sampo
New Member
Posts: 5
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Post by sampo on Sept 8, 2008 1:37:39 GMT -5
Hi, I just joined this board in hopes of getting a really butchered A-3 working. Someone has modified the organ very heavily and I'm not comfortable even plugging it in before I can get a good understanding how it's supposed to be wired up. The power cord is even missing the plug which could indicate that it is not in a safe condition. You can see a few extra circuit boards and controls here: sampo.garageflower.net/urut/03092008397.jpgAnd a new PSU: sampo.garageflower.net/urut/03092008398.jpgDoes anyone here have the service manual in digital form? .. Or know a source where I could buy it? I'm sorry if this has already been discussed on this forum, but I couldn't search for A3 or A-3 from the forum as the search prohibits words as short as that.  |
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Post by Rod MPS on Sept 8, 2008 8:02:42 GMT -5
You can check here... www.wdgreenhill.com/AtoZ/schematics.htmThey don't show one on the site but they didn't show the manual for my Elka either. Send them an e-mail and ask. I will keep my eyes open and keep us posted. |
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sampo
New Member
Posts: 5
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Post by sampo on Sept 8, 2008 9:54:51 GMT -5
Thanks. I just sent them an email. I'm still keeping my hopes up for a local repair store. I was very positively surprised that they lent me their YC-20 service manual when I needed it some years ago. |
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Post by karl on Sept 8, 2008 23:18:39 GMT -5
Hi Sampo,
You may know this already, but..
If you have an ohm-meter I would check across the wires that used to go to an AC plug. If theres a low resistance or short
(o or near zero ohms ) it may have been blowing fuses and this would cause someone to cut that plug off. Also it's difficult to see in the picture but that round(toroidal) transformer looks new. Can you tell if the wires running to it are newer than the other wires in the circuit? These are used for lower noise, but I rarely see them in gear like this.
Keep me posted
Karl
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sampo
New Member
Posts: 5
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Post by sampo on Sept 9, 2008 4:09:57 GMT -5
Hi Sampo, You may know this already, but.. If you have an ohm-meter I would check across the wires that used to go to an AC plug. If theres a low resistance or short (o or near zero ohms ) it may have been blowing fuses and this would cause someone to cut that plug off. Hi! I haven't measured the thing yet as by the looks of it it could be seriously broken. The fuse will be the first thing to measure though. Thanks for reminding me. Also it's difficult to see in the picture but that round(toroidal) transformer looks new. Can you tell if the wires running to it are newer than the other wires in the circuit? These are used for lower noise, but I rarely see them in gear like this. It's a new toroidal transformer. I'm guessing 1990's or even just a few years old. The power supply capacitors also look brand new. Does anyone happen to know if there are "usual" modifications done to A3's? Maybe this board looks familiar? sampo.garageflower.net/urut/03092008405.jpg Will do. I will be calling the local repair guy today and ask for the A-3 service manual. Keep your fingers crossed. Sampo |
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sampo
New Member
Posts: 5
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Post by sampo on Sept 9, 2008 10:02:08 GMT -5
Hi,
I got the manual! The modifications are also starting to make some sense. I will report back once I get to work on testing the organ.
Sampo
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Post by karl on Sept 9, 2008 14:53:52 GMT -5
Hi Sampo,
Looking at that modification board. Looks custom to me. (and old) I am thinking its some kind of filter circuit. I guess it's not in the service manual?
Karl
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sampo
New Member
Posts: 5
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Post by sampo on Sept 10, 2008 1:15:19 GMT -5
Hi, No, the boards are not in the service manual. I would have been a bit surprised if Yamaha had used perfboard for production organs ;D One source tells me that the large board is a phaser circuit, probably from the mid 70's (at least that is the age of the opamps). It's possible the organ has been modified to have stereo output as the phaser circuit seems to have two channels. The toroid is probably there only to supply a bipolar voltage for the opamps. There is also a board which looks as if it's the regulator for the opamp psu. Haven't taken a new look at it yet though. Feels like I'm finally grasping what's going on here. But there is still at least one mystery board (see left of the keyboard sampo.garageflower.net/urut/03092008397.jpg ) in there which I haven't figured out. Also, it looks as if something is connected to one of the key "crossbars" sampo.garageflower.net/urut/03092008404.jpg . Sampo |
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