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Thread: Shutting up SX speaker interference /w 286xpres card

  1. Default Shutting up SX speaker interference /w 286xpres card

    Posting this incase it helps anyone out there with a similar setup as my own

    So I was installing a HardMPU in my SX today and while I had the box open I did a couple of tweaks. I stuck some heatsinks on my 286xpress, 8088, and math coprocessors. More importantly i think, I put a couple of ferrite beads on the internal speaker wire. Well it helped reduce the general noise when running in 8088 mode, but in 286 mode I no longer hear the crazy high pitched whine. I had to run PC-Tools to be sure everything was up and running.
    Tandy 1000EX/SX/HX/TL3/RLHD, Tandy 2500SX-MultiMedia/SX-33, Coco 1, Coco 3, TRS-80 4p

    Looking for a 1000TX mobo, EX/HX Serial / Parallel cards, and that little tab from the upper right corner of a Tandy keyboard that holds the function key labels in place

  2. #2

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    This is very interesting to me. Can you link these ferrite beads and maybe take a pic of where you clipped them on? The whine is really annoying -- I'm sure in a few more years I won't even be able to hear it any more but for the time being it would be nice.

    Also would be interested in seeing what heatsinks you used -- I noticed that 286express does get hot!

    Thanks and have fun with that MPU!

  3. Default

    The beads are cake. You want to put one as close to the motherboard connector as possible, and the other as close to the speaker as possible. I didnt have enough slack to put one outside of the metal casing, so I ended up with them right next to each other. Maybe if you have more slack or smaller beads you'll be able to. Taking the plastic retainer off and taping them shut might do the trick too. Still I am happy with the results. I got a multi size pack since i wasn't sure what size to use, but I can tell you now that you want the smallest one. The "3 mm: outer dimension-25 mm x 13 mm"
    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

    The heatsinks are ones I had previously grabbed off ebay. I put them on everything, because, yeah... that 286xpres gets surprisingly hot. I also tried to position the card with as much airflow next to it as possible. And the heatsink on the 286 is sort of low and to the left to give some clearance for the cable. The little ones are 13mm, the big one on the 286 is 20mm. They all came with adhesive backings. Getting them on the 8087 was tricky because long expansion cards sit right over that extension cable, but I managed to get two on there by moving some of the shorter cards over. I went a bit overboard with the amount i put on, but I have more heatsyncs than I really needed.
    https://www.ebay.com/itm/5pcs-lot-20...72.m2749.l2649
    https://www.ebay.com/itm/12pcs-Black...72.m2749.l2649

    The HardMPU works great by the way! Even came with a nice long cable that goes right to the MT-32 so I dont have to share the MPU-401 with my 486. It might be time to look into MIDI switchboxes...

    IMG_2723.jpgIMG_2722.jpgIMG_2721.jpgIMG_2726.jpg
    Last edited by GrandPoobah; August 12th, 2018 at 08:47 AM.
    Tandy 1000EX/SX/HX/TL3/RLHD, Tandy 2500SX-MultiMedia/SX-33, Coco 1, Coco 3, TRS-80 4p

    Looking for a 1000TX mobo, EX/HX Serial / Parallel cards, and that little tab from the upper right corner of a Tandy keyboard that holds the function key labels in place

  4. #4

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    Nice! Does the 8087 actually get hot? I never felt any heat on the ICs until I used the 286Xpress, I didn't feel the 286 but I assumed it probably would since the 8088 gets hot on that daughterboard.

    By the way I see the IDE cable from your lowtech is going to the front of the case -- did you replace one of the floppy drives for a CF 3.5 bay or something like that?
    Last edited by InfiniteClouds; August 12th, 2018 at 02:39 PM.

  5. Default

    I haven’t noticed the 8087 getting hot, but every chip on the 286xpress does, even the 287 in 8088 mode. The 8088 still gets hot in 286 mode. It’s probably overkill, especially on the 8087, but given the age of the machine I figured if I waisted a couple of dollars overprotecting it, I wouldn’t lose any sleep. I can’t for the life of me think of anything I do that actually uses the co-pros, they’re just in there so I can say my SX is the best one on my block.

    The CF card is just stuck to the side of the drive bay with some outdoor tape and a piece of plastic I cut out of a box for insulation. I did it that way to try to maximize airflow, and because I had to give up the CF bay in the expansion slot for the MPU.

    63B6E545-CB7D-4F89-A9B0-32DC2265747D.jpg
    Tandy 1000EX/SX/HX/TL3/RLHD, Tandy 2500SX-MultiMedia/SX-33, Coco 1, Coco 3, TRS-80 4p

    Looking for a 1000TX mobo, EX/HX Serial / Parallel cards, and that little tab from the upper right corner of a Tandy keyboard that holds the function key labels in place

  6. #6

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    The rings don't seem to have any affect on my speaker's noise levels. I went with these: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 and them them up identical to yours.

  7. Default

    Weird. Mine is practically silent in 286 mode now. Maybe try swapping the cards around to mirror my setup? Other than the heatsinks, that’s the only other thing I changed. Do any of the chips on your MB have capacitors soldered over them? Maybe motherboard revision matters?

    I can pop my beads off later and see if the noise comes back.
    Tandy 1000EX/SX/HX/TL3/RLHD, Tandy 2500SX-MultiMedia/SX-33, Coco 1, Coco 3, TRS-80 4p

    Looking for a 1000TX mobo, EX/HX Serial / Parallel cards, and that little tab from the upper right corner of a Tandy keyboard that holds the function key labels in place

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