Forum etiquette

Our mission ...

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.

This forum has been around in this format for over 15 years. These rules and guidelines help us maintain a healthy and active community, and we moderate the forum to keep things on track. Please familiarize yourself with these rules and guidelines.

Remain civil and respectful

There are several hundred people who actively participate here. People come from all different backgrounds and will have different ways of seeing things. You will not agree with everything you read here. Back-and-forth discussions are fine but do not cross the line into rude or disrespectful behavior.

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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Stay close to the original topic being discussed
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Contribute something meaningful

To put things in engineering terms, we value a high signal to noise ratio. Coming here should not be a waste of time.
  • This is not a chat room. If you are taking less than 30 seconds to make a post then you are probably doing something wrong. A post should be on topic, clear, and contribute something meaningful to the discussion. If people read your posts and feel that their time as been wasted, they will stop reading your posts. Worse yet, they will stop visiting and we'll lose their experience and contributions.
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"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.

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.

Reporting problematic posts

If you see spam, a wildly off-topic post, or something abusive or illegal please report the thread by clicking on the "Report Post" icon. (It looks like an exclamation point in a triangle and it is available under every post.) This send a notification to all of the moderators, so somebody will see it and deal with it.

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
  • Use Google, books, or other definitive sources. There is a lot of information out there.
  • Don't make people guess at what you are trying to say; we are not mind readers. Be clear and concise.
  • Spelling and grammar are not rated, but they do make a post easier to read.
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Compaq Portable 286 Sprague line filter (JN17-5259E) autopsy

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    Compaq Portable 286 Sprague line filter (JN17-5259E) autopsy

    This is not so much a request for advice but rather documenting the innards of a not-so-common part for a Compaq Portable 286. It's the Sprague line filter unit (JN17-5259E) which houses the Class X and Y capacitors as well as the mains power connector, fuse and switch.

    When I first powered up my Compaq it predictably released the magic smoke. Doing some research I thought that a RIFA line capacitor might be the culprit. However taking a look at the power supply board I couldn't find any line filter caps. It turns out the caps are located in this sealed box manufactured by Sprague Electric for Compaq. I thought at first the box was welded shut, so I took my Dremel to the perimeter and tried to open it up at the seal. However my Dremel kept slipping so I gave up on that idea pretty quick. I then thought the box might have been soldered shut, so I took my soldering iron to the seal and cranked up the iron to the hottest setting and used solder wick to get as much of the solder out as possible.

    (The lid was rusty too, which made me think a electrolytic had leaked from the inside but this turned out not to be the case)

    This ended up working well, and after half an hour I was able to prize the lid open. To my amazement the Class X capacitors were Mallory polyesters, both of which were intact, while the Class Ys were ceramic disc caps. Additionally the fowl odor I had smelt when magic smoke got released was not present anywhere inside the Sprague box.

    Here is the diagram from the front of the box:

    Unfortunately everything is epoxied together so even if there were a RIFA inside there's not much I could do to extract it. I think this Sprague unit is totally fine though; I got the rust off the lid with a wire brush and some vinegar and will be taping it shut. I've ordered a spare on eBay just in case however.

    I went back to the Compaq and inspected the power supply board, and I think I found the culprit:

    A blown tantalum at C22. Can't get a good register on it or else I'd write the specifications. Looks like I'm going to have to replace all these tants wherever I see them, not looking forward. Hopefully this post will help out a fellow faulty Portable 286 owner rule out the Sprague unit at least.