. I confessed before that I killed a few components on the process, and I could not yp replacements for some of them: You can see the power supply slowly increasing the current at turn on until it gets too high before it starts regulating the voltage, and quits.
There is 7004a current sense resistor and this is what current looked at turn-on try:.
I bought this cheap A color ph as faulty. Could this be fixed? Do you see that suspicious potting that squeezed outside the can in one of them?:.
HP A SERVICE MANUAL Pdf Download.
Many suggested changing every capacitor in the board, something I was not going to do, I wanted to find what the fault really was all capacitors turned to be ok:. After many hours of testing and probing, and and few components that exploded in the process most times my fault I found there was a transformer with a 14 ohm leak between primary and secondary.
Something was drawing more current than expected and the current-limit protection was 70004. Knowing I had nothing to loose, I went and opened the transformer can with a Dremel, and removed the resin with hot air and tweezers, carefully to not damage the windings. I did not know where to start.
This paid for itself in just this repair. Home Projects 70004z Photo. This last one required some improvisation because it is a quad-transistor instead of dual, and the DIP package is very different.
HP 70004a Spectrum Analyzer Display Mainframe W/ HP 70841b Pattern Generator
This is the 700004a on the bench, that PCB looks very timidating to me. I was lucky to have bought a FLUKE D differential voltage probe this year at Friedrichshafen to the nice guy with grey hair and glasses that sells mostly Fluke stuff.
One day, it refused to turn on. And a final picture of the twin transformers in the working power supply. You’ll probably want to use an isolation transformer and differential probes, and keep 700004a hand on your pocket at all times. I was happy to find it actually worked