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| HP 3455A strange problem around 14 - 80 V DC Input |
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| Kleinstein:
The relays are kind of special types for high voltage and low thermal EMF. Chances are they are (could be internal) 2 contacts in series so that the voltage rating adds up and thermal EMF largely compensates. If simple heating does not work, there may still be a chance to fix the old relay. As far as I understood it, the problem could be with the side where 2 reed contracts are joined, in some cases with some spot welding that did not last for ever, but one may be able to get to that joint. |
| kblue:
I sourced the "last" 0490-0663 "NOS" from ebay for around 30 € including shipping. So i hope it is indeed "NOS" and will work for the next decade or so. After that, i can try to fix the old one. So ye, simple heating only works for a couple of minutes, before it goes haywire again. I was a bit confused about all these contacts but it seems 2+2 are connected with each other measuring around 220 Ohms (guess its the coil) while the more "gold plated looking" contacts in the middle are the actual reed-relay i guess. /edit: Somehow attachments wont work, but img-tag does. |
| Kleinstein:
From the resistance 220 ohms, especially if stable make sense for the coils. In this case the design looks more like a classic high voltage reed relay, not a special low EMF solution. The question is than of the problem is more with the contact or the coil. If really needed rewinding of the coil would still be an option. |
| kblue:
Need to correct myself ... 220 Ohm are the smaller ones. K5 is around 340 Ohms which is the same as other relays with the same part-number. I already removed K5. Applying 5 VDC the "normally open contacts" are closing (i can hear it too) but the lowest resistance i got was around 7 Ohms and the highest value around 200 Ohms (or rarely even megaohms). Most times it settles around 60 Ohms per actuation which sounds way too high. So ye ... i guess K5 is the culprit all along. Big thanks to you, Kleinstein! |
| kblue:
The reed-relay arrived (was the last one sold / NOS) ... its the same part-number and appearance (it arrived in a cylindrical HP paper box) but while the old one had big copper-like pins for the relay-switch itself, the "NOS" part all legs are silver and react to magnetism. Kinda strange (like cheepish resistors from ali). It does look legit and not reprinted but mayhaps someone re-stuffed whatever-reed-relay into the actual part. eBay-seller has overall very good rating. Aaaanyway it works! |
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