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stahlhart
Platinum Member
1318 Posts |
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diggum12
Silver Member
USA
282 Posts |
 Posted - 09/09/2006 : 18:20:28
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| Why does he have 2 PCBs? I don't think the cap is bad. I'm confused, he swapped both boards with the case, using the DC jack from the case? It doesn't sound like a Zener to me, but who knows. Are you gonna buy it? |
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stahlhart
Platinum Member
1318 Posts |
Posted - 09/09/2006 : 21:42:32
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Nah, I already have three DD-2s at this point -- all of which I purchased broken and fixed, and all of which just had a shorted zener diode.  It seems to be a common problem with that particular board.
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diggum12
Silver Member
USA
282 Posts |
Posted - 09/09/2006 : 23:04:12
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| Wow that kind of surprises me. I've never come across a bad Zener on a Boss pedal. Thanks for that insight! |
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stahlhart
Platinum Member
1318 Posts |
Posted - 09/09/2006 : 23:19:42
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It looks like it's put there to clamp the AC adapter voltage down to 9VDC before hitting the 5VDC regulator and the rest of the circuitry. I'm not sure if it's a bad batch of diodes, or users plugging in the wrong AC adapter, or otherwise applying/removing power incorrectly -- but it's shorted to ground, and you've got no operation, no check light, no bypass, and if you connect a battery it overheats.
All three of my once-broken DD-2s had the identical problem when they arrived. If you ask me, that's a good circuit design where some sort of external abuse like that only takes out a cheap component and leaves the rest of the circuit unscathed.
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diggum12
Silver Member
USA
282 Posts |
Posted - 09/10/2006 : 02:53:50
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| Oh absolutely. I've bought four broken MXR Phase 90's that only needed the Zener replaced. Two ToneBones as well! (Score!) |
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lazzrath
Bronze Member
Canada
103 Posts |
Posted - 09/10/2006 : 09:09:44
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I wish I could fix that ole PH-1 I got off ebay with the blown Zener in it, but that can't be the only problem - I've replaced that part six times now, and the pedal works for two seconds and then it blows again. and now one of the traces has started peeling.
It makes me very sad. |
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stahlhart
Platinum Member
1318 Posts |
Posted - 09/10/2006 : 19:14:06
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I've yet to see a schematic for the original PH-1, which is unfortunate because a direct short circuit like that ought to be fairly easy to locate.
I'll open up my PH-1r, in the hope that it's similar enough in design in that part of the circuit. Are you applying power with a battery or an AC adapter. If battery, does the battery get hot to the touch?
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diggum12
Silver Member
USA
282 Posts |
Posted - 09/10/2006 : 19:44:50
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| Y'know, that could be the very problem. Have you tried direct jumpers to each side of the Zener to the next component? Maybe the Zener is shorting on the clampdown side. |
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lazzrath
Bronze Member
Canada
103 Posts |
Posted - 09/11/2006 : 03:40:46
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I've tried bypassing the zener, and then it worked for a couple of seconds again, and then just stopped - nothing else blew (I don't think!) but when I tried to solder in another diode, it did the same thing - play, stop. again - play, stop. I do believe the battery got hot...
I actually purchased a schem from Ranger Audio - I live down the highway, so the shipping was cheap. If anybody thinks they can help, that would be greatly appreciated! |
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stahlhart
Platinum Member
1318 Posts |
Posted - 09/11/2006 : 03:45:19
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I hope that you didn't bypass the Zener with a short circuit -- it usually sits between DC (+) and ground...
Try taking it completely out of circuit (just remove it completely) and try power with a battery -- the Zener doesn't really need to be in the circuit for battery power anyway.
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lazzrath
Bronze Member
Canada
103 Posts |
Posted - 09/11/2006 : 04:56:04
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quote:
Originally posted by stahlhart
I hope that you didn't bypass the Zener with a short circuit -- it usually sits between DC (+) and ground...
Try taking it completely out of circuit (just remove it completely) and try power with a battery -- the Zener doesn't really need to be in the circuit for battery power anyway.
nope, no sound, no light.
hey, congrats on becoming a platinum member! |
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stahlhart
Platinum Member
1318 Posts |
Posted - 09/11/2006 : 05:05:26
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Thank you!
Well, that seems to indicate that you aren't getting power into the circuit at all now (they don't have passive bypass).
Now we'll need a schematic -- and if we don't have a voltmeter it will have to be trial and error.
What I'd want to see now is, with the Zener diode removed, connecting a battery and a signal or patch cable to the input jack to power the pedal up, and then measuring voltage across the battery terminals. If you've got 9VDC or better, it's an open circuit, but if there's a voltage drop then you've got a short circuit pulling the voltage down (and your battery is probably going to get quite hot as it is drained of power quickly).
I wonder if there's that series doide and resistor in the DC input line -- I think that it's there to drop 12VDC adapters down to 9VDC? I can't remember for certain; I'd have to go back and look at earlier posts... someone explained what the purpose of that was, I think that it might have been Andreas. I'll see if I can find it...
edit: nope, it was Steve! http://www.bossarea.com/forum/topic.asp?TOPIC_ID=572
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Edited by - stahlhart on 09/11/2006 05:11:37 |
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stahlhart
Platinum Member
1318 Posts |
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lazzrath
Bronze Member
Canada
103 Posts |
Posted - 09/13/2006 : 08:56:50
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| I've got the schem, I just don't know exactly how to fix it. I'd like to get better at this, and I figured this would be an easy job, but it's proving rather difficult. |
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stahlhart
Platinum Member
1318 Posts |
Posted - 09/13/2006 : 09:30:59
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quote:
Originally posted by lazzrath
I've got the schem, I just don't know exactly how to fix it. I'd like to get better at this, and I figured this would be an easy job, but it's proving rather difficult.
If you have it electronically and could forward it to me, I'll help with this. Do you have a volt-ohmmeter (VOM)?
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Another Bad Zener Diode?
