HP 264x tape drive write current for Athana/DC2000 tapes (was HP 5420)


 

Thanks, very helpful. I see, it's on the main control board, not the PCB of the tape drive itself. This circuit below, R42 is the resistance in the emitter of Q16. If I follow this right, When Q15 is conducting, due to the Zener CR4, it should bring the base of emitter follower Q16 to ~4V, and the emitter of Q16 to ~4.5V. Then the resistor R42 sees 7.5V across it. So that would provide a 10 mA current source, not dependent on the head impedance. To increase it by 20% I would have to make the resistor 625 Ohms. Does this sound reasonable to you?
What's the funny business with all the diodes between the Collector and Emitter of Q16? Clamping the signal that goes to Q17's base both ways? What's the RIP signal?
Marc
 




 

Hi Marc,

 

I haven’t looked in the schematics, just looked it up 😉

But I think your conclusion is the right one.

I quick look, I think the zeners are for protection of the 74145 (Vce max is 15V).

The RIP signals seems to be some kind of feedback of the write signal.

 

-Rik

 

 

 

Van: VintHPcom@groups.io [mailto:VintHPcom@groups.io] Namens CuriousMarc
Verzonden: maandag 13 maart 2017 6:26
Aan: VintHPcom@groups.io
Onderwerp: Re: [VintHPcom] HP 264x tape drive write current for Athana/DC2000 tapes (was HP 5420)

 

Thanks, very helpful. I see, it's on the main control board, not the PCB of the tape drive itself. This circuit below, R42 is the resistance in the emitter of Q16. If I follow this right, When Q15 is conducting, due to the Zener CR4, it should bring the base of emitter follower Q16 to ~4V, and the emitter of Q16 to ~4.5V. Then the resistor R42 sees 7.5V across it. So that would provide a 10 mA current source, not dependent on the head impedance. To increase it by 20% I would have to make the resistor 625 Ohms. Does this sound reasonable to you?
What's the funny business with all the diodes between the Collector and Emitter of Q16? Clamping the signal that goes to Q17's base both ways? What's the RIP signal?
Marc
 


 

Another trick question for HP264x afficionados. This one is specific to the HP 2647. The HP 2647A came with tapes but no flex disc, and the HP 2647F came with the flex disc but no tapes. Does one know if it is possible to add 2 tapes to an HP 2647F? So it ends up with both tapes and disc, and can copy one to the other? I am sure I can add the tape hardware (there are at least two slots available for the cards and space for the tape drives), but does anyone know:

- Would I need to add a tape ROM firmware support top the F? Or is it included in the 2647F base set, inherited from the A?

- Would the firmware allow to copy tape to disc and vice versa?

If that were possible, that would be quite convenient to archive 264x tapes to 5.25" disc, then make dump images of that on a PC.

Marc


Jack Rubin
 

I don’t know the answer but after visiting the treasure trove of 264x service manuals on bitsavers, I’ve got to believe the information you need is in there somewhere. I’m still digesting the cartridge tape manual (13255-91032) that Rik pointed to. I wish HP had continued that level of detail with their other desktop machines.

 

Jack

 

From: VintHPcom@groups.io [mailto:VintHPcom@groups.io] On Behalf Of CuriousMarc
Sent: Monday, March 13, 2017 10:12 PM
To: VintHPcom@groups.io
Subject: Re: [VintHPcom] HP 264x tape drive write current for Athana/DC2000 tapes (was HP 5420)

 

Another trick question for HP264x afficionados. This one is specific to the HP 2647. The HP 2647A came with tapes but no flex disc, and the HP 2647F came with the flex disc but no tapes. Does one know if it is possible to add 2 tapes to an HP 2647F? So it ends up with both tapes and disc, and can copy one to the other? I am sure I can add the tape hardware (there are at least two slots available for the cards and space for the tape drives), but does anyone know:

- Would I need to add a tape ROM firmware support top the F? Or is it included in the 2647F base set, inherited from the A?

- Would the firmware allow to copy tape to disc and vice versa?

If that were possible, that would be quite convenient to archive 264x tapes to 5.25" disc, then make dump images of that on a PC.

Marc


 

Yes I am pretty sure it's somewhere in there (500 pages of service manual!). I was just hoping someone already knew and would save me the digging ;-) . I'll report when I find out.

Marc