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Old 02 December 2014, 21:11   #1
Targ
 
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A1200 - black screen & power LED blinks

Hey everyone. I recently wanted to get back into the Amiga & dug out my 1200. It worked fine for a few weeks but now I just get a black screen and the power LED blinks 7 times. The 7th time is a short flick, then there's a 1 or 2 second pause, then it starts blinking again.

I've read other similar posts but none seam to apply. There was no corrosion, burns or other marks on the board, barely any dust. No colors come up on screen. It's just black, but I can see it's a signal black. It's not a black like the monitor isn't on, and when the led just flicks real short the 7th time, the screen flicks too. I tried the composite out to a Panasonic TV & RGB out to a NEC multisync. Nothing happened after the last time it worked like lightning strike, brown-out, power surge, etc.

I tried removing the accelerator, the HD, even the floppy drive. The only thing that stops it was removing either or both ROMs. Obviously, that stopped everything. I finally checked the power supply & it was pretty wonky. All 3 voltages read about 2/3 to 3/4 their normal rating, and were pulsing over about 1/2 volt, 1/2 second apart.

I rigged up a PC power supply & it still does it. I removed the board & cleaned both sides with isopropyl & a soft tooth brush. Still the same. The only change is with the 030 board in it takes about 4 or 5 seconds to start blinking again. My worst fear is that the power went & took something on the board with it. Anyone have any ideas?
 
Old 02 December 2014, 21:27   #2
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Welcome to the board!

When the Amiga crashes, it blinks the power LED a few times and then reboots. I don't remember if it's exactly 7 blinks but it could match the symptoms. It can't be a software crash as such if you have taken the hard drive out, but perhaps the Kickstart ROMs are somehow corrupted. My first try would be trying another pair if you have some.
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Old 02 December 2014, 21:39   #3
Merlin
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Are there any domed capacitors on the board, or any fishy smells? Domed caps are a sign that the cap has failed and they can cause all sorts of weirdness on voltage rails.
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Old 02 December 2014, 23:00   #4
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ajk:

Thanks for the sugestions. Unfortunately, this was the only Amiga I still had, and I don't know anyone else around here to try swapping parts. Heck, even back in the day I didn't know any other local Amiga users. Also unfortunately, being disabled, I can't just throw a bunch of money at this & start buying parts. I can afford to fix it, if it can be, but I'd have to know what's gonna do it the first time.

Merlin:

Nope. No damaged caps, leakage, or signs of dried residue. This board is beautiful, you'd swear it was made earlier this year. No smell I can detect. Even in the power supply, there were dark areas around components from the heat, but no signs of anything split, leaking, or swelling.

It's frustrating that there's no official diagnostic for the LED's blinking. More people seem to have that then getting stuck on a solid color screen.
 
Old 02 December 2014, 23:11   #5
kipper2k
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Hi,

remove both ROM chips carefully bit by bit and evenly, then replace them again, do one at a time so you dont mix them up, and make sure you put them back in same way/location as they came out


some of this info may be helpful...

http://home.arcor.de/kickstart/TKA/T.../trouble1.html

http://home.arcor.de/kickstart/TKA/T.../trouble2.html

Last edited by kipper2k; 02 December 2014 at 23:16.
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Old 03 December 2014, 20:57   #6
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No go. tried the ROMS & everything on those charts that applied. If it makes any difference the caps light works & Ctrl-A-A makes it reset immediately. Otherwise, I guess its gone - sad day. I'll put it on ebay as-is for parts & the 030/33, unless anyone knows a place that still repairs Amigas.
 
Old 03 December 2014, 21:06   #7
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You can ask AmigaKit. Most of the time the faults aren't really that complicated, there are dozens of people who [ Show youtube player ]. It's just often difficult to diagnose problems over the internet. Need to be able to probe around the board with a meter and a scope
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Old 03 December 2014, 22:48   #8
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These are the Kickstart error colour codes.

Red - An error in the Kickstart rom as detected.
Green - An error in the Chip Ram was detected.
Blue - An error in the custom chip set was detected.
Yellow - The CPU encountered an error before the system's error-trapping code (the code the calls up the Guru) was in place.
Black - No CPU detected.
Grey - CPU Passed the test.
White - CPU failure.

I suggest that you carefully try reseating the Kickstart ROM, as it can 'creep' out of it's socket slightly over time.

Here are the keyboard blink error codes, but I think your problem lies with re-seating the socketed chips. When the Amiga is first switched on the keyboard might blink a number of times to indicate one of the following errors.

One Blink = ROM (Kickstart) Checksum failure
Two Blinks = RAM test failed
Three Blinks = Watchdog timer failed
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Old 03 December 2014, 23:04   #9
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But the A1200 doesn't have any other socketed chips than the Kickstart, and he's already tried that... I don't think there is any trivial procedure to follow at this point, a more thorough investigation will be needed. My guess would be capacitor issues even if it is not visible.
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Old 03 December 2014, 23:11   #10
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Other than checking the supply voltage at the Vcc pin of the 68020 chip, there isn't much else, I agree.
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Old 04 December 2014, 04:27   #11
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I emailed AmigaKit & opened a support ticket. Waiting for estimate but I'm afraid shippng cost will kill that option. Lowest rate I found so far was $78 (about £128) each way. If anyone on EAB does repairs in N.America let me know. Thanks.

Tried the ROMs again anyway - still the same. Trying a re-cap myself might be a possibility. I don't really trust my skill working that small, though, & don't want to make things worse.
 
Old 04 December 2014, 08:35   #12
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Blinking power led means most of the system is working. One common reason for early guru (intuition not yet initialized = led only flashes reboot loop) is broken CIA or connections to CIA, vsync or hsync TOD counter is not counting or counts incorrectly. (This also happens if monitor has too high load on sync lines causing graphics.library to think there is genlock connected, enabling external sync mode, vsync and hsync both stops, timer tests fail..)

Quick easy test: power up without monitor connected. Led still flashes? (Normally only happens with some VGA monitors without buffered adapter)

Quote:
Originally Posted by Merlin View Post
Black - No CPU detected.
Grey - CPU Passed the test.
White - CPU failure.
White and black are not error codes. CPU is needed to get error codes

Grey only means first early (KS1.x) ROM code tests have passed. It is CPU that executes the test code. It basically means "all important hardware is working, at least partially".

White or black is the most common color value in color0 register when Denise/Lisa powers up (seems to depend on revision or something like that). Many other broken parts of chipset can cause white or black screen stuck at power up.
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Old 04 December 2014, 15:29   #13
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Quote:
Originally Posted by Targ View Post
I emailed AmigaKit & opened a support ticket. Waiting for estimate but I'm afraid shippng cost will kill that option. Lowest rate I found so far was $78 (about £128) each way. If anyone on EAB does repairs in N.America let me know. Thanks.

I can take a look at it for you, i live in Canada, you can send me just the motherboard itself. let me know.
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Old 04 December 2014, 22:05   #14
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Toni - I tried a composite monitor, RGB monitor, both, & none - same thing. I don't think it's the CPU because with the stock 020 the blinking starts immediately, as soon as the power switch is pushed. With the 030 board installed it takes about 4 seconds to start blinking on both power-on & each reset. This is the same time it takes the accelerator to start booting over stock.

Kipper - Thanks for the offer. I ordered the caps last night and was going to give it a try. I've been watching RetroGameModz's videos and they gave me the confidence to at least try it myself. He really clued me in to what to look for, too. On reinspection I found there are very small spots I mistook for finger smudges, and lint or fuzz, that are probably cap leaks after all. I was looking for signs closer to battery corosion. I'll see how I feel when the caps get here. If I chicken out, flub it, or it still won't boot, I'll be in touch. Thanks again.
 
Old 04 December 2014, 22:52   #15
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Yeah, capacitor leaks can be quite slight, like a little oily spill under the cap. You can see it depending on the lighting and also dust and stuff tends to stick to those spots more. They will cause problems in two ways; the capacitance is reduced so you don't get the intended voltage smoothing effect, and if left untreated, the electrolyte will start eating away at the board.

Here's a video clip I recorded showing [ Show youtube player ]. You can manage without the hot air gun, there are various other ways to get the old caps off.
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Old 29 January 2019, 11:21   #16
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Quote:
Originally Posted by Targ View Post
I'll be in touch. Thanks again.
So, any outcome? Because yesterday I got very the same situation with my 1200
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