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Terminating cheapo SCA -> 50Pin SCSI adapters

max1zzz

Well-known member
As requested I took some pictures building the Mark 2 of these adapters so anyone interested could put them together

Parts:

Chepo 80Pin SCA to 50 Pin adapter (http://www.ebay.co.uk/itm/130772715339)

18x 110ohm resistors, i suggest you use 1/8 watt or you will be pushed for space (1/4 should just about be ok) (http://cpc.farnell.com/_/mf25-110r/resistor-0-25w-1-110r/dp/RE03728)

OR 110 Ohm resistor packs pulled from dead drives

1x 1N4001 diode (or anything similar) if your adapter doesn't have a diode on it already you will need 2 (though i haven't seen any without it)

1x Small electrolytic cap (I used a 10uF non polarized one, any small value should work, and it dosen't need to be NP, just the ones i have are)

Total cost of the parts should be under £2 ;)

This adapter just terminates the lines on the 50 pin connector, it will not help with any fussy SCA drives that want their extra data lines terminated.

First thing is to solder the 110 ohm resistors, Connect all the tops of them together:

photo-14.JPG

Then the cap, which goes between the the common contact of the resistors and ground, i find the best thing is to fold the legs other tho the other side of the board:

photo-16.JPG

photo-15.JPG

And finally, solder the diode between the side of the term power jumper closest to the edge of the board and the common contact of the resistors. Cathode towards the resistors.

photo-17.JPG

Also I recommend you cut the trace going from the term power to the 50 pin connector, otherwise you may find in some macs you cannot switch off termination.

Installed and it works ;)

photo-18.JPG

 
Last edited by a moderator:

max1zzz

Well-known member
Thanks ;) glad i could contribute something usefull :)

and i should have probably noted, the contacts you solder the resistors to are:

r r r r r r r r o r o o o o o o r r r r r r r r r

o o o o o o o o o o o o o o o o o o o o o o o o o

(that is with the 50 pin connector towards you) r = resistior o = no resistior

 

max1zzz

Well-known member
yes, let me take pics of my one using resistor packs from a dead 120mb quantum pro drive ELS it is much much neater

I did consider using SMT parts, however i find they are very fiddly in situations like this, However an interesting idea would be to produce a small cuircuit board using smt parts, with pads right at the edge of the board. Then you could just stick the board down and solder it right to the pins, easy and neat :) (like the QSB's used in the xbox modding community)

EDIT: Here is mk1, using the res packs, however it is permanently terminated

photo-19.JPG

 

max1zzz

Well-known member
Yep, that is another good option, passthrough 50 pin terminators are a good option aswell

Just had been wondering for a while how easy it would be to make a terminated adapter, and the answer is very easy

 

MacJunky

Well-known member
I thought for some more modern drives you needed to terminate some pins of the 80pin connector, so the drive would know that it is being used with ancient things?

That or use a 68pin cable with it's own terminator on the end and hook that to the motherboard and drives with adapters.

That is what I remember hearing anyway.

 

max1zzz

Well-known member
Yes that is correct, some 80pin drives need the extra lines terminated, whereas others don't, so this will only work for ones which don't need them terminated

I do plan to make one that terminates the extra lines on the 80 pin connector, but first i need to find a drive that doesn't work without doing that

 

MacJunky

Well-known member
I have a Compaq BD0366459B (36GB 10k RPM) that appears to need termination on the 80pin, or use a 68pin cable.

I can just use it with a 68pin cable but in a cramped space that might not be as nice unless I also used a flexible extension on the mobo side of the the 68 to 50 pin adapter.

*shrug*

 

max1zzz

Well-known member
Ordered a BD0366459B, hopefully i should have it tuesday

Will see if terminating the extra lines gets it working :)

 

max1zzz

Well-known member
extra lines terminated, works on my sca drive, hopefully it should help with picky drives, will be seeing next week

photo.JPG

 

max1zzz

Well-known member
initial tests with the BD0366459B seem sucessfull, it is recognized and is currently being formatted.

Once it is formatted I will test it on the adapter without the extra lines terminated and see if it still works

Edit, well, it seems that it gets it recognised where it otherwise wouldn't. However it failed in formatting and is now saying it can't get the required data from the disk...

 

max1zzz

Well-known member
Wow, a new record! the drive failed after being powered up for 10 min... so much for fully tested.

oh well, hoefully the seller will agree to just send me annother.

However, the test was successfull, the drive was recognized using mk3 of the adapter, where it wasn't with mk2

 

James1095

Well-known member
I like that idea, I've been using cable-end terminators for drives that need them but this is a tidy approach for space-cramped compact and pizzabox machines.

YMMV but I've found that the Savvio drives seem to work fine without any additional termination. I assumed the drives have onboard termination but I could simply be lucky.

 

mcdermd

Well-known member
I picked up a handful of 50-pin inline terminators for $1 each last weekend. I've used them before and they work pretty well in between the adapter board and ribbon or between the ribbon and the logic board if there's room.

 
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