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Alastair_in_oz
Copper Member
Australia
13 Posts |
 Posted - 12/12/2008 : 08:00:45
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I have a DS-1 MIJ, which is playing up. It plays OK for a while, then sort of fades in and out, gets thin sounding.
I have checked over the board with a magnifying glass looking for dry joints and bad connections. I have tried turning the pots, but no joy.
The problem only occurs every 30min and then for maybe a minute.
Any ideas folks? |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 12/12/2008 : 08:15:52
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Hi Alastair_in_oz
Welcome to the forum.
Please be more specific.
Is this happening with a power adapter, or a KNOWN GOOD Battery?
Or both?
And which type of adapter do you have?
Regulated? Or some generic unregulated-unknown brand?
Test it with a KNOWN GOOD battery & report back to us.
And are your guitar leads known to be good?
Regards Dr. Bob |
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DeFrag
Moderator
USA
3409 Posts |
Posted - 12/12/2008 : 08:16:53
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Welcome to Bossarea Alastair_in_oz!  |
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Alastair_in_oz
Copper Member
Australia
13 Posts |
Posted - 12/12/2008 : 08:29:58
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Hi Dr bob. I have not tried it with a battery. I use a 9v 1A regulated power supply using a LM7809. It runs all my other pedals no trouble.
It does not matter whether I run the DS-1 by itself or with all the other pedals. The fault will occur either way. I can't do anything to make the fault happen: its random.
I bought this just a few days ago off a bloke cheap because it had a known fault.
It runs OK on bypass, so its not the input or output buffers.
Regards
Alastair
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Alastair_in_oz
Copper Member
Australia
13 Posts |
Posted - 12/12/2008 : 13:07:02
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OK, so I tried a battery, does the same thing. My leads are all good. Tried different leads, same problem. There are 2 things I have noticed, though.
The pedal has a damp, moldy smell. And I have not been able to reproduce the fault with the pedal open, only closed. So it could be damp related. There is no visible moisture, only the smell.
The other thing is the insulation plastic between the PCB and backplate, causes some strange noises when placed against the PCB and when you move a finger across it. (But not the same sound as the fault I am looking for).If you take the plastic way and rub your finger over the same spot on the PCB, then there is no noise. (except for certain spots that create hum anyway). I held the plastic close to the PCB and waved it back and forward like a fan and there was an audible noise. tried a plastic ruler over the same spot, no noise.
I went over the entire pedal poking and prodding with a chop stick, and was unable to produce the fault.
I suspect a component is going off value, possibly a cap. So I guess the only way is to start replacing components, starting with the most likely to be effected, like caps.
What do you guys think?
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 12/12/2008 : 14:12:38
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quote:
Originally posted by Alastair_in_oz
OK, so I tried a battery, does the same thing. My leads are all good. Tried different leads, same problem. There are 2 things I have noticed, though.
The pedal has a damp, moldy smell. And I have not been able to reproduce the fault with the pedal open, only closed. So it could be damp related. There is no visible moisture, only the smell.
The other thing is the insulation plastic between the PCB and backplate, causes some strange noises when placed against the PCB and when you move a finger across it. (But not the same sound as the fault I am looking for).If you take the plastic way and rub your finger over the same spot on the PCB, then there is no noise. (except for certain spots that create hum anyway). I held the plastic close to the PCB and waved it back and forward like a fan and there was an audible noise. tried a plastic ruler over the same spot, no noise.
I went over the entire pedal poking and prodding with a chop stick, and was unable to produce the fault.
I suspect a component is going off value, possibly a cap. So I guess the only way is to start replacing components, starting with the most likely to be effected, like caps.
What do you guys think?
Hi Alastair_in_oz!
Can you post a pic of the plastic? Do you own any other Boss pedals - if so, does the plastic look the same?
There isn't enough heat generated in the pedal for it to be heat related unless a component (opamp) has failed.
That smell is interesting... "damp" could indeed be an electrolytic capacitor failure.
Any chance of some hi-res closeup pics of the board (front and back)? |
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DeFrag
Moderator
USA
3409 Posts |
Posted - 12/12/2008 : 15:40:31
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Caps seem to be one of the most often component to fail.
Leaky bastards! |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 12/12/2008 : 15:56:48
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Hi Alastair_in_oz
I know this will sound silly, but try making a new insulator, out of some stiff clean cardboard, or some shirt box type thin plastic.
Even from some overhead transparency clear sheets.
Use this temporarily as the replacement insulator.
Put the pedal back together, & test it.
Does it still make noise strange noises, or does it still fade out?
Use the battery when you first try this.
I was thinking that there might be some conductive gunk on the insulator.
Is the insulator clear or is it a black one?
Does it look original?
Please report back with your findings/tests.
quote:
I bought this just a few days ago off a bloke cheap because it had a known fault.
What was the known fault? Was it this fading issue.
Regards Dr. Bob |
Edited by - Dr. Bob on 12/12/2008 15:58:14 |
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Alastair_in_oz
Copper Member
Australia
13 Posts |
Posted - 12/12/2008 : 23:06:18
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Here are the pics.
The plastic is a yellow/orange colour and clear. It looks origional.
All I know about the DS-1 is that it was known to have a fault.
now closeups
Bottom Left
Top Left
Top Right
Bottom Right
Back of PCB
The plastic
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leonard d rock
Silver Member
Philippines
301 Posts |
Posted - 12/13/2008 : 03:56:41
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don't worry Alastair, somebody's gonna come up with a cure for your DS1 sooner or later. these guys eat boss pedals for breakfast, so to speak.
regards,
ldr |
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Alastair_in_oz
Copper Member
Australia
13 Posts |
Posted - 12/13/2008 : 04:32:06
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I made up a new plastic insulator. While I could still hear some sounds when rubbing my finger around the plastic, it was in the same locations on the PCB that pickup hum from your finger. I no longer got the crackles and pops/scratching sounds that I had with the origional plastic. I actually picked up the old plastic and rubbed it between my fingers, and it make crackling static noise. I think its just the wrong type of plastic for an insulator.
Go figure that!
I have noticed one thing, that the schematic for the MIJ model has a 470 ohm resistor (R38) in series with a diode that drops some volts when connected to a power supply. When running off a battery this resistor is not connected.
I did think the LED was dimmer than the old DS-1 I had 20 years ago, anyway I tried it on the battery again, and it still did the same fault, but I measured the battery under load, puts out only 7v. Measured 8.9v straight off the terminals, battery is on the way out.
I dug around and found another 9v battery, this time runs the pedal OK, LED nice and bright. No more thin sound.
My LM7809 power supply puts out 8.97v. I measured the voltage drop across the resistor and diode, I get 6.37v! Is this normal? Even with a boss 9.6v PS that would only provide 7.2v to the circuit after the resistor and diode.
I noticed that the modern version of the DS-1 does not have this resistor, and the diode is across the supply, not in series.
So my question is: what do people run their old MIJ DS-1 pedals off? 9.6v? 12v?
Is it OK to mod the DS-1 so the PS section is the same as the modern version?
Regards
Alastair |
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Alastair_in_oz
Copper Member
Australia
13 Posts |
Posted - 12/13/2008 : 04:45:52
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| Woops I got it wrong about the diode. The MIJ and MIT schematics both have D1 across the supply, the MIJ has R38 and D3 in series with the neg supply from power socket. |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 12/13/2008 : 08:14:49
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Hi Alastair_in_oz
Ok, So here is what Dr. Bob does.
I put a small insulated link across the resistor in series with the diode, I place this on the PCB/Solder side of the board.
I leave the Diode in place.
It protects the battery in case you accidentally or stupidly, leave a battery in the pedal, at the same time that you are using a power adapter.
Yes, it's another 0.6-0.7V drop, but that's still OK in my opinion.
A lot of the modders place a shoring link across the Resistor & the diode.
Or remove the res-diode & replace them with linking wire.
People argue with me, that the diode becomes ineffective & is shorted out anyway once you have a daisy chain, & a couple of pedals connected.
And that's correct as well.
Or leave the pedal as it is (as an ACA) and use this method to connect the pedal in your board.
http://www.bossarea.com/other/aca.asp
(Powering ACA pedals with a PSA power supply)
Thanks once again to Stinkfoot.
I'm glad that it was only a flat battery.
But if you recall, I did ask you to test it with a KNOWN GOOD battery.
Regards Dr. Bob
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Edited by - Dr. Bob on 12/13/2008 08:29:52 |
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Topic |
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DS-1 fault finding
