Announcement

Collapse

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.

This should be obvious but, just in case: profanity, threats, slurs against any group (sexual, racial, gender, etc.) will not be tolerated.


Stay close to the original topic being discussed
  • If you are starting a new thread choose a reasonable sub-forum to start your thread. (If you choose incorrectly don't worry, we can fix that.)
  • If you are responding to a thread, stay on topic - the original poster was trying to achieve something. You can always start a new thread instead of potentially "hijacking" an existing thread.



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.
  • Do not bump threads.
  • Do not "necro-post" unless you are following up to a specific person on a specific thread. And even then, that person may have moved on. Just start a new thread for your related topic.
  • Use the Private Message system for posts that are targeted at a specific person.


"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:
  • "PM Sent!": Do not tell the rest of us that you sent a PM ... the forum software will tell the other person that they have a PM waiting.
  • "How much is shipping to ....": This is a very specific and directed question that is not of interest to anybody else.


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.
See more
See less

IBM 5160 faulty power good line

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    IBM 5160 faulty power good line

    Trying to resurrect an IBM 5160 which doesn't post and I've figured out with the excellent troubleshooting guide at minuszerodegrees.net that my power good line voltage in the PSU is bad .. it is almost zero volts

    I haven't done any PSU repairs before, is there anything in particular that usually goes bad when the power good voltage is bad on the IBM 5160 PSU's?
    The PSU brand is "Schrack"


    #2
    A quick-and-dirty fix would be to tie the +5 to PG via a simple RC network. Probably good enough.

    Comment


      #3
      Its normally a tantalum cap on the motherboard that prevents power good from going high in these machine.

      Are you sure the PSU is faulty ?
      Current fleet
      TRS80 Model 4 - BBC B - Tatung Einstein - PCW9512 - PET 3032 - C64 - ZX81 - Spectrum 48K - Amiga A500 - Apple II europlus - Apple iMAC G3. Sharp MZ-80K. - IBM 5160 XT - Multibus 286/10 - Micro PDP 11/73 - Rainbow PC100A - MicroVax II - MicroVAX 3100, 3300, VAX 4000 VLC & 4000 Model 96 - AlphaStation 225Apricot PC - Apple Performa 6200 - Apple Mac IIcx

      Comment


        #4
        Originally posted by Gary C View Post
        Its normally a tantalum cap on the motherboard that prevents power good from going high in these machine.

        Are you sure the PSU is faulty ?
        Yes, I am positive.

        It fired up and booted into IBM Basic with a spare AT PSU I have.

        Comment


          #5
          With nothing connected to the PSU, Do you get any DC output voltages, +12v -12v +5v -5v or is it just the missing PG

          Comment


            #6
            Fair enough.

            So the PG signal is produced by the PSU when the power lines have come up to voltage and stabilised, so the question is, are the lines coming up to the correct voltages or is the detection circuit faulty. An AT supply gives about 0.5 seconds before it gives up.

            Do you have a storage scope so you can see the rise on each of the lines and see if they are reaching spec ?

            If they are all coming up to normal, you 'can' tie the +5 to the PG line to tell the motherboard all is good (not recommended) but i would then try to fix the fault.
            Current fleet
            TRS80 Model 4 - BBC B - Tatung Einstein - PCW9512 - PET 3032 - C64 - ZX81 - Spectrum 48K - Amiga A500 - Apple II europlus - Apple iMAC G3. Sharp MZ-80K. - IBM 5160 XT - Multibus 286/10 - Micro PDP 11/73 - Rainbow PC100A - MicroVax II - MicroVAX 3100, 3300, VAX 4000 VLC & 4000 Model 96 - AlphaStation 225Apricot PC - Apple Performa 6200 - Apple Mac IIcx

            Comment


              #7
              This thread http://www.vcfed.org/forum/showthrea...T-power-supply they changed a couple of caps in the PSU.

              Difficulty seems to be getting a drawing for this PSU.
              Current fleet
              TRS80 Model 4 - BBC B - Tatung Einstein - PCW9512 - PET 3032 - C64 - ZX81 - Spectrum 48K - Amiga A500 - Apple II europlus - Apple iMAC G3. Sharp MZ-80K. - IBM 5160 XT - Multibus 286/10 - Micro PDP 11/73 - Rainbow PC100A - MicroVax II - MicroVAX 3100, 3300, VAX 4000 VLC & 4000 Model 96 - AlphaStation 225Apricot PC - Apple Performa 6200 - Apple Mac IIcx

              Comment


                #8
                Originally posted by Malc View Post
                With nothing connected to the PSU, Do you get any DC output voltages, +12v -12v +5v -5v or is it just the missing PG
                Correct

                Comment


                  #9
                  I had to attach some load to this PSU to get it working. It wouldn't start with one 5.25" MFM hard drive, but did work with two 5.25" MFM hard drives.

                  Comment


                    #10
                    So all the lines are good, you can jump from +5 to PG I believe.
                    Current fleet
                    TRS80 Model 4 - BBC B - Tatung Einstein - PCW9512 - PET 3032 - C64 - ZX81 - Spectrum 48K - Amiga A500 - Apple II europlus - Apple iMAC G3. Sharp MZ-80K. - IBM 5160 XT - Multibus 286/10 - Micro PDP 11/73 - Rainbow PC100A - MicroVax II - MicroVAX 3100, 3300, VAX 4000 VLC & 4000 Model 96 - AlphaStation 225Apricot PC - Apple Performa 6200 - Apple Mac IIcx

                    Comment


                      #11
                      As I mentioned earlier, doing so with a small RC network (series R, C to ground) will provide a bit of a delay that might result in more reliable operation.

                      Comment


                        #12
                        Originally posted by Amigaz View Post
                        Correct
                        If all other DC outputs are within spec, I'd trace from the PG wire where it connects to the PSU PCB and test components along that line after looking for obvious signs of damage, Keep in mind the dangers of working on PSU's, Don't power it up and make sure the Caps are drained, The outcome really depends on your experience and what tools you have, What chuck suggested is an option though never gone that route myself.

                        Comment


                          #13
                          Originally posted by Chuck(G) View Post
                          As I mentioned earlier, doing so with a small RC network (series R, C to ground) will provide a bit of a delay that might result in more reliable operation.
                          Example at [here].

                          Originally posted by Gary C View Post
                          So all the lines are good, you can jump from +5 to PG I believe.
                          I brought out one of my IBM 5150 motherboards.

                          I tried about 10 power-ups of the motherboard, and in about half of those power-ups, I had the POWER GOOD connected to +5V (done by connecting pin 11 of the 8284A chip to +5V).

                          In the times that POWER GOOD was connected to +5V, the motherboard did not start. That will be because the 8284A (never seeing POWER GOOD in a LOW state) did not generate its RESET signal at motherboard power-up time, and therefore, the CPU was not reset. Related information at [here].





                          Comment


                            #14
                            Thanks for all your help and suggestions, guys. really appreciate it
                            Haven't had any time yet to tinker with the PSU because life and work came in between
                            Think I'll start by cracking the PSU open and look for obvious damage and take it from there with your tips and suggestions ...

                            Comment


                              #15
                              Look at today's post by me under "hardware" for a high-tech simple solution. here

                              Comment

                              Working...
                              X