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LCIII is not working... no picture, no sound...

dragon_x

Well-known member
Hello,
I purchased two macintosh computers. Performa 450 and LC III. Performa works perfectly. The problem is with the LCIII. After turning on, the fan starts, the drive ... and that's it. No sound, no picture. The processor and some chips get slightly warm.
Could capacitors be the cause or could it be something serious about him? The seller uploaded photos of a working computer and sold it as working. The power supply has also been checked and works. Extra ram works, hard drive works.
Where to start? Can you first bathe your motherboard in ISO? Parts for recap will only be in a few days and I would like to try to start it, since it supposedly worked before shipment.
best regards
Daniel

 

bibilit

Well-known member
Clean the board first and have a try. 

The board will need new caps for sure. 

Cap goo is conductive, so a short is a possibility. 

 

mmx01

Active member
Provided you don't want to return LCIII (I would not accept return after someone messed with the board) definetly do the caps first. While this is not 100% bullet proof, I use vinegar to deactivate leaked acid and then flush it with isoprop. alc. Do this with caps removed and let the area soak in vinegar. Not all caps are the same but in home conditions nothing better comes to mind.

Since PSU & voltages were checked - I assume under the load - it should be fine.

Try re-seating ROM chips, could be upset in travel - but check seating and orientation. Chips are shorter than sockets.

Dead silence means whatever happens happens before boot process init.

If you have an oscilloscope it would greatly help. Otherwise check with a regular meter set to V mode what is the voltage on PIN 15 of U7 (reset circuit). Crystal of U7 likes to fail too. If you get 5V this is good, if 0V reset is not released and nothing will happen. This is important as U7 looks after few things before allowing CPU to init - in particular voltages, hence question if checked under the load.

FAN and hard disk headers have no an logic built into power section, no IC controls them and it is a simple passthrough of voltages from the PSU. The fact these are on confirms nothing really. FAN will operate at 9V as well as on 12V.

 
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dragon_x

Well-known member
Clean the board first and have a try. 

The board will need new caps for sure. 

Cap goo is conductive, so a short is a possibility. 
Hello
it was the first thing I thought of to do. I bought caps for recap but I will have to wait a few days for them.

Provided you don't want to return LCIII (I would not accept return after someone messed with the board) definetly do the caps first. While this is not 100% bullet proof, I use vinegar to deactivate leaked acid and then flush it with isoprop. alc. Do this with caps removed and let the area soak in vinegar. Not all caps are the same but in home conditions nothing better comes to mind.

Since PSU & voltages were checked - I assume under the load - it should be fine.

Try re-seating ROM chips, could be upset in travel - but check seating and orientation. Chips are shorter than sockets.

Dead silence means whatever happens happens before boot process init.

If you have an oscilloscope it would greatly help. Otherwise check with a regular meter set to V mode what is the voltage on PIN 15 of U7 (reset circuit). Crystal of U7 likes to fail too. If you get 5V this is good, if 0V reset is not released and nothing will happen. This is important as U7 looks after few things before allowing CPU to init - in particular voltages, hence question if checked under the load.

FAN and hard disk headers have no an logic built into power section, no IC controls them and it is a simple passthrough of voltages from the PSU. The fact these are on confirms nothing really. FAN will operate at 9V as well as on 12V.
Hi, thank you so much for informations

I bought this LC as working. Seller sent me photos with working computer. I ve written him about the situation and he answered that hi has chcecked computer before hi put for sell. The seller claims that the machine was operational before shipment. Maybe something was damaged during the transport.

PSU was checked under the load. Ive connected the preforma board and run some benchmarks and tests. PSU is working good.  

I suspected that the power supply and the drive are only passing the voltage :(

Unfortunately I don't have oscilloscope, I will check the board  according to your instructions.

I hope LC III will work again :)

Is it a good idea to bath the board in isopropyl alc. and clean it with toothbrush and check it after before capacitors for recap will come?

greetings 
Daniel

 

cheesestraws

Well-known member
Um, if the seller sold it as working and the seller arranged postage/courier, then the machine arriving in working order is their responsibility, generally.  Whether it worked when it left their place is basically irrelevant.

 

dragon_x

Well-known member
Um, if the seller sold it as working and the seller arranged postage/courier, then the machine arriving in working order is their responsibility, generally.  Whether it worked when it left their place is basically irrelevant.
Yes, the seller arranged courier. I am thinking about it. Iva written the seller about the situation. He only answered that hi is surprised and have a hope that I will find solution to run Mac correctly .... 

I bought two Mac from one seller. both should be in a working condition. Performa works perfectly, LC III not.

 

mmx01

Active member
Washing in isoprop. with battery removed will not do it any harm but caveat here, these are old boards. You may knock-off something by accident even with a tooth brush. First question as I said is, do you want to play with it or return it as the item is not according to the description. You don't have to do anything with it.

ROM re-seating and removing all expansion RAM / VRAM is generally what I would consider as exhaustive user troubleshooting one could expect and relevant to an issue which could have occurred in transit. Maybe visual check if nothing is missing in an unusual way indicating something fell off when it was thrown or whatever. There are some unpopulated parts but solder pads are nice and never touched so easy to spot the difference.

If these turn out okay and machine still won't boot then I would not do anything more unless you want to keep it and fight for it. Then you have wash, caps, reset circuit.. only you know if it is worth it. 

 

dragon_x

Well-known member
Washing in isoprop. with battery removed will not do it any harm but caveat here, these are old boards. You may knock-off something by accident even with a tooth brush. First question as I said is, do you want to play with it or return it as the item is not according to the description. You don't have to do anything with it.

ROM re-seating and removing all expansion RAM / VRAM is generally what I would consider as exhaustive user troubleshooting one could expect and relevant to an issue which could have occurred in transit. Maybe visual check if nothing is missing in an unusual way indicating something fell off when it was thrown or whatever. There are some unpopulated parts but solder pads are nice and never touched so easy to spot the difference.

If these turn out okay and machine still won't boot then I would not do anything more unless you want to keep it and fight for it. Then you have wash, caps, reset circuit.. only you know if it is worth it. 
The return is rather unpayable, because a foreign shipment is half of the value of this computer. it wants to bring it back to life. I talk to the seller about some compensation. 
I have repaired my LC I, I think that with the help of the forum people I will manage the repair. 
Because I still have to wait for the delivery of condensers for replacement anyway, I think if I really don't drip the headboard in isopropyl alcohol and clean it. 
I did not notice any damage or suspicious solder, nothing is broken or destroyed. One thing that draws my attention is the suspicious raid on the capacitors, which may indicate that they have been spilled. Maybe the computer was working before shipping to me but the shock during transport caused the computer to not start now.

I tried to run it without additional RAM and batteries, with no results.
 What do you mean by reset circuit... ? How to do it?

Besides, there are fewer and fewer of these computers. I would like to bring another one back to life.

 
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cheesestraws

Well-known member
Yeah.  I had a couple of these boards that were dead on arrival but recapping and cleaning made them came back.  Worth a try, anyway, if you're willing to take it on as a project machine, especially if you can get some compensation.

 

mmx01

Active member
Well then, your decission opens new paths ;)

Wash it. I do wash my boards (with all power sources removed) with regular dishwash(er). Then rinse in isoprop alcohol and bake in the oven at 50c for abt. 2hrs. I do wash and rinse both sides.

Then do the caps, all electrolyitc ones.

Have you tried removing and reseating ROMs? Good to use some deoxide on pins & sockets. I normally do that before washing/rinsing to also wash out all residue after deoxide.

Reset circuit is the U7 / PIN15 check. Some call it EGRET chip as it has such marking on other non-LCIII boards. No need to dig deeper if PIN15 is high = 5V after power on.

These 4 things should keep you busy for starters.

 

dragon_x

Well-known member
Well then, your decission opens new paths ;)

Wash it. I do wash my boards (with all power sources removed) with regular dishwash(er). Then rinse in isoprop alcohol and bake in the oven at 50c for abt. 2hrs. I do wash and rinse both sides.

Then do the caps, all electrolyitc ones.

Have you tried removing and reseating ROMs? Good to use some deoxide on pins & sockets. I normally do that before washing/rinsing to also wash out all residue after deoxide.

Reset circuit is the U7 / PIN15 check. Some call it EGRET chip as it has such marking on other non-LCIII boards. No need to dig deeper if PIN15 is high = 5V after power on.

These 4 things should keep you busy for starters.
This is a new  project :)  Maybe next Mac will have a new life :)

WhereI should take a GND for  Pin 15 measuring?

 
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dragon_x

Well-known member
Yeah.  I had a couple of these boards that were dead on arrival but recapping and cleaning made them came back.  Worth a try, anyway, if you're willing to take it on as a project machine, especially if you can get some compensation.
Yes, this is my next project machine. I bringed to life my LC I. I hope LCIII will be next :)

 

dragon_x

Well-known member
hi, I'm starting a Macintosh renovation.  on pin 15 of the u7 chip, the voltage is once and once not.  I checked on a working performe and I had over 3v there.  in LC the voltage oscillated around 2.7V if it appeared.  disassembled capacitors.  as you can see in the photos they poured out, luckily the pads are intact.  a strange raid is on the ROM dice.

7520956A-42BD-4C49-B6D6-372A15F7933C.jpeg

E18A05F5-448E-4F7C-8807-9A48B430C70D.jpeg

FFFAF231-3C43-4503-922A-9418DE37F2F3.jpeg

59B40BC3-49B7-46D8-BFEC-66CEC00FCF30.jpeg

5A26AF09-C74D-46EC-89B4-745AE521916C.jpeg

871D8DC8-9744-41A7-B4A1-321F626858D1.jpeg

D806B10F-8441-4B94-9B45-2AAB84B081B6.jpeg

 
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dragon_x

Well-known member
Next Mac is alive :)

I did a motherboard iso bath and recap.

Mac is backed to live

next thing will second iso bath and PSU recap.

5FA7CE45-A3E4-477D-AB1A-2DB7F6A8B704.jpeg

4D9B1590-3CA1-42BF-AEC2-253A91D3B1BC.jpeg

 
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