VOGONS


First post, by Thermalwrong

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A few weeks ago, I discovered that there is out there somewhere, a laptop with its own built-in wavetable, provided by the Yamaha OPL3-SA3 audio and the OPL4 wavetable chip.
This resulted in me getting hold of one working one, and one very broken one, because the broken one had some parts the working one needed. The broken one has a broken screen, damaged casing, what looked like some damage from being taken apart previously and battery corrosion, but it did have a working CD drive, which the good one lacked 😀

So now I have an unworkable laptop motherboard with a YMF721 attached to it. I have the same OPL3-SA3+OPL4 combo on an Intel AL440LX motherboard, but they're stuck to the motherboard, which is no good, I want something movable.
The OPL4 wavetable chip is something I've wanted on an ISA card for a while - there are occasionally YMF719 cards that pop-up on ebay that have the OPL4 chip attached, but they sell for too much imo. There was also Tiido's card (which I'm still pretty interested in) but that's not cooked yet.

The broken laptop has a YMF721 chip on the board, which is the first one I've got hold of where the thing it's attached to is in a non-working state. Which is great, it means I can use it for other things, without harvesting from a working device.

There are a few YMF719 cards that have the square outline of the YMF721/YMF704 on the card, but no chip fitted though.
This MF-719 that I purchased from a seller in Ukraine seemed like a perfect candidate:

MF-719-before.jpg
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But strangely there are no pictures of the "MF-719" board ever having an OPL4 chip fitted. Tiido's got some of the best pictures of YMF71x cards, including a few different cards with the wavetable chip fitted and those were great to check for a reference.

So here it is all put together:

MF-719-withOPL4.jpg
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The datasheets on here say the wavetable chip should just need the 74LS245 (SN74LS245N) IC that goes in the bottom left.
I soldered the SMD components and chip with solder paste, which I haven't used before and it got messy. That's how I ended up damaging most of those pads in the lower left - which thankfully are not connected to anything.
I used 10k resistors and 0.1uf capacitors for each of the unpopulated SMD resistor and capacitor pads. I'm not totally sure that R39 & R40 are needed, it was working without those.
Note there's a blue jumper on JP3 - that changes something to do with the mode the soundcard is operating in and without that, the YMF721 output was really badly distorted but did 'work'.

With the chip fitted, the card behaves in Windows & DOS just like my AL440LX does, with a fairly good sounding basic wavetable.

Reply 1 of 1, by Tiido

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I have done a similar thing to few other YMF71x cards having a spot for YMF704/721. It works pretty well ~

T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
Newly made 4MB 60ns 30pin SIMMs ~
mida sa loed ? nagunii aru ei saa 😜