I've just uploaded some German 8870 Micro 7 documentation.
Looks like my old scanner couldn't handle the workload and died mid-document. Anyway, a replacement scanner is now up and running and I'm back to scanning documents whilst watching TV.
I've just uploaded some German 8870 Micro 7 documentation.
This morning I reorganised the entire site. A lot of the pages I'd previously written weren't actually accessible or were difficult to find. Ohh come on, it was my first attempt at a website.
Anyway, I went though everything and made sure that all the pages are now accessible... I think.
Now, all of the information on this site has either been extracted from the scraps of documentation that I've got, from my failing memory or from information that readers have supplied. If you spot anything that isn't clear or just plain wrong, PLEASE let me know so I can correct it. None of us are getting any younger and if this information isn't recorded soon it may be lost forever.
Likewise, if you've been squirreling documentation under your bed please let me know. I'll happily take it off your hands and give it a good home, or scan it and return it to you if that's your wish. Whatever I get hold of will end up on this site... eventually.
Happy new year to everybody.
Once again, I need to apologise for neglecting the site. I just don't seem to have much time these days. Anyway, I've spent some time over the festive season scanning in manuals. It's amazing how simple it is to do whilst watching TV. I've added a BASIC manual (original English version) and a BASIC program tuning manual, again in English. I never knew this second manual existed. It's an interesting if not short read.
The next manual I will scan is the Micro 7 one I have.
Firstly my apologies for leaving this site alone for so long. I've been so busy at work and with other projects that my on-going 8870 adventures have been a long way down the list.
I'm desperate to get more of the information I have accumulated over time onto this site but it's a slow job.
Now, a HUGE thank you to Vaxman and his lovely wife.
I had an Email out of the blue from Vaxman (followers of my blog will know that Vaxman and I have corresponded many times and he has been able to supply me with 8870 related documentation in the past), saying he had found an 8870 / Micro 7. I was very excited for him. The Micro 7 is a lovely machine and it's nice and compact. We exchanged several Emails on how he could attempt to get the machine working, but unfortunately it became clear there was something very wrong. He also didn't really have the time to invest fiddling around with this as he has many other projects on the go, and this was just a distraction to him.
I also secretly think his wife wanted this piece of junk out the way :)
Anyway, the Micro 7 is now sitting on my workbench and after a few nail biting hours, I eventually got it working... mostly.
I will write more about it soon and include pictures. I've also got some very useful documentation to go with this machine.
So, once again, a huge thank you to Vaxman and to his wife for packing it up so well and arranging it to be shipped to me in the UK. Oh, and to his cat for supervising and making sure the job was done properly.
The peripheral tier on an M25 can accommodate three devices. Slot 1 (left) is usually the SMC backup tape drive, slot 2 (middle) is for use by the disk drive, but the right-hand slot 3 seems to be multi-functional. It's usually empty, or has a floppy (8" or 5 1/4") installed. However, looking at the backplane in detail and inspecting the backplanes from the three machines leads me to think you can add a second disk drive. There are a few tell-tale signs to corroborate this too.
If you look in the above picture inside the red box, there is a connector. On one backplane I have, there is a "bridging board" plugged in here.
All this "bridging board" does, is connect all the pins on the left, to their counterpart pins on the right. This has the affect of connecting the right hand slot connector in parallel with the middle slot connector.
Also, the data sheet for the disk drive states that the highest drive number should have a termination resistor pack installed. This MUST be removed from the other drives.
The above picture shows the inside of one of my M25 disk drive enclosures. You can see the configuration switch highlighted centre-left. Below that is the resistor termination pack. But look in the top right corner of the picture - there is a blue resistor pack. This isn't connected to anything and the resistance is the same as the yellow pack. This is actually a storage socket to hold the resistor pack when it's removed from the disk drive. No idea how this drive ended up with two packs (probably had the disk drive exchanged at some point). Both my other enclosures have this blue pack missing. So it looks like you are supposed to remove the resistor pack if needed, and store it in the empty socket.
I've still not been able to get a second drive to work. CONFPROG seems to be configured correctly, but when I try and mount the second drive - "INSTALL 0.2" I get an error "DISC ERROR READING INDEX" and the system just hangs. I know the second drive works as it's just been formatted and had an operating system installed and will happily boot a system if it's set as drive 0.
I'm missing something... but I don't yet know what... yet.
I've previously stated that I've obtained three M25s over the last few years and number 3 pictured above is in a really sorry state. I've no idea what happened to it but it looks like it's either been dropped or a lorry hit it. You can see the crack down the top of the left-hand side. Also, both the top and bottom tier cages are bent. Amazingly the backplanes are intact and all the plates and disk drive were still working when tested in my main machine.
Anyway, this thing has been taking up valuable space so I thought it worth removing anything of value and scrapping the rest. Absolutely everything electrical has been removed including the fans and plastic plate-slot blanks. The outer shell will go to the scrap-metal people.
However, I have a second chassis that's in a perfectly serviceable state once it's been cleaned, so I've decided to construct a second machine.
I'll be taking pictures thought it's rebuilt process, but not during it's tear-down. This second chassis was absolutely filthy and mice had been living in it and I didn't fancy having to keep washing my hands to hold my camera just to take a couple of pictures. You will be able to view the re-build pictures in reverse if you want to see how to tear-down a system :)
As for what I'm going to do with it, it will replace my current chassis as I cut a couple of corners when cleaning it originally, and there are a couple of jobs that I wish I'd done.
Once this second chassis is up and running, I'll gut the first one for all the useful bits and either drop it on Ebay as just an empty chassis (at least it's clean), or off to the scrap metal dealer. Nobody except me seems to what this stuff anyway.
After pulling my hair out as to why I couldn't get a second port working, I posted the question to the Nixdorf group on Linked-In.
Quick as a flash Malone came back with some useful technical information about cable part numbers to use, which whilst completely different from mine I was still pretty sure that my wiring was correct, and also made a comment that the second ALME channel on the first ALME is reserved for the remote support connection.
I'm sure in the past I've used this channel for a normal VDU connection, however, it was worth a try.
He was dead right. So, another useful lesson learned.
Thanks Malone for the valuable info.
I wrote my first decent business BASIC program last night. Amazed at how much I'd forgotten but it slowly came back - working in Visual Basic for 20 years hasn't helped.
I wanted a routine to search through a specified list of files and look for pieces of text.
The LIBR list file contains all the *C (contiguous) files that are likely to contain German text that's used by the operating system. For example, I wanted to find where the machines original owner name was stored - In MESSAGES, record 147 for the record.
It was a fun exercise and a real blast of nostalgia. I really need to get a second terminal up and running as just having the one is a real handicap.
I've actually managed to repair a second terminal. Next I need to assemble a suitable connecting cable for it.
As an update to this post, I've been messing around all day trying to get the second DAP4 to work over an IHSS connection for I'm having problems for some reason.
I know the DAP4 works ok, because if I put a V24 card in it and connected to the master port channel on the ALME it works fine. I've tried a different ALME and it's not that.
So it's either a problem with the interface cards (and I've tried several) or the cabling but if it is I'll be dammed if I can see the problem. I'll have another go tomorrow if I get the chance.
I've been doing a lot of site updates over the last few days and I'm not finished yet. I've added a pile of stuff to the hardware page, especially under the tape and plates headings including articles on how to service SMC drives and attempt to repair a damaged tape. There are also lots of high resolution photographs of all the plates I have plus other technical information.
Still lots more to do so keep checking back.
The nice man from UPS just delivered my replacement SMC drive wheels that Tandberg so graciously gave me.
Looks like I know what I'll be doing over the weekend now.
Major spare parts testing was completed last night.
I'm suspicious of the 1830 hardware arithmetic unit but that could be because I'm not 100% sure how to configure it in NIROS. I know you have to deactivate $DEC14H then activate a $DEC18H driver in it's place, but I've got a niggling feeling there is something else that needs to be done. It could be one or more DISCUBS but I just can't remember.
Whilst I have an 8" FD and a box of new discs as it happens, I think that either I've got the wrong controller (apparently it's for a 5" FD not 8"), or the controller / FD is faulty as the system becomes unstable when it's installed, but I need to experiment more with this.
I've not tested the PLC2 I have because to be honest I don't need it and it's certainly not a requirement for a minimum running system. Also, if memory serves you need to have the BCU (Batch Communication Utilities) software (or the MAFI), and I don't.
The only failed parts I have that are required; excluding the 2 x SMC drives but see a previous blog about those, is a 3109-02 PSU. I've got two working ones but the 3rd is playing up.
I suspect it's a leaky capacitor. Electrolytic capacitors don't age well and really don't like high temperatures, and a high proportion of failures in any SMPS (switch mode power supply) can usually be attributed to leaky or failed electrolytic capacitors. There are 16 high-value capacitors in this PSU and a job on the list is to get replacements then swamp them all out. It will either work or it won't... it's one of those types of repairs.
The 8870 modules are unfortunately packed with tantalum capacitors which, IMHO are the spawn of the devil as when they fail they nearly always go short circuit usually with pyrotechnic results, along with a smell you wouldn't believe. This PSU contains several so I'll probably swap them out for safety, if replacing the main electrolytic capacitors fixes the problem; pointless otherwise.
So, all in all and except for DAP4 replacement parts, I'm in pretty good shape for now.
I'm a software developer, an engineer and I love vintage computers, but the 8870 has a very special place in my heart.