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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: Super TWiT on May 17, 2010, 11:08:35 PM
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I noticed today as I started my a500 that the drive light is bright one second and VERY dim the next. Is this a sign of something or is the light burning out?
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LED's last for a very, very long time. You getting proper voltage readings out of your power supply? Power cable going to the drive good? Solder connections at the mobo good going to the drive?
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I don't know. Last time I had the amiga open, everything looked okay. But this is NOT normal huh. The dimming seems to follow a drive seek pattern.
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The dim Drive light on the A500 was a Low pass filter function, it was an indicator of mode changes loading. I think it has something to do with the Extra Half Brite function in the newer Denise Chip. (A500 and A200 Rev 5 and later, not on A1000)
Shaf
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The dim Drive light on the A500 was a Low pass filter function, it was an indicator of mode changes loading. I think it has something to do with the Extra Half Brite function in the newer Denise Chip. (A500 and A200 Rev 5 and later, not on A1000)
Shaf
Dim 'power' light indicates the audio filter bypassed - not the drive light.
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I just recently put in an ecs agnus chip. Could that be it?
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I thought that was the power LED.
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I just recently put in an ecs agnus chip. Could that be it?
Agnus could care less about the power going to your disk drive. She told me so :)
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Agnus could care less about the power going to your disk drive. She told me so :)
We need an Amiga Whisperer LOL. So, what should I do next?
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We need an Amiga Whisperer LOL. So, what should I do next?
RE-read my first reply :)
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I am not real good with a multimeter so you will have to walk me through where to put the probes (ie black and red) for measurement.
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I am not real good with a multimeter so you will have to walk me through where to put the probes (ie black and red) for measurement.
Oh boy. lol Be careful you don't accidentally short anything out. First things first... red is positive, black is ground or negative.
First check the power supply not hooked to the Amiga. On the bottom of the supply, there is a legend that tells you what pins are responsible for what voltage. Be careful not to accidentally short your leads testing that and write down the results.
If you're spot on or extremely close, now present a "load" to the power supply by hooking it to the Amiga. Now you can place the black lead of the DMM To anywhere that's ground on the Amiga (any of the screws) or even the black lead going to the drive. Red to red, black to black. Comparing the with the notes you took, read if the voltage is much different. If so, you may have to re-build or get a new power supply.
Check to see if there is cold solder by "wriggling" the drive's power cable though. While a disk is spinning, apply pressure to the power cable at both ends (computer and drive, one at a time) and see if the light gets brighter or not. When I say "apply pressure", I don't just mean pushing down. Maybe pull up a little bit, twist it or bend the connector left or right. If the drive light gets brighter when you're fooling with the cable, then you have a bad solder joint that needs to be re-soldered.
If you suspect that new Agnus chip is at fault, maybe try removing her and ensuring all her pins are in the correct position. I guess it's possible that if one of her legs is shorting against another, you may experience a low voltage scenario too...
Lot's of various things to check! Welcome to vintage computer repair 101 :)
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The computer works, but does this indicate a larger problem? Is it so bad if I just ignore it?
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The computer works, but does this indicate a larger problem? Is it so bad if I just ignore it?
It's up to you whether you want to ignore it or not. I wouldn't be fine with it if it were my computer, but if you're not technically minded and you don't really care about diagnosing this thing, then yeah - I guess I'd just leave it and enjoy what you have for now while it still works :)
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While I might test the power supply because I think I can manage that. I just read that you have been an electronics repair person for the last 30 years in another thread. That makes me look really bad! Please forgive my newbishness... I just don't want to break this thing.
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So if I test the twelve volt pin, do I put both the positive and negative probes on the same pin?
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It's all good! I don't mind helping out with the lighter stuff. And actually, I have a friend into Amiga now that's complained about some of these forums not being exactly "friendly" when it comes to questions. That a lot of Amiga people are kind of "snotty" that way compared to other computer enthusiasts. He's newly into Amiga and for the moment, he's avoiding subscribing to any forum for that reason. Hmm... can't say I've ever noticed anything like that here. lol
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So, since you are willing to help with the light stuff, here's something REALLY light. If I want to test the 12 volt dc pin, should I put both the positive and negative probes on it at the same time?
BTW, this is off topic, but I bought my multimeter cheap, and noticed in the manual that it takes a "9 volt transistor-type battery". I was upset until I realized thats just a regular 9 volt. Why in the world do they call it transistor type battery anyway?
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Why in the world do they call it transistor type battery anyway?
Probably because it was a popular battery when transistor radios were hip.
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I guess. I thought of that too. It's not an old multimeter its digital, so I really have no idea.
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LOL! Whoa, now that's going back. 9v batteries are still sometimes called that because they were popularly used, perhaps originally designed for use in most of the first truly portable handheld transistor radios. Little bit of trivia for 'ya!
And no.... you will never get a reading touching both DMM leads to one DC pin. Black to ground and Red to positive.... always. Ground, minus or negative is what you're looking for.
http://www.hardwarebook.info/Amiga_500/600/1200_Power_Supply
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Well, plugged it had the red connected to pin 1 and the black to pin 2 as indicated on power brick, and I must have shorted something because I began to hear a high pitched ringing sound, so that's enough of that for now, atleast until I gather courage. LOL
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Whaaat? :( Well, there's a fuse inside of that supply - so hopefully that just needs to be replaced. Sorry man, but that was my very first cautionary rule - don't be shorting leads!!
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Maybe I didn't short anything. I just started hearing that noise so I shut it off. I double and tripple checked the pinouts.
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If you want to test it safely get a set of leads that have crocodile clips on them. Have a crocodile clip and a probe plugged into the multimeter. Once you know which is the GND pin is put the crocodile clip on that. Then use the probe to touch the other pins. It won't slip around, so you won't short it.
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Yeah, I guess I should get a pair of those. I swear the leads weren't touching! Wow, now save2600 has abandoned me. LOL Is there a chance I didn't short it? Well, off to home depot!
Oh He's back
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Yeah, I guess I should get a pair of those. I swear the leads weren't touching! Wow, now save2600 has abandoned me. LOL Is there a chance I didn't short it?
Oh He's back
Hey, a guys gotta eat you know! lol
Ummm... alligator clips are great, but I've found that unless you get some real small ones, you actually risk the chance of shorting a little easier in this case. Just my $.02.
So... did you plug it back in and retest?
BE CAREFUL! =P
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No, not yet. I still am thinking about those clips. I probably need some anyway, so I will try to get the smallest size they have, and if they won't work well thats that. Come on now after my recent adventure you want ME to retest?
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Come on now after my recent adventure you want ME to retest?
Alligator clips are a good investment, so yeah - you'll need 'em sooner or later anyway. And don't test your power supply by plugging it into the Amiga after that high-pitched whine scare. lmao
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I tested again and this time there was a louder noise than before. I KNOW nothing shorted this tims because I had some help holding the connector this time. I noticed a volt reading didn't register but that might be because it was only on a fraction of a second. So, maybe its time for the local electronics repair guy to take a look at this. There is a shop down the street. Where you serious about not plugging it into the amiga or was that where the lmao comes into play, because that would validate basic psu function.
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Do not plug that into your amiga! Power supplies are not supposed to hum, vibrate or whine loudly normally. That indicates something is wrong. Keep it turned on and keep the leads on the pins to ensure voltage is correct or not.
You know... if you swear you didn't short it, you know what? I bet that power supply just happened to take a dump on you and coincidentally, did it while it was not plugged into the machine. Fuses don't always blow and power supplies can and do (often) leak wrong current out of 'em when they fail.
I bet it's bad and you can count your blessings it didn't take your Miggy with it. :) The dim drive light was a pretty good indication a component was starting to fail. It's all diodes and caps now buddy! lol
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Maybe its not my fault then. The first time, maybe it shorted but I didn't think so. The second time definitely not. There's an electronic repair shop down the street. Maybe I should have the look at it.
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So, the whining doesn't mean its going to blow up and kill me?
LOL! Nah.
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There is an electronics shop down the street. They look like they repair pretty much anything. Should I take the psu down to him and have him look at it. I really feel like I shouldn't look inside a psu without knowing anything. I am a software guy!
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There is an electronics shop down the street. They look like they repair pretty much anything. Should I take the psu down to him and have him look at it. I really feel like I shouldn't look inside a psu without knowing anything. I am a software guy!
Yep - that sounds like really sound advice at this point. PS for these machines can be had relatively cheap, so remember that before paying someone more than double-triple the cost of a replacement. I say double or triple because often, purchasing something that's been properly refurbished will last longer than something of this vintage that hasn't.
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I will go down there soon, and report back my findings. And to think I almost didn't say anything about the light! I don't know how much they charge. I only paid 35 bucks for the 500 and the psu together so... Also, how hard is the at power supply hack?
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Good luck and let us know! Also, let them know what the stuff they may be working on is worth so that way, they know not to rape you on service. Mention that you'd like some preventative maintenance done too, like all electrolytic caps replaced. Same with the diodes/bridge rectifiers. Those things are small and they should be able to quickly give you an estimate.
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I wish I was competent enough to do this all myself. Sounds like I might be in for a pretty penny....
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Also, how hard is the at power supply hack?
Not hard at all if you want to go that route. There's schematics out there and with a little common sense, you can wire it up to the blown power supply connector yourself. Amigakit sells an adapter already wired also, and maybe someone else on ePay.
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AT power supply and its wires dangling all over like an octopus out of water is FUGLY! lol
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Hey, I don't know if this means anything, but when I turn on the power supply with nothing connected, there is no noise.
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I can so good things about learning electronics and it is not hard to learn the basics. Learn Ohm's law, resistors, and then DC power supplies. It will give you the confidence to crack something open and replace fuses or clean up internals.
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double post
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Good news! It turns out that I wasn't really testing it properly because I put the test probes against the pins not on the pins. Because of that I was getting the humming noise. I got good voltages (I will post) but I have one more to check: the negative 12 volt lead. Is it okay to use my meter's positive lead to check the negative 12 volt lead? It should be right? Because even though the positive lead is called positive, it actually excepts any voltage.
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Sure, it'll just show the minus sign in front of the value -12 (or close to it) instead of 12 in the window.
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Okay, how do these voltages sound:
Pin 1 (+5 volts): 5.16 volts
Pin 3 (+12 volts): 12.19 volts
Pin 5: (-12 volts): -11.97 volts
All of these voltages sound good except Pin 5 seems a bit low.
No humming either! Before I must have shorted the pins against the ground container shield. Hmm.. sounds like a great way to mess up my psu. I know a little more than before as I have been reading up.
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Those values are all good. Nothing wrong with the -12 line, well within spec. Oh, okay... I thought a while back you said the PS was humming - that's why I freaked out and said to not plug into the Miggy :)
You should be all set. Amperage is another value you can check for if you ever suspect something funky - but I bet your PS is fine. Good luck!
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I did say it was humming, but that turned out to be because of the way I was testing it (laying probes against pins instead of on top of I think I made contact with the grounded shield.) I guess I'll just have to open up the amiga and snoop around in there. I'll do some continuity checks. That audible buzzer is a really nice thing to have. My multimeter doesn't do amperage so I can't check that.
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It sounds like something is taking a lot of power. Perhaps your floppy drive is clogged with dust. Otherwise a component could be on the way out.
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By the way, I can't fry a circuit or something with the continuity check can I? It uses a marginal amount of voltage but still, I want to be careful. Because well checking around some resistors, I heard the continuity buzzer (buzzes when there is continuity or a lack of resistance) go off and then slowly die out. I have some compressed air. I'll try that in the disk drive.
EDIT: Nope no dust in the floppy drive
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I can't test the cables too much, because I found out my test probes are too large to fit in the pin holes:angry: I guess I'll go down to radioshack and see if they can help me....
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You never test for continuity with the power on to the device. Voltage yes, continuity no.
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Yeah, I know. I have the amiga unplugged. I just wondered if the voltage used for the continuity check could damage anything. You can't test anything resistance related with power going to the circuit.
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Yeah, I know. I have the amiga unplugged. I just wondered if the voltage used for the continuity check could damage anything. You can't test anything resistance related with power going to the circuit.
Ahh, I see. Your hunch is correct - the minute electricity coming from the leads of a DMM isn't going to hurt a TTL or CMOS circuit. Only really sensitive alien technology, like those from abductee's implants, will it might hurt. lol
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I can't seem to find any smaller test probes. The ends of them are just too big to fit in the pin slots. Do they sell smaller ones?
EDIT: Can I use electrical tape and tape like needles or something to the ends of the probes?
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Well, I tested my floppy power cable and no shorts as confirmed by a continuity test. After that, I thought maybe the cables were just loose before so I should try plugging everything back in before checking anything else. Now, the drive light is on the second I power on the machine, and it stays on. I get to a workbench disk request screen, but when I put the disk in the screen stays white, the drive led remains on, and the floppy drive does not spin up. I know the cables aren't backwards because they are keyed, and I took pictures before unplugging them so I could observe polarity. The pictures match too. Do I have a bum drive or cable?
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It sounds like the floppy drive motor. You'll need a new floppy drive.
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Great news everybody! The drive isn't dead, the data cable was just loose on the motherboard. And no more dim drive light! Thanks everybody for helping me out. I learned a lot.
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Great news everybody! The drive isn't dead, the data cable was just loose on the motherboard. And no more dim drive light! Thanks everybody for helping me out. I learned a lot.
Congrats, you are now a certified electronics technician! :lol: j/k
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Glad to hear nothing got fried along the way, there were a couple of scares!