Identify Missing Capacitor in Oatley Kit - diyAudio
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Old 23rd March 2011, 07:25 PM   #1
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Default Identify Missing Capacitor in Oatley Kit

Hi All-

First post here...really enjoying all the great info.

Anyway, I've got a little problem with a brand new Oatley Electronics RIAA Stereo Preamp kit that I got yesterday. I got shipped the BRAND NEW revision...the K301. So there's not much out there about it. Nothing really.

It seems that I'm missing a pair of Zener diodes that are right in the main power path...ZD201 and ZD202. I'm wondering if any of you guys can help me identify them. They're in the bottom left area of the PCB and the top right of the schematic. Here's the PDF of the assembly instructions...

http://secure.oatleyelectronics.com/files/k301notes.pdf

It looks to me like they're just simple 5volt zener diodes I could pick up at 'The Shack'...in a two pack luckily.

I wrote Oatley, but have not heard from them sadly, and I'm afraid to just try this as I think I could fry the thing if I'm wrong.

Thanks a million for any clues/ideas!
Andy
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Old 23rd March 2011, 08:16 PM   #2
Marra is offline Marra  United Kingdom
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Schematic reads 15V for the zeners. Unless my eyes deceive me.
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Old 23rd March 2011, 08:35 PM   #3
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Thanks Mara-

I wasn't sure if I was seeing 15 or 5. Do you think that simple Radio Shack zeners will do the trick here? They sell them in 15s in the stores.
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Old 23rd March 2011, 10:51 PM   #4
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Quote:
Originally Posted by Marra View Post
Schematic reads 15V for the zeners. Unless my eyes deceive me.
You are right - two 15v zeners for the 30v supply...
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Old 23rd March 2011, 11:34 PM   #5
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Shoot, the local radio shack only 12s.


Any recommendation for a quick online source?

Thanks again for the info!
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Old 24th March 2011, 12:47 AM   #6
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Quote:
Originally Posted by andytanguay View Post
Shoot, the local radio shack only 12s.


Any recommendation for a quick online source?

Thanks again for the info!
digikey or Mouser are the popular online sources, though it seems a shame to pay shipping for a few cents worth of parts.
Time to stock up you parts bins?
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Old 24th March 2011, 01:03 AM   #7
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Boy, you said it. What a shame...two diodes. I'm sure I can find some goodies over there to tag along.

Hey, you read those instructions as taking AC straight in also right?
They shipped the kit with a wall wart that I don't think it needs anymore. They had an old revision that took those, but I'm 99% sure they don't anymore.

I'm pretty confused. I don't want to fry the thing , but the board says right on it 'AC IN'.


The notes also mention this...

"The incoming Mains AC supply is connected to the transformers primary. This can be configured for 100-120V or 200-240V AC operation."

But nowhere in there do they mention how to configure it for those loads.


Thanks SO much for the insights and having mercy on a bit of a newb.
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Old 24th March 2011, 04:40 AM   #8
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For the zeners, they need not match provided their total voltage rating adds up to 30 volts. You could use 2x 12 volt and 1x 6 volt. (Mount one zener in the board as normal. In the other position, put one end of each remaining zener into a hole so that they stand up vertically from the board. Twist the free leads together. Solder them together and snip off excess length. Make sure they are all connected "nose to tail", or "anode to cathode".)

You won't need the "wall wart" if you are using the on-board transformer. Note that the transformer has two primary windings. The last picture in the PDF shows it wired for 200-240v operation.
(Mains in to pins A and D, pins B and C connected together, putting the windings in series.)

For 100/120v operation, the windings have to be connected in parallel.
Connect pin A to pin C.
Connect pin B to pin D.
Connect the mains to pins A and D.


If you are not using the onboard transformer and want to use a wall wart:
Remove the onboard transformer.
Connect a wall wart that outputs 12 volt AC (not DC) voltage, to the two empty holes left where you removed the onboard transformer.
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Old 24th March 2011, 05:46 AM   #9
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Wow, thanks for the info Don! This is really great stuff.

I honestly would have probably ruined the thing without knowing this.

I think I will go with the AC and your wiring recommendations.

I like what's Oatley is doing with these little amps, but it seems like they're kind of dropping the ball a bit. Between not sending me all the parts I need and not sending out proper instructions. Bit of a disappointment.

At any rate, thanks again! I will wire this for AC like you said. Any recommendations for a fuse rating? I found some 3amps in my parts bin.
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Old 24th March 2011, 09:19 PM   #10
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Good news! Found a local source for 15V zener diodes.

Thanks again to you guys for the clarifications.
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