TRS-80 Model 1 mini disk drive termination/resistor pack/dip shunt question

[Dokken]

I have a model 1 mini disk drive I'm trying to get working. I have the proper cable and a working EI as well as one working mini disk drive.

This drive has the shunt socket and resistor socket like the diagram from the service manual (picture attached), but both are unpopulated. I connected the shunt pins 2, 3, 4, 5, 7, 8 like the manual shows, and the drive attempts to read (spins, LED on) but I get disk error from a working formatted LDOS disk. I understand the last drive needs a resistor termination pack. short of taking my working drive apart, can I make a resistor pack? what values, and what pins in the socket?

thank you!

 

[Chuck(G)]

Pretty standard for floppy drives. Value not critical, so anything from 150 ohms->2K should be fine. Non-bussed, so that R1 goes from 1 to 14, R2 2-13, and so on. For a 1K shunt, try Bourns 4114R-001-102 or equivalent.

 

[Dokken]

thank you, made a resistor pack and shunt with dip sockets and it seems to work! formatted and verified a floppy.

 

[mrwebber35]

Good to know. I wanted to transfer a resistor pack from a Tandon 360k TM65 2L to another one with a totally different PCBA. I suppose they both can use the 4116R 1-332 Resistor Networks & Array in the DIP16 sockets they have. The only thing the same between the two same models... LOL.