Identify Missing Capacitor in Oatley Kit

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andytanguay

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Joined 2011
#1
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
 
#7
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.
 
#8
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.
 
#9
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.
 
#11
Sadly, this didn't do the trick. 8-(

I installed the zeners, got the hookups going, and when I hooked up the AC, I got all buzz and zero signal. When I tried going with the wiring they suggested, I got no buzz, but no signal there either. The LEDs are lighting, so I know I'm getting juice.

The piece of paper that Oatley includes with the kit says something about a modification that needs to be made, but of course they don't answer emails asking for these instructions. I would really not order from them again.

Any thoughts/ideas would be much much appreciated.
 
#12
I'm not a SS guy, so can't help much- though I have built some SS projects on PCBs. Checking some voltages on the board against the schematic might give you some ideas.
You had to install the components on the board? Double-check the identity/value of each component. Also check for any unsoldered connections.
If you don't come up with an answer fairly soon, perhaps a new thread in the SS amps section ('Troubleshooting SS phono amp problem'??) would get the attention of some SS experts.
 
#13
Hi I looked at the instruction sheet and it really is very light on in information. The fact that they don't actually say how to wire the transfromer for 120V or 240V is very bad.

I'd understand if the web based pdf was just an overview and full instructions were included when purchased but it doesn't sound like this is the case.

I'd check the orientation of all the semiconductors and valves. Also check your solder joints with a magnifying glass for any that look like they haven't taken properly.

Also check you have 30V at the output of the power supply. Be careful though since the mains is terminated on the PCB!

Tony.
 
#14
VG - Thanks for the ideas. I will start poking around and checking voltages. See what I come up with.

WM - Yeah, I thought this was all weird too. I don't understand why they would send out a kit without proper instructions available, and then worse yet, not answer the email address they tell you to write to for the instructions.

It's a shame, I don't want to be a jerk and/or be the squeaky wheel, but I did pay for this kit, and as it stands now, it's completely useless. I'm justing hoping I didn't ruin the parts already.

Thanks again you guys.
 
#15
Well, here's some good news...

I checked all of the solder points like Tony suggested and hit anything that looked weird, then ran new ground wires a bit and knocked down the buzz, then started to get signal, then regrounded pretty much EVERYTHING and now I'm getting a reasonably clean signal!

Getting some high pitched hum, but I'm sure I can find a way to clean that up.

Hallelujah! No thanks to Oatley, that's for sure.

But thanks you guys.
A
 
#16
good news 🙂 one way to help make sure the joints are good is to clean all of the component legs prior putting them into the board and soldering. I use some 600 grit wet and dry sandpaper and then wipe down with methylated spirit. Takes a little bit longer but worth it 🙂

Tony.
 
#18
Well well, today I FINALLY got the updated notes for the K301 from Oatley.
For anyone reading this in the future, but hasn't received the notes, here's the link I got:

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

Come to find out, the outputs weren't grounded AT ALL...this was the mystery mod the note spoke of. This would explain the buzzing and lack of signal until I ran my own grounds. They also finally explain how to hook up the 120v AC in the US. Luckily, I learned that here.

They said they've been short staffed, but honestly, if you're that short staffed it might be smarter to just wait on sending kits out don't you think? I mean, parts were missing from mine as well as parts I didn't need coming with the kit.

In the end it works, but only through the help of my friends here.
 
#19
andytanguay said:
The piece of paper that Oatley includes with the kit says something about a modification that needs to be made...
Click to expand...
That's explained at the bottom of the pdf.
wintermute said:
The fact that they don't actually say how to wire the transfromer for 120V or 240V is very bad.
Click to expand...
Also explained in the pdf.
andytanguay said:
Well well, today I FINALLY got the updated notes for the K301 from Oatley.
For anyone reading this in the future, but hasn't received the notes, here's the link I got:

http://secure.oatleyelectronics.com/files/k301notes.pdf
Click to expand...
That's exactly the same pdf you linked to in post one of the thread. Am I missing something? Did they (belatedly) update it or something?
😕
 
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