Reviving A1200 that does not boot

[tygre]

Dear all,

I wanted to use my Amiga 1200 has Web server... Everything was running smoothly until, two-three weeks ago, my hard disk blew... I ordered a CF replacement from AmigaKit and it arrived today. I try it in the Amiga and then... nothing works at all anymore

I am very puzzled Here is how far I am in trying to find out (and fix!) my Amiga: I removed all peripherals, including the Blizzard 1240, hard disks, connectors/adapters. I even removed the top shield (following this thread). So, basically, the Amiga is naked but for the floppy disk and the flicker fixed, which I need it because I only have a VGA monitor, no more TV or 1085S...

Then:

1. When I switch on the power, the green light shines, the floppy drive does its familiar "dong" sound once. Then, the green light dims and nothing happens anymore...
2. I also tried unplugging the floppy disk. When I switch on the power, both the green and orange (floppy) lights shine. Then, the green light dims and nothing happens anymore...
3. I also tried unplugging everything, including the flicker fixer, and got the same behaviour as in 2.

As I was fixing my Amiga 1200, it is possible that I inverse the +12V and +5V in the floppy drive... Would that be the source of the problem? But, then, why doesn't the Amiga boot up when I remove the floppy drive?

Any idea of what's going on?
Thank in advance for your help/advice!
Yann

[Hewitson]

First thing I'd do is verify the power supply is outputting the correct voltages.

[tygre]

Hi Hewitson,

Thanks, I did check, using the schema that I found on-line:

• The power supply is providing +12V and +5 and -12V as expected.
• Inside the Amiga, near the connector for the expansion, there is this connector, I check the voltage and I get +12V and +5V as expected (?).

So, it seems to me that the power is okay? I have a spare power supply (for A500 though), should/could I try with that one?

Take care!
Yann

[Hewitson]

You can if you like, many users (including myself) use A500 PSU's on their A1200 as they generally have a considerably higher output amperage.

[Loedown]

What do you mean your hard drive blew? We talking sparks and smoke or just not working any more?

The clue here is that it's almost coming on but somewhere near the end it's shutting down with the green light dimming, that indicates a short circuit or power drain.

Verifying the power supply is a good start but a CF solution will draw less power than a standard HDD, when a motor is first started the amperage draw is immense for a very short fraction of a time, CF has no moving parts and doesn't suffer the same issue.

[tygre]

Hi Hewitson and Loedown!

I mean reading errors and, at one point, the Amiga reported this disk error that freezes the computer No fireworks though

Power drain or short-circuit: I will take out the motherboard from it shield, so nothing should short-circuit, right? Then, I will power it on with the A500 PSU, does it make sense?

Thanks, talk to you soon!
Yann

[tygre]

Dear all!

Thanks again for your help and advice! I took the motherboard out of its shield and slowly rebuild my Amiga and now... it works again!

That's the good news... The so-so news is that I couldn't find an obvious reason for the dim green light of yesterday night so it might happen again

Anyhow, now I will try to replace my 3.5" very old hard disk with this CF 4GB disk that I received from Amigakit...

Take care!
Yann

[Loedown]

Originally Posted by tygre

Hi Hewitson and Loedown!

I mean reading errors and, at one point, the Amiga reported this disk error that freezes the computer No fireworks though

Power drain or short-circuit: I will take out the motherboard from it shield, so nothing should short-circuit, right? Then, I will power it on with the A500 PSU, does it make sense?

Thanks, talk to you soon!
Yann

It's not the shield, or unlikely anyway. What I mean is that a part of the circuit is being activated that is suffering from a short circuit. I'll use a car simile to see if that helps.

If you have a car that the alternator is faulty in, say it's gone short circuit through the windings, when you start the car everything is fine for a few seconds, but because there's a short in the alternator it creates a drain on the car electrics and it kills the engine, this might be what's happening in your Miggy.

I would check for any unusually hot chips in the circuitry or burning smells.

[tygre]

Dear Loedown!

Thanks for your example, I understand what you mean now... The short-circuit happened again... I will again take it all apart and this time I am planning to put a layer of tape between the shield and the motherboard, does it make sense? I did try to find something hot or smelly but could not find anything unusual...

Take care!
Yann

[Loedown]

Originally Posted by tygre

Dear Loedown!

Thanks for your example, I understand what you mean now... The short-circuit happened again... I will again take it all apart and this time I am planning to put a layer of tape between the shield and the motherboard, does it make sense? I did try to find something hot or smelly but could not find anything unusual...

Take care!
Yann

I would do away with the shield althogether, unless you are somewhere especially RF noisy or you're worried about how much RF the Amiga will produce.

I think this is going to be one of those obscure sorts of faults, keep us posted.

[tygre]

I'll try and I will sure keep you posted!

Take care!
Yann

[tygre]

Dear all!

I need your help! As I dived into my problem, I am getting more and more puzzled...

1. I removed everything, except the disk drive, and the Amiga boots fine (it shows the hand with a disk).
   
2. I added back the SanDisk CF hard disk and the Amiga boots fine (it shows a CLI with BlizKick complaining that it cannot (obviously) find a Blizzard card).
   
3. I added back the Blizzard 1240 and... nothing happened! The green light shined but the Amiga did not boot, the screen stayed black, I could not access the boot menu, the disk drive went "bonk" once and then felt silent
   
4. I removed again everything as in (1) but added the Blizzard 1240 and... nothing happened either! Same behaviour as in (3)

I also tried with a Blizzard 1230 and nothing happened again, I got the same behaviour as with Blizzard 1240. I don't think that I have a problem of power anymore, because the green light shined but maybe I am wrong?... Has anyone an idea of what is happening? Any advice?

Take care!
Yann

[kipper2k]

Hi,

It is possible that when the drive blew it damaged the power supply and the PSU is not putting out enough power to supply the expansion card. I have accidentally reversed the 12v and 5v line to the floppy before, you would probably hear a high pitched whistle and then need to shut off the power real quick before your board traces become toaster elements.

If you have a multimeter, connect all your accessories and watch the voltages to see if they drop below the 12v and 5v. If you have another PSU then try that.

Also, remove all except floppy drive and put in a bootable game and see if the floppy drive chirps merrily as it loads

[tygre]

Hi Kipper2k!

Well, I don't remember a whistle but I sure did switch off the computer fast... I measured using a multimeter the voltages, they are +5V and +12V. I also tried another PSU with no change. The only change is that nothing works at all now: with only the floppy drive, when I switch on the computer, the floppy goes "bonk" and fells slilent and then nothing...

I am really getting crazy! I mean: yesterday, it worked fine, with the floppy disk, a hard disk, and a CF disk, and this morning, after I removed the hard disk, nothing works...

Hypothesis: Could it be that, this time, my Gayle really blew? (See my previous cry for help ) The Amiga seems to be waiting for something and the hard disk, when plugged in, does not seem to be talked to by the computer: it spins but there is no access light. Is that a reasonable hypothesis? How could I test whether Gayle works or not? I have a multimeter, and the motherboard is totally naked.

(A possible further argument is that my PCMCIA Ethernet card behaves the same as the disk: its light goes green when I switch one the computer and then off and never shines again...)

Any advice, idea?
Yann

[rkauer]

IF the HD light shows up once and not again, chances are the reset circuit is knackered.

I'm thinking if a skilled Amiga guru lives near you to change the SMD 555 and do a complete recap (change ALL electrolytic capacitors on the motherboard).

The Gayle is not a super-sensitive chip and is one who dies last on a +5V surge.

You can also check if a PCMCIA pin is bent and touching one of the around.

Only after all this steps you can blame the Gayle.

[tygre]

Hi Rkauer and all!

Thanks Rkauer for your reply, always much appreciated!

Sorry for the long text , here are two scenarios that I tested that could maybe help in finding the problem:

Scenario 1: Minimalist

Configuration:

• bare-naked mother board, no bent pins anywhere that I can see, no strange-looking capacitors. +5V and +12V remains "still" when switching on the computer;
• only the floppy disk plugged in;
• also plugged in the external Indivision flicker fixer and a PC keyboard through adapters.

Behaviour when switching on the Amiga:

• the green light shines;
• the floppy disk goes "bonk" only once (even after a reset, it stays silent);
• no hand with the floppy;
• the keyboard works (e.g., the led of the caps lock goes off and on when the key is pressed);
• when reseting the Amiga, the green light dims and then shines again, nothing else happens.

Scenario 2: Wish it works!

Configuration:

• bare-naked mother board... (as in Scenario 1);
• floppy disk plugged in;
• 3.5" hard disk plugged in;
• SanDisk CF hard disk plugged in;
• also plugged in the external Indivision flicker fixer and a PC keyboard through adapters.

Behaviour when switching on the Amiga:

• the green light shines;
• the orange light of the hard disk also shines;
• the floppy disk goes "bonk" only once (even after a reset, it stays silent);
• no hand with the floppy;
• the keyboard works (e.g., the led of the caps lock goes off and on when the key is pressed);
• when reseting the Amiga, the green light dims, the orange light goes off, then the green and orange lights shine again, nothing else happens.

Hypotheses

Here is what I think , please correct me if I am wrong:

• the PSU and power circuit of the Amiga are okay;
• the floppy disk is okay;
• the hard disk and SanDisk CF are okay;
• keyboard and others external adapters are okay.

Yet, it seems that the Amiga is "waiting" for something that never happens. Rkauer, you kindly suggest to change the SMD 555 and the electrolytic capacitors. I did some homework and I understand that the 555 is a timer/oscillator, which is surface mounted, and that I am not the first one to have related problems (at least craggus2000 and kixs did...). I am willing to try (practicing first on an old PC motherboard ) but I would need you advice for:

1. Your two-soldering-irons technique.
2. Finding the SMD 555 on the motherboard! (I have checked carefully my A1200 revision 1B motherboard but could not see anything suspicious... and could not find the 555 .)

Thanks in advance!
Yann

[Hewitson]

Just had a look at a picture, the only 8 pin IC I can see is just below the RF modulator so I think you'll find that's the 555.

[rkauer]

You said the HD light goes on and don't goes off? You get a validation issue on the CF!

Use a powerful 030 JIT emulation setting with lots of memory in WinUAE and pop in the CF into the PC. If a validation problem is what you get, after half an hour you'll see your Workbench back to life in the pc.

I wonder if you used the correct max_transfer setting for CF card ( 1xFE00 ). Any other higher setting will render the CF partitions trashed after few time of use and will demand a complete reinstall.

Also a combination of CF and HD will not work, as far as I know you can only use IEFix97 to have more than one device in the IDE and it dislikes profoundly any CF card.

Can you test the Amiga with the old HD if it is still alive? Chances are the floppy bit the dust and your CF is just invalid.

[tygre]

Hi Hewitson and Rkauer!

Thanks for your answers and advices. I formatted the CF with "max_transfer" set to 1xFE00.

I will try as you suggest: just the mechanical hard disk but, if the floppy disk is dead, how long should I wait until the Amiga boots in the hard disk or until I can access the boot menu...

I did try the configuration that you suggested and waited for 10 minutes, nothing ever happened... What do you think?

Cheers!
Yann

PS. The hard disk works in a A4000.

[ajk]

Did you actually see a kickstart screen with the hand and floppy image at some point? Just curious.

[tygre]

Unfortunately, the screen remains black in all the configurations that I tried so far...

[tygre]

Ah, I see it: is it indeed the IC labelled "D215"?

In my Amiga, it is written on the IC:

286X
385-12

no "555" to be seen on it...?

Thanks!
Yann

[rkauer]

U29

[tygre]

Thanks! Found it

So, it is really a 556 (a 14-pin combining two 555)... I am going to test the input and the two outputs to see if there are indeed some pulses... Any idea of the frequencies that I should get?

Cheers!
Yann

[rkauer]

No frequencies: when the Amiga is turned on, expect to see one of the outputs switching to low (or high, cannot remember).

Check the schematics to see which pin is the correct.

[tygre]

Ah, so it is really in "pulse" mode... Okay, I will check and keep you posted!

Thanks!
Yann