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  #1  
06-09-2013, 08:28 PM
Argalby Argalby is offline
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I'm involved in replacing the 100+ electrolytic capacitors in my AG1980. It's quite a daunting task

I'm almost done, but I'm wondering if it's also necessary to replace any of the SMD capacitors?

There's also a nasty double-sided circuit board (the one with the metal case attached) that has the capacitors soldered on both sides of the board, has anyone dealt with that?

Thanks!
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  #2  
06-09-2013, 09:17 PM
volksjager volksjager is offline
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the detachable board with the metal covers is very important - it is the Y/C card.
if the caps go bad on that you get nasty diagonal red and blue lines in the picture
many AG-1980's get this issue

IIRC the tuner also has metal covers - that shouldn't be a real concern
the tuner is the card that has the RF/VHF connectors -the ones that use coaxial cables
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  #3  
06-09-2013, 10:15 PM
rumburaski rumburaski is offline
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volksjager is right about the y/c video section. Replaced several 1uf and 10uf smd caps. Too many to count. Just replace them all. Bad, bad smd electrolytic caps. Also, try to maintain the uf specs. Don't go up in your farads. Also, there is at least one bad cap on the display pcb. I believe is the 220 uf or 100uf (right side of display, about midway of the pcb. Good luck. In addition check motherboard for high esr 47uf electrolytics. Finally, it should have been first, there are leaky disc type filter caps in power supply. They are housed in a clear rubbery boot. Hard to see the leaky oily cap in the circuit because of the overcrowdedness. Let us know how it goes.

Last edited by rumburaski; 06-09-2013 at 10:24 PM. Reason: clarification
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  #4  
06-10-2013, 10:45 AM
Argalby Argalby is offline
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Thanks so much guys! I appreciate the help. I haven't found any "exploded" or buckled capacitors yet, but I have found two that were reading only about half of their marked ufd (can't remember where they came from now, it's been a long haul)

Yes, volksjager it's the Y/C board... that's the one I fear working on. Since it's double-sided it looks like I may have to cut off the electrolytics to get at the solder joints under them, then also desolder the other side too. This will be fun

Thanks rumburaski for your tips on the Y/C SMDs. There's probably no way to tell which one's are bad, so as you suggest, replace them all. I may leave the SMD's until the end, and see if replacing the tubular electrolytics helped (picture was black & white and muddy looking, before I started on this project)

This may take a few weeks, a board at a time, but if I haven't shot myself by then, I'll report back
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  #5  
06-10-2013, 02:31 PM
NJRoadfan NJRoadfan is offline
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Removing SMD caps is likely the tricky part. I just did a board with them and found that cutting them off with side cutters then wiggling/pulling off the cap works best. The leads that remain on the board can be easily desoldered without lifting pads. For long life, polymer or ceramic caps should be used to replace them. They cost more, but are worth it. I don't recommend tantalum caps for beginners mostly because they explode if installed in the reverse polarity.

Just take your time and use a temperature controlled iron. Too much heat is a bad thing as it can damage the PCB. Make sure you throughly clean the leaked electrolyte off the board too. If you aren't confident in doing the job yourself, I can send you a link to someone I have used for SMD recaps in the past with excellent results.

Also..... this thread needs pictures! A parts list would be nice too, the service manual's part list leaves a lot to be desired.
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  #6  
06-10-2013, 02:37 PM
volksjager volksjager is offline
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i dont do soldering work - only mech repairs.
i have 2 bad Ag-1980 Y/C cards i would like to get re-capped if anyone can do the job for reasonable
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  #7  
06-10-2013, 02:52 PM
rumburaski rumburaski is offline
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When I said smd caps I meant smd aluminum can electrolytic caps. These are polarized caps. I don't think they can be replace with nonpolarized polymer or ceramic, do they NJRoadfan? I would be afraid to use side cutters on these due to their delicate pcb. It doesn't take much to lift up those traces. For example, too much pulling. I use a hot air station. Very fast. When is time to install them I use soldering iron. Perhaps two soldering irons set to 350C would work. I rarely seen a leaky/bulged smd aluminum cap. Don't rely on the bulge, as they are completely flat because they are dry. Usually they are dry/high esr when they fail. Definitely, pictures are the weakest link.
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  #8  
06-10-2013, 03:21 PM
NJRoadfan NJRoadfan is offline
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Dried electrolyte isn't all that visible. An indication of leaking is dulled/dirty looking solder on the components in question. Hot air stations can be very dangerous in the hands of the unskilled. I was actually surprised how well the cut'n'pull method worked. Usually the can pops right off the leads leaving the plastic base to chip away. I must have had beginner's luck because the method resulted in no lifted pads or any other board damage.

They do make SMD "tweezer" style soldering irons for the job, but I don't have one laying around here.

http://upload.wikimedia.org/wikipedi...ing_a_0805.jpg

I'd love to get a hold of a broken down AG-1980/5710 to repair and document a re-cap, but they are crazy expensive in busted form!
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  #9  
06-10-2013, 03:48 PM
Argalby Argalby is offline
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Yes, I think a hot air station is the way to go. I have one of those smd "tweezer" type soldering irons....mine is more clunkier looking than the one in your photo. It doesn't work as well as I'd hoped.

And yes, those broken AG1980's go for too much..everyone says "plugged it in and it powered up"......but you know it's gotta have bad caps, or worse
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  #10  
06-10-2013, 03:53 PM
volksjager volksjager is offline
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Quote:
Originally Posted by NJRoadfan View Post

I'd love to get a hold of a broken down AG-1980/5710 to repair and document a re-cap, but they are crazy expensive in busted form!

i'll give you a whole broken 1980 if you'll recap a Y/C card for me
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  #11  
06-10-2013, 03:59 PM
Argalby Argalby is offline
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NJRoadfan - Thanks for your tips on removing the SMD caps.....I appreciate it!
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  #12  
06-10-2013, 04:20 PM
rumburaski rumburaski is offline
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Nice tweezers NJRoadfan. Who makes them? I could use some for some smd inductors.
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  #13  
06-10-2013, 04:38 PM
NJRoadfan NJRoadfan is offline
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Quote:
Originally Posted by volksjager View Post
i'll give you a whole broken 1980 if you'll recap a Y/C card for me
Photos would be handy, I'm curious as to how many need to be replaced. I'm also curious if recapping the display board fixes the dim display issues.

Quote:
NJRoadfan - Thanks for your tips on removing the SMD caps.....I appreciate it!
Remember, I am not liable if anything breaks. Proceed at your own risk, work slowly and watch a few tutorial videos. Practice on scrap boards you don't care about to get a feeling for it beforehand.
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  #14  
06-10-2013, 04:45 PM
volksjager volksjager is offline
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1 of the decks i have has a dim display, both need the Y/C cards repaired.
not sure how many caps would need to be replaced



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  #15  
06-10-2013, 05:41 PM
NJRoadfan NJRoadfan is offline
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I don't see the tell tale signs of leaking electrolyte, but its not always visible. I'm guessing there are more caps under the metal shield? The parts list shows 33 electrolytics and 16 are visible there. Jeez, no wonder why repair centers hated these things!
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  #16  
06-10-2013, 05:46 PM
rumburaski rumburaski is offline
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In my particular case, half of the smd aluminum can electrolytics were bad, low uf. On the other hand, through hole caps were fine. Does it make any sense? There are more under those shields.
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  #17  
06-10-2013, 06:09 PM
NJRoadfan NJRoadfan is offline
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Quote:
Originally Posted by rumburaski View Post
In my particular case, half of the smd aluminum can electrolytics were bad, low uf. On the other hand, through hole caps were fine. Does it make any sense? There are more under those shields.
I'm not surprised. Early 90s SMD caps seem to use a crappy electrolyte recipe that lasts about 15 years tops. Meanwhile, all my stuff from the 80s with old school through hole radial caps work fine.
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  #18  
06-10-2013, 07:01 PM
Argalby Argalby is offline
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Here's some close-ups of the Y/C board with the metal cover removed. This is the "business side", the reverse side is mostly tiny SMD caps.

http://www.rentalmouse.com/samples/AG1980board.jpg

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  #19  
07-30-2013, 08:44 PM
Just_a_hobby Just_a_hobby is offline
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Argalby , Did you get the AG-1980 working? Did you have to replace all the SMD caps as well? I'm starting on the same project myself any advice would be helpful. Thanks
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  #20  
08-04-2013, 02:56 PM
Argalby Argalby is offline
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Hi: I haven't had a chance to work on it yet, and it might be a while. I'm working double shifts now, and I really need a big block of time to work on this. Everything I've read indicates it's the SMD's on the color board, that bears out what I suspected. I have second unit that works perfectly in BW mode, but color is screwed up, so it also looks like the color board. Lots & lots of SMD's on there Hope it works out well for you. Good Luck!
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