Announcement

Collapse

Forum Rules and 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.


Rule 1: 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.


Rule 2: 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.



Rule 3: 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.


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:
  • "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.

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.


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

486 board covered in tantalum capacitors

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

    486 board covered in tantalum capacitors

    I bought two 486 boards recently, a DTK PKM-0038s and a PKM-0037s. The 0038s has been great and is in a build now (details in a different post).

    I'm rather worried about the 0037s. It is covered in tantalums. I have heard that those are likely to fail in an explosive way after 20+ years. The good news is that the board does boot now and actually works well. An ohmmeter check on each did not reveal anything suspicious.

    Nevertheless, any recommendations on replacing them? It seems like it would be big undertaking. How necessary is it given no current evidence of a problem?

    Pictures:

    IMG_20140322_071019686_HDR.jpg

    IMG_20140322_071010203_HDR.jpg

    #2
    If everything is working fine now I would just leave them.

    When they fail, they make a big noise but that's about it. I've had a few boards with tantalum caps blow. Once the caps are replaced everything works fine again.

    Comment


      #3
      They won't usually damage the motherboard. You'll just need to brush off some carbon and a few little yellow bits.

      It's likely re-soldering would actually do more damage. Those buggers are usually attached to thick ground planes that are difficult to heat up.

      But if you have a bare board out on a workbench that you haven't powered up in 10 years - you might want to duck when you first turn it on.

      Comment


        #4
        Originally posted by commonlySeenStatement
        ...that board has *tantalums*! Tantalums can explode and/or short over time which is even worse than a failed electrolytic. Shorting damage from a bad tantalum can take out hard-to-replace ICs...
        ok, guys... so i see a lot of statements like this quote on the forum:
        i was considering recapping my 5150 & 5160 before i got too involved with them.. i don't WANT to recap a board if i can just replace them as they blow.
        this includes motherboards and power supplies... am i misunderstanding something??
        Wanted: Sony CDU-535 or CDU6250 CD-ROM Drive (Caddy drive) for 8-bit Sony Interface Card
        sigpic <-- This is me using my IBM PC 5150 over Ethernet TCP/IP network with assignable drive letters

        Comment


          #5
          Jeez... talk about alarmists!
          PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

          Comment


            #6
            Honestly I think the problem prone ones were earlier on like 1980s boards. I have had two 486 boards with those so far and none blown

            Comment


              #7
              Aluminum electrolytic caps are far more likely to cause issues than are aging tantalums. I've never seen a tantalum blow and take a component along. Just some noise to be ignored, most of the time.
              Reach me: vcfblackhole _at_ protonmail dot com.

              Comment


                #8
                When tantalums blow I just clip off the remains and keep on chugging. I've had hard drivee formatting on the bench when they smoke up a tant. It's always a pretty show.
                [Need something to waste time on? Click here to visit my YouTube channel CelGenStudios]
                --------------------------------------------------------------------------------------------
                [No time for videos? Click here to visit my Twitter feed @CelGenStudios]

                = Excellent space heater

                Comment


                  #9
                  Surface mount Tantalums can do some damage.
                  The epoxy ones just make a lot of smoke and short.
                  Often with a strong supply they just blow open.
                  I've seen serious damage from the little square
                  surface mount ones. There is no real age rule that goes
                  with them. I've seen them fail after 1 year and some
                  tantalums in my oldest computer that have been
                  working fine now for 43 years.
                  I would never think of replacing them with electrolytics.
                  They do not provide the same bypass capabilities without shunting
                  them with large ceramics.
                  Dwight

                  Comment


                    #10
                    I don't think anyone was suggesting replacing tants with electrolytics, Dwight. Fortunately, there are some more alternatives. If you're replacing a SMD tantalum, for modest capacitance (22-47 uF), there are stacked MLCCs (a bit expensive). For larger values, I wonder about the characteristics of sold-polymer electrolytic caps might suit many applications.
                    Reach me: vcfblackhole _at_ protonmail dot com.

                    Comment


                      #11
                      Originally posted by Dwight Elvey View Post
                      I would never think of replacing them with electrolytics.
                      They do not provide the same bypass capabilities without shunting
                      them with large ceramics.
                      Dwight
                      I've done that just fine with an ISA card with bad tantalums (shorting 12V to GND). It's been 13 months since I did that repair and the card still works fine. And technically, aren't tantalums a type of electrolytic capacitor anyway?
                      Looking for: Needham's Electronics PB-10 Microcontroller Adapter (looking for one since early 2012!).

                      Comment


                        #12
                        Yes technically they are but when most people refer to electrolytic,
                        they refer to aluminum electrolytic.
                        Tantalums get their higher capacitance and better frequency response
                        at high frequencies by having thinner oxide layers. This means a small
                        flaw is more likely to cause a failures as well. Since they are a dry
                        electrolyte, they don't suffer from gradual increased ESR and reduced
                        capacitance.
                        Dwight

                        Comment


                          #13
                          Thanks everyone for the replies. I will forgo any replacements until one breaks -- should be an interesting post if one does!

                          Comment

                          Working...
                          X