Forum Rules and Etiquette

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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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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.

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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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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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5150 and 5160 problems

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  • SpidersWeb
    Originally posted by modem7 View Post
    That mirror is almost 2 years old. Best to point to the master:
    Ah sorry, that's pretty bad of me (I'm a software dev, I should know better). Thanks for the fix.

    Leave a comment:

  • bobba84
    Hi guys, thanks for all your help. Just an update...

    Sorry! I meant to say C7 on the 5150. It's next to the keyboard port.

    I followed the instructions modem7 sent me for the minimal diagnostic. The 5160 board itself has all the right resistance and voltage readings. It ended up being a shorted tantalum on my 384k expansion card causing the power supply to cut out. I removed it and it now powers on. But even with no cards installed it won't POST or beep at all when powered on.

    I got to the end of the instructions where it asked me to swap the RAM chips in banks 0 and 1 - which I did, but it still won't post.

    Everything seems fine, but it's dead. The speakers makes a 'tick' noise when power is applied, but I remember it doing this when first powering on even when it worked.
    I also pressed on all socketed IC's to make sure they were snugly fit.
    Is there anything else I can try? Or is my board likely dead?

    Again thanks so much - you guys are awesome!


    Leave a comment:

  • modem7
    Originally posted by SpidersWeb View Post
    modem7 has been good enough to keep track of faults,
    That mirror is almost 2 years old. Best to point to the master:

    Leave a comment:

  • modem7
    Originally posted by bobba84 View Post
    I've also got a 5150 64-256k board I bought for $1 online (lol) and it constantly blows the C6 tantalum when replaced. Without it, it boots fine. Should I just leave it out or has anyone had this as a sign of further problems?
    I have just looked at a 64KB-256KB 5150 motherboard, and looked at the corresponding circuit diagram. I cannot find a C6 on either.

    Leave a comment:

  • bobba84
    Sorry, I posted a reply but it somehow disappeared.

    Thanks very much for the replies guys! I'll check the resistance on the 5160's power connectors tonight and take it from there.

    The 5150 seems to work fine now - I left it powered on for a good 15 minutes. I hadn't thought of the new cap being bad too, I bought it from an old guy at a local electronic shop. It might have been there a while.

    Cheers! I'll keep you posted with progress!

    Leave a comment:

  • bobba84
    Thanks to both of you for the replies. I'll do as you said and check resistance on the motherboard's power connectors and take it from there.

    I'm pretty sure I put the (two legged) replacement cap in the 5150 correctly - positive lead to the center hole and negative to either of the two other holes (I chose the bottom one)... is that right?

    It could be old stock... I didn't think of that. I bought 6 of them from an old bloke at a local electronics shop. Seeing it's working for now I think I'll just leave it out. I intensely dislike the firecracker experience when they get upset.

    Thanks! I'll post an update after I play further with the 5160 tonight.

    Leave a comment:

  • SpidersWeb
    There is multiple connected in parallel across the power lines, so a bit of guess and check is required.
    Using a multimeter, find which power lines / capacitors show a low resistance (often 0 ohms). For the caps, focus first on the caps near the PSU connector and near the ISA slots.
    Because they are connected in parallel - you wont be able to easily find the specific culprit - but this guides you to finding the likely suspects.

    If your multimeter is able to read (even if inaccurately) down to 0.01 ohm resolution, you might even be able to tell which location is more likely.

    modem7 has been good enough to keep track of faults, - C56 and C58 are popular, and I've had to remove those myself.


    What you really should do: desolder all of them, install new ones
    What you should do: desolder offending caps one by one until resistance increases, then replace any that were removed
    What I do: grab likely suspect with fingers, bend back and forward until it comes off - repeat until the short goes away (then solder in replacements later if you want to or if the machine has trouble after)

    I'm not sure what's going on with your 5150 board, unless you installed the cap backwards or it's really old stock?

    Leave a comment:

  • Chuck(G)
    That you can read voltages says that you must have a multimeter. That's good. Leave the PSU unplugged, set your meter on the continuity test setting (or low ohms if you don't have one of those) and check at the power supply connector between ground and the various supply pins (+5, -5, +12 and -12). See if any measures short. That will narrow things down quite a bit.

    Leave a comment:

  • bobba84
    started a topic 5150 and 5160 problems

    5150 and 5160 problems

    Hi guys,

    I don't get on here much but was wondering if anyone could help me out a bit.

    I've got an IBM 5160 with 64-256k board that I've owned for about 15 years. It has been in storage for the last 7, and it won't power on. The power supply showed 0v on all lines, until I unplugged it from the motherboard, at which point it came good. So I'm assuming there is a tantalum capacitor shorted on the board (or maybe a bad expansion card - haven't pulled them yet). Can anyone tell me the most likely culprit? I've got a few spare caps but not enough to change out all of them at the moment.

    I've also got a 5150 64-256k board I bought for $1 online (lol) and it constantly blows the C6 tantalum when replaced. Without it, it boots fine. Should I just leave it out or has anyone had this as a sign of further problems?

    Thanks in advance for any help received!