Heathkit H11A - Austin, TX

[Bruce Tomlin]

I found this boat anchor years ago at a thrift store and got it because I knew it didn't deserve to be junked. But I never powered it up, or even had the guts to try until today. I just now tried it and got some kind of monitor program at 9600-8N1, but I can't even figure out how to dump memory so far.

It came with a stack of dusty manuals (RT-11, BASIC, Fortran, etc., all of which I have scanned) that indicated it might once have had a floppy disk interface, but it didn't have one when I found it. The manuals are all photocopies, though most are in Heathkit binders.

It has two serial ports on the back with crazy 6x4 male molex connectors, and one even has a short DB-25 adaptor cable on it. The cards inside are:

* M7270 CPU
* two H-11-5 serial I/O
* two H-11-1 4kx16 memory
* WHA-11-16 16Kx16 memory
(that's 48K bytes, all DRAM)

I'd like to sell it for a reasonable offer, but I really don't want to ship it. It's big, it's heavy, the insides are not very well secured, and it's heavy. I'll happily give you the manuals, or offer them to anyone else who wants to pick them up before trashing the paper.

So you need to be in or near Austin, TX, willing to drive there, or have a friend who can pick it up for you.

 

[Bruce Tomlin]

I've had a couple of inquiries about it, but I needed to give a bit of a status update.

I learned enough on how to use the monitor that I was able to tell that a few of the 4116 DRAMs were bad (stuck 1), and was in the process of swapping them around, applying power, starting system, etc., and then the power supply blew its DC rail fuse. I got a couple of 20 amp "slow-blo" fuses at Fry's, but one blew right away, and after disconnecting the card cage from the power, it still blew a fuse. I haven't had time since then to poke around and see if there was someting obviously shorted.

EDIT: I don't think that power supply will be fixable without hardware documentation and a lot of work, but at least it looks like the H11 pre-regulates the power for the cage. This is unlike S-100 and SS-50, which leave regulation to each individual board. I don't see anything on the boards that looks like a power regulator. It may be easier to replace it with a switching power supply, and there's plenty of room for one.

 

[Lou - N2MIY]

Bruce,

It can all certainly be fixed. I restored an H11, and there is another fellow that I met here (Larry) that was a Heathkit bench technician and is big H11 enthusiast. I encourage whoever you sell it to to take their time and repair the power supply that came with the unit. It is fairly straigthforward and well documented in the manuals that you have.

Although you don't have the H27 floppy system, all is not lost. Larry and I have both put "modern" dec RQDX3 controllers in our H11s and now have MFM and 5.25" floppy drives attached.

Lou

 

[Bruce Tomlin]

I don't have any of the hardware manuals with it. Just some sheets about the 16KW RAM card with the block diagram and X-ray view.