Europlus problem

Horizontal hold control on the monitor...?

Hello Theart02,

2 chips related to the timing and shifting of the video data are:
74LS194 at location A10 resonsible for timing of the shifting conversion
and 74LS151 at location A9 responsible for the conversion to shifted data itself.

The generation of the sync signal starts at the mixing of V1, V2, V3 and V4,
this signals pass along 74LS04 at location C11 from pin 3 to pin 4
and along the 74LS08 at location B11 from pin 9 and pin 10 to pin 8,
and mixing together in the 74LS51 where the finished sync signal
leaves the 74LS51 at location C13 at pin 8

-and the Blanking at pin 6.

All signals ( Video Data, Color Burst and Sync are joined together in the
2N3904 Transistor Q3 close to the trimming resistor R10 nearby the videooutput
connector.

So working that path backwards
first chance by adjusting the trimming resistor at the chinch videooutputconnector
second chance by changing the 74LS51 at location C13 ( or at least inspecting the pins
and cleaning from oxydation and by extraction and reinsertion cleaning contacts in the socket.....

maybe change of the 74LS04 at location C11 or the 74LS08 at location B11
and finally last chance a change of 74LS194 at location A10....

some additional points:
the videocable should be 70 Ohm videocable and it´s length should not exceed 1 yard ( or 1 meter )

- if the chinchjack can be opened - examine if there is a minor shortcut or bad wire connection inside...

- and at most monitors at the rearside is a trimming pitch for adjustment of the horizontal sync signal
if you have chance to examine the videosignal at alternate monitor i´d recommend to do that first....
that would verify if the problem is located at the Monitor itself or at the computer....
( bearing in mind that possible trouble might be caused by a bad horizontal sync detection electronics in the Monitor.... )

a short feedback which task solves the problem would be welcome....

sincerely speedyG

Okay, seems to me I'll be busy next weekend
Still, I found time to try a couple of things
- adjusted trimming resistor (blue knob on tob) -> decrease and increase in brightness, but nothing else -> did I get something wrong here?)

Besides of adding the signals together in the transistor that trimming resistor adjusts not only amplitude of the signal - but also a bit of adding or taking some "offset"-voltage of the total signal..... so sometimes enlarging the signal gets the sync trigger in the monitor to better catch the trigger signal.

- reseating C13, C11, B11 (ICs look good to me)

C11 and B11 only have small effect to the horizontal sync but C13 is the keypart in making the horizontal sync signal.
even if this chip looks well at the outside of the case it might have reached its limits by internal aging.....
sometimes it´s just a very tiny shifting in the internal timing to keep within limitations or not.....
So the replacement of that 74LS51 should be recommended .... maybe trying alternate the military version ( 54LS51 ) or a faster version 74F51 instead ( only very rarely required )

- exchanged D11, D12, D13

This ICs do rather more the task of setting the adresses for pulling the videodata from memory to the shifting process
- so they are not realy involved in the creation of the horizontal sync signal....

All this didn't solve the problem. As for A10, I would have to de-assemble the motherboard and I won't have time for that until next weekend.

A10 is responsible for syncing between timing generator and access of the videodata at memory

My questions now: Would you wait for the check on A10 or just buy the whole bunch of ICs in question?
What about A12?

A12 is rather more involved in the creation of the video-mode switch ( generation of the signals textmode, hires and selection of the hires pages..... its influence to the horizontal sync signal is nearly undetectable...
Its influence is related to switching between text and graphic modes and vice versa...

the question of buying the entire bunch of ICs is rather more a question of "religious kind"....
some like me are aware that every kind of chip ages by usage and therefor have the entire set of chips
of the mainboard availiable at the sparepart shelve......
others prefer only to replace chips at the time they have to carry out a task of replacement
and don´t bother about time needed for the ordering and mailing that one or 2 chips
( often also requires several days and price for shipping of 2 chips often being same like shipping 40 or 50 chips...)
and in fact the very most of the chips are rather cheap in large electronic stores
- most of the availiable "standard" ones at some 30 to 60 cent per chip but at the other hand :
some of the chips are getting obsolete and the prices are rising ( for example the 8T97 and 8T28 chips
are not that easy to find like in former days and several LS chips share same fate like the 74LS283 and the 74LS259 ).....
so finally its up to you to decide how large the amount of availiable spare parts at the shelve will be....

PS. The monitor works fine - I use it for several Apples. Same for the cable.

The advice trying alternate Monitor was related to the fact that the horizontal sync isn´t that well adjustable at the Original Apple Monitor, - as it is at Monitors of other brands ( having larger adjustmanént range ).....
sincerely speedyG

In case this is the only euro apple you tried with that monitor I strongly suggest you to try another monitor FIRST.

At the end of posting #5:

PS. The monitor works fine - I use it for several Apples. Same for the cable.

In case this is the only euro apple you tried with that monitor I strongly suggest you to try another monitor FIRST.

Hello Georgel,

before entering a thread:

IT´s REALLY USEFULL - TO FIRST READ PREVIOUS POSTINGS !!!

just 2 postings before your remark has been answered... you just should read it....

in case the posting was just to mention your presence....
yes we have recognized your presence....
besides that your presence can also be recognized by 2 other facts without posting:
1: besides your Logo in threads earlier posted is a remark: ONLINE indicating your presence the period you sign in till you logoff
2: At the left side there is a window listing members currently online....
the moment you sign in your membername appears there till you logoff....

sincerely speedyG

theart02 has never said the Apples he tried with that monitor were EURO except that one particular unit that is out of sync.Plus I am trying to ignore you, SpeedyGuy. Your posts are so long that one can hardly read such novels. Try to find the essence, not fairy tales like this:

the videocable should be 70 Ohm videocable and it´s length should not exceed 1 yard ( or 1 meter )

or

even if this chip looks well at the outside of the case it might have reached its limits by internal aging.....
sometimes it´s just a very tiny shifting in the internal timing to keep within limitations or not.....
So the replacement of that 74LS51 should be recommended .... maybe trying alternate the military version ( 54LS51 ) or a faster version 74F51 instead ( only very rarely required )

Hello Georgel,

before entering a thread:

IT´s REALLY USEFULL - TO FIRST READ PREVIOUS POSTINGS !!!

WHAT!!