Apple //e DHGR issue

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amauget's picture
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Hi to all !

I'm currently restoring a PAL Apple //e motherboard ref 802-0073-B.
It was modified at some point to be //c enhanced (65C02 with modified ROMs and extra wires).

I revert all the modifications and it works great except while displaying DHGR screens : there are verical lines.
Here are the screenshots.

All the IC seems okay (MMU and IOU have been tested with another motherboard). I'm pretty sure it's a missing or bad connection.
I do have checked all the connections to the RAM (Figures 3.9 and 5.2 in Understanding the Apple //e). All good.

Any ideas ?

Thanks a lot.

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Antony
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Re: Apple //e DHGR issue

I assume that you mean it is a //e enhanced. (I have never
heard of a //c enhanced) and it has a 65C02 not 65C05.

That could be the problem. The extra wires. It might be
a modification of some sort. Did it come with documenatation of such.
I assuming it was just a unenhanced ][e and the //e upgrad was installed.

Your pictures are in Black and White. Why?
Is the colour switch on? Has the trim dial been turned down.
Check these first. Maybe post a motherboard pic to see if
any unusual differences or irregularities.

amauget's picture
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Re: Apple //e DHGR issue

In fact, I want to write //c.
The mainboard was tweaked to be a //c with EPROMs containing the //c Monitor and additionnal wires.
Hence the 6502 was replaced by a 65C02 (typo in my firt post).

As previously said, all the extra wires have been removed.
Still, there are wires on the MB because I have destroyed some tracks in the repair process. Initially, the Apple wasn't working at all.

My pictures are B&W because it's a PAL Motherboard connected through the video cable.
The color switch doesn't affect the display.
I will add pictures of the board soon.

If you look carefully, the white areas, like PoP titles, are never corrupted.
This is puzzling.

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amauget's picture
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Re: Apple //e DHGR issue

The album has been updated with 2 hires pictures of the motherboard that you can download for zooming.

I also tested the MMU, IOU and Video ROM with known good ones. Same problem.

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Re: Apple //e DHGR issue

The extra photos you have posted are not clear enough.
When you zoom on them all writing is blurry. Can
you take better ones?

Having said that I would start off here.
Re-check the RAM. On the 2nd photo of the
underside motherboard there are wires connecting
the 1st and 2nd RAM chips. Remove those.
Also check the AUX RAM in your extended 80 column
card.

You are missing 3 chips also. Replace these.
See how that goes.

amauget's picture
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Re: Apple //e DHGR issue

Thanks for the reply.

Like I have previously written, you have to download the pictures. They are 3000x4000 and zooming is not a problem with that size.

All the RAM IC (MB and Aux card) is okay. The MB RAM ICs have already been changed as well as the Aux card.

I cannot remove the white wires connecting RAM : it would result in an non working machine.

amauget wrote:

Still, there are wires on the MB because I have destroyed some tracks in the repair process.

The 3 missing ICs are all related to the PAL signal.
The problem arises with ou without them.

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Re: Apple //e DHGR issue

I have downloaded the pictures and there is a problem.
When I enlargen the picturs as mentioned previously the image is
not clear and alot of the information is unreadable. So this is
a problem in viewing the motherboard.

Why would removing the RAM wires result in a non working machine?
Your pictures are not accurately displaying the graphics so it
makes sense to start with areas of RAM to check it.
You said the RAM is OK. What does that mean? Have you tested it
to find out? (Not just putting into another machine but running tests?)

amauget's picture
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Re: Apple //e DHGR issue

Thats weird. When I download a picture, I can zoom in until the screen isn't large enough to display a single IC. I can see the tracks accurately and read the components reference.
Nevermind, I will try to upload more detail pictures.

As already mention, I have made restoration on this motherboard wich was non functionnal at first (some tracks were damaged).
This include desoldering nearly all the ICs and put sockets. In the process, tracks were destroyed.
This is why I can't removed the wires near the RAM : they replace missing tracks and the Apple //e won't even boot without them.

Yes, I've run different diagnostic programs (MECC computer inspector and XPS Diags) as well as the self test and the RAM ICs are okay (both MB and Aux Card).

Also please note the problem appears only in DHGR mode.
Everything is okay in HGR mode. This is another fact that leads me to conclude there is no problem at all with RAM.

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tokabln's picture
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Re: Apple //e DHGR issue

It's just an idea as I just read the following at wikipedia...

"... The 1 K 80-column card also enabled one new graphics mode, Double Lo-Res (80×48 pixels). The extended 80-column card enabled two, Double Lo-Res and Double Hi-Res (560×192 pixels). Both modes doubled the horizontal resolution in comparison to the standard Lo-Res (40×48) and Hi-Res (280×192) Modes; in the case of Double Hi-Res, the number of available colors was increased as well, from 6 to 15. Apple IIes from the very first production run could not use Double Hi-Res. Neither of these modes was directly supported by the built-in BASIC, however, so the user had to resort to the use of lots of POKE and CALL commands in BASIC, or assembly language programming, or one of a number of software Toolkits to exploit these modes...."

Maybe this is of help for you.

If you are using a 80 column card... maybe this is defect...

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Torsten aka tokabln

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Re: Apple //e DHGR issue

What might be worthy of note is that there are 20 lines across the screen. There are 20 groups of 4 bytes which displays 7 colored pixels with each pixel needing 4 bits to display its color.

The sequence of 4 bytes is in memory like so: AUX,MAIN,AUX,MAIN.

If you can isolate the colors, bits, or pixels that the lines are on, you can better isolate the memory the lines are in.

Try changing the screen to each of the 15 colors.

Also count the number of bits the line starts within the 4 byte group. You can do this from the monitor, which will do the bytes in main memory at least.

2000:1
2000:2
2000:4
2000:8
2000:10
2000:20
2000:40

amauget's picture
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Re: Apple //e DHGR issue

News pics added :

Thanks Torsten, but the motherboard is a Rev. B, DHGR capable.
And I've tried two different 64 Ko Aux card, also tested in another machine which display DHGR without an issue.

Robo Robby,
I have activate the DHGR mode from the monitor :
C057
C050
C05E
C053
C00D:0
The screen is full of garbage.

I need more directions to complete the test, perhaps in this tutorial.
And remember, as my display in black&white only, I can't see any color.

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speedyG's picture
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Re: Apple //e DHGR issue

Bon jour Antoine,

i´ve examined the pictures very carefully.....
One thing that i'd mention:
it seems to me that somebody has been "frying" the board with the soldering iron.....
That results in technical term that the flux used in the soldering lead to get it flowing constant
when in correct temperature that portion of fluid has evaporated and then the soldering lead looses
it's capability to flow and starts making blobs with reduced flow.....
such soldering habit also bears a second risk:
In "worst case scenario" it causes - when a socket or chip is desoldered - that also the contact through sleeve
gets loose and gets removed together with the chip or socket - resulting to a missing contact between the
traces at the component side and the solder side of the main board at that junction.

I'd recomend to examine that very carefully !
I marked some of the most wierd spots by red arrows:

it might be a good idea to remove the bad solder lead and replace it by using new good solder lead
to get clean junction..
If it refuses to enter the soldering hole that might indicate the loss of the sleeve as mentioned above !

I'd also recommend to examine the entire board very carefull with strong magnifying glass for cuts at traces
with sharp blade ???

good luck
sincerely
speedyG

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Re: Apple //e DHGR issue

Yeah that board is full of bad soldering.

I'd just reflow any solder point which does not look right and check for continuity on all of them.

speedyG's picture
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Re: Apple //e DHGR issue

Hello amauget,

just some basic thougt:
the DHGR pages are located in the RAM of the 80 col card and not at the mainboard....
so the suspected trail is :
auxiliary slot > MMU > IOU > 74LS245 ( at UB1 ) > and 74LS374 ( at UE7 )
and then later the path of the video signal:
74LS166 ( at UC13 ) > 74LS164 ( at UC14 ) > then 74LS175 ( at UA15 ) and finally the video output transistor....
Due to the fact that the problem isn't ralated to the Lores screen or text display
it's rather more located between the auxiliary card or slot the IOU and MMU ....
and the IOU and MMU may not be affected in normal display from normal RAM but it might
be in trouble while switching between RAM and aux RAM while display of DHGR.....
sincerely speedyG

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amauget's picture
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Re: Apple //e DHGR issue

Hello speedyG,

Thanks for all your relevant suggestions.
I will test the IOU and MMU with another motherboard.
I will also fix the soldering spots you've pointed to.
Then I will report back here.

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amauget's picture
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Re: Apple //e DHGR issue

For the record, I was able to fix the issue at last.
The culprit was the PAL HAL. Replacing it with another one solved the issue.

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speedyG's picture
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Re: Apple //e DHGR issue

Also just for the records:
that PAL HAL with the ugly bad solder joints and red wires
from the picture of the solderside mentioned above....

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In early days I had a lot of money but no time - now I have no money but a lot of time....
the second part includes less friends but a lot more joy on life....