@ALL: A team effort indeed!

@Speedy: Replacing Q1 was *the* key part in reviving this power supply.
Decades ago in our laser lab we had these socketed for easy swappage.

I have on order (and due in mid-week) Q1,Q2, and Q8. I believe the order
processor said these (Q1,Q2) are original Siliconix parts and appropriately
period-dated around 1980 or 1981. NOS basically.

Q8, the main voltage regulator, seems to be functioning within spec. But
considering it was pushing into a near short circuit and getting hot I'm going
to replace it for reliability reasons. Though these are self limiting and seem
to handle overloads quite gracefully.

Well, the voltage regulator I ordered is NTE1924 (SG340K-24 equivalent).

I had to replace a 74LS04 (U11) because something was wrong with the
output of pin 2. It wasn't bang-bang operation or something, and the red IN-USE
led was flickering around 10-15Hz. This has something to do with the IRQ line.

Don't worry, I plan on checking the oscillator out in detail like you asked in
msg #295. And considering I had to do a repair to the logic side I think I'm
going to check all the data/address/control lines to ensure they are going
hi-lo with definitive action. We were always swapping the 74LS245 tri-state
transceivers in a certain box.

So far, with IRF122 (VN64GA equivalents) temporarily patched in, the chassis
has been hosting 3 cards for 3 days now.

I didn't see anything unusual anywhere else so far. And nothing's smoking, so
it must be good!

Once I've got Steven's box burned-in and rolling with the new parts I'll be
more than happy to begin in-depth scope measurements.

One step at a time.

Possibly no updates from me till Thursday. Some parts arrived yesterday, saturday. FED EX tracking says next package to be delivered on wednesday.

Then I can put them in, burn-in test over the weekend, and ship it out to you the week after.

That's the plan.

Hello Macnoyd,
just sent you message demanding for email because i will send message with attachments
( gerberfiles for IFcard )....

Hello to all AF members,
while creating the gerberfiles for macnoyd, i reviewed some of the stuff from the mainboard
and added the components soldered at the solderingside to the MOS FET´s to the
general plan with the detected traces ( the one with red and blue layer in posting #122 )
and i also added that components to the circuitplan ( posting #161 ).
i also will update the MCEB.doc within next days with that updated parts....
besides i will also create in my own website a page dedicated to the MCEB with
several pictures and documentation and several explenations so that page
will contain the information in compacted structure....
i will publish the link to that page here, when it is completed....
sincerely speedyG

Hello to all AF-members,
as announced i started to create a kind of "home" for the mountain computer expansion box.
Allthough only few pages have been made yet, i target to issue a kind of "compacted" infopages
that permits owners of the box to view the information "cleaned" from those parts, that have been
first issued and then later updated by following informations. This thread has become in the meantime
quite complex with more than 300 postings at the moment and expecting at the end to contain more that
350 postings.

Of course i will continue here to publish the results
from our efforts and further steps in the running tasks too.

But for normal owner of the box, who wants to get fast access to information to solve task of repair
it turns out to get rather difficult collecting the infos here and filtering out what has been updated in the meantime and what is still valid the way it was published....

Of course i also mentioned the copyrights to this site and the members who provided pictures to me.
At the moment i only have used pictures that i recieved ftom other sources, but next step will be to collect permission from gsmcten, Keatah and macnoyd to use selected pictures from the huge pile i have recieved from this members for use in further pages, to explain details of the units.

@ gsmcten,
@ Keatah,
and to macnoyd,
i here kindly ask for such a permission to use several selected pictures for that pages.
please also visit that pages and checkout if you feel O.K. with text and copyright notes.
@ eeun and
@ Tom Owad,
of course i have mentioned this thread and set a link to the basic entrypage of the Applefritter.com
Without this platform this task could have never been executed.

the entrypage of that pages is:
http://www.harrowalsh.de/APPLEBOX/MCEB/appleboxMCEB01.htm

any kind of feedback upon that pages is welcome....
sincerely speedyG

Speedy,

Of course you have my permission.
I wouldn't have it any other way.
The site looks great!
You and Keatah deserve almost all of the credit.
I admit, I'm just a picture guy.
But I also admit that quite a few hours went into this whole thing.
I think that this is one of the most definitive articles on the MEC.
What it looks like, the schematics, how it is supposed to operate, the problems encountered,and the troubleshooting, repair, and testing processes.
It could just about be made into a manual all by itself!

Yea Team! :)

Hello gsmcten,

well if you follow up those pages, you will find that i allready started explaining the functions in detail at page 3 and that will be continued in the next days... reading page 3 will provide eash owner with deeper understanding how the parts work together....
and finally when thread is completed and when i have finished this pages i am currently working on -
well that will result to a downloadable PDF-file similar to the MCEB.Doc i have made but updeted and corrected and rather far expanded....

thanks very much for granting to me your permission.... i have several pictures in mind taken by you that i want to use in the documentation ... i will mark you up as source...
sincerely speedyG

nearly ... in Germany we have "summertime" ... so it´s 02:00 and it´s just the time to turn around and start listening to my pillow.....zzzzzz...
off duty...
sincerely speedyG

UPDATE: after nice bunch of sleep i´m adding stuff again to that pages expanding more and more the
"deeper insight" to the functions of the Expansionbox.

@macnoyd:
i urgently recommend that you follow up that pages before touching the box for repair....

http://www.harrowalsh.de/APPLEBOX/MCEB/appleboxMCEB03.htm

it might save you a lot of pain !

sincerely speedyG

@macnoyd:
i urgently recommend that you follow up that pages before touching the box for repair....
http://www.harrowalsh.de/APPLEBOX/MCEB/appleboxMCEB03.htm
it might save you a lot of pain !
sincerely speedyG

Yes, surely I will check this out -and carefully.
Also, regarding anything I post on this site, you have full access to do whatever you want with any photos or info that has originated from me, as I do this to share with the community at large and seek nothing in return. Strictly a hobby for me and my "payback" is the enjoyment I get from you and others who contribute to this Forum.
And as always, my thanks.

I have yet to post high resolution photos of my MCEB, but they're coming soon.

@gsmcten,

Yes, indeed I did!
So this means I have you to blame for paying the higher price? (kidding!)

You are correct regarding the accessories. It came with literally nothing. No book, card, etc.
It had 1 tall capacitor rattling around inside (it broke off) as well as the matching capacitor in bubble wrap.

Overall, the unit was in pretty good shape. Nothing burned on the PCB and the 2 capacitors basically broke loose from the base. No damage to the traces.
The dent in the cabinet was fairly mild and flattened out nicely between 2 pieces of flat plate aluminum and a C-clamp.

I've already installed (replaced) the 2 capacitors with 2 having the same foot print but about 1/3rd the height. As I told speedyG, I'm relatively certain Mountain Computer would have used a shorter capacitor if they had that choice.

I'll be firing up the unit to check voltages (if I'm lucky) this weekend, as I found a power supply transformer that closely matches the original.

The interface Card that goes into the Apple, that's another story.
I have no issue making up the 16-pin and 50-pin ribbon cables, but it looks like I'm stuck either prototyping a card or making a several hundred dollar investment on prototype PCB's.
I've studied the card and schematics, and I might give the prototype a shot. I used to do that type of work back in my younger years and still feel comfortable doing it.

I do have a couple questions regarding the card and cable...
1. How long is the 50-pin ribbon cable?
2. Are those 83R100Ohm resistor packs simply 4 separate 100 ohm resistors in a SIP? Looks that way to me...

Here's a long-shot... If anyone has a spare interface card to a Mountain Computer Expansion Chassis, please let me know!

Hello gsmcten and macnoyd,

well gsmcten, macnoyd answered partially to you... besides i had contacted macnoyd allready
few days after the bid... and we had quite a bit communication besides the thread....

the 50 pin flatribboncable may be up to 80 or 90 centimeters long. here just a hint:
such cables have been used for years in SCSI systems..... and they match pretty well the longest ones
permitted in such systems ( which have also been limited to the same length ).....

and the 16 pin flat is exactly the same like used at the old 16kB language cards ! same length and
same plugs ! - so if you have an old languagecard at the shelf just check if it also has the cable along with it....
or if one is sold at flea-bay you might purchase it with the card as spare and the cable for use.

But pay attention: the pins on that kind of plugs easily break off often.... i allways stuck the plugs
of such cables in styroporfoam and fixed the foam with tape to the plug, to protect the plug against damage, if it was not in use....

and the best finally: i´m quite sure i have such both cables somewhere around in my dungeon.... so if i start searching
for them ( while not frightening kids - har har har ;-)! ) i´m sure i´ll find them between the remaining bones of former meals... har har har LOL

as explained also i have in the meantime continued the explenation of the functions within the MCEB, so troubleshooting
will turn to easy session.... till uprising weekend also similar analysis will be completed on the interface card to....and published and i guess macnoyd is reading that page every few days and discovering that it gets prolangated and expanded day by day with more fascinating details .....

this is all happening, while i´m still waiting for my CFFA1 to arrive... ( ordered nearly 7 weeks ago and shipped by list nealy 6 weeks ago - but probably beeing delayed at customs... probably they do research, if it´s not kind of rocket science.... ? ):-(

and just by the way macnoyd has recieved the gerberfiles, that would permit him to order a very new interace card from any PCB manufacturer in his area as prototyp board.... at the moment we´re stuck at one point...

unless the CFFA1 has not arrived i can´t complete the test on the Apple 1 expansioncards i developed... but i do want to ensure clean smooth operation with such card also inserted in any kind of replica ( i have completed in the meantime all 3 availiable ones - the MIMEO, the newton NTI and the Newton1 )... so i´m still waiting for the arrival of the card urgently... upon arrival i´ll immeditly solve the remaing test´s and then i´ll immediatly start the ordering process.... the very moment i know haw many cards will be ordered i will also immediatly contact the PCB manufacturer and launch the order... that´s the very moment i also will ask the manufacturer about the additional price if a PCB for the interfacecard is added and i will pass over that price to macnoyd and offer him to "jump on the train" and add the order of his missing interfacecard to the bunch resulting from the expansioncard orders....

so by that he gets chance to probably recieve within August a PCB for the interfacecard together with the ordered cards from the Apple 1 expansioncards in one shipping....

here within the pages i have published the links are also somewhere published for the download of both versions of the manuals of the mountain expansion box, the version from Keatah and the version from gsmcten....
both are downloadable from my pages in PDF format....

and when i have completed this new pages where i am currently working at .... there will be also a new revised, corrected, updated and expanded version of the famous MCEB.doc availiable in new format as PDF file for download from my site too..

having that document and both manuals downloaded and printed there will not be anything more required to know everything about the MCEB at unleashed / unrevealed status.... the pages i am working at the moment will have also tips and routines for systematic search and repair and they will also contain similar to the famous series from former days from SAMs also the osciliscope pictures added which i will get within the next days from Keatah !

That will be the point to make one "big roundup" session here and thereafter we can think about the point, if the thread might be closed successfully and remain only for communication on troubleshooting such units....
sincerely speedyG

@gsmcten,

2. Are those 83R100Ohm resistor packs simply 4 separate 100 ohm resistors in a SIP? Looks that way to me...

the resistorpacks at the mainboard are "pullup"/termination resistorpacks with 8 resistors tied up to one "common rail" together ending at pin 1.
but be aware ! : the resistor packs at the interface card are definity not the same but instead 4 resistors single besides eachother. Within this thread there are pictures with details on each of the packs ! must be pictures i published about a month or 2 ago...
sincerely speedyG

The 1982 edition of the chassis has 2 caps, 1/3rd height, and these caps also have an
additional dummy lead, or anchor pin. With 3 points for soldering there's no way they're
coming off. Other things would break before that happens!

@Speedy:
You may use any of my pictures (or request re-shoots for clarification) as you see fit.
I'm just a hobbyist putzing around and take'n pics. So whatever anyone does with them I
don't give a hoot! Have fun!

Perhaps I can begin 'scope measurements right after I send back Steven's box. I plan for
that to happen at the beginning of the week. All 4 parts are finally here!

TRIVIA!
When Mountain Computer shipped these units, the original shipping box had 9-12" of foam
around it on all six sides.

This product, while advertised in Creative Computing, weren't really intended for the
consumer. These were for corporations and industry and lab environments. That's why you
don't see many of the ~2000 (total built) boxes today.

The most common logic part to fail in the box is one of the LS245 chips, mainly U8,
followed by U6 and U7.

The most common analog parts to fail are Q1 or Q2. Later designs had replaced these
drivers transistors with part# IRF122. Which seemed to run cooler. And typically boards
that had IRF122 drivers also had balancing pots tacked on in the driver-oscillator
circuit to fine tune them.

Later REV-B versions didn't have a prototyping area.

REV-B has bigger "post-transformer secondary side" electrolytic capacitors, typically
bigger by 150uF.

REV-B has the oscillator gain/balance control built-in to the board. Not a sloppy hack
job that required turning TWO pots; but an elegant single potentiometer that worked even
better. All in the name of lowering the power consumption of the FETs by changing the
time they stayed in (or out) of bang-bang operation. IIRC.

REV-B has better higher-frequency noise suppression caps near the slots.

REV-B chassis came with a slightly different interface card. This one had dip switches to
permanently activate/deactivate a given slot in the box.

REV-B corrects the "shorted" -5 & -12 test points. The -12 point is connected to -5 and
thus reads the same. Their solution (at the time) was to remove the -12 point. REV-B's
-12V TP works correctly.

Hello to all AFmembers,

i have added further text and pictures to the page:

http://www.harrowalsh.de/APPLEBOX/MCEB/appleboxMCEB03.htm

and i have traced back the lines that are responible to enable the Apple to detect if there is a box "present"
and that that box is in status to be "selected" or "de-selected". Though i have been able to uncover the related routing and the way the logic has been connected
- i still have rather large problem to understand the logic behind that kind of "trace-knitting" of the logic !

here is a riddle to be solved by an engineer:

please view that page and the topic about that what i marked to be the "special-lines" and that i marked with
violett background.

If anybody really understands whats happening there

sincerely speedyG

To All AF Members interested in this project,

The replacement Capacitors I used were bought off eBay: (less than $7 shipped to your door. US.)
http://www.ebay.com/itm/270896273239

I've also posted the front and back of my MCEB mainboard with the new Capacitors installed at a fairly high resolution. They can be viewed here:

Component Side:
http://imageshack.us/a/img541/3310/o9vf.jpg

Solder Side:
http://imageshack.us/a/img835/7386/pva2.jpg

I did not clean the solder side prior to taking the photos. The residue was there. (though I added a bit when soldering in the new caps)
I'm preparing a few more photos showing the switches and internal wiring a bit more clearly in a day or two.

@speedyG:
I've looked at the traces on the Apple][ interface PCB, but I can't sort out why 1 of the 2 traces wouldn't autorun. I've not read through your posts to discover what PCB CAD system you're using. Please let me know and I'll give it a try on my end. (if I can) I found a simple route by hand (as I'm certain you have) but I'm sure your preference is for your CAD system to do it automatically.

hello macnoyd,

i have had to quit job after 2nd severe heartstrike 5 years ago....
therefor i was forced to choose a free CAD system....
name: KiCAD .... can be viewed at:
http://www.kicad-pcb.org/display/KICAD/KiCad+EDA+Software+Suite

if you have better system - and i quess it will be better than a free system ... then give it a chance....
but of course :
i have set minimal stregth of trace to a old standard, to keep it like made in 1980´s...
if you use modern traces ( which are far more less thick ) it would have been easy to solve that 2 traces...
and if i would have spent more time for manual review i surely would have solved it too...
but don´t mind about that.... if you have better alternate solution... take it !
that´s completely O.K.
i´ve never stated to be a final solution....
sincerely speedyG

Macnoyd,

I've already installed (replaced) the 2 capacitors with 2 having the same foot
print but about 1/3rd the height. As I told speedyG, I'm relatively certain Mountain
Computer would have used a shorter capacitor if they had that choice.

Please place the link for those Caps up here so I (and all of us) can have a source.
1/3rd the height?
Damn! I wish I had known about that.
They sure would have been easier to install.
Probably would be less prone to breakage too.

Steven :)

@Steven:
Regarding these 1/3rd-sized replacement caps, don't fall into the I shoulda' woulda'
coulda' trap. I believe the original Mallory caps are one of the best choices due to the
techniques and materials used in their construction. It was a good choice to seek out
near identical replacements.

In a world of counterfeits & cost-cutting I promote brand-name parts. There are
several features (both visible and non-visible) that make "big" name brands like Elna,
Mallory, Nichicon, Panasonic, Rubycon, and some others "the choice" for replacement parts.

Some of the non-visible and seemingly intangible items I'm referring to are the
smoothness of the plates or electrodes, the composition of the electrolyte fluids,
air-tight sealing where the leads enter the main body. All areas where a low-tier mfg can
save a penny at your expense!

A "big" name-brand component can contribute greatly to longevity. The original Mallory
capacitors on my 1st box from around 1981 are still above 3300uF and the ESR meter barely
indicates anything at all, which is good.

ESR = Equivalent Series Resistance = something like putting a resistor in series with the
capacitor. You reduce its effectiveness at opposing changes in voltage levels. A high-ESR
capacitor makes more heat and doesn't filter as well. A low ESR capacitor basically gives
you a good efficient punch without sweating.

For your evening reading enjoyment - Remember the big capacitor scam of the Pentium-III era? Thankfully it didn't really affect the classic-computing age much.
http://www.dashdist.com/1u2u/company/capacitor.html
http://www.badcaps.net/pages.php?vid=4

Progress Report:

Steven, your expansion chassis is now functioning correctly with the replacement parts. You
will be pleased to know that the board and its power supply circuit are operating within
established and intended parameters.

Remaining tasks:

1) Re-assembly into metal box.
2) Shipping.

I have a Vodka Exhibition and Festival of Lights to host now; so I expect return shipping to
take place on 6/26 or 6/27.

Hello Keatah and gsmcten,
i just read that about the presentation.....
different kinds of Vodka from different locations ? ( Russia, Poland and other sources...) ?
- Keatah are you forced the also make taste probes? Then you should have real good "basement" below with much fat....
- otherwise Steven, -i guess you should expect the shipment to be executed on Wednesday, resulting from the probes... LOL
Don´t take that for serious Keatah... it just was "demanding for kidding a little bit around"....
meanwhile i´ve been continuing the text at the 3rd page about the MCEB and the analyzing of the function blocks....
in the meantime with the added graphics it´s getting close to the intimacy of the box.... it´s a pitty that up till now nobody replied to the posting above related to "the riddle"....

Steven, if you have time you could view that pages starting at:
http://www.harrowalsh.de/APPLEBOX/MCEB/appleboxMCEB01.htm
and continued up to :
http://www.harrowalsh.de/APPLEBOX/MCEB/appleboxMCEB03.htm
..... maybe interesting also and expanding knowledge till the box turns back....

have a nice weekend both of you, Keatah and Steven...
and thanks to you Keatah for granting the permission to use your pictures in that pages...
several pictures will be used in the followup pages of that analysis...

sincerely speedyG

Hello AF-members,

in the meantime i started within the next page the details:

http://www.harrowalsh.de/APPLEBOX/MCEB/appleboxMCEB04.htm

by adding a number of selected detail-pictures of the box
corresponding to the function blocks explained at the previous page.

in the next days that page will be continued with another amount of
selected pictures of details of the box.

so enjoy it.....

sincerely speedyG

Hello to AF members,

page 3 has been updated at several points and page 4 with details about the box is completed...
next step will be page 5 related to the IFcard.

feedback about the first 4 pages are welcome...
sincerely speedyG

Really nice page you got rolling there Speedy. Looks to be the definitive goto guide!

I have not yet read through it all (and the recent posts of this thread).

It's great to see another user following along with another box. And I am looking to acquire another mainboard. Unfortunately no box or accessories or anything. This is a malfunctioning board that is known to be non-functional. But if I can save it, then so be it!

Really nice page you got rolling there Speedy. Looks to be the definitive goto guide!

well it´s just like i said... a compression of the entire knowledge about the box.....

the idea behind the pages is aiming to the goal i disputed with Steven....

in final stage this pages should turn out to be a kind of "final in depth manual"
that shall permit to perform any kind of diagnostics to detect malfunction of the box or the IFcard
by understanding each single part of the box and the card and how they interact with each other...
and probably in final stage make a downloadable PDF file from this pages as a kind of
"how this works and how to repair"...

i started something like that with the MECB.DOC

- but at that stage it was just uncovering the traces and the circuitplans...

this will go a step far ahead.... if we can add scope pictures it could reach quality of the
books from SAMs published to other hardware....

at least i try to find how far we can uncover the entire operations of the units... in a later stage i will also update the material Circuitplans and pictures also with the measurements you have performed ...

but at the moment i want first to complete a kind of "mainframe structure" by this pages...

sincerely speedyG

Hello to all AFmembers,

well today i had several other tasks too...., so i just started the next page with some of the stuff ...
that fifth page will be the more difficult part of analysis - the Interfacecard and the thing what i call
the "logic knitting", because here somewhere in the deep dungeons of the connections the "Trick" is hidden,
how the card handles both - the slots in the Apple II and the slots in the MCEB box besides each other - deciding
which of the units is used at the very moment and detecting the current status of the box ( if it´s switched to
the mode "selected " or "deselected" )....

up to the moment i have just uncovered the easy part of the card.... but that´s worth a "second view" too....
at least if you want to understand the performance of the card....:

http://www.harrowalsh.de/APPLEBOX/MCEB/appleboxMCEB05.htm

sincerely speedyG

Hello to all AF members,

well this is the second day that i´m working on the re-arrangement of the circuitplan of the IFcard.
This shall permit better visbility and better recognition of the function groups.... but it´s a real
tough task..... we´ll find out if the efforts stand up for the result....

i hope that i will finish that timeeating task within this weekend.

sincerely speedyG

Not to worry! I re-engineered the box with superstition-proof components. To fight the paranormal forces, the added circuitry itself is invisible too and resides in the same continuum. It's all automatic and needs no attention from the user.

Hello to all AFmambers,

just for the moment to give impression, what is the sense of the term "rearranging the entire circuitplan"
for better readability the following picture:

if you compare this Interfacecard circuitplan with the former plan, you will be able to recognize the difference....
the busstructure is better visible and you can view where signals have been taken from the bus away for decoding
purposes...
the IC´s inserted to the bus to amplify the signal are taken away from the other bunch of IC´s used for coding and
inserted to the bus itself ...
the IC´s used for coding have now hierarchical structure and it can be viewed how signals are processed within
stages that followup each other.... resulting to the fact that you now may recognize which gates are rather more
at the front and which IC-gates are then arranged as "followup" stages behind the "frontgates"..... that will
make analysis of the relations within the logic more transparent....

sincerely speedyG

@Speedy: Maybe this week I can get into scope measurements. If not this week, then
'prolly next week.

I've been itching to do a MicroModem II writeup, non technical and more for nostalgia sake.
Stories and reminisces and the like.

And then a photo teardown of the First Class Peripheral's 10MB sider disk. Stopping short
of taking apart the disk assembly (not exposing the platters). This is a 30+ year-old disk
and it is ripe for an inspection. Yet, at the same time, I don't want to risk contaminating
the HDA itself. More like a photo session!

@GSMCTEN:
For testing your chassis. You might want to hook it all up, power, cables, disk
controller card, all that. Chassis interface card in slot #4 perhaps. Disk controller card in slot 6 of the box.

Then you turn on Apple II+. The chassis power-on light lights up.
Press the button and then do PR#6. And the disk should boot.

Hello to all AFmembers,

well in the meantime i have continued that task at the page:

http://www.harrowalsh.de/APPLEBOX/MCEB/appleboxMCEB05.htm

there the story is continued with more pictures of selected groups of signals......
further details will be continued within the next days.....
but at the moment i´ll make a break for some days....
i must get my head cooling down from "smoking".....
sometimes it´s a good idea to step back and "let the stuff settle down".....
before making next attempt of analysis....

sincerely speedyG

Yep. I put away all my MHEC stuff for a while. Next activities with it will be 'scope
measurements.

I'm really looking forward to concert traveling this week, and writing stories about the
Micromodem II and Sider HDD. Mostly BBS and scientific oriented. A little fantasy could be fun!

@GSMCTEN:
If you at all *think* the Duo-Disk blew the chassis then don't put it in right away. But
it is standard stuff and they do work in the box ok. I mean it doesn't suck power or do
anything different than the regular disks. And we had 10 drives going in a copy station a
long long time ago.

Here. Just put the IF card in slot 4 or 5 and turn on the Apple. The PWR light on the box
mirrors the power state of the II+ computer.

And you should be getting a ] prompt.

Pressing the black button on the front faceplate selects the slots in the chassis
OR slots in the computer. And the other light should toggle appropriately. There
is a POKE X,Y command that does the same thing. Check the manual.

No component anywhere in the box should get warm. In fact, the warmest parts, when the
box is lightly loaded with 2 cards, are the LS245 buffers! The power supply stuff should
be just slightly above ambient temp.

The power supply should not be squealing or making funky noises. Typically if the supply
is loaded down too much it starts hissing like a pissed-off cat then it starts squealing.
Even at this point you can still pull the power and be alright.

In an "emergency" - The best way to kill power to the box is by turning off the Apple
II+. The sensing transistor in da'box responds much faster and shuts down half of the
supply instantly. Thus limiting damage to one of the MOSFETs, if any damage at all. Then
quickly thereafter pull the box's power brick.

You see, if you pull the power on the box first, then the "big caps" still have energy to
run the supply for bit of time. And this can let logic levels float in the middle,
neither hi nor lo. Sometimes this will blow up more parts if you get in a bind and are
running it near overload and discover you overloaded the box with memory cards and
co-processors. So kill the computer and then the box, or do both at the same time.

And if you have drives with disks in them, door closed, and connected to the box -
unplugging the power brick will likely blast the disks. Then you have to re-format the
disk or at least fix the blipped track. So always let the box sense the II+ power state
and follow along with it. Yep! I just blew up my Eliminator disk doing exactly that! I
had to reformat it and re-copy it back from a disk image via ADTpro.

Or do everything from a power-strip. Simultaneously.
The II+ power dies quickly, then the box senses this and shuts off its oscillator quickly
and cleanly too. Thus there is no ambiguous or undefined logic levels going on. See? And
the "big caps" don't have time to glide down through levels that are ambiguous.

This info is more for folks powering up one of these for the very first time in 30 years
and are afraid of power supply circuits! And it is absolutely not meant to scare you!

It is what it is! It's like the hard disks of yore! Remember that shit? You had to run a
small binary program named ParkHeads so that the controller would pull the heads
to a textured landing zone. Failing to do that would be deadly to many disks. Today it is
automatic. And in flash SSD you don't have this bullshit going on.

@Speedy:
I so wish I could find my manual addendum, it was 2 or 3 pages and it listed some really
short example programs for controlling the box. I fear it has been lost to the depths of
time. And we'll need to "re-write" it. What a pisser.

Hello AF members,
in the meantime i have developed the analysis a bit more far by removing parts that have been discussed in previaous parts of the mentioned page.
this permits far more readability for the rest of the circuit and this remaining "logic knitting"
by the remaining circuits can now be easily examined.

Some of the powerlines +5V and GND have been left in the picture, because some of the lines within
the logic have been tied up to the +5V using a so called "pullup-resistor" and some are tied directly to GND.
Only few resistors have been used as so called "impendance resistors" in lines running along the "long path" by the 50 pin flatribboncable.

In the previous pictures the datalinebus and the adressinglinebus have been displayed in general
while passing along through from the IFcard to the rear 50 pin connector to the MCEB.

Therefor in this picture the display of the busses has been reduced to the remaining lines "split off"
and used within the logic.

I have marked 3 lines of special interest: the reset line, the User1 line and the
Read/Write line ( R/W ). I have left the U6 ( 74LS74 ) within the picture, because
it is very close "knitted" within the logic and is very important for timing portion of the logic.

sincerely speedyG

I'm pinging this thread back from the dead, as I have come into possession of a MHEC, with card, cable, power supply... still looking for the original manual and software. The unit is in practically flawless condition but I haven't powered it up.

Are pics needed for comparison, or were all revisions of this item accounted for? I'll read the entire thread later when I have more time.

hello sfahey,
it might be usefull to also visit my pages at:
http://www.appleii-box.de/appleboxMCEB01.htm
resulting from this task. the pages contain a summary of this task
and at the end of that pages there is a PDF file with the sum of
all informations....
sincerely speedyG

Hello to all AF members,

after nearly 2 years of silence it seems this thread will become revoked back to life.....

Few days ago i have recieved several pictures of a very much newer version of the box to be sold here in europe.

There are several remarkable differences to the boxes treated up here yet:

the new interface card has a switchblock of 8 DIP switches on top border
at the box itself there has been removed the "prototyping area"
and this version has been made for european market running with 220 Volt supply.

So i got curious about that box and at the moment i am trying to get more pictures and
scans from the manual ( hoping to succeed with this attempt )......

in case i get enough material i´ll reopen the thread with a set of pictures displaying the differences of this box to the previously discussed versions....

sincerely
speedyG

Sounds good to me.
I've got a box with a missing card.
Haven't had the time to "point to point" wire one up or spend the $$ to get a board made.
Hoping I would find one for sale, but ...

Speedy, looks like I found the Chassis and card you might be looking at. I don't know if this is the reference you're describing, but check out eBay item #371227685954 ... Looks like it's being sold out of France and looks to be the newer version you're describing above.
I'm interested, but not $1000+ USD interested if you know what I mean. Looks like a nice unit for sale though. Wish the price were lower, but that's the way "things Apple II" are these days.

Hello macnoyd,
you´r right.... it´s the item i´m talking about....
the seller seems to have contact to stynx and i try to get contact via stnyx...
i´m asking for detailed pictures before item gets shipped....
if we´re lucky we´ll get some usable detail pictures from unit and manual and
i hope the details will uncover the details that far,
that i can expand here documentation for future reference....
speedyG

I'll sell mine eventually.