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This forum is part of our mission to promote the preservation of vintage computers through education and outreach. (In real life we also run events and have a museum.) We encourage you to join us, participate, share your knowledge, and enjoy.

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Conduct yourself as you would at any other place where people come together in person to discuss their hobby. If you wouldn't say something to somebody in person, then you probably should not be writing it here.

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To put things in engineering terms, we value a high signal to noise ratio. Coming here should not be a waste of time.
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Rule 4: "PM Sent!" messages (or, how to use the Private Message system)

This forum has a private message feature that we want people to use for messages that are not of general interest to other members.

In short, if you are going to reply to a thread and that reply is targeted to a specific individual and not of interest to anybody else (either now or in the future) then send a private message instead.

Here are some obvious examples of when you should not reply to a thread and use the PM system instead:
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Why do we have this policy? Sending a "PM Sent!" type message basically wastes everybody else's time by making them having to scroll past a post in a thread that looks to be updated, when the update is not meaningful. And the person you are sending the PM to will be notified by the forum software that they have a message waiting for them. Look up at the top near the right edge where it says 'Notifications' ... if you have a PM waiting, it will tell you there.

Rule 5: Copyright and other legal issues

We are here to discuss vintage computing, so discussing software, books, and other intellectual property that is on-topic is fine. We don't want people using these forums to discuss or enable copyright violations or other things that are against the law; whether you agree with the law or not is irrelevant. Do not use our resources for something that is legally or morally questionable.

Our discussions here generally fall under "fair use." Telling people how to pirate a software title is an example of something that is not allowable here.


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If you are unsure you may consider sending a private message to a moderator instead.


New user moderation

New users are directly moderated so that we can weed spammers out early. This means that for your first 10 posts you will have some delay before they are seen. We understand this can be disruptive to the flow of conversation and we try to keep up with our new user moderation duties to avoid undue inconvenience. Please do not make duplicate posts, extra posts to bump your post count, or ask the moderators to expedite this process; 10 moderated posts will go by quickly.

New users also have a smaller personal message inbox limit and are rate limited when sending PMs to other users.


Other suggestions
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Bi-Metal Control Valve With Heater

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    Bi-Metal Control Valve With Heater

    I picked up a new-to-me heater for the workshop, manufactured sometime in the 1960's. It's a gas heater, but they didn't have combination gas valves back then, so it's got a separate pilot valve, regulator and electronic gas valve. Everything is pretty normal, except the gas valve.

    The first oddity I noticed is that the nameplate said it was a 21V AC or DC valve. Its control transformer was also 21V. The transformer tested as good, so I connected it to the gas valve and...nothing. I removed the top of the valve to find what I thought was a standard solenoid gas valve, which lifts a plunger and opens what amounts to a poppet valve in the valve body. It showed a low resistance with my multimeter, but nothing moved when powered up. After taking a closer look, I realized that what I thought to be a solenoid coil was really a slide gasket, and that what I thought was the return spring and lever of the solenoid was a metal plate with a zig-zag of wire sandwiched between two pieces of mica!

    After applying 21 VAC for around 45-60 seconds, the valve starts to move a little, and then snaps open. The supposed return lever is apparently bimetallic, and flexes up when heated, opening the gas valve. Just as it takes a while to open up when power is applied, it takes around 30-45 seconds to close when power is removed, as the bimetal spring cools down.

    Has anyone ever seen a control valve like this? It's a new one to me!
    Check out The Glitch Works | My Retro Projects | Vintage Computer Services | Glitch Works Tindie Store -- Vintage Computer Kits and More

    #2
    sounds like a standard furnace setup to me. I'm going to ask the stupid question; "is the pilot light LIT?" there should be a copper "wire" going from the gas valve to the pilot light, its called a thermocouple. They stop working OFTEN. If the pilot light wont stay lit, replace this and everything else should work.
    It is a mistake to think you can solve any major problems just with potatoes.

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      #3
      Yes, after cleaning the pilot assembly, the thermocouple lets the pilot stand (there was some sort of insect nest in the air-gas mixer). What's weird is this bimetal device controls the /gas valve/, it's not a limit switch. When the thermostat turns on, it heats up the bimetal lever in this valve, and that turns on the gas supply to the main burner. The rest of the setup is normal (it's a Reznor unit heater...I don't think anything has changed in their gravity vent natural gas models since they created them!). It all works fine, just I'd never seen a control valve that operated in this manner, or that operated so slowly -- I'm used to putting the control voltage on the valve, you hear a click, and it's on. I'll see if I can take a picture of it later today.
      Check out The Glitch Works | My Retro Projects | Vintage Computer Services | Glitch Works Tindie Store -- Vintage Computer Kits and More

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