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| HP 8566B - What to look for? |
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| W4PJB:
Voltages all looked good, except the "18V Typical" on the A18 was low at 16.2v. The -10v side of that test port was bang on, relative to the "REF GND" on the A19. C4 and C19 on the A21 board are looking a little sus, though in-circuit they seem to measure OK. They're also over $40 EACH! :o |
| KE5FX:
Just use whatever's handy to replace them, same or higher voltage, same or (slightly) higher capacitance. Might have failed shorted if they appear OK on the ESR meter while looking like that. |
| EggertEnjoyer123:
Have you checked the RF switch? Had an issue with another model where the switch clicked but the contacts didn't actually make contact well. |
| W4PJB:
--- Quote from: EggertEnjoyer123 on June 21, 2024, 01:23:31 am ---Have you checked the RF switch? Had an issue with another model where the switch clicked but the contacts didn't actually make contact well. --- End quote --- Thanks for your reply. Not yet.... but it's high on the list! I've been doing through the service manual and three things are pointing me in that direction. 1: looking at common points of failure, that's one of the first in the chain for this issue. 2: I do not have any errors, such as "YTO Unlock", on the display. 3: Switching from 2-22Ghz to the low band the "click" from the relay is crisp and fast. Switching to 2-22Ghz is kind of "lazy". But there's a bit of teardown to get to that component, and with a "real feel" of 107*F in Maine today, this evening I've switched from inspecting vintage HP instrumentation, to inspecting a nicely chilled bottle of Chianti. Meaning it's probably best I keep my hands out of electrical devices for the evening. Cheers! :D |
| W4PJB:
Well, it wasn't the switch. Pic of a 1MHz - 7GHz sweep attached. Ignore all of the ripple, it's most likely reflections in the cheap SMA cables. On to the next thing! I have no errors on screen, so I doubt there are any issues with the YIG itself, but if it saw some DC it's likely the mixer diodes are fried. It's my understanding this will not cause any error messages. So perhaps I'll pick one up and try it, they're cheap enough these days. |
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