What are 7A16P used in / good for?


Jeff Kruth
 

In going thru the local stash, I found a few 7A16P vertical amps. They look nice, IIRC they use a 6800 uP.What are they used in and are they any good for any application? Looks like a 7A26 would be easier to use.Thanks, Jeff Kruth        !


Harvey White
 

They were used mostly in the 7912 digitizer, I think.  They will work in some of the 7000 mainframes, but there's a jumper you need to change to patch 5 volts into the processor.  There are IEEE488 connections on some of the unused pins in the mainframe to remote control them, IIRC.

if you rewire the mainframe a bit, you might be able to talk to them, but you'll have to duplicate a 488 bus interface to the plugins.  May be as simple as running wires.  I haven't looked to see if the 488 interface per plugin is standard.

Harvey

On 9/20/2021 1:42 PM, Jeff Kruth via groups.io wrote:
In going thru the local stash, I found a few 7A16P vertical amps. They look nice, IIRC they use a 6800 uP.What are they used in and are they any good for any application? Looks like a 7A26 would be easier to use.Thanks, Jeff Kruth        !





Dave Casey
 

They were used in the 7612 and 7912, though the 7A29P was probably better
suited to the bandwidth of the 7912.
They could also be used in the 7854 with the addition of the 021-0374-00
GPIB decoder.
Beyond that, they can be used manually in anything that can support the
power requirements (I think the 7854 may be the only non-GPIB mainframe
that was officially powerful enough).

Dave Casey

On Mon, Sep 20, 2021 at 1:05 PM Harvey White <madyn@dragonworks.info> wrote:

They were used mostly in the 7912 digitizer, I think. They will work in
some of the 7000 mainframes, but there's a jumper you need to change to
patch 5 volts into the processor. There are IEEE488 connections on some
of the unused pins in the mainframe to remote control them, IIRC.

if you rewire the mainframe a bit, you might be able to talk to them,
but you'll have to duplicate a 488 bus interface to the plugins. May be
as simple as running wires. I haven't looked to see if the 488
interface per plugin is standard.

Harvey


On 9/20/2021 1:42 PM, Jeff Kruth via groups.io wrote:
In going thru the local stash, I found a few 7A16P vertical amps. They
look nice, IIRC they use a 6800 uP.What are they used in and are they any
good for any application? Looks like a 7A26 would be easier to use.Thanks,
Jeff Kruth !










Ed Breya
 

I had a couple 7A16Ps a while back. As noted, they were for the 7612 and 7912. They can function in a 7K mainframe, but may mess up the readout if not jumpered or modified properly (I think there may be provision for this, or maybe it takes extensive circuit mods). As I recall, the reason is that the readout lines were used in a multiplexing scheme to share them with inter-plug-in GPIB lines. I experimented with them a few years ago, and decided they weren't worth using as-is, in 7K. I don't think I ever managed to get them to fully work, and not screw up the readout, reliably. But, they are cool, and the programmable attenuators are nice. I think I still have one intact, and the other I took apart to build a custom plug-in.

So, if you build custom plug-ins, they are nice pieces to re-use, but that's about it.

Ed


Roger Evans
 

The manual says that the 7A16P is intended for programable 7000 series mainframes but if you search back through earlier posts here several people have them working in other models, I have used mine in a 7904 and a 7934 and other references are to a 7704A and maybe others as well. I did get mine to work in a 7603 but only with a lot of 'bodging' in order to allow the low supply voltage check to drop its threshold to around 4.8V, not a reliable set up! In most cases you need to add a jumper to P1622 at the rear of the processor board, it is marked in the component layout but I have never found it on the schematic. It connects the '5.1V' digital supply to the +5Vlights on the 7000 backplane and should allow sufficient current for a single 7A16P. I have also got a 7B90P to work in the 7934 but it draws a lot of 5V current and does not work with some combinations of plugins.

Nice features of the 7A16P include the switchable 1M / 50R input impedance and the A/B input switching. My 7A16P shows less high frequency noise than a 7A26 on the high impedance input, this may just be individual samples, although I do have two 7A16Ps and two 7A26s, or it could be better screening on the later design. I have only ever had the readout problems that Ed refers to when the 5V supplies of the mainframe are overloaded.

If you have one, enjoy it!

Regards,

Roger