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| Counting on the HP 5328B |
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| jrharley:
Appreciate that Tony_G! :-+ The reed relay specs are: 500mA, 5V coil, 1B form, 100VDC, GORDOS part# 0490-1183. The tough part about these so far, is that they're either not stocked or crazy expensive, or both. There's an interesting ebay store called F-4 Technologies that carries lots of obsolete technical parts, HP in particular, and they actually have a couple of the exact replacement relays. With shipping, one would be about $25. It looks like GORDOS has been absorbed into another company, but I think I found an old data sheet from the original product line. I'll study that tonight. I also may need to browse some "second tier" supply houses. Something about these specs quickly narrows your choices using the inventory filters. I'd like to find a source where I could get a handful of them for a few bucks each, but we'll see how we go with it. Holler at me if this is stupid, but it seems like I should be able to put a DMM across it in continuity mode and tickle it with 5V to see if it connects. I suppose I should limit the current to 250mA or so. Anyway, that's where things are. I'm about half way through touching up the solder joints on the board. -JRH PS - Just noticed that the installed relay part numbers don't really match those listed in the parts list. Maybe they've been replaced, a couple of them don't seem to be seated perfectly. |
| Tony_G:
I would lean towards trying to find a current part that matches or is at least reasonably close before I pay those exorbitant prices for exact replacements - Often those prices are calibrated to generate the seller the maximum income from companies who have done the cost analysis of replacing the part with a different one and then redoing "certification" compared to just getting exact old parts. Look forward to seeing where you end up. TonyG |
| coromonadalix:
i would check the ic socket on your A12 board, i had some in the past who became weak on contact strenght, you need to fell some tightness ... |
| jrharley:
I hear you TG! I set a budget for restoring these old kits, kinda' a limit in my mind before it goes into BER status. I ain't there yet! ;D Still, it adds up quickly and it doesn't seem to make sense to spend much on a reed relay. So far though, there's encouraging developments on that front..... Diving a little deeper into the info on the data sheet, they show schematics of the different relays. It would seem that this one is "normally closed", and has a diode in it to arrest back EMF from the coil. Made sense, so I tested it in circuit, no power applied of course. Diode is present and there's continuity across the relay, indicating to me that those reeds are touching. Power supply is warming up to see if I can get it to open. Thanks for that feedback coromonadalix! Appreciate it. Good advice for sure. Hey, if it's not a capacitor, then it's a connection! Amirite? I've spent a fair amount of attention on the card edge socket connections, but not entirely sure, that is what you're referring to. When you say "IC socket", is that the one you mean? Appreciate the comments guys, it really helps in the discovery. - JRH |
| jrharley:
OK- we have a small bit of progress here. :-+ After tacking a couple small wires onto the K5 relay pins on the back of the board, a DMM set to continuity was connected across them. Since the relay is normally closed, continuity was indicated, annoying the rest of the household. Touching a current limited 4VDC across the same pins, activated the reeds and interrupted the continuity signal. The relay appears to be functioning! :phew: The data sheet schematics were very helpful for the setup. I do think I'll brush a little UV resin onto the cracked end though, just to seal things up. With that distraction out of the way, I'll be able to keep studying the schematic and find out why this thing doesn't recognize an input. Later. - JRH |
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