Vintage Computer Manuals

Vintage Computer and Classic Computer Manuals Online

Saturday, August 26, 2006

Apple IIe Repair Guide

Open your computer and take a look at the motherboard. Looks confusing, eh? Not really. The big black things are called integrated circuits, and these are what break down or fail most often. The other things we will not worry about at the moment.
Up and down the left side of the motherboard you will see letters A-F, and along the bottom the numbers 1-14. This is the way Apple locates their chips on the board - much like a city map with grids. Here are the names, and locations, and the approximate costs for each of the chips on the board. Don't let the names of the chips scare you or anything on this chart. It is mainly for information, and you won't need to know anything about the chips on the board (aside from the fact they are broken, which will come later).
IC # Location Approximate $ Description Notes ------------------------------------------------------------------------------- 74LS02 B8 0.78 Quad 2-input NOR 74S10 C5 0.78 Triple 3-input NAND 74S109 C1 1.34 Dual JK Flip-flop 74LS125 E1 1.12 Tri-state quad buffer 74LS138 B5 1.22 Expandable 3/8 Encoder 74LS154 C10 2.80 4-16 decoder/multiplexer 74LS166 F5 1.84 8-bit serial in, parallel out shift register 74LS244 B1,B3 2.80 Tri-State octal line driver 74LS245 B2 1.70 Tri-State octal bus receiver 74LS251 C11 1.55 Tri-State 8-input multiplexer 74LS374 D3 1.98 Tri-State octal-D flip-flop NE558 A12 2.00 Quad 555 timer MC741 A11 0.75 Operational Amplifier ULN2003 Analog Card ???? 7-channel input (from Apple) driver LM3146 Analog Card ???? Transistor Array (from Apple) MC3470 Analog Card ???? Floppy disk (from Apple) read amplifier MC3764 F6-F13 20.00 64k x 1 bit RAM 6502B B4 14.00 8 bit microprocessor KB ROM D12 8.00 Keyboard ROM VID ROM F4 12.00 Video ROM CD ROM D10 20.00 Applesoft ROM EF ROM D8 20.00 Monitor ROM HAL D1 56.00 Programmed Array (from Apple) logic IOU D6 56.00 I/O unit (from Apple) MMU D4 56.00 Memory Mgmt Unit (from Apple) AY3600 D14 16.00 Keyboard Decoder
Ok, that's all of the chips on the motherboard, and a few from the Analog card, that is the one inside your disk drive (apple drives only). If you need to order one of these chips from Radio Shack or some other local electronics store, then you ask for the chips by the number in the left hand column. For example, if your paddles were not working and the cables were good, you would need to start with the NE558 chip, and that is what you order. More about that later, though. Don't worry about the big costs of the ROM chips or the CPU. Most computer breakdowns are of the 74LSxxxx series and you will most normally have to deal with those only.
Now, before you go poking around your motherboard popping out chips and sticking them back in, a few tips and reminders to keep your apple running right, and how not to screw anything up...
1) Never touch ANYTHING in or on your computer, including your disk drives, before grounding yourself on something. Static electricity, especially in the wintertime can reach as high as 10,000 volts - enough to fry any of the delicate chips inside your computer.
2) Buy a chip puller. They are cheap, and you will save your fingers from getting pins from the chips stuck in them, and blood all over everything.
3) Always note the orientation of the chip you pull out, so that you can put the new chip in the same way. There is a notch in one end of the chip, or a dot at one end. Either way, be sure the new chip has the notch or dot in the same place as the old one.
4) Use power strips and surge protectors. The surge protector for obvious reasons, and the power strip for preventing wear and tear on the switches. 5) Keep your coke off the keyboard. Liquids can blow every chip they touch. 6) Take special care about static electricity when messing around with the CPU, the ROM chips, the MMU and the IOU chips. These are quite sensitive to static charges.
7) Don't open your monitor. This is stupid, xrays and 30kV's are running around inside and if you don't know what you are doing, you will have radiation damage, or worse yet, your parent will smile when they collect life insurance on you.
8) Don't pull cards out or put cards in when the power is on. You will kill either the card or the computer, I promise.
9) Check everything outside of the computer before you start fiddling around inside. Usually cables, switches or other shit like that are the cause of the problem.
Now: I am dividing up this series into 5 parts as follows:
1) Start-Up Problems 2) Run Problems 3) Display Problems 4) Keyboard Problems 5) Other I/O Problems
And I will release them as I type them. Don't hold your breath, as I am in school and hardly have lots of time...
Part I - Start-Up Problems --------------------------
This section covers all problems that occur at the time you turn the power on, or at start up, including no power, no boot up, no beep and no display...
1) No power light, no beep, drive won't run: Probable defect: 1) 74LS125 at E1 is bad (replace and test) 2) 74S109 at C1 is bad (replace and test) 3) 74S02 at B8 is bad (replace and test)
2) Power light on, no message, no beep: Probable defect: 1) 74S02 at B8 is bad (replace and test) 2) 74S109 at C1 is bad (replace and test)
3) Power light on, message, no beep: Probable defect: 1) (experts only) PAL 16R8/8323T at D1 is bad
4) System won't boot, power light on, drive won't run, garbage on screen: Probable defect: 1) Bad EF ROM at E10 (replace and test) 2) Bad 6502B at C4 (replace and test)
5) System won't boot, power light on, message on screen, drive won't boot: Probable defect: 1) Clean connector pins 2) Clean or replace ribbon cable 3) Bad ULN2003 on analog card (replace and test) 4) Bad regulator on analog card (replace card)
6) System won't boot, everything on, drive keeps running: Probable defect: 1) Reseat disk, check disk, check cable, reseat card. (coming later if this doesn't work)
7) System won't boot, disk drive runs and then stops: Probable defect: 1) Bad DOS 2) Bad Disk 3) Bad RAM chip on motherboard (f6-14) replace and test
8) System boots and then stops, no display: Probable defect: 1) Video cable bad (replace and test) 2) Video connector bad (replace) 3) Brightness knob on monitor? 4) 74LS02 at B8 bad (replace and test) 5) 74LS10 at C5 bad ("""""""""""""""") 6) 74LS166 at F5 bad (replace and test) 7) 74LS374 at D3 bad (replace and test) 8) IOU at E5 bad (replace and test) 9) 2732 ROM at F4 bad (replace and test)
If you need advance help, you can reach me at my board by chat or by mail. If you have questions or suggestions, also call my board.
Part II - Run Problems ----------------------
1) Disk drive will not read (I/O error or disk just runs on and on)
Probable Defect: Remedy: ---------------- ------- a) Bad Disk Replace Disk b) Wrong DOS Try another disk c) Disk not seated Reseat disk d) Read head not reading Replace head e) Cable loose or bad Reseat or replace cable f) Bad chip on analog card Replace Analog Card
2) Disk drive will not write (read is OK)
Probable Defect: Remedy: ---------------- ------- a) Write protected Remove tab b) Protect switch bad Replace switch c) Disk not formatted format disk d) Cable bad or loose Check/Replace cable e) Corroded connectors Clean connectors f) Bad 74LS125 replace (analog card) g) Bad CA3146 replace " " h) Bad MC3470 replace " " i) Bad ULN2003 replace " " j) Bad Write head replace k) head alignment off realign head
3) Disk reads or writes occasionally
Probable Defect: Remedy: ---------------- ------- a) Cable corrosion clean connector pins b) Connector corrosion clean connector pins c) noise interference good luck d) disk tracking off realign head
4) Occasionally keyboard locks up and computer locks up
Probable Defect: Remedy: ---------------- ------- a) Program error debug program b) no keyboard out put coming later c) bad RAM chip replace and test d) bad MMU chip replace and test e) bad CPU at C4 replace and test
Part III - Display Problems ---------------------------
1) No Display - Screen all White
Probable Defect: Remedy: ---------------- ------- a) shift register latch-up replace 74LS166 at F5 and test b) ROM data hung up replace 2732 character ROM (F4)
2) No Display - No Video
Probable Defect: Remedy: ---------------- ------- a) Bad Cable Replace and test b) low signal adjust brightness c) Bad monitor test monitor d) Bad 74LS02 at E8 replace and test e) Bad 2N3906 at A14 replace and test f) Bad 2N3904 at A14 replace and test g) Bad 74LS10 at C5 replace and test h) Bad 74LS166 at F5 replace and test i) Bad 2732 ROM at F4 replace and test j) Bad 74LS374 at D3 replace and test k) Bad IOU at E5 replace and test l) Bad PAL 16R8 at D1 replace and test
3) No Display - Screen Black
Probable Defect: Remedy: ---------------- ------- a) Brightness bad Adjust b) Bad monitor test monitor c) Bad IOU at E5 replace and test d) Bad 2732 ROM at F4 replace and test
4) No Color
Probable Defect: Remedy: ---------------- ------- a) Bad IOU at E5 replace and test b) Capacitor C32 shorted replace (soldering required) c) Inductor L3 Bad replace (soldering required)
5) No Syncronization
Probable Defect: Remedy: ---------------- ------- a) Bad IOU at E5 replace and test b) Bad monitor replace or repair
6) Bad cursor or no cursor
Probable Defect: Remedy: ---------------- ------- a) Bad EF ROM at E10 replace and test b) Bad 2732 ROM at F4 replace and test
7) Bad inverse or flash
Probable Defect: Remedy: ---------------- ------- a) Bad 2732 ROM at F4 replace and test
8) No text
Probable Defect: Remedy: ---------------- ------- a) Bad 2732 ROM at F4 Replace and test b) Bad IOU ROM at E5 Replace and test
9) Video - Bad color
Probable Defect: Remedy: ---------------- ------- a) Bad HAL at D1 Replace and test
10) Bad Graphics (lo and Hi bad); text ok
Probable Defect: Remedy: ---------------- ------- a) Bad IOU at E5 Replace and test
11) Bad Graphics (HI), low and text ok
Probable Defect: Remedy: --------------- ------- a) Bad IOU at E5 replace and test
Part IV - Keyboard Problems ---------------------------
1) Bad key action - some keys or no keys work
Probable Defect: Remedy: ---------------- ------- a) Bad Key replace key b) Bad or loose cable check and replace cable c) Bad AY3600 at E14 replace and test d) Bad 2716 ROM at E12 replace and test
2) Bad key action - prints wrong characters
Probable Defect: Remedy: ---------------- ------- a) Bad 2716 ROM at E12 replace and test b) Bad AY3600 at E14 replace and test
3) Bad key action - unwanted repeat
Probable Defect: Remedy: ---------------- ------- a) Bad AY3600 at E14 replace and test b) Bad capacitor C71 replace (soldering required)
4) Repeat key won't work
Probable Defect: Remedy: ---------------- ------- a) Bad Key replace and test b) Bad AY3600 at E14 replace and test c) Bad Capacitor C70 replace (soldering required)
5) Key top pops off
Well, just glue that fucker back on or get a new keyboard.
Part V - Other input/output problems ------------------------------------
1) Speaker - volume too low
Probable Cause: Remedy: --------------- ------- a) transistor Q5 marginal replace (soldering required)
2) Speaker - won't click
Probable Cause: Remedy: --------------- ------- a) Bad speaker Replace speaker b) speaker wires bad or loose check or replace c) Bad transistor (Q5) replace (soldering) d) Bad IOU at E5 replace and test
3) Cassette - can't load data
Probable Cause: Remedy: --------------- ------- a) Bad cable Replace and test b) Volume not set pproperly Retry at different volume c) No signal on tape Replace tape d) Bad LM741 at A11 Replace and test e) Bad 74LS251 at C12 Replace and test f) Bad 74LS154 at C10 Replace and test
4) Cassette - Can't write data
Probable Cause: Remedy: --------------- ------- a) No signal to tape reconnect or replace cable b) Tape bad replace tape c) Bad IOU at E5 replace and test
5) Game paddle - does not work at all
Probable Cause: Remedy: --------------- ------- a) Bad cable Replace b) Bad 558 timer at A12 Replace and test c) Bad 74LS251 at C12 Replace and test d) Bad 74LS154 at C10 Replace and test
6) Game paddle button won't work
Probable Cause: Remedy: --------------- ------- a) Button bad Replace button b) Broken wire Replace wire
7) Game Paddle - knob does not work correctly
Probable Cause: Remedy: --------------- ------- a) Bad pot in paddle Replace pot b) Broken wire in cable Replace wire
8) Card in peripheral slot does not work
Probable Cause: Remedy: --------------- ------- a) Bad 74LS138 at B5 replace and test b) Bad 74LS154 at C10 replace and test c) Bad 74LS10 at C5 replace and test
Additional hints: -----------------
Look and smell and feel the chips in your computer for things that seem to be bad or out of place. Feel for hot spots, smell for blown capacitors, etc etc. Notice anything out of the ordinary and replace it if it doesn't look, smell or feel right. You can search for heat-blown chips by cooling each chip one at a time with freon from a can and examining the results on the operation of your computer. I f you find a chip that allows the computer to work cold, but when it warms up, p hooey, replace it.

0 Comments:

Post a Comment

Links to this post:

Create a Link

<< Home