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JDW

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Everything posted by JDW

  1. @ZaneKaminski We've not heard from you in a long while, and I've not received any replies to the PMs I sent to you way back in August 2020. I see on your profile page your last visit here was Jan. 13th 2021 though. That indicates you are still visiting this forum, and as such I'd certainly love to hear your thoughts regarding my report about your 8MB ROM SIMM, used in an SE/30. I put more details in the PMs to you, but my public report is in the following post: Thanks, Zane. I hope all is well!
  2. Actually, the real reason to build a cable rather than merely EXTEND the stock cable is if your stock cable has corroded contacts and aging wires that show higher than normal resistance, which I have seen on my own SE/30's. The end result of a lackluster stock cable is lower than expected voltage when measured at the motherboard under full load. Building a brand new cable exactly the length you need, leading from the analog board to the mother board (without using the stock cable at all) benefits from brand new wires and connector terminals. You get the lowest resistance connections that ar
  3. Just play a few hours of Wolfenstein 3D and then read through it again. You still won't understand it, but it will be far more enjoyable!
  4. JDW

    Walkmac

    @pinto_guy I certainly appreciated our private conversations, and I must say that I am also very appreciative of your willingness to share further insights publicly in your latest post today. That MacColby makes me think of the Lisa, only portable. "Portable" back in those days being more of a "luggable" than anything else. With a metal case, that thing must weight a ton! I look forward to seeing your YouTube presentation.
  5. I do not have one of those over-price crimpers which are made specifically for particular terminals. I have a cheaper, general use crimper that I simply take care in using. The dedicated crimpers are better, but I don't do enough crimping to justify the sky high cost.
  6. As to the best replacement wire, there's a tradeoff between the lowest resistance and wire flexibility. As much as I'd love to use 16AWG wire, it won't fit the terminals, so we need to stick to 18AWG. See page 3 of the chart below for 18AWG wire. As you can see, the lowest resistance wire shown there has 19 strands of size 30 wire that is Concentric (as shown in the image below). The higher the number of strands, the more flexible the wire but the higher the wire resistance. https://philatron.com/pdf/wire-strand-construction-charts.pdf Insulation thickness is
  7. @ymk Thank you! More specifically... For those wanting to make a cable that merely EXTENDS the stock SE/30 cable, you will need 1pc of the Female connector here (which has pins already inside): https://www.amphenol-icc.com/minitek-pwr-4-2-101278201422lf.html And then you will need 1pc of the Male connector here: https://www.amphenol-icc.com/minitek-pwr-4-2-1012781514lf.html And for use with the Male connector you will need 14pcs of these terminals: https://www.amphenol-icc.com/minitek-pwr-4-2-hcc-101341702220lf.html — —
  8. There are times when you want to make a very long, custom cable so as to pull the SE/30 motherboard outside the chassis for easier testing while still being able to power up the machine. Until now I've been soldering wires onto testing points and pulling those wires outside the chassis, but that is fiddly, time-consuming, and prone to accidental shorts. Rather than mod an existing cable by making it longer, it's better to create a new cable. Surely someone here has done this before. If so, could you please provide the connector part number (or exact web page on Mouser or Digikey) as well a
  9. I've not had the time to add the International Analog board to my Google Docs Spreadsheet. Another problem is that I do not own one so I cannot give it a physical look-over like I did with the US Analog boards. The yellow glue/epoxy in the photo of the flyback looks to be in great condition. The axial caps on the motherboard can be replaced with tantalum, as I demonstrate in one of my recent videos. I can't really comment to much further on the Analog board without a high-resolution top-down photo. But take a magnifying glass and look for any dark spots on
  10. If someone can find data sheets for those sound chips, I would be delighted to have have a copy! But for now, I am not holding my breath. The choice of a 1uF was likely deliberate. Sometimes they are used in timing circuits so you have to be careful. When it doubt about the purpose of a given capacitor, only swap with the factory capacitance value. I still think it won't affect the stock look to use just one 1µF tantalum cap; but if you absolutely must have the stock look, then your only recourse would be to use a fluid-filled aluminum electrolytic, which would need to be repla
  11. I would just use a 50V 1uF Tantalum (Solid or Polymer). It’s only one cap so it won’t detract from the stock look if all other replacement caps are OS-CON.
  12. Details are found on the 68080 wiki here.
  13. I've never felt compelled to do that. The only PPC machines I currently own are my G4 Cubes and PowerBook Wallstreets, mainly because if I want a fast Mac that runs modern software, I will use a modern Intel Mac. My primary love is for older 68k Macs, especially the 9" CRT Macs like the SE/30. The SE/30 runs reasonable well at its stock speed, but I must say I enjoy it more with a 50MHz 68030 accelerator installed. And its that upgradability that makes the SE/30 king of the compacts! My Daystar Turbo 040 40MHz PDS accelerator makes it faster still, but there are software comp
  14. Actually, Jeff mentioned he has a Classic II, so I checked the 47µF & 10µF motherboard caps which are commonly replaced with Tantalum and highlighted all of those in Yellow in this modified Classic II Bomarc schematic. Specifically: C3, C4, C5, C6, C7, C8, C10, C11, C12, C13, C14 C5 sees 12V through a 47µF resistor, but it should still technically be derated to 50% of working voltage. C13 & C14 see 8V which means a 16V rated Solid Tantalum is OK. The other caps are a part of the audio circuit. C10 & C4 might be vulnerable to spikes,
  15. @JC8080 mentioned to me today that he recapped his Mac Classic motherboard with 16V Solid Tantalum capacitors. I downloaded the schematics and had a look. Unfortunately, C8 & C9 definitely have 12V across them; and C1, C2, C3 & C4 are all on the Sound chip which means some might see 12V as well, but that would need to be measured on a scope when switching on the power and when playing audio at full volume. I marked all the capacitors in Yellow in these modified Bomarc schematics so you can see what I am seeing. As such, our discussion in this thread applies
  16. I personally don't mind your posts here because what you have written thus far provides important proof which shows Solid Tantalum capacitors do fail even when chosen by big name manufacturers, and no doubt the voltage rating of those caps played a big role in those failures. With that said, a new thread would bring more attention to your repair, so you might want to do that to ensure you get more eyes on it. I would encourage you to post updates in this thread which are specific to your Tantalum capacitor replacement though, as that info is relevant, in my opinion, despite the t
  17. To reiterate what I said in our email dialog, I would once again like to say you are to be commended on bringing that machine back to life, @JC8080! I did offer some advice, but you got your hands dirty and maintained the determination and passion to get the job done. You also did a lot of leg-work by reading through the Larry Pina repair books which helped, and having that second machine from which to swap components was also extremely helpful too. All said... Great work! I actually have a working HD20, but despite that, I too highly recommend the FloppyEMU. It's the main rea
  18. Supplementing the excellent thoughts of @aeberbach, I do find it interesting that such a large capacitance was used in the first place. The difference between 47µF and 2200µF is huge. When we talk about "ripple" in this particular case (rising and falling voltage), we are most likely talking about having a large enough capacitance to ensure there are no major drops in voltage that would potentially cause the motherboard to freeze or produce an error. Picking 2200µF indicates to me that some pretty major voltage drops were experienced on those early board revisions, and rather than do the no
  19. Thank you for the extra analysis. I think that adds something important to this discussion, and nothing I'm about to say in any way undermines that. In terms of low-resistance paths, C10 sees incoming +12V from the PSU while C9 sees -12V from the PSU, while C3 & C4 see 11V or so (in accordance with my testing) via the SONY sound chips, regarding which we have no datasheets and therefore cannot say exactly what goes on internal to those chips. So the lowest resistance paths would be C9 & C10. Because they get hit with off-board voltages, C9 & C10 are technically the m
  20. Your card looks quite similar to my card, just that yours lacks the heatsink. There must be a bad chip on your card.
  21. Could you post a photo of the front and back of your Turbo040 card?
  22. Below is some of the information I provide in the text description under my General Advice video... Rather than give you a Mouser Cart for the SE/30 motherboard, I instead provide links below to individual capacitors on Mouser. That gives you freedom to choose a Can-shaped capacitor for a stock look, or your favorite tantalum. The links below also let you choose the proper lead spacing for C11, which varies by motherboard version (2 types). There are ten 47uF caps on an SE/30 motherboard: C1, C3, C4, C5, C7, C8, C9, C10, C12, C13. I dislike liquid electroly
  23. A lot of people ask the same question when it comes to the fluid-filled electrolytic capacitors on computer parts that "most people" refuse to recap, and yet I made an 800K Floppy Drive Recapping video about that because you really do need to recap those drives too even though they aren't failing left and right due to failing caps. A lot of decisions about capacitors often comes down to consensus among peers, which in turn is driven by practical personal experience too I will admit, but the reality is this: 1. Operating a tantalum capacitor at a voltage higher than it's manufactur
  24. Thank you for your kind words, @ttb. Thank you @ttb & @ScutBoy for correctly pointing out that the 2 Axial caps are the Nichicon VX caps in that Tantalum kit. I have just added a new temporary Comment under my video to announce the formal correction along with my apology for the foolish oversight. I have also submitted an edit of that video, cutting out several seconds from that section to exclude my incorrect remarks, and that will take a day or so for YouTube to render the video (at the same video URL). I will later delete my Comment, since the video wil
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