(Question) 1990 Maxtor Terminator Resistors

[raoulduke]

I'm missing the two terminator resistors on a 1990 Maxtor 7080SR 80 mb drive.  They are 11-pin SIP (? I think that's correct).  Does anyone have any thoughts on proper resistance?  Someone had suggested 330 ohms and 220 ohms.  Does anyone know what the standard was?

Follow-up, and I should say I don't really understand what I'm asking, should they be bussed or isolated?  

 

[max1zzz]

they should be 10pin sip, commend.

As for the resistiance it seems to vairy, 110 ohm is what the scsi spec says should be used for active termination, I have seen adapters with 150 ohm resistiors (and i have used them on my scsi -> SCA adapters) and I think I have also seen 220 ohm ones used

The 220 and 330 ohm combo is used for passive termination, I haven't seen this combo on drives before (but maybe some members here with more experiance than me have?) But a thourght does come to mind, if the packs are 11 pin it is possible that it is a combined pack (with both the 220ohm and 330ohm resistiors ) but again, I haven't seen this before

 

[raoulduke]

I guess I'll try the 110 ohm setup and work backward from there.  They are definitely 11-pin; my questionmark was about SIP as I don't really know what that is/means.  The ones on Amazon seem to be differentiated between "isolated" and "bussed", also.  Any thoughts on that?  Is that misdirection (I gather not)?

 

[max1zzz]

SIP stands for Single in Parallel (So it has a single row of pins), isolated means that it contains a number of seprate resistiors (so pin 1 & 2 are connected to one resistior, pins 3 & 4 are connected to annother and so on) Bussed means all the resistiors share a common contact

(this is proabley a much clearer explination ) :

can you take a pic of the drive's board? being 11-pin dosen't make much sense to me (unless it is a pack that contains a pair of resistiors) as there are only 18 pins that need to be terminated, so it's normally 2 x 10 pin packs (9 resistiors a pack) of 3 x 7 pin packs (6 resistiors a pack).
 

 

[trag]

If it's old enough to use Resistor SIPP packs, then you want the 220/330 networks.   The 110ohm resistor packs won't provide good termination.     When one measures the resistance into the 220/330 networks, the combination of series and parallel resistances show approximately 110 ohm, which has a lot to do with why folks think that will work, but it's not a good termination solution.

This is the kind of thing you need:

http://www.ebay.com/itm/230885118855?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

But you probably need the 4611X series, since you said you have 11 pins.

There's a thread around here somewhere where I posted a much more detailed discussion on this topic.   It's the one where I go on for a while about the Bourne 4610 series vs. some other series and related matters.

Look at this article:

https://www.bourns.com/pdfs/scsitermap.pdf

 

[max1zzz]

I must be missing something here, in the dual 220/330 networks how could you messure 110ohms? surley buss from one pin you will get 330 and from the other 220?

I'm also sure I have pulled packs from drives that are 110 ohm bussed packs. But i'll go and double cheack that quickley..... Edit: just cheacked one and it was a simple 110 ohm bussed pack, my guess is that the drive it is from is using active termination and there is a 2.85v regulator connected to them

 

[raoulduke]

Yes.  The guy I had been talking to sent me a similar diagram.  He had suggested the 220/330 setup also.

Here's a picture; it's most definitely 11 pins.  There are, indeed, two resistors.  Unfortunately, trag, I couldn't find the topic, searching for 'bourne 4610.'  I apologize if this is rehashing.

The question then is bussed or isolated?  I get the difference conceptually now, I just don't know what if any standard existed or how the difference would affect this setup.  My thought is bussed; but I am very open to any thoughts on that. 

 

[trag]

I must be missing something here, in the dual 220/330 networks how could you messure 110ohms? surley buss from one pin you will get 330 and from the other 220?

I'm also sure I have pulled packs from drives that are 110 ohm bussed packs. But i'll go and double cheack that quickley..... Edit: just cheacked one and it was a simple 110 ohm bussed pack, my guess is that the drive it is from is using active termination and there is a 2.85v regulator connected to them

Look at the diagram in the pdf to which I posted the link.   If you measure resistance from a pin to ground you do have a 330 ohm resistor to ground, but you also have a network of 8 550 resistors (220 + 330 in series) in parallel to ground in series with a 220 ohm resistor.  Similarly from any pin to +5.   Pin to pin it's 440 in parallel with 660. 

 

[trag]

Yes.  The guy I had been talking to sent me a similar diagram.  He had suggested the 220/330 setup also.

Here's a picture; it's most definitely 11 pins.  There are, indeed, two resistors.  Unfortunately, trag, I couldn't find the topic, searching for 'bourne 4610.'  I apologize if this is rehashing.

The question then is bussed or isolated?  I get the difference conceptually now, I just don't know what if any standard existed or how the difference would affect this setup.  My thought is bussed; but I am very open to any thoughts on that. 

To be more certain, I would get out an ohmmeter and see if there's continuity between pin 1 of the connector on the hard drive for each pack and the ground pin on the power supply and pin 11 of each pack and the 5V pin on the power supply input.   The only caveat being that there might be a 5V regulator or some such on the hard drive between the termination pack 5V pin and the input power supply pin.

Actually, just finding that the pin 1s and pin 11s are common between the two termination pack connectors is probably dispositive.

If the resistor packs are 220/330 networks then pin 1 will be GND and pin 11 will be +5V.    If they're bussed or individual resistors, then the pin arrangement will be different.  A bussed resistor arrangement would have only one pin of each connector common.   An isolated resistor arrangment should have none of the pins common, or maybe every other pin common.

If they're 220/330 resistor networks, then you want bourns 4611X-104-221/331 or Bourns 4311R-104-221/331.  The only difference between them is the packaging.

 

[max1zzz]

Look at the diagram in the pdf to which I posted the link.   If you measure resistance from a pin to ground you do have a 330 ohm resistor to ground, but you also have a network of 8 550 resistors (220 + 330 in series) in parallel to ground in series with a 220 ohm resistor.  Similarly from any pin to +5.   Pin to pin it's 440 in parallel with 660. 

Ahhh... Now I see what your talking about

That explains some odd readings i got on some resistor packs i measured when i was designing my scsi -> SCA adapters

Thanks for the info!

 

[trag]

Ahhh... Now I see what your talking about

That explains some odd readings i got on some resistor packs i measured when i was designing my scsi -> SCA adapters

Thanks for the info!

You're welcome.  I'm glad I could help to make that clearer.  Looking back, I probably should have mentioned that you should look at the last page of that PDF and at the diagram for the 4611X-mumble.  But you figured it out anyway.  For anyone else reading along, that top left diagram on the third page is the relevant one.

Attaching the file, in case the web link goes stale.

scsitermap.pdf

 

[raoulduke]

In case anyone uses this as a future guide, it seems the correct answer is bussed.  I will let you know if it works when the resistors arrive.