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ChristoMephisto
Platinum Member
Canada
1288 Posts |
 Posted - 05/20/2008 : 23:03:32
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Curious to see if its the same pcb, the first one was an A version.
The original with the ET-5214-510, and the others added the letter code A and B.
Guess I'm getting old too, you're right they are ICs, was using opamps as a general term. Don't even know the difference, to me its the same, input it->output out.
My cats keep hiding my pills...
cheers |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 05/20/2008 : 23:11:19
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quote:
Originally posted by Dr. Bob
Perhaps you're just getting old, & suffering memory loss...  
What is this place and who are all you people? |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 05/21/2008 : 01:38:03
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My DM-2 arrived today. Described as "very good condition" in the ebay ad. The missing base-plate screws are the "obvious" problem. The thunbscrew is also bent, and the pedal retaining screws are missing their clear plastic washers. Sheesh... "road worn" is the best I'd give it. Not "very good". At least it sounds perfect!
The seller is giving me the option of a full refund. What do you guys think? Is it worth $170 as is or should I send it back and wait for a better one?
And one last question.. do these pedals usually have a kind of "light fizzy buzz" added to the echos?
EDIT: Decided to keep it. Nothing like a little challenge, eh?
I think I've found the source of the "fizz"... all the trim pots have been fiddled with (I can see where a dirty driver blade has been used in the pot). The CLOCK trimmer is hard over to one stop - can't be in the right spot. Looks like someone did the old "there must be more delay in here - let me just turn it all the way around" trick. It will be fiddly, but think i should be able to set them properly once I've cleaned it up and fixed some fraying wiring.
Anyway... here are the pics. The bridging resistor appears to be because R48 was replaced at some point with a 16k resistor for some reason, and the track is cut and a 2k2 is added to bring it back up to the original 18k. D4 has also been replaced (oops). BUT it does sound OK. Actually, it sounds very good.
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Edited by - Laurie on 05/21/2008 05:07:02 |
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BASN
Copper Member
USA
17 Posts |
Posted - 05/21/2008 : 02:15:40
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Hi Laurie,
I often wonder how Ebay sellers come up with discriptions of the merchandise they list. The DM-2 pedal you bought definitely looks rough--it's a good thing the Boss pedals were built like tanks. For what it's worth, if you decide not to hang on to the pedal let me know--I'd consider giving you what you paid for it--(just a thought).
Thanks |
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BASN
Copper Member
USA
17 Posts |
Posted - 05/21/2008 : 02:47:30
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Hi Laurie,
I could be wrong, but it's possible that the "light fizzy buzz" you described is caused by an incorrect bias setting. As you can see the DM-2 has three variable resistors on the circuit board--one is labeled "BIAS". I think some guys make the mistake of messing around with the bias resistor and end up degrading the pedals overall sound quality. Maybe someone with more technical expertise could tell you exactly what the "light fizzy buzz" is all about. |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 05/21/2008 : 05:08:01
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quote:
Originally posted by BASN
Hi Laurie,
I could be wrong, but it's possible that the "light fizzy buzz" you described is caused by an incorrect bias setting. As you can see the DM-2 has three variable resistors on the circuit board--one is labeled "BIAS". I think some guys make the mistake of messing around with the bias resistor and end up degrading the pedals overall sound quality. Maybe someone with more technical expertise could tell you exactly what the "light fizzy buzz" is all about.
Thanks BASN! That will be it for sure. Made some edits in my post above explaining what I found... |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 05/21/2008 : 09:56:28
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Posted on behalf of BASN
It looks like it might be a factory mod, as you can clearly see a diode, in the bottom LEFT corner of the PCB,
on the left side of the picture, near the MN3102 clock IC. (component side)
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 05/21/2008 : 10:25:28
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Hi Laurie
Good decision to keep the DM-2
Any DM-2 is a good DM-2
And you have the technology to fix her.
Not all my pedals have the little clear plastic washers on the pedal screws either.
These look so much like the Ibanez AD9 analog delay pedal.
I posted some pics, in the pedal Internals thread, of the one my friend Justin purchased.
I wonder who copied who?
I wish I could do a comparison.
Oh yeah -- Congratulation Laurie.
Regards Dr. Bob
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 05/21/2008 : 13:59:52
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quote:
Originally posted by Dr. Bob
Posted on behalf of BASN
It looks like it might be a factory mod, as you can clearly see a diode, in the bottom LEFT corner of the PCB,
on the left side of the picture, near the MN3102 clock IC. (component side)
My apologies for hijacking the thread to carry on about my recent purchase... anyway, back to the topic!
Interestingly my DM-2 has a "Rev A" board, with a diode. BASN's Rev A board doesn't have the diode but does have the mod... Looks like the change happened in mid 1982 prior to the Rev B board. I wonder when they started doing the diode mod?
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Edited by - Laurie on 05/21/2008 14:10:54 |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 05/21/2008 : 14:11:35
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Hi Laurie & Guys
Perhaps you can use the pics to get a rough setting for the pots in your unit?
Did you guys notice that the blue wire on pin 4 of the PCB, as been cut off/disconnected, on both pedals?
And some of the wire colours are different on both pedals as well.
This getting stranger that the stuff that magically appears on desk at work overnight.
Hey Christo
WHAT Dam CAT??????
And who's this Laurie guy, that keeps PM-ing me?
Regards Dr. Bob |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 05/21/2008 : 14:26:18
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| Christo's cat is pregnant? Oh no, I'm confused... |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 05/21/2008 : 14:27:20
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| Another thing I noticed on my DM-2 is that the knobs all use set screws. I've never seen this on an MIJ pedal before. Is it standard? |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 05/21/2008 : 14:31:48
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quote:
Originally posted by Dr. Bob
Hi Laurie & Guys
Perhaps you can use the pics to get a rough setting for the pots in your unit?
Did you guys notice that the blue wire on pin 4 of the PCB, as been cut off/disconnected, on both pedals?
And some of the wire colours are different on both pedals as well.
This getting stranger that the stuff that magically appears on desk at work overnight.
Hey Christo
WHAT Dam CAT??????
And who's this Laurie guy, that keeps PM-ing me?
Regards Dr. Bob
Blue wire is connected to the center pin of the power jack on mine. Can't see how it would work from the adapter without it?
I should be OK with the pot settings - the service notes are pretty clear about how to do it. Only question I have is what does the 0dBm input mean in this context? (just a 0.775 VRMS input signal? seems high?)
Thanks for the helpful suggestions as always Dr. Bob!
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 05/21/2008 : 15:12:28
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quote:
Originally posted by Laurie
Another thing I noticed on my DM-2 is that the knobs all use set screws. I've never seen this on an MIJ pedal before. Is it standard?
Hi Laurie
A few of my very old CE-2's, DS-1's & SD-1's have the set screw knobs, they usually have the non spline, D-shafts on the pots.
I would keep the input signal more around the 100 to 250mV figure.
Regards Dr. Bob |
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BASN
Copper Member
USA
17 Posts |
Posted - 05/21/2008 : 22:57:32
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| Hi guys--there's an explaination for the clipped blue wires on my DM-2's. As you guys know the DM2's were originally designed to be powered by either a 9 volt battery or the Boss ACA adaptor. The ACA adaptor as I recall was a 12 volt unregulated power supply that was routed through some circuitry to bring it down to 9 volts. I clipped the blue wires and rewired the DM-2's so that I could power them with a standard 9 volt power supply instead of the 12 volt ACA adaptor. When I got my first DM-2 I noticed that the LED was brighter when I powered the pedal with a 9 volt battery--when I powered the pedal with a standard 9 volt AC adaptor the LED was less bright and the pedal didn't sound as good. After doing some research and learning about the ACA adaptor I clipped the blue wire and re-wired the pedals for use with a standard 9 volt AC adaptor. I left a short section of the original "blue wire" as a way of remembering the way the pedal was originally wired. |
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Topic |
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DM-2 Diode Mod
