EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: SaabFAN on July 20, 2019, 08:57:14 am
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As you can see by the attached pictures, I have bought a HP 8614A for next to nothing on ebay more or less by accident. ;D
It was advertised as non functional / not tested, as the previous owner did not have the proper power cable.
From a first look, the unit seems to be in good shape.
There's not a single spec of dust in there and apart from the ALC-Button not locking and somewhat turning knobs, it looks really well. It also smells like it was all oiled up just a few days ago.
I've go a little problem, however: The AC-Cable is of a type that I haven't been able to find anywhere. Does anyone recognize this type of connector?
Once I've found this cable, or managed to refit a more modern connector, what would be the things to look out for? Checking capacitors is obvious, but are there any other things that I should check before plugging it in?
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Another point to check for are selenium rectifiers - the higher voltage ones may look like an electrolytic cap at first sight. They age and if they blow up, they are supposed to produce a lot of smelly smoke.
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The AC connector can easily be bypassed for testing. Once everything else is working you can easily make or adapt a similar one. I have taken one of those similar ones made with soft rubber and cut them so I could plug each pin independently. Really easy to do.
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Take that power socket pic over into the TEA thread as I'm sure the guys there will know what it is.
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The ac socket was called : HP Oval AC power cord
model 163 on this page
http://madrona.ca/e/powerConn/index.html (http://madrona.ca/e/powerConn/index.html)
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I believe that that power connector is the same as that used on the 1960s Tektronix equipment.
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... The AC-Cable is of a type that I haven't been able to find anywhere. Does anyone recognize this type of connector?
Power cords for those connectors (referred to as type PH-163) are still available, but are expensive, e.g:
https://www.ebay.com/itm/173947829836 (https://www.ebay.com/itm/173947829836)
Cable part numbers:
Belden/Volex 17952
HP/Agilent/Keysight 8120-0078
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Another source, but not any cheaper (USD$22), their stock #860172-B00:
http://surplussales.com/Electrical/ElecCords-1.html (http://surplussales.com/Electrical/ElecCords-1.html)
Probably more than what you paid for the 8614A.
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I ordered a IEC C6 Connector and a cable. Those should fit in there more or less. I have to drill out the rivets of the old connector however. The usual connector found on PCs and Test and Measurement-Equipment doesn't fit.
Upon a more closer inspection, I did find two gears that are not made out of metal and are a bit broken: A large one that moves the cam for the resonator of the Klystron and a small one attached to the same drive mechanism.
I probably have to print those some time in the future. The other gears look like they're made out of metal and with a bit of grease should last an eternity.
Do you know of a place where 3D-Files for these gears are available?
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I've heard these cords can sometimes be found at sewing-machine shops, so you might try that.
It probably doesn't have any selenium rectifiers, but it may have germanium power transistors in its power supply as series-pass regulators. Those will almost certainly be leaky, and you definitely don't want that. They should be replaced with modern Si parts. Look for parts with similar power ratings, Vceo, etc., and reasonably low fT.
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Maybe just replace the connector with a regular one, like I did with my HP332A?
https://www.eevblog.com/forum/testgear/list-your-test-equipment-score-here!/msg1152942/#msg1152942 (https://www.eevblog.com/forum/testgear/list-your-test-equipment-score-here!/msg1152942/#msg1152942)
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I replaced the connector with a IEC C6 type connector. I had to scrape off a bit of plastic to get it to fit and probably have to drill a hole to secure it with more than just friction :)
A first test showed that the device is working and putting out up to 6 dBm with a noticeable dip around 1.6 GHz, where a relay switches modes of the Klystron. Signal quality is pretty good: First order harmonic almost vanishes in the noise of my Spectrum Analyzer and the second one is -27dB down.
I noticed however that the bearing of the fan is quite stiff and there's a noticeable 50 Hz hum coming from it that decreases once the fan speeds up.
It is specified in the Service Manual that the fan is supposed to run at 3000 RPM (I guess with 60Hz AC normal in the US), but it's clearly not even reaching half that speed. I'm hoping that I can address this with just some oil and I don't have to disassemble the entire fan-assembly.
All the other moving parts are moving quite smoothly now, after using them for a bit.
So this brings the issues down to two things so far:
- Fan bearing (probably dried out grease).
- ALC-Button does not stay in depressed position. (I'm thinking about modifying the circuit so that ALC-Mode is always enabled unless the button is pressed if I need a replacement for the button.)
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Well, WD-40 did the trick.
Fan is now spinning much more freely and the ALC-Button stays in place. ;D