The Big Score! Mountain Expansion Chassis!

Socket success!

It would seem there was a bit of excess flux which
was acting like an adhesive. Once I cleaned the
problem area and warmed the board they came off very
easily.

It will be a day or three before I get time to mess
with this again.

In the meantime enjoy these transistor, diode, & capacitor
photos.

Hello Keatah,
that´s good news !
just to give to all an impression of the current status of the analysis of the topside of the board
the following picture....
BUT: please also recognize : this is not the final status - it´s not finished !
so please just treat it as a kind of "preview"....
Here is the topside now:

and here is now the solderingside:

i hope i´m able to complete it within the next days...

i´ll add the compressed pictures from Keatah tommorow, after i finished compression....

sincerely speedyG

Hello Steven,

i can´t rell about what kind of emails you get... but at least for me its just the reverse engineering to get a complete valid circuitplan - which is not in the manual.... unless i trace back the connections i can´t analyze the circuitplan.... as far as i speak for myself - it´s just a task like any other one i´ve done on creating documentation on apple hardware....
if i sometimes use the term "job" its rather more to be understood as task on my todo list, what i like to do....
and i for sure won´t start any kind of production....
but one thing is also true: if i complete the reverse engineering the CAD-system permits to generate so called Gerber-files that would enable a person to pass over to a PCB-company to reproduce the box....
up till now i haven´t planed to publish that data too and i surely won´t without the required permissions - specialy because this might turn out to become a violation of copyrights......
so far the films just are a step to get the circuitplan...
that permits - in case that something goes wrong with the box - with this material to find faliure and repair it...
without a circuitplan such a task is nearly impossible, because the poor owner will only be guessing and trying with
the "try and error" method....
and besides i just complete the plans in the manual with correct partlist and correct values in the plans ....
and if i talk about a math-job.... well that´s more a joke to myself... i have besides the degree in electronic engineering also a degree in mathmetics ... so that´s realy no challenge to me to do a little arithematics....

the only thing i´m running as a kind of "production" is the development of a few apple I cards for a very small comunity of maximum 10 members here.... and even that´s only hobby as nonprofit task....

i didn´t get any mails about reproducing that box....
did you ? and if just ignore them....
i guess you recognized and agree that i didn´t compress and publish all the pictures - but instead rather more selected those to get a complete overview of the boards and only few related to details that might become interesting when wanting to repair such a box...
sincerely speedyG

It is my intent to provide pictures for parts identification and troubleshooting and signal
tracing. Perhaps schematic creation and historical documentation.

If anyone is planning on making a production run from this info; all I can say is best of
luck! At the time these boxes were made they were near state-of-the-art for consumer micros.
Today there would be far more effective methods for achieving expansion.

These boxes were built with a purpose in mind. Perhaps for including multiple modems, or
drive cards, or data acquisition cards. Today we'd go about that completely different -
even on the original Apple 2 series hardware. Today we'd use CFFA3000 for storage for
example.

What would be a nice thing is to get a schematic drawn up. This would essentially fill in
the missing material and provide the best troubleshooting reference.

@GSMCTEN - Who is sending you emails? Just seemingly random people?

ADDED - This activity has allowed me to scrutinize the condition of my box. It's like
almost 34 years old depending how you measure the dates exactly. So far everything seems
to be in order. I did screw down the transformer. Cheapskates and cost cutting, forgot to
put the screws in.. And I found a missing test point post, which I fixed up. And all the
sockets and chips got a good burnishing and polishing with an eraser.

I'm also considering evaluating the capacitors next. That would ruin originality, but
people don't usually care about that with something like this. The best case would be to
keep the old ones in a baggie or container with date of replacement.

This project will be hot for a while. But like any aspect of any hobby - it will subside and something else will become more important sooner or later.

I agree...
next projects on the todolist:
1.finishing the apple 1 cards and their documentation....
2.writing epromburningprogram for the apple 1 romcard
3.making several Eproms with utility content for the apple 1 ROMcard like basic from Eprom, assembler and disassembler from Eprom, something similar like programmers aid from Eprom and Graphicexpansion routines in machinecode for Apple 1 from Eprom.....
4.finishing the Sound- and speechcard....
5.writing programm for speechrecognition of the Sound- and speechcard
6.reverse engineering of the Apple IIe diagnostic card...
then i´ll see what comes up....
7.and besides when having some time organizing the disks for Apple II and backing them up
8.and scanning user magazines and magazins and manuals.....
i guess i don´t have to worry about doing nothing - except i realy want to do so....
lol speedyG

Well today i turned back to the Interfacecard, starting with the reverse engineering of the card
and starting with the creation of the circuitplan.......
what´s amazing in this state is the fact the you can recognize how many signallines run straight
along from the slot to the connectionplug of the cable to the box.....
well O.K. quite a bunch of them pass over the resistornetworks RP1 to RP6 - but in fact up till
now the majotity of the IC´s on the card don´t even have a connection with any of the signals traced up
till now ! So we can asume that only rather few lines are in fact really used for adressdecoding and control signals.....
please bear in mind that this is only a preview of today´s work..... and of course there is still a bunch
of time needed to complete this task....

sincerely speedyG

Absolutely fantastic! That is what the hobby is all about.

It would be an interesting exercise to make this work with a //e system.
While I have not studied this in detail, I would imagine the 16-pin ribbon cable
that connects the interface card to the motherboard carries some sort of signal.

I would imagine a different connection needs to be made elsewhere, and perhaps a
tiny software driver or ROM edit to trigger it.

maybe...
we´ll be able to check that, when tha analysis is completed, because i´ll add info´s about the signals drawn by that cable....
usualy the chip at the Apple II mainboard is a decoder responsible for the slot selection with the:
/IOSEL
/IOSTRB
/DEVSEL
signals....
just have taken a short look at jim sathers "understanduing the IIe"
chapter 7.1
it seems that in the IIe these signals are generated by the same chip ( 74LS138 ) at location B5.....
so if that chip is not soldered there might be a good chance to use the equipment at the IIe too....
anyhow ... i´ll try to complete the circuitplan of the IFcard tommorow and thereafter i´ll switch back to the mainboard....
Keatah sent this evening a large bunch of perfect pictures - i´ll view them also tommorow and hope that they
uncover the last open questions....

so have a nice day together....
sincerely speedyG

I checked a standard (and enhanced) //e mainboard, the LS138 at location B5 is socketed.

But on the PLATINUM //e (the one with the numeric keypad for those of you not
in the know) has its loc B5 LS138 soldered in place.

Considering how easy it is to work on these old-school computers, installing a socket
would be 20 minute evening project.

As it seems to appear now, the -12V TP is in parallel with the -5V TP. This seems to be a
dumb mistake by the designers.

I'm thinking of cutting a trace and making a jumper wire to connect the -12V test pin to
D7 and D6. That and adding a manual/auto on/off switch. Perhaps bringing over some other
signals, video and sync stuff. And making switchable pull up & pull down resistors. Extra
buffering. Well, just some musings..

And don't reference google for any pinouts. Get something official from a book.
Had I used any of this shit my hypothetical project and system would have exploded for
sure.

One had pin 8 and 9 listed as -12V and -5V respectively. Pin 8 & 9 are smack-dab in the
middle of the address bus for chrissakes!

Another had pin 50 listed as -12V. This is a +12V line! And yet another had +5 and -5
reversed.

Just for fun I had a couple of junker //e units that work. And I connected the interface
card and ribbon cable to B5/LS138. The system just displayed low resolution graphics
garbage. Keyboard totally not responsive. I removed the card and put the real LS138 back
in and it fired right up normally. I did not have the actual box connected via 50-pin connector.

So making this work on a //e will require more sleuthing. But it was fun! I'll have to
investigate this more, if I have time. Doubtful in the immediate near term.

I'll have to pull out one of the II+ units to give this box a proper shakedown. It really
hasn't been powered up in 25+ years.

I think with a little more discussion we'll have enough information to write a theory-
of-ops and repair manual for this. Or at least add a few appendices to existing manual.
Something I'd really like to do, perhaps beginning it this summer and finishing it by
early 2014. Of course it will be free to the community!

Hello Keatah,
i just can give advice to resign from testing with the IIe unless the analysis is completed....
in the Apple II there are 2 74LS138 resoponsible for the decoding of the slots ( H2 and H12 )
the one delivers the /IOSEL and the other the /DEVSEL and unless i haven´t analyzed the corresponding
decoding at the IIe completely it´s too risky for just trying....

in the meantime the circuitplan for the IFcard is nearly complete ... only some minor points have to be resolved....

within the circuitplan that points are marked with LARGE "X" ( the small "x" indicate that a pin is "not connected" )
but logic says if output is used - there must be some kind of input too.... and some parts are just below the Plugconnector that runs with the 50 pin cord to the mountain box.... and therfor is quite diifficult to detect...
so probably some measurements still have to be done to uncover the last missing points for completion of the
IFcard.....

in the IFcardplan that points are marked with intense light blue lines....UPDATE: Corrected !
UPDATE : THE CIRCUITPLAN HAS BEEN COMPLETED !

AFTER THE CIRCUITPLAN HAS BEEN COMPLETED THIS PLAN OF THE INTERFACECARD IS NOW AVAILIABLE AS DETAILED LARGE SCALE PDF-FILE:

http://www.harrowalsh.de/Upload/IFcardCircuitplan.pdf

so please don´t treat this like finished result ! there is still some homework to be done....

UPDATE: In the meantime the mystic traces have been detected and you´ll see now that corrections as red lines....
sincerely speedyG

Success!

I had my chassis powered up and running on my Apple II+. I completed a very elementary
test. I booted from a Disk II attached to the chassis. PR#6 was echoed to the disk
controller card, or not, depending on the select/deselect switch. I was able to perform
some read & write operations and play some games.

I was elated since this hadn't been used since the early 1980's. And especially with all
the poking around these past weeks, measuring, cleaning, and all manners of dick'n
around inside.

I think this chassis is in much better shape now. Like when it rolled off the factory
assembly line. Not that anything was wrong with it to start. Just dusty and that sort of
thing. It's a good thing to go over old electronics in this manner. You gain confidence in
their operation and get a good handle on how they work and how things are put together.

It is important to note that both the computer and the chassis have to have power going to
them. And the chassis should be already plugged in prior to turning on the Apple. The
chassis turns on its power supply when it detects the II+ is turned on. Also, if the
chassis is not plugged in to AC mains, then the computer will display garbage. It will be
impossible to use the computer. Either have all of it hooked up, or nothing. If you just
follow the manual and do as it says, it will work.

The first thing I did was to test the voltage levels and they seemed good. I already
forget what they were, as it was intended as a quick readiness test. Nothing more. No
components were running hot, which is a good thing. I also quickly measured the power
supply frequency. It seemed to operate between 53.87KHz - 54.00KHz. It probably varies
based on the load caused by the installed cards' activities.

My long-ago-abandoned dream of having a BBS with 12 300-baud Hayes MicroModems seems one
step closer to reality now!

@SpeedyG - I will be busy several days this week, so may not reply to emails in a timely
fashion. Just send the questions and I'll get to them soon.

I have not forgotten about T1 measurements either and those are on my list to do. I have
the graphic you sent pasted on my desktop.

Hello Keatah,

i´ll walk along the mails from tonight throughout today.....

have a nice week...

hopefully i recieve the last missing parts of the Newton NTI this week,
so i probably can complete the assembly of that board for the VCFe.....
so till you´re back online i´ll still have plenty things to do
- the assembly, the analysis of the mainboard
and getting the topside of the film finished and
then the transcription to a circuitplan of the mainboad....

so i´ll try to complete today the circuitplan of the IFcard and
switch thereafter to the remaining tasks.....

thanks a lot for the great support in this task....
without the huge amount of your cooperation -
it would have been impossible to solve this task up to this point....
sincerely speedyG

Hello to all AF members...
the first giant leap is completed ! The Interfacebard of the Moutain Computer Expansion Box is de-mystified !
the graphics 2 post above updated by the upload themselves.
I added in the posting 2 steps above the link to the PDF-file that contains the large scale circuitplan.

Next step will be to get hands on the "guts" of the box itself......
i´m on that task right now.... the film of the solderinside is nearly complete and the film of the topside should
be complated with the next 2 or 3 days too.... in the very moment that´s complete i´ll start analyzing the traces
and reverse engineer the circuitplan of the box too....

up to the moment just a preview of the ropfilm of the mainboard .... again -> it´s not finished yet -
it´s just to give information how far the task is "on the road"....

due to the fact that Keatah is "off shore" for a couple of days i´ll have to wait for some measurements to
perform some arithmateics.... this will be focused to get precise data from the coil of the power switching device...
i guess therefor that the cicuitplan will be rather faster finished than the precise partlist - because in the partlist
the data of the coil should come alomg with the normal parts....
then i will also add up some dara of voltage measurements to the plan for better diagnosis of hardwaredamages...
and finally i will also go along all the pictures and add some more pictures with details of the box in this thread.

We all should also thankfully give some preyers to gsmcten here....
without his purchase and the huge bunch of excellent pictures i would not have dared to tryout the task
of reverse engineering the box and the interface card...
so specially here at this point many thanks from me to gsmcten for his patience and great ccoperation in this task !

and i guess that gsmcten will grant some additional great pictures of the box,
after he has re-assembled this gem of apple history that he purchased after long years of hunting for it.....

Hello to AF members,

in the meantime the topside and the solderingside of the board is nearly complete and only 1 or 2 points to be researched when Keatah is back....

the updated pictures are now up above to be viewed in posting #102.

Next step will be to convert the layers to color ( top red and solderingside blue and connect the layers.....
thereafter i can start reverse engineering and creating the circuitplan.....

- when the cirrcuitplan is completed i will update the plan from the mainboard and ad a sheet with data on specialparts like coils and used nerworkresistors...

enjoy it
sincerely speedyG

So here we now have the 2 Layers combined - the layer from the solderingside in red and the topside in blue.....

and here the components have been added as green layer for better orientation....

with this 2 pictures i can start the analysis and create the circuitplan....
i´d expect the circuitplan to be completed till Friday or Saturday in the evening.....

up till then have some nice days...
sincerely speedyG

Hello gsmcten,
it´s the privilege of our age ( as dinosours ) to take time for a hangout if we feel to need it....
and it´s wise to listen to that needs....
in the meantime here a preview of the circuitplan from the mainboard....
of course there still a lot to do in that task....
but again in the interim process the view permits some intersting things to recognize:
The datalines D0 to D7 just run alomg the cable into the box without any change except being buffered
by a bustranciever and adding some pullupresistors....
and nearly the same is valid to the adressinglines A0 to A15.....
but what´s realy interesting:
allthough the signals run along a long flatribboncable the lines listed above runalong that cable without
and adding of groundedwires between.... so it does seem not to be a problem along with interferencing fields....

and it seems that the adressing of the slots is organized in a kind of cascading technic :
output 0 to 6 of the first 74LS138(U3) is used directly and the output 7
leads to the input of the second 74LS138(U2) making the outputs from 0 to 7
getting ordered to new values from 7 to 15 ......
( it´s quite similar to the technic of cascading counters in a row for creating large dividers ... )
the analysis of the powerswitchingsupply isn´t complete yet... this will have to wait till further
data is availiable - but it´s clear that the 9-pin connector down cloce by the corner at U1 should be examined further for better understanding....it seems to become clear that U1 ( a 555 Timer ) is a kind of delay to switch on power and syncronize signals, when it detects that the Apple has been "powered on"....

For those who like to take a closer view a hires-picture is availiable at:
http://www.harrowalsh.de/Upload/MainboardCircuitPlan.jpg

so enjoy this part of the task and spend some happy time exploring the detected details that have been uncovered till now...
sincerely speedyG

just updated logic-part and added link to hires-picture above....

Hello to all AF members,

well now i´m able to claim the task to be nearly completed.....
the circuitplans have been updated and can be claimed to be in "final condition".

there are some minor points i´m trying to validate:
the data of the coil in the switching powersupply... ( data of the windings in the coil )

within the 2 layer picture in the thread above please note a point that i nearly had lost out of sight..
but Keatah brought me back on the track: there is a mod that seems to be executed from
Mountain Computer themselves : in the upper left edge at IC U9 there have been 2 traces cut
and instead of using the logicchip ( which would have caused a delay and the inversion of the signal )
they have inserted a wirebridge as passby of the chip.

In the next days i´ll view the entire pile of pictures i have recieved from Keatah and gsmctan and start compressing the best that permit edditional views and upload them and place them here in a further posting.

I guess it might be a good idea for those, who own such a box, that i´ll bind the pictures, circuitplans and other additional information together as a kind of "manual addon" in pdf-file format for download....

sincerely speedyG

Hello AF-members,

i just made a "preview" of the resulting final Document
that will result from this thread......
it contains the bundled information from this thread:
Deviceplans with partvalues added
topview of device
solderside of device
film from topside of device
film from solderside of device
partslist of device
layerview of device
circuitplan of device

but be forwarned - the document as Word-document has size of 17 MByte !

the link to this "preview" is:

http://www.harrowalsh.de/Upload/MCEB.doc

UPDATE: Link corrected

sincerely speedyG

Hello gsmcten,

thanks for the kick... that was typical mistyping error insted of MECB the correct spelling is MCEB....
i corrected the link...
i´m curious about the feedbacks...

if the fuse has blown that should be visible....
i´d rather more guess that the disk has mistake...
did you try that disk and the duodisk in same configuration in the apple itself - before - to certify that it works there ?
Then when moving to the box, did you check jumpers on the IFcard ?

only if it works there but fails in the box - then it´s time to call Houston....

sincerely speedyG

@SpeedyG - I will try to find time for voltage measurements at various spots in the power-supply circuit. Could be as late as Tuesday.

Hello Keatah,
it´s not a task that runs away... and it is surely not that important for turning out to become a "must"
within few days... so just do it, when you can spend the time.... when i recive the data, i will integrate it
in the circuitplans and hopefully it will enable me to uncover the data upon the coilwindings in the transformator...

I´m also waiting for the pictures from gsmcten, when he get´s his box up and running and making pictures from details of the assembled box.

That will enable me to update here the thread with further pictures and complete and update the documentation.
When that is completed, i will revise the entire material, integrate the last corrections here and in the documentation
and state the task to be completed and upload the final documentation for download and list here all important links
in a final posting....

sincerely speedyG

Hello Steven,

well i´ll just line up acording to the analysis the function and how to connect....

1. when removing the chip from the mainboard where the MEB is to be plugged in with the 16pin flatcable
2. that chip ( it must be a 74LS138 decoder ) is to be placed on the IFcard just in the place straight left
from the socket ( U11 ) where the 16pin flatcable is coming from.
the notch at left side indicates at this chip where pin 1 is.
it also indicates that the pin 1 at the cable is tooo at the left side.....( same as the notch on the IC )
that side should be marked on both end of the 16pin flat on the cableplugs for better orientation.....
the marked pin1 side of the flatribbom cable should be inserted correct at the side with pin 1 in the socket on the mainboard at pin1
( indicated by the orientation of the notches of the other IC´s ! )
3. then the 50pin flatribbon cable should also be marked at both ends where the pin1 is located
( if there is no arrow )
( this can be done by pluging in the cable in the box connector
( there you can´t insert it in the wrong way because of the notch on the plug ! )
and marking the correct side on the cable ....
then when both sides are marked correct you can leave the cable plugged in the box and
connect the cable to the IFcard that way that the side marked as pin1 is attached at the bottomside
( closest to the slot ! )
4. leave the languagecard in slot 0 of the Apple and set PP2 to position "A"
( most top position ) which ensures that the languagecard is allways active in slot 0 in the Apple independent if the box is selected or not....
5. keep sure that the jumper in PP1 is in the lowest position at FE
( factory default for the first expansion box ! )

IMPORTANT ! THE BOX MUST BE POWERED UP FIRST !

Otherwise the detection circuit of the box indicating the powerup of the Apple won´t work but instead inject mistake!

then do the first test by keeping the diskinterface card in the Apple and starting boot from the Apple
with the box deselected.... the Apple should boot normal and just ignore the presence of the box.....
if that fails there is trouble on the IFcard....
- check if for example a pin is bent from the 74LS138 while inserting in at position U11 or if chip is shifted to left or right from correct position !
- check if for example a pin of the plug is bent or plug is shifted to left or right while inserting in at position in the Apple !

If booting from Apple with the Diskinterfacecard in the Apple is O.K. then you might move that Diskcontroller to the slot in the box and select the box to perform booting from there....

sincerely speedyG

I had to chance to read through this thread and I just want to tell all involved with this project that you are all doing a fanastic job on documenting and re-engineering this product. Everything is to detail and likes of having SpeedyG in our community is invaluable to say the least. Keep up the great work!

Let's review the basics first.

I used my daisy-chained 5.25 disks with DB connector, both of them. This is very much a
duo-disk configuration except the drives are in separate boxes. I also tried my standard
Disk II interface with the original Shugart Disk II drive - the metal case, the one with
the flat ribbon cable. Both drives worked.

I happened to use slot #4 in my standard stock Apple II plus.
I do not know if there is anything "special" about a Bell & Howell motherboard.
There were no kinks or twists in the 16-pin ribbon cable.

Regarding the 50-pin ribbon cable:
The red stripe is close to the slot connector on the interface card.
The red stripe is close to the fuse on the expansion mainboard.
If these are reversed no harm should come to anything, in fact I did it once or twice.

Figure 4, 5, and 6 in your manual are accurate and make sense.

Both computer and box should be plugged in.
Powering on the computer powers on the expansion chassis.

Jumper PP1 = FE
Jumper PP2 = A

The next step after this is going to be checking the voltages on the expansion mainboard
slots. Verify +12 +5 -12 -5. Do this with everything powered up.
http://apple2.info/wiki/index.php?title=Pinouts#Apple_.2F.2Fe_Expansion_.28Peripheral.29_slot

The expansion chassis supply comes on when the Apple II is turned on.

Spot check chips for anything hot. Some may run warm. That's ok. We're looking for
hot-spots.

Report back with results.

In the process of taking my chassis apart I took the opportunity to clean the sockets and
the chips. Though they weren't too bad to begin with I thought now's a good time. I
polished the socket pins, and both the inner and outer faces of each IC pin. Sockets make
contact with the inner side of the IC pins, yet most folks just hit the outside with an
eraser!

I am most certainly not the best with troubleshooting unless I'm hands-on. But, instead, I
can tell you what I do that makes things work.

If these hints and Speedy's hints don't fix anything then we'll need to look into it
further. The beauty part is you can purchase all the ICs and all the other parts for dirt
cheap or pull them from scrap boards. So parts aren't going to be a problem.

@GSMCTEN
Yes I have two chassis. The one discussed in this thread is the 1980 version - the first
version. My second one is a later model (1981), and copyrighted as such.

The motherboard on the 1981 revision has some minor power supply differences, like a
balancing pot for the transistors that drive the bigger transistors. There tends to be
more attention to RF noise suppression by way of extra (and BIGGER) capacitors distributed
over more areas of the board. It does not have the prototyping area, that big array of
solder points and vias. In place is a just a large copper etched ground plane. The logic
and IC interconnections appear to be identical to the 1980 version. If there are other
differences, they're minor.

Other than that it is substantially the same as "our" two chassis being inspected in this
thread. I believe it would be interchangeable and present no operational differences.

I have all the stuff to go with it except for some of the board standoffs. I believe it
can be made operational with a minimum of work. Electrically it is sound and complete. May
need a screw here and there.

I have not decided if I will keep it as a pile of parts - ready to fill in as replacements for
my pristine model or if I will completely clean and re-assemble it. Or even make a
monster-sized project box of it. I had even thought of building in a modern i7 machine in it.
Like a case-mod thing. Except I wouldn't be cutting or drilling, tape and glue and
adhesives, yeh! ..So it could be restored at a future date.

@SPEEDY
One lazy day when I'm all caught up with other minutiae I'll sit down and review check the
diagrams. I always like to wait a while and come at things like this totally fresh. But
they are looking real good right now. If you could check the Resistor Pack, I see only
one of them, but the diagram implies there are two. There are several areas where they
could be stuffed, but are not.

Hello to AF members...
hello gsmcten..... i´ll wait for feedback....when the box comes up and working i´m cute about some pictures
of the assembled box ( cables wired and showing the inside of the box ( connections to frontpanel in wired condition )and
some additional views....
@ Keatah,
i prefer same as you to make the revision when some time has passed.... it prevents one from some kind of
"blindness to own behaviour" and forces one to attempt with accuracy to get in the stuff again....
but i won´t start with revision and completion unless the missing data get´s somehow completed....
i can´t calculate the windings of the powertransmissioncoil - unless i have more data from the measurements of the
connectionpoints... so i´ll wait for them to complete the task.... then when that task is completed i´ll carry out
the task of the revision and i´ll revise the entire stuff....

a remark on the additional resistornetworks that haven´t been populated:
i guess at the time the layout of the box was designed by the engineers, they didn´r know, if it was better to
add pullup resisitors in the beginning of the data chain or at the end.... ( for example at SCSI chains the resistors
must be added at the end ) so the film permits both solutions - but in the practical examination they found out,
that only those at the beginning have been needed amd therefor didn´t populate those at the right end close to Slot 7 ....
and it seems that the resistornetworks on the IFcard did their job perfect and the box therefor required less buffering...

that will be confirmed, when the posting is issued, that
the "additional manual" is completed - in "final status and revised"...
untill that point is reached i must ask the community to stay with patience...... i can on make steps ahead on the
ladder - if the ladder has further steps.....
so lets wait with patience till the additional info´s arrive....
i usually perform my part of the tasks within 48 hours after i recieve data....
and i´m confident that this task will be completed within a limited amount of time.....
sincerely speedyG

Did you measure the +5 +12 -5 -12 voltages at one of the expansion slots on the chassis motherboard?

This can help determine if we troubleshoot the power supply section or the digital logic
side. And *if* we work on the logic side, without a probe or scope, you can just take $10.00
and buy all the chips from digi-key and blindly swap them.

The symptom you describe is the same I had when I forgot to plug in the chassis power brick.

Hello gsmcten,
i read your description.... but i didn´t see that you checked out the pins of the 74LS138 at posision U11,
and checked correct pins and position of the 16 pin flat, and the correct position and connection of the 50-pin flat.....
if the 50pin flat was not inserted the following might happen:
several control signals are pulled up or down by pullup / pulldownresistors....
so if one of the signals must change polarity by the power in the MCEB
(caused by the fact that when power is availiable at the MCEB it switches on itself
after Apple was turned on and the box switches the signal to indicate, that the box to be ready,
and then that signal pulled down or up in the IFcard permits the Apple to start....
to understand this trail: when Apple power is turned on - and the IFcard is inserted that card must find out if
the box is selected or not ( by the switch on the front panel )
and thereafter it sets itself to the condition to permit the Apple to boot from it´s own slots
- or if the box is selected - that the Apple has to wait
for the signals coming from the booting card in the box .....
if that condition is not given - because the 50 pin cable is missing - the IFcard won´t be able
to get to the defined condition and then prevent the Apple from booting.....
maybe you have executed this steps but forgot to mention them in the listing above.....
but after they have not been mentioned, i think it may be possible that one of that steps have been missing ?
my first suspect in case that all steps have been performed, would be something wrong with the 74LS138.....
maybe it´s just a small tick to slow and a change to another ( maybe faster chip ) may solve the problem....
could you just make few pictures of the setup when starting with the box so that i can see the setup
( IFcard inserted and connected from the topside and MCEB connected with the connections to frontpanel and
at the connector with the 50 pin flat ? )
after you changed the capacitors just checking the correct polarity might make sense.....
i have enters the correct polarity in the Plan here in the thread.... so you can check that by the plan....
sincerely speedyG

Ohh hell if you can work on turbines then using a DMM is super easy. No electronics
knowledge necessary other than don't short stuff out with a slip of the test probe.

If you're confident everything is hooked up right - I'm going to recommend getting or
borrowing a basic DMM (Digital Multi-Meter) for troubleshooting this. And it isn't hard to
use at all!

You basically turn it on and select DC volts.
Connect the black test lead to a GND test point, like TP2, TP3, or TP4.
And then use the red test lead to measure the voltage like so:

Contact #25 +5 volts DC
Contact #33 -12 volts DC
Contact #34 -5 volts DC
Contact #50 +12 volts DC

Each of those measurements are on any one of the 8 slots. Take your pick. Measure at the
very edge of the contact to avoid shorting anything with the probe tip.

If those readings are present then we know the power supply is powering up and working. And that
means half the circuitry in the expansion box is good. Seeing as how a big portion of it *IS* the
power supply!

It may be possible to use a continuity 12v tester light. Just expect the +5 and -5 points to give
a very dim indication. Use it in the same fashion I described above.

We're basically cutting the cake in half and picking a side.

I'm also not opposed to recommending you take each IC out, one by one, and re-insert it
several times to give a cleaning effect to the contacts. I did this (and more) prior to
powering my box up for the first time in many years. Whether it had an effect I'll never
know for certain. But I can promise you that the reliability is up significantly.

Other than that I don't know any other techniques or tests we can do to start narrowing down the
problem, might as well start swapping chips one by one. Consider doing the interface card too.

From the pictures you provided I did a visual inspection as best I could.

The Fuse looks ok.

There is some mild oxidation on some of the chips on the interface card. Try that chip
re-seating thing I mentioned. It's easy and free and takes about 1/2 hour to go through
the board carefully.

Is C6 in order and not damaged? It looks a little skewed in the photo. This is below the
black square-looking heatsink.

I also didn't see anything obviously smoked or blown up.

Are the 8 flathead screws secure? Firm but not tight is all that's needed.

And is your power-brick in order? A DMM would help here. This puts out about 2x the power
of a 12v continuity light/tester so it would probably blow it. So don't use that as a test
method.

And in going back to post #130, you seemed to have had it working then.
Am I correct? Did the DuoDisk make the calibration/grinding noise?

So maybe something blew or broke contact somehow someplace between the time the DuoDisk was
running and the time you restarted it to boot a disk?

I (once again) have my Apple II+ 48k and the chassis hooked up. I have the opportunity to
make live circuit measurements during the next several days. I have at my disposal an
averaging DMM today. Shortly thereafter a true-RMS DMM.

Primarily this will aid in power-supply and transformer examination.