Mystery after market jumpers

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Mystery after market jumpers

Hi all:

So I started refurbishing one of the Apple II+ machines I recently aquired.  So it seems like the previous owner (unknown) not only made some of his own periheral cards but did some under mother-board mods that surprised me.  My background is computer use, networking, coding, etc and while I have some basic understanding of electronics and circuits, I could use some bigger brains to help me slueth out what this previous owner was up to.  Attached is a photo of the MB. The red lines I drew in represent the jumpers (excellently done mind you) under the board.  I have identified the pins in the destination chips.  2 of the jumpers come from the keyboard socket. The other from a chip in the upper right by what I think might be video circuits?  I am looking over the Apple II+ schematic and researching the chips to see what I can conclude.  If anyone has thoughts on these mods please share.  I don't think they were jumper fixes as there don't appear to be damaged traces.  I think they were deliberate, but to what end.  I left the image at full resolution to help see the details.  Sorry its so giant.

Mark

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Lower-case mod

The wires to the keyboard connector are part of a lower-case modification. The pin F14-5 is a video soft-switch that controls inverse text mode, and B7-5 is a pin that controls bit 7 of each character read from the keyboard (which signals to software that a key was pressed). They are connected to pins 4 and 9 of the keyboard connector, which are unassigned on a stock Apple II. The keyboard would also have been modified to use these signals. The "LOWER CASE ©1983 VIDEX" character set EPROM is definitely a clue.

Pin 6 of K13 is the amplified output of the cassette in port. It already connects to R29, so this appears to be a repair wire to fix a broken trace under the chip.

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THANKS!

Thanks!  This makes total sense.  The machine had a Videx Enhancer II installed which I removed and replaced with an OEM Apple II+ keyboard encorder.  I'd replace the lower case chip with an original version chip but I do not have one and, as I understand it, I dont' really gain anything by having this or the orignal since the Enhancer II is removed.  I also have a Videx Soft Switch card that I will explore further once I finish the cleaning part of the restoration.

But, this helps me understnad what my other II+ might have done, which does still have an Enhancer II installed.

I will check the underside for the Pin 6 to K13 to see if I missed a bad trace. 

Cheers,

mark

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VAstargazer wrote:Thanks! 
VAstargazer wrote:

Thanks!  This makes total sense.  The machine had a Videx Enhancer II installed which I removed and replaced with an OEM Apple II+ keyboard encorder.  I'd replace the lower case chip with an original version chip but I do not have one and, as I understand it, I dont' really gain anything by having this or the orignal since the Enhancer II is removed.  I also have a Videx Sof

 

Please inform me if you want to part with that. I have a few spare CHR ROMs, too.

 

P.S. Don't forget to put the 9334 from the SoftSwitch into the socket at F14 that is unpopulated (will be marked '9334'). If it does not make good contact, you can often use a machine pin socket and stack it, as the SoftSwitch pins were too large for the old sockets, tending to distort them. 

 

Without this, you will not have video page select. A good sign of an intermittent connection on the 9334 IC is that graphics in games will suddently be converted to various random text. 

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Time Lord,Baldrick expressed

Time Lord,

Baldrick expressed interest in the Enhancer II.  If decides against it, I'll let you know.

But here's an interesting event. Once I finished cleaning the case, etc and reassembled the machine it worked beautifully.  Dark black screen and crisp white characters. Then I turned it off and reinstalled the Saturn 128k card (slot 0)  and the Disk Controller II card (slot 6).  Then video became full of colored lines, staticky and an unstable background.  Characters still visible and keyboard responded appropriately.   So I turned it off and pulled the cards. Back to beautiful screen.  Reinstalled just the drive card.  Ugly screen and no activity on the attached drive.  Installed another drive card. Same. Removed the drive card. Installed the Saturn solo. No video or sometimes a flashing ugly display. Pulled all cards.......back to crisp and clean.  

Since the LEDs on the Saturn didn't light up and the drive showed no activity, my initial guess is no power to the expansion slots??  And, slots interfering with the video circuit.  

Also tried installing a Video SoftSwitch card.  9334 was already populated so I'm assuming it's the right chip installed by the previous owner.  (See earlier pic). Still learning my way around the peripherals.

 

Mark

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VAstargazer wrote:But here's
VAstargazer wrote:

But here's an interesting event. Once I finished cleaning the case, etc and reassembled the machine it worked beautifully.  Dark black screen and crisp white characters. Then I turned it off and reinstalled the Saturn 128k card (slot 0)  and the Disk Controller II card (slot 6).  Then video became full of colored lines, staticky and an unstable background.  Characters still visible and keyboard responded appropriately.   So I turned it off and pulled the cards. Back to beautiful screen. 

 Sounds like it could be a flakey power supply.

Check the voltages at the power supply.  Especially +5V.  The others are -5V, +12V (usually 11.8V) and -12V.

You have a non-standard power supply connector - it looks like a Molex type connector and not the standard Apple power supply connector.

Do you have an aftermarket (Asian) power supply?

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Great minds think alike. 

Great minds think alike.  Checked the PS.  It is a non-Apple brand.  The + and - 12v values are off from specs.   -10.18, 11.64,  -4.24,  5.15.

Both Apple II+ non-clone machines with Apple brand MBs have the same after-market PS with the Molex connector. Same issue when using the other PS in the above machine 

Correction from before. When a card is in the slot and the video is not proper, the keyboard is not read/displays key presses.  

Spare PS:

I have 1 Apple branded PS. Values checkout at specsecond is non-Apple. Specs similar to the other.

These spares both have the same plug style as the apple brand.

Would the above described mods for Videx boards be a factor?

What nomenclature should be on the chip in the 9334 socket?  One MB chip says 9334 but the other machine says N9334N 8130.  I am assuming they are equivalent. 

 

 

 

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74LS259 is equivalent to your

74LS259 is equivalent to your 9334 and can be used in place of it if you're short on spares.

And both your 9334s are the same.

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Acceptable replacement and ok to mix

I assume this is an acceptable modern replacement https://www.mouser.com/ProductDetail/Texas-Instruments/SN74LS259BN/?qs=SL3LIuy2dWxBzmfNX75CKA%3D%3D

Also, is it ok to mix and match these with the originals?

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Latest update

So I have tested the above machine with a genuine Apple II+ power supply.  Same issue.

Crisp cleat video with no cards installed.  Install a card and wonky video.

Disk II controller in slot 6 not driving the disk drive.

Definitely seems like a power issue, but not a result of the PS.

Any suppestions welcome.

My next planned steps are to measure the power going to each periphreal slot to see if it matches specs.

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VAstargazer wrote:So I have
VAstargazer wrote:

So I have tested the above machine with a genuine Apple II+ power supply.  Same issue.

Crisp cleat video with no cards installed.  Install a card and wonky video.

Disk II controller in slot 6 not driving the disk drive.

Definitely seems like a power issue, but not a result of the PS.

Any suppestions welcome.

My next planned steps are to measure the power

 

I might suspect dirty or poorly connecting slots...

And yes, check the power to the slots - all four voltages.  If the drive motor doesn't turn on it's likely because there's no +12V or there's high impedance on the 12V pin due to dirt or oxidation.  Check the power connector on the motherboard for cold solder joints or ill-fitting pins.

 

A while back I couldn't get serial communications to work on a II+ clone.  I couldn't figure out why there were no RS-232 signals getting out of the SSC properly, but it could receive.

I thought the SSC was bad.  Putting an RS232 monitor on the line told me what I needed to know - that the pins were not asserting properly. 

Fault:  no -12V. 

Odd becasue the machine seemed to work ok otherwise.

Found a broken line from the -12V to the slots, jumpered it with a short piece of wire and presto.

Not saying that's what's wrong with your machine, but I'd probe the slot power points with an oscilloscope and multimeter to see what's up.

 

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Steps taken

Hi Baldrick,

Here is an update on the diagnositcs:

All contacts were cleaned with WD40 electronic contact cleaner

Tried different cards to make sure its not bad cards.  Working with the most common of periphreal cards (Disk II Controller) I have tried 3 of them.  All same result.

I checked every power pins (all voltagges) on every slot......all reading properly

Visual and DMM check on power connector pins - all good.

There are no visually obvious blown chips.

There is a hot SN74S195N and ROM E0 is also rather hot.  A good 10+ degrees hotter than similar chips.  Same on both machines.

 

I have not done this yet, do you think it is possible the jumpers the previous owner installed for the Videx boards could be causing a problem?  Or even the lower case chip in the specialty ROM socket?  Since I don't plan to put a videx card back into this machine, I was thinking of giving this a go.  What has me so puzzled is 2 machines from the same source have the same problem.  So do the clone machine.

There has to be some commonality of modifications the previous owner did that I am missing.  Whomever he was, he seemed to be 31173 given some of the homebrewed cards this guy made.

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VAstargazer wrote:I have not
VAstargazer wrote:

I have not done this yet, do you think it is possible the jumpers the previous owner installed for the Videx boards could be causing a problem?  Or even the lower case chip in the specialty ROM socket?  Since I don't plan to put a videx card back into this machine, I was thinking of giving this a go.  What has me so puzzled is 2 machines from the same source have the same problem.  So do the clone machine.

There has to be some commonality of modifications the previous owner did that I am missing.  Whomever he was, he seemed to be 31173 given some of the homebrewed cards this guy made.

 

It's a bit of a mystery for sure.

Have you got an oscilloscope?  What I'm thinking is that maybe installing cards into the slots are causing the system clock to go wonky.

Check the chip at B2 and make sure it's a 74S86 qnd not a 74LS86.  While they have similar functions the former has a higher current output.

The other bits I'd check are the video generation chips.  There are a lot of them in the B-C-D areas around the RAM. 

You have more than one II+ right?  Are the other II+ machines doing the same thing?

 

Also my opinion on the VIDEX lower case chip is to leave it in place.  It's completely innocuous and you sould be able to display lower case with it when some applications warrant to do so.

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Thanks!

I will definitely check the chips.  B2 and the video generation chips.

I do have an oscilloscope but have not used it in this capacity, troubleshooting chips and such.  If you have any guidance or recommended writeups to investigate it is much appreciated.

Yes.  I have three Apple II+ (2 genuine Apple, 1 clone).  All three are doing the same.  The only exception is one machine has alphabet soup characters in the display.  The others do the crisp video proper start up without cards.  It occurs with any card, the ones in the lot I got as well as other kown good cards I have.  I was concerned the cards may have been to blame but logic says that shouldn't be the case.

Would a photo of the display changes be of any value?  I could take on and include it.

 

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I'm not sure how I did it,

I'm not sure how I did it, but I got the Apple II+ working.  It is booting from a floppy.  Looks like I had some connection issues in the floppy drive, which I resolved.

Now I can boot to a diagnostic disk.  The diagnostic disk says all parts pass, particularly happy that all RAM passed.

From watching some videos on YouTube, it looks like my intermittent video issue my be transistors Q3 and/or Q4.

Thats next.

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VAstargazer wrote:I'm not
VAstargazer wrote:

I'm not sure how I did it, but I got the Apple II+ working.  It is booting from a floppy.  Looks like I had some connection issues in the floppy drive, which I resolved.

Now I can boot to a diagnostic disk.  The diagnostic disk says all parts pass, particularly happy that all RAM passed.

From watching some videos on YouTube, it looks like my intermittent video issue m

You don't happen to have any links to those YT videos? I'm trying to find possible causes for the video problem on my II+..

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First in a 5 video series

Here is the link to the first of the 5 videos.

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VAstargazer wrote:Here is the
VAstargazer wrote:

Here is the link to the first of the 5 videos.

 Thank you, much appreciated!

 

More precisely, how does the video problems show on your Apple? Is the signal too low as in the YT video, or is it something else?

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On/off video

My issue seems to be an on/off video issue.  I am suspecting a failing Q3 or Q4 transistor.

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SUCCESS!!!!!

So the Apple II+ is alive and functioning perfect.  Passes all diagnostics.

I did not have to change Q3 and/or Q4.

I pulled the ICs associated with the video circuits (at leaset I thing they are).  Cleaned the sockets.

This same action on the ROM sockets fixed my D8 ROM problem.

The BIGGEST jump occured after reading a post somewhere here on AppleFritter about monitor capabilities.  It must have come back to my thoughts since I had an epiphony to try a 3rd monitor (large LCD TV) and BAMM!!! Beautiful, stable video.  Original monitor was a crappy off brand LCD TV, which has worked for everything, including my Apple IIe during its restoration.  What worked was my Samsung TV.

Floppy drive is working great after I discovered a loos connection.

On to the next machine, a clone Apple II+ with an Apple IIe Platimun style keyboard.  This has a colored verticle stripe issue which I am feeling a lot more confident in solving.

THANK YOU to everyone who helped here with suggestions and input.

Cheers

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