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homestar_kevin
Copper Member
USA
34 Posts |
 Posted - 07/05/2007 : 08:03:37
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So I stopeed at gc today because my accessories girl called me and told me that they got a dd-5 and an analog man bi-comp in. I got there, was amazed by the bi-comp(it was amazing) and then she brought out the dd-5. She said it wasn't working at that she could give it to me for 20 bucks, So I figured hell yeah. So I'm not too worried about it, just bought it for a "project", I cracked her open and there was a chemically smell coming out and dried up brown liquid on the plastic guard between the circuit board and the bottom plate. The pedal is not taking power through the adapter slot or a 9volt battery. I'm assuming something leaked/blew up considering that is what it looks like, but does anyone have any ideas?
I searched and found threads on broken dd3 and one with a dd5 but nothing that helped clarify it to me...
does a dd5 have a zener ?
I haven't had a chance to see if sound passes through the pedal yet, but anyone have any ideas? |
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bossarea
Forum Admin
United Kingdom
3652 Posts |
Posted - 07/05/2007 : 10:40:36
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| Bets guess is that someone connected it to a power supply with the wrong polarity or voltage. Sounds like one of the larger capacitors may have blown up (and spewed out the brown liquid). When I bought my PS-2 it was in that state and I didn't need to change any other components than the capacitor to make it work. |
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homestar_kevin
Copper Member
USA
34 Posts |
Posted - 07/05/2007 : 16:17:36
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| Yeah thats what I'm thinking as well. When I took the board out none of them looked in dire shape though? I guess it just isn't as obvious as I'd like it to be.. |
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stahlhart
Platinum Member
1318 Posts |
Posted - 07/05/2007 : 23:11:39
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You should be able to trace this out without a schematic, as it will more than likely be the DC input filter capacitor, which should be a short distance circuit-wise from the battery and/or AC adapter (+) lead.
It's possible that the capacitor failed without exhibiting physical damage to the outer case -- you'd only be able to see this, if it were at all visible, if you removed it from the board, as radial-lead caps tend to have the case weakest on the flat side where the leads protrude, which is up against the board.
I'd replace both the Zener diode and the capacitor just to be on the safe side -- they more than likely got toasted by reverse DC polarity from use of the wrong adapter (or one of those universal ones that lets you reverse polarity to the plug at the flick of a switch). The Zener's probably a 9.1v one, if it's at all like the ones I've replaced in DD-2s.
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stahlhart
Platinum Member
1318 Posts |
Posted - 07/05/2007 : 23:14:06
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Look for one with a value of 100uF.
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homestar_kevin
Copper Member
USA
34 Posts |
Posted - 07/06/2007 : 20:41:22
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| and most electronic/computer supply stores have these? This won't be my first time soldering, but it's my first time messing around with pedals.. and circuit boards really. |
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stahlhart
Platinum Member
1318 Posts |
Posted - 07/06/2007 : 21:47:08
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If you don't have an electronics parts store locally, I just checked http://www.smallbearelec.com, and they've got both parts, or just the capacitor, if the diode is okay... you could even get the soldering supplies here if you need them. Make sure that you get radial leads on the capacitor (both on the same side, for vertical PC mounting).
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homestar_kevin
Copper Member
USA
34 Posts |
Posted - 07/06/2007 : 22:03:21
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I have more pics I'll upload later, but my internet is being slow. ok so on the bottom of the board, the leak looks like it stemmed from the round metal piece right next to the adapter input, but I have no idea |
Edited by - homestar_kevin on 07/06/2007 22:05:31 |
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stahlhart
Platinum Member
1318 Posts |
Posted - 07/06/2007 : 22:26:16
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The photo is a bit on the blurry side, but if you're referring to the light blue component, that looks like the culprit -- the leakage is pretty much a dead giveaway, as an electrolytic capacitor is going to be the only component on the board with fluid in its construction.
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homestar_kevin
Copper Member
USA
34 Posts |
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homestar_kevin
Copper Member
USA
34 Posts |
Posted - 07/07/2007 : 00:39:50
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So i plugged it in finnally, I was getting really quiet, distorted sound from it. I tried running a 9volt through it and the battery was burning up within a couple minutes.
I remember when I searched coming accross something with a really hot battery, but can't seem to find it now.
kevin |
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stahlhart
Platinum Member
1318 Posts |
Posted - 07/07/2007 : 03:07:57
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Shorted zener diode. Remove it and the input filter capacitor, and re-test with a fresh battery (the one that overheated is no longer any good). The diode and the capacitor aren't necessary for battery operation; they're only there for AC adapter power.
I've purchased two dead DD-2s off of eBay that had this problem (hot battery), and that was the fix for both of them...
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 07/07/2007 : 03:18:14
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quote:
Originally posted by homestar_kevin
So i plugged it in finnally, I was getting really quiet, distorted sound from it. I tried running a 9volt through it and the battery was burning up within a couple minutes.
I remember when I searched coming accross something with a really hot battery, but can't seem to find it now.
kevin
Hi Kevin - homestar
If the battery is getting hot, then you have a shorted input protection diode.
As Stahlhart mentioned in a previous post to you, on this thread.
If you measure that 9V battery it is now probably flat.
I can't tell you the actual value of the Diode in a DD-5 as I don't have one, or the schematic here, to look at.
Stahlhart said it was probably a Zener, & I would thoroughly trust his opinion. he has opened - Repaired & moded more Boss pedals than I have.
Pull the Diode-Zener & the cap, it looks like someone plugged in a reverse polarity plug pack, & the diode DID it job.
This is a common problem - when you get old pedals.
The shorted diode thread you are searching for, is probably in a DD-2 thread.
Good luck - we know you will be able to repair it. 
Regards Dr. Bob & reference to Stahlhart
PS - In your other 2 pics.
Are you looking-talking about the brown-creamy stuff on your board, near & on all the cables, thats glue, to hold the cables in place, you probably just have a shorted diode-Zener. Which would make it easier for you.
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Edited by - Dr. Bob on 07/07/2007 03:20:23 |
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stahlhart
Platinum Member
1318 Posts |
Posted - 07/07/2007 : 03:20:56
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Here's the DD-2 schematic, as an example:
http://www.freeinfosociety.com/electronics/schemview.php?id=126
Locate connection 22 -- see all of those components shunting to ground? One or more of them is short-circuited, which is placing essentually sero resistance across the battery, which is why it's overheating.
One both of my DD-2s that I repaired, the circuit was good from the 5V regulator (IC10) forward -- I had bought replacement regulator ICs, but didn't have to replace them in either case... though it could still theoretically go bad, I suppose.
Really what you need to do at this point is have an ohmmeter from the input side of the regulator to either the pedal chassis or the ground side of the output jack, then pull components on that line one at a time until you've got an open circuit.
It's looking to me that reverse polarity on the adapter input took out both the capacitor and the diode, unless the capacitor short-circuited on its own.
edit: Dr. Bob and I responded at the same time here...
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Edited by - stahlhart on 07/07/2007 03:23:40 |
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stahlhart
Platinum Member
1318 Posts |
Posted - 07/07/2007 : 03:27:25
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That's a good point about the adhesive -- I hadn't considered that... thought that perhaps the capacitor spewed electrolyte when it failed. In electronics school we used to put them across the AC line to encourage that sort of result.* 
* -- don't try this at home!
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 07/07/2007 : 06:42:11
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Hi Stahlhart & Guys
Stahlhart, am I correct in assuming, that the protection diode-zener on the DD-5 is an SMD Surface Mounted Device?
This might make it a bit more difficult, for homestar_kevin to repair his pedal.
From the Pics homestar_kevin sent-uploaded, it seems that the entire PCB is populated with SMD's.
Regards Dr. Bob
PS - Your story about putting Electro's across AC, reminded me of the day we built a One Sidchrome Capacitor, in our workshop, when I was also in my youth... 
But that's probably a story I should tell you about in a PM, as some younger less experienced Tech might attempt to recreate the experiment.
A One Sidchrome Capacitor is a very dangerous thing. |
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So I bought a broken dd5
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