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Heathkit H11A Repair

ThisPostContainsComputers

Experienced Member
Joined
Oct 31, 2015
Messages
102
Location
Minnesota
Hello,

Over the last few days, I have been trying to get the Heathkit H11A I have running again. I don't have any of the documentation and was not able to find any online, nor do I have any experience working with LSI-11 systems. I'm hoping to get it working to run something like RT-11 or LSI-UNIX/LSX (if that even still exists, or possible to run). The system came with the following cards:

-LSI-11 CPU Module with 4KW of memory
-M8029 Floppy Drive Controller
-M8017 Asynchronous Line Interface
-M8047 Multifunction Module
-32KW Memory Module (Unknown brand?)

The system is in pretty rough shape as of right now (Both RS232 cables running out of the M8017 and M8047 module look like they have been damaged, and the M8047 has a blown fuse), so I want to try bring it up to some sort of prompt with as little cards in it as possible. IIRC later PDP-11 systems like the LSI-11 have a serial monitor in ROM, so I would want to make booting that up my first priority. I was hoping that removing the M8029, M8017, and the 32KW modules, leaving only the CPU and Multifunction Modules in place would allow me get bring up the console, but I am unsure of if this would work. The CPU module and all of the cards on the right hand side (M8047, 32KW Module) are upside down, but I am assuming that this is normal.

Also, the system did not come with any RK02 disk drives, or the Heathkit equivalent, so I was wondering if there was a way to get the M8029 talking to either an emulator or a real 8 inch floppy drive. My understanding is that the RK02 disk drives used an internal interface board that the M8029 communicated with, but I am unsure.

Below are some pictures of the cards, and their placements in the system I have.

IMG_20190429_173045.jpgIMG_20190429_173054.jpgIMG_20190429_202909.jpgIMG_20190429_202916.jpgIMG_20190429_203030.jpgIMG_20190429_203036.jpgIMG_20190429_203052.jpgIMG_20190429_203119.jpgIMG_20190429_203126.jpgIMG_20190429_203255.jpgIMG_20190429_203307.jpg

Thank You
 

AK6DN

Veteran Member
Joined
Aug 23, 2010
Messages
979
Location
Silicon Valley USA
Also, the system did not come with any RK02 disk drives, or the Heathkit equivalent, so I was wondering if there was a way to get the M8029 talking to either an emulator or a real 8 inch floppy drive. My understanding is that the RK02 disk drives used an internal interface board that the M8029 communicated with, but I am unsure.

Yes, you have an RXV21 M8029 interface, and it does use a protocol interface that is specific to the RX01/2 drives from DEC. Not a standard 8" floppy interface.
There is a hardware/software emulator for the RX02 that is available that would work with this card.
See: http://www.vcfed.org/forum/entry.php?667-RX01-RX02-Drive-Emulator-using-Arduino-and-a-custom-shield for more info (I am the creator if it FWIW).

That being said it would appear that you have a fair amount of work to get to the point of getting a console command response.

Once you get there, you can configure your serial port card (M8017) to act as a TU58 serial interface and run the TU58EM (or TU58FS) serial emulator on a PC to act as a disk unit for your system. From that, you can run the XXDP diagnostic OS and diagnostics, and even run RT-11 from TU58 disk images.
You can get some info about using TU58EM here: https://www.ak6dn.com/PDP-11/TU58/ and here: https://github.com/AK6DN/tu58em (also mine).

Don
 

RichCini

Experienced Member
Joined
Aug 7, 2005
Messages
491
Location
Long Island, NY
I have a fair amount of information on the H11 on my site, including manuals. http://www.classiccmp.org/cini/heath_h11.htm

I agree with Don to get the easiest stuff working first -- the CPU and SLU so that you can get to the ODT prompt; IIRC the ODT does not need RAM to run. Then I would configure the second SLU for use with the TU58 and install the RAM. The Heath backplane is a serpentine backplane rather than the one used in the BA11 chassis. The H11 manual tells you how to install the cards.

Rich
 

DDS

Veteran Member
Joined
Sep 5, 2013
Messages
526
From the factory, the H-11 wasn't meant to connect to an RX02 at all. The Heath/Zenith H-11's 8" floppy option was the H-27. It would seem like yours was "upgraded" by a previous owner who swapped out some of the Heath/Zenith cards and the 8" disk system with their DEC equivalents. My understanding is that substitutions like that were quite common. For one thing, the Heathkit H11-5 Serial I/O card has only one port, where the DEC equivalent has four. So using the Heathkit cards to expand beyond one serial port would eat up spare slots more rapidly.

My "two switch" H-11 is not where I can put hands or eyeballs on it at the moment, but I was able to grab the box that the Heathkit card set came in, including the original anti-static bags. Each bag has a label on it that reads in part "Use in 18 bit backplanes only, (solder side up)".

Further, each has some info on the card and a drawing as to where the card is to be placed in the backplane as follows:

M7270 -- LSI-11/03 CPU with Floating Point option. Install this board in the first slot. (The drawing show the first slot to be the upper right hand corner.)
M8044-DB -- 32K Words (64Kbytes) Ram. Install this board in the second slot. (The drawing shows the second slot to be in the upper left hand corner.)
H27 Floppy I/O Card. Install this board in the third slot. (The drawing shows third slot to be the second slot down on the right hand side.)
H11 Serial I/O (Console) -- Install this board in the fourth slot. (The drawing shows this board to be the second slot down on the left hand side.)
 

DDS

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Joined
Sep 5, 2013
Messages
526
I see that some H-11's came with a quad with CPU card, the M7264, that took up the entire top row of slots.
 

RichCini

Experienced Member
Joined
Aug 7, 2005
Messages
491
Location
Long Island, NY
The connectors are still available on Mouser.com and I'm sure Digi-Key as well. IIRC from the bulkhead its 3 wires and a jumper between two of the pins. The SLU to connector is more labor intensive.
 

ThisPostContainsComputers

Experienced Member
Joined
Oct 31, 2015
Messages
102
Location
Minnesota
After doing to reading on the sources, I have decided that I am going to start by trying to get a ODT prompt using the CPU module and the M8017AA modules. The M8017AA module has a number of wire wrapped jumpers on it for what I am assuming to be configuration. I found a number of manuals that show what the blocks mean on the M8017 module models, but the layouts are different for my module so I don't know how mine is configured. I understand that my module needs to be configured to address 017756 to act as a console, among other things. I also soldered a DB9 DCE plug onto the M8017AA cable using the instructions found here, replacing the previously broken connector.

Also, looking at the jumpers on the CPU board, it looks like they can be set so the system powers on into Mode 1, which is the ODT prompt. If I understand correctly, the system can also be brought into the ODT prompt by hitting the HALT switch on the front, so I wouldn't need to rework any of the jumpers.

I am also still a little confused on how the boards go into the Heathkit backplane. None of the reading so far has told me in what direction the cards are suppose to go into. The CPU boards, along with all the boards on the right hand side came with the solder side facing up, but besides the in the assembly manual for the CPU card, I have not seen anything else that relates to the direction of the boards.

Below are some pictures of my M8017AA

IMG_20190430_190749.jpgIMG_20190430_190758.jpgIMG_20190430_190802.jpgIMG_20190430_190830.jpgIMG_20190430_191301.jpgIMG_20190430_191305_1.jpgIMG_20190430_191310_1.jpgIMG_20190430_191317.jpg

Thank you
 

PG31

Experienced Member
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May 31, 2011
Messages
483
Location
Sefton, Meresyside, England
The M8047 MXV11-AA in your photographs has memory and two serial line units. This may be configured for console, check the wire links. The second SLU can be connected to your PC to run one of the TU58 emulators. It also has a line time clock. You can put just this and the CPU card in and should be able to get ODT on the console port.

Check out Willsworks http://www.willsworks.net/pdp-11/boards#MXV11A
 

DDS

Veteran Member
Joined
Sep 5, 2013
Messages
526
After doing to reading on the sources, I have decided that I am going to start by trying to get a ODT prompt using the CPU module and the M8017AA modules. The M8017AA module has a number of wire wrapped jumpers on it for what I am assuming to be configuration. I found a number of manuals that show what the blocks mean on the M8017 module models, but the layouts are different for my module so I don't know how mine is configured. I understand that my module needs to be configured to address 017756 to act as a console, among other things. I also soldered a DB9 DCE plug onto the M8017AA cable using the instructions found here, replacing the previously broken connector.

Also, looking at the jumpers on the CPU board, it looks like they can be set so the system powers on into Mode 1, which is the ODT prompt. If I understand correctly, the system can also be brought into the ODT prompt by hitting the HALT switch on the front, so I wouldn't need to rework any of the jumpers.

I am also still a little confused on how the boards go into the Heathkit backplane. None of the reading so far has told me in what direction the cards are suppose to go into. The CPU boards, along with all the boards on the right hand side came with the solder side facing up, but besides the in the assembly manual for the CPU card, I have not seen anything else that relates to the direction of the boards.

Below are some pictures of my M8017AA

View attachment 52874View attachment 52875View attachment 52876View attachment 52877View attachment 52878View attachment 52879View attachment 52880View attachment 52881

Thank you

Solder side up!

Page 2-16 in the "Operation Manual" states "Modules must be installed in the backplane with the components facing row 4 as shown in Pictorial 2-10."

Row 4 is the bottom most row of connectors. Therefore the boards go in solder side up.

In addition, look at Pictorial 2-11. Notice that the boards and connectors are keyed. Assuming the connectors weren't soldered in upside down, a board inserted incorrectly will not fully seat into the connector. If your board won't seat all the way, before you force it in, investigate what's blocking it. Per the note on the top of page 2-17:

"CAUTION: The H11 modules and the backplane assembly mounting blocks may be damaged if the modules are plugged in backward."
 
Last edited:

ThisPostContainsComputers

Experienced Member
Joined
Oct 31, 2015
Messages
102
Location
Minnesota
The M8047 MXV11-AA in your photographs has memory and two serial line units. This may be configured for console, check the wire links. The second SLU can be connected to your PC to run one of the TU58 emulators. It also has a line time clock. You can put just this and the CPU card in and should be able to get ODT on the console port.

Check out Willsworks http://www.willsworks.net/pdp-11/boards#MXV11A

I was originally going to try it with the M8047, but it needs a little bit of work done on it. Both the onboard fuse and the fuse the original owner bodged into it have been blown for undisclosed reasons.
 

ThisPostContainsComputers

Experienced Member
Joined
Oct 31, 2015
Messages
102
Location
Minnesota
Alright, so I just got finished checking out the power supply, and everything seems fine.

IMG_20190504_214819.jpg

When I tried to take the fuse out and check it, the entire fuse holder crumbled. I was able to get a replacement in there at is more or less that same. Checking voltages, it looks like 5V+, 12V+, and 5B+ all seem to work fine. 12V- does not have any voltage on it, but looking on the power supply schematics, it seems like that 12V- was never connected up in the first place.

I have configured my M8017-AA to the console address and vectors. The CPU board has a number of jumpers on it, but I haven't gone and seen how it is configured yet. Later tonight I am planning insert the CPU board and the M8017-AA directly under it to see if I can get an ODT prompt on halt.
 

ThisPostContainsComputers

Experienced Member
Joined
Oct 31, 2015
Messages
102
Location
Minnesota
A small continuation of yesterdays post. After checking all of the voltages and adjusting the pots, I put the CPU card in to see if I could get any activity. The first thing I noticed is that the RUN/HALT light does not respond to the position of the respective switch, and neither does the LTC switch. I jumpered the M7264 to Mode 1 so it will execute the ODT microcode on startup, but still no dice. I checked the switch outputs onto the backplane, and they seem to be good, so I think the issue is somewhere on the CPU board itself. I then inserted the M8017-AA board into the slot directly under the CPU board on the right hand side. Turned it on and still nothing on the front panel or out of the serial port.

View attachment 53044

I'm not exactly sure where to go from here. I can't seem to find any schematics of the M7264 board anywhere, and I don't really want to risk damaging the boards in my 11/73 so I don't have much to test with.
 
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