68kMLA Classic Interface
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| Help to identify IC Supermac 8*24 PDQ | |
| Posted by: johnnyilblasco on 2024-01-26 07:50:02 Hi guys, I've a faulty 8*24 PDQ, provably is something around U24 or the U24 itself. I can't find anything about this card: schematics, parts list and so on... The IC is a clk-02 9146 (see the photos), but I dont know what it is. Maybe a clock buffer but I dont know. Any help ? Thank you so much   | |
Posted by: Phipli on 2024-01-26 07:57:26The IC is a clk-02 9146 (see the photos), but I dont know what it is. Maybe a clock buffer but I dont know.It's a PS047301. 9146 is the date code, 46th week of 1991. It is a RAMDAC manufactured by Bt. 473 family RAMDACs were pretty common on 24bit cards. Attached datasheet might not be the exact part, but it is the same family. | |
Posted by: cheesestraws on 2024-01-26 07:58:36It's a PS047301. 9146 is the date code, 46th week of 1991. that's U26, not U24 | |
Posted by: Phipli on 2024-01-26 08:00:34that's U26, not U24My bad 🙂 I got distracted by the huge RAMDAC in the photo. | |
| Posted by: johnnyilblasco on 2024-01-26 08:01:52 Yes the U24, not the U26... | |
| Posted by: Phipli on 2024-01-26 08:06:02 Its probably the dot clock generator if it is any help. SuperMac PDQ, Spectrum 8, 24, Thunder ROMsI have this card, which appears to be a Spectrum 24 IV, but looks very similar to higher end cards. I was wondering if it might just be a Spectrum 24 IV ROM in a higher end card, but it also has an ASSY sticker with 0008235-0001. Here is a closeup on the ROM, and it also has a 40MHz crystal...
68kmla.org
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| Posted by: johnnyilblasco on 2024-01-26 09:20:50 From a quick check it seems to me that the pinout is not compatible. I don't know if it's because one chip is clk-02 and the other clk-03. But anyway it's a starting point... | |
| Posted by: Arbee on 2024-01-26 09:26:37 That's the dot clock generator. What problem are you having with the card? If it creates a syncable image at all, that chip is doing its job. By way of speculation, it's likely a remark of something off-the-shelf. Programmable PLLs were pretty new in the early 90s so there weren't a lot of options. Apple used the National Semiconductor DP8531 (Q700/900/950) and DP8534 (Wombat) and the Sierra Semiconductor SC11412 (Q605/LC475/LC575), to give some popular examples. | |
| Posted by: johnnyilblasco on 2024-01-26 09:48:46 At the beginning the card generated a wobbly image which was stabilized by touching the R39 resistor. Now she is completely dead. There was a moment that generated something by holding down the IC. I reworked all the soldering and checked the traces... I probably damaged the IC further by doing some checks on the traces and shorted it out. All the components around are ok... | |
| Posted by: johnnyilblasco on 2026-09-16 13:28:08 Ok, I’m reopening the discussion in the thread because I finally managed to find another 8*24 PDQ, and it turns out that the problem is indeed the dot clock generator. Once I swapped them, the board started working perfectly again. The problem now is finding a replacement. I tried an ICS1394, but it doesn’t work. Is there any way to figure out the chip based on the resolutions supported by the card and, above all, the frequencies? I don't know, I'm just taking a shot in the dark because I have no idea what to go by... | |
Posted by: zigzagjoe on 2026-09-16 15:02:24Ok, I’m reopening the discussion in the thread because I finally managed to find another 8*24 PDQ, and it turns out that the problem is indeed the dot clock generator. Once I swapped them, the board started working perfectly again. The problem now is finding a replacement. I tried an ICS1394, but it doesn’t work. Is there any way to figure out the chip based on the resolutions supported by the card and, above all, the frequencies? I don't know, I'm just taking a shot in the dark because I have no idea what to go by...It likely is a ICS1394/ICS1494, but the caveat is those are mask programmable parts. They are not programmable PLLs in the sense you can dial any arbitrary clock, you pick from a list of frequencies that was set when that chip was created per the customer's requirements. The markings would reinforce that it's a special order or has been deliberately remarked to obscure the original part. Unfortunately that means you won't find a drop-in replacement unless you find another card with the same custom part to steal it from. For example, the frequencies programmed into the ICS1494 used by the Micron Xceed cards.  | |
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