A500 disk drive stopped!

[Laughy]

Hello,
Wondered if anyone can help. I just dug out my old A500, checked it worked on a friend's compatible TV, it was fine. Took it home waited a couple of days, while trying to scrounge a TV off anybody I could!
Anyway, set it up, all good. Put one of the same disks in as I had checked it with, it failed to load! Got a little way then power light flashed. That's it!

Had a look on you tube for tips on cleaning disk drive, took Amiga apart, disk drive out. Couldn't get it completely out of casing, not having proper size tiny screwdriver, so cleaned as much of the fluff out of it, and the reading heads as I could with cotton buds and alcohol. Put it back, loads a bit more but not properly.

The other thing is I couldn't tune it in to the TV. Controller doesn't seem to be working, even with new batteries. I'm going to get an RGB to SCART cable as I have found out that TV is compatible.

Any help is much appreciated, as I don't know anything about fixing computers!
Thanks

[Laughy]

Wow, Thank you all for your replies! I will try to answer all your questions!

Thankfully it's an A500 not the 500+! Have seen the damage caused to the motherboard from the leaking clock battery. When machine turned on, it does make the normal clicking noise from the empty drive, so I assumed it will have the screen with the hand and disk. No way yet to confirm this yet as I can't seem to find the signal from the amiga using the RF cable. It was fine on friends TV just days before I tried it at home.
I have tried everything I could think of on the controls on the TV itself (changing input on EXT, AV, VCR, etc) I was hoping that if I get the RGB to SCART cable I have seen recommended on this site, that the TV will recognise it, and I won't have to tune it. Works fine with a dvd player. Just thought there would be more options and ease of use with the TV remote.

I will go through all that you suggest and get back to you all.

Thanks again!

[Laughy]

The 500 doesn't output RF, it's only got (monochrome) composite and - much preferable - RGB. (Plus digital RGBI, but you wouldn't want that either.)

For RF you'll need an A520 modulator but as long as your TV has any way of directly inputting a video signal you won't really want that.

Try connecting the RCA jack on the left edge to your TV's AV input (any RCA cable will do). There's no color but you should be able to see something.

I've got the 520 Modulator, perhaps that has stopped working, as I put the RCA cable into the mono output on the Amiga, as you suggest and yes, I can see the usual screen with hand and disk! Fuzzy and not stable!

I tried the Workbench 1.3.2 disk, just to see what happenend, it did load a bit, but stopped..

[Laughy]

The power light flashing means the machine crashed. It probably has nothing to so with the floppy drive. To help you further, can you say whether it's a 500 or a 500+ , or if it comes up with a white or purple screen with no disk inserted. Also, what game(s) made it do this? trust me, it's all relevant.

On checking again it just crashes, power light just goes dim, no flashing. Though I could swear it did flash a couple of days ago (prior to taking apart and attempted cleaning).
It's a 500, with white screen. Games I played the other day which were fine, and not now : Turrican 2, Nitro and Project X.

[Laughy]

If there's a memory expansion in the trapdoor slot remove it and see if it changes anything. Usually, they've got a battery inside which leaks and eats up the board. If the fuzzy stuff has already spread to the board it'll need a good cleaning at best.

No battery on this trapdoor expansion, it looks absolutely clean, no damage. Have taken it out.

[Laughy]

Hi,

A couple of things first!  You need to count how many times the power light flashes, and is it consistent?  Ie. happening at same point or various random times?  Are you getting a picture at all, you mentioned your remote isnt working?  At this stage it could be (off the top of my head) the PSU, floppy drive (some models have surface mounted caps that fail related to rotation speed), CIA or worst case RAM (not socketted, hard to remove).

Simple things you can do to start with are to remove RAM expansion and retest, take cover and shielding off and make sure all socketed chips are firmly in place.  If its an a500+ you could have a leaked nicad battery, the same battery issue occurs in the 512Kb RAM expansions also.

Socketed chips all firmly in place, the whole motherboard is in good condition. I can get the screen, followed suggestion from Zac67, without using the 520 Modulator.

[Laughy]

Just to be clear, have you removed the modulator when using the black and white composite signal?  maybe you plugged the modulator in whilst it was powered up or something?  If video output is faulty it could be a problem with hybrid.  Could be denise but unlikely I think.  Try swapping the 2 x CIA chips around and check behaviour, if swapping them around changes behaviour it will be faulty CIA - i've got several spares.

Edit: when you swap them make sure they are installed the correct way around.

Modulator was unplugged when using the mono output. Just tried it again, get a picture both connected and unconnected. Just not through the modulator.
Had a go at removing the CIA chips, but they are well in and am a little worried that I will damage the chip and/or motherboard taking them out. I will have to get one of those PIL tools to grab both ends at the same time. It's going to take quite a bit of force in any case though.

[Laughy]

Do you have a multimeter? It's worth checking all the voltages are there from the PSU. Doesn't sound like a PSU issue but I am wondering if that modulator needs a 12v or -12v source or something, could explain the loading problems as well as the drive probably needs the 12v line also, whereas most if not all of the logic on the main part of the board will probably work with +5v line regardless of the +12v / -12v lines - they tend to be used for comms, and audio output.
 
EDIT: Regards my comment on the message previous to this one, see this video:-
 
https://www.youtube.com/watch?v=RkSCh53fO6Y
 
Around the 2:59 mark you can see how the guy remove the DIP chip from the socket. The smaller the blade on the screwdriver the better, he's used quite a large one there imo.

No multimeter, but could probably borrow one. You'll have to forgive my lack of knowledge of electronic stuff. I'll have another go with the CIA chips.
Just so I get it straight in my head, you think that it is one of the CIA chips that has stopped the drive from loading and stopped a signal going through the modulator?

Maybe I was a little misleading with my description of the mono picture, it is there, just not great, needs a bit of tuning. No flicker or anything like that. Sorry, shouldn't have said not stable.

I will have to look up PSU as I don't know what that is. I wouldn't know where I would have to test to find out the voltages. Shall I see if I can get a multimeter, and get back to you? I'm not sure what the hybrid is, sorry, I assumed you meant the RGB to SCART cable. I don't have one yet. But then, if the RGB output is buggered, no point getting one until I fix it?

[Laughy]

Thanks all, suggestions taken on board. I will try swapping the CIA chips in daylight, I don't want to damage my computer! Have taken out RAM expansion. No change as yet.
Will also get hold of multimeter asap. As soon as have done chip swapping, will get back to you..

[Laughy]

Have swapped the CIA chips, that was a bit nerve wracking! Especially as one of them was really hard to get out. It all popped up in one go really quickly, and all the pins on one side were still in the socket, and got bent!!

Straightened them out, turned on. No picture through the modulator, so went back to the mono output. Get the white usual hand and disk screen. Tried loading a game, drive the same, makes two turns with the disk, then stops. Difference now seems to be that the power light doesn't dim!

There is something showing on the screen, it turns blue as the disk stops, and then, goes to what could be a white screen with something small being displayed. It is unstable at this point, diagonally flickering..

RAM is out too.

What should I try next? Getting the multimeter and checking power to RGB socket?

[Laughy]

The pinout of the PSU can be found here:
http://www.hardwarebook.info/Amiga_500/600/1200_Power_Supply

And for a photo:
http://www.ianstedman.co.uk/Amiga/amiga_hacks/Amiga_Power_supplies/body_amiga_power_supplies.html

When using a multimeter, hold the common ground probe of the meter (usually black) to pin 2 - common ground. Then use the other lead (usually red) and hold on the voltage pins (1, 3 and 5) one at a time. You need both probes to touch one pin each to get a reading. Sorry for sounding too informative but I do not know how much electric/electronic skills you have.

Maybe that you can borrow a multimeter from can help you to check? Ask for help but stay with that person during the test and see what he/she does. And ask questions. Learn. And then get your own multimeter. For just checking basic voltages you do not need an advanced one. I paid ~AU$20 (~GBP14) for the one I have. And it's a decent one to to basic stuff.

Good luck!

Thanks mrknight,

Got myself a multimeter, think you are right it is a PSU problem. Tried black lead on pin 2, and put red lead on pin 1,3 and 5. Nothing at all showing. So tried black lead on pin 4, signal ground (going by the diagram). Results:
Pin 1, 10.9v
Pin 3, 26.2v
Pin 5, 0.0v

Pretty scary! Does this explain why modulator not working, does it mean that there is no 5v supply going into the computer?

Would getting a new PSU solve all my problems?

[Laughy]

It could be a dozen things.  Load Workbench first (if you have it) and then insert the disks they could come up as bad and that might be normal depending on the disk. But at least you should get an error of some type.

Put in workbench disk, it does load for quite a while, can't remember if this is normal. When it eventually stops, there is something showing on the screen, but the picture is so bad can't see if it is anything, or just more static!

[Laughy]

You could try cleaning the drive heads first.  Use a cotton bud with alchohol and rub the heads lightly, just to rule floppy drive out.  Then check power using multimeter, and if that doesnt reveal anything you are looking at a faulty chip probably.  Sounds like you can rule the CIA chips out, my next guess would be the RAM, which is soldered on board and hard to remove if you dont have experience.   Have you pressed the Agnus chip down to make sure its firmly socketed?

Edit: Ignore comment about RAM for now, its probably not that - I was forgetting that your modulator isnt outputting.

Have cleaned the heads on the drive as best as I could, I reckon you are right, and that it is a PSU problem, tested outputs. Don't think they are what they should be!
Pressed the Agnus chip, it was fine. If it is as simple as the PSU not working, problem may be solved, just have to look on ebay!

[Laughy]

Thanks for everyone's help.

This may be better than trying to reply individually! It took me a while to be able to get to a shop to get a multimeter. This is all new stuff to me, never thought I would be mucking about trying to fix a computer!! I'm happy to be learning though, thanks for your patience!!

I posted results of testing the PSU outputs, here they are again Pin 1, 10.9v, Pin 3, 26.2v and Pin 5, 0.0v

Seems like there is no 5v going into the machine. Sounds like that is the cause of all the problems?
My concern was how this all occurred just from moving the machine! But then it is over 20 years old!!

What should I test next?

[Laughy]

I am not sure you've measured using the correct ground pin. If there was no 5v you wouldn't get the image of the hand holding the disk on the white background etc. The +5v powers most of the logic chips so 0v would mean nothing happening at all. Put the black wire of the multimeter on signal ground and see what voltages you get, and then try the black wire on the shielding ground and see what you get.
 
It's sometimes best to actually measure the voltages under the board whilst the amiga is powered up - that way you get 'under load' voltages which can vary wildly from what you measure coming out of the PSU when its not connected to the Amiga. I've seen +16v on 12v line drop to +12v when connected to the amiga etc.
 
EDIT: I've re-read and realised you said PIN 5, not the 5v line =)
 
Pin 1 is 5v
Pin 3 is +12v
 
So your +12v is mega high - could have damaged the FDD or modulator.
And your +5v is very high also - again could have damaged chips.
 
Check the voltages under load as ive described and use your multimeter on the pins under the board where the socket mounts the PCB. See what you get under load, just to be sure.

Ok, sorry about confusing post. When testing PSU unloaded (not plugged into machine), with black connector on Pin 2, always had a zero rating when red connector put onto Pin 1,3 and 5. So had another look at the diagram and put black connector onto Pin 4 Signal ground, then got those readings.

Have been testing PSU underload, took mother board completely out of machine, but was reluctant to bend back metal casing, as I don't think I'll ever get it back in place.
So worked which pin is coming out through the inside of the connection.

Got some very varied results. When putting black connector on Pin 2, there is some reading, strange how there was nothing when it wasn't plugged into the machine.
Anyway tried lots of the chips and floppy power supply, mono output, etc. Both with black connector on Pin 2, and Pin 4.

The mono output measures 3.5v with both,
RGB output measures 10.4 Down to 3.1, depending which pin red connector is placed on. So I suppose that there is one pin that is the power source for the modulator? You can see that I know absolutely nothing about electronics.

Sorry if this seems too long winded..
Other results are: with black connector on Pin 2;

DENISE 2.0v
ODD CIA varies between 2.3 and 10.6v (depending which pin on chip)
EVEN CIA 10.4v highest
PAULA 10.3v
GARY 10.6v
Trap door 8.6v
Floppy power source 10.6v

And with black connector on Pin 4

DENISE 8.1v
ODD CIA 10.4v
EVEN CIA 10.4v
PAULA 10.3v
GARY 10.6v
Trap door 8.3v
Floppy power source 10.6v

I've realised that certain pins on the chips carry the power, so the low readings should probably be ignored when there is a higher reading across the whole board of around 10.6v?

Hope that makes some sense!