jake18125 Posted November 29, 2020 Report Share Posted November 29, 2020 I've recently acquired a pair of 1gb scsi drives which work absolutely fine... so long as the system has an external scsi terminator installed. As it turns out they are both missing the resistor termination packs, which I only now realise are a bit more complex than a SIL resistor pack. Does anyone know where I could possibly find replacements or a suitable alternative? Quote Link to post Share on other sites
max1zzz Posted November 29, 2020 Report Share Posted November 29, 2020 (edited) There are two types used as far as I know, the first is a simple SIL resistor pack, typically 9 elements with a value of 110 ohms. Drives using this arrangement typically have two resistor packs The second has two elements per pin, one pulling up to TERMPWR and one pulling down to GND, typically the pull up element is 220ohm and the pull down one is 330 ohm. Drives using this arrangement typically have 3 resistor packs It's pretty easy to work out what kind the drive expects, you just need to test for continuity at the ends of each resistor pack to ground, if one end is grounded you need the second type, if neither ends is grounded you need the first type. As for replacements, I believe the second type is actually still made (Or at least NOS ones are easy to find one eBay) the first type I actually found to be really hard to get hold of in the past (At least in the UK, it might be different elsewhere) you can substitute 150ohm resistor packs (which are easier to find) in place of the 110ohm ones and it will normally work fine but keep in mind this is not in spec so might cause issues in some circumstances. Edited November 29, 2020 by max1zzz Quote Link to post Share on other sites
jake18125 Posted November 29, 2020 Author Report Share Posted November 29, 2020 3 hours ago, max1zzz said: There are two types used as far as I know, the first is a simple SIL resistor pack, typically 9 elements with a value of 110 ohms. Drives using this arrangement typically have two resistor packs The second has two elements per pin, one pulling up to TERMPWR and one pulling down to GND, typically the pull up element is 220ohm and the pull down one is 330 ohm. Drives using this arrangement typically have 3 resistor packs It's pretty easy to work out what kind the drive expects, you just need to test for continuity at the ends of each resistor pack to ground, if one end is grounded you need the second type, if neither ends is grounded you need the first type. As for replacements, I believe the second type is actually still made (Or at least NOS ones are easy to find one eBay) the first type I actually found to be really hard to get hold of in the past (At least in the UK, it might be different elsewhere) you can substitute 150ohm resistor packs (which are easier to find) in place of the 110ohm ones and it will normally work fine but keep in mind this is not in spec so might cause issues in some circumstances. Yep it needs three resistor packs. so they are literally just SIL resistor packs? Quote Link to post Share on other sites
max1zzz Posted November 29, 2020 Report Share Posted November 29, 2020 If it needs three I would expect them to be the split packs with two resistors per pin, I can't be 100% on that but all the drives I have had with 3 packs have used the split packs, if you have continuity form one end of where the resistor packs go ground you need the split packs Something like this is likely what you need: https://uk.farnell.com/bourns/4610x-104-221-331l/res-n-w-dual-terminator-330r-0/dp/2908124 Quote Link to post Share on other sites
jake18125 Posted November 29, 2020 Author Report Share Posted November 29, 2020 Just checked, pin ones goes to ground on all three of the packs, and pin 8 goes to termpower Quote Link to post Share on other sites
jake18125 Posted November 29, 2020 Author Report Share Posted November 29, 2020 Hang on I think I just found suitable replacements Does this look right? https://www.mouser.co.uk/ProductDetail/Bourns/4608X-104-221-331LF?qs=zRaq9JBfD9%2B12SkSx27ilw%3D%3D Quote Link to post Share on other sites
max1zzz Posted November 29, 2020 Report Share Posted November 29, 2020 Yep, they look like the ones! Quote Link to post Share on other sites
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