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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70004A Color System Display

The block diagram was invaluable, this switching power supplies are complex. One day, it refused to turn on. This is the beast on the bench, that PCB looks very timidating to me. You’ll probably want to use an isolation transformer and differential probes, and keep one hand on your pocket at all times.

HP a Spectrum Analyzer Display Mainframe W/ HP b Pattern Generator | eBay

I was happy to find it actually worked 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. This paid for itself in just this repair.

Something was drawing more current than expected and the current-limit protection was tripping. You really need to know what you are 7004a before probing and testing a thing like this live. This last one required some improvisation because it is a quad-transistor instead of dual, and the DIP package is very different.


After many hours of testing and probing, and and few components that exploded in the process most times my fault I found 70004q was a transformer with a 14 ohm leak between primary and secondary.

I confessed before that I killed a few components on the process, and I could not find replacements for some of them: 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:.

I bought this cheap A color display as faulty. There is no way to check one of the blocks of the power supply alone, you have to give it power and hope for the best. High voltage, big and the troubleshooting will need to be done live.

Can you tell one from the other? 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.

I built this “adapter” thing as a temporary solution, you too know what that means: You can see hhp power supply slowly increasing the current at turn on until it gets too high before it starts regulating the voltage, and quits. 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 could see the power 70004a flash briefly upon turn-on and then There is a current sense resistor and this is what current looked at turn-on try:.

Home Projects Music Photo. No surpise, the secondary jacket was burned and touching the primary in one spot:. Do you see that suspicious potting that squeezed outside the can in one of them?:. I used a thin teflon tube and a copper wire to recreate the four turns that form the secondary and guess what, it worked!!

And a final picture of the twin transformers in the working power supply. Could this be fixed? This board is a latter revision than the ones that appear on the schematics but there are not many changes.

I did not know where to start.