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Old 9th September 2010, 10:58 PM   #501
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Default Pearl Two issue

Bump.

Replaced the + and - regulators. Supply disconnected from circuit board steady at 35v output at C2 and C3. Connected to circuit board plus supply starts dropping and negative supply starts increasing. Voltage at positive regulator input and output are the same, dropping in synch. Input to negative reg. Climbs but output of 7924 stays at - 24v for a while.

Any suggestions?
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Old 10th September 2010, 12:14 AM   #502
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I really dont know much about how these things work (I just follow the recipes) but that sounds like your ground plane (or whatever reference your using) is drifting towards one rail.
So perhaps look for something that prevents the ground from draining off current or something that feeds too much current into the ground, in the later case I suspect something would be getting hot?

Are any regulators getting hot?

I guess also this would be consistent with a regulator working opposite and trying to bring the ground up to the intended rail voltage?
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Old 10th September 2010, 12:29 AM   #503
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"For that project I will use Vishay 1% resistors, Vishay MKP 1% caps for the RIAA correction and bypass output capacitor, Muse for the output ones (22uF/25v); Elna 3300uF/35V and for the 10000uF/40V, the new Mundorf M-Lytics AG séries
Input and output RCA connectors will be Silver Bullet ones "

Nar or anybody sourcing "special" parts; if its possible could you list sources and part numbers I never have much luck locating the special audio parts.
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Old 10th September 2010, 01:18 AM   #504
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Default Pearl Two Issue

Fritz,

Thanks for the input. I'll check that out tomorrow.

Rudy
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Old 10th September 2010, 06:32 AM   #505
nar is offline nar
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Quote:
Originally Posted by Fritz View Post
Nar or anybody sourcing "special" parts; if its possible could you list sources and part numbers I never have much luck locating the special audio parts.
Hi Fritz,

Yes that's terrific to have more than 4 sources or parts. You can try Digikey or Mouser, I had some problems with Farnell so definitely won't buy anything from them again. I deal with RS Components, which are not cheap but they do 24h delivery for free, or Digikey France now available, local dealer here in my place for various, including 2SK170 which I got at 0,70€/pc by 100pc, enough for matching I guess

So for parts number, it really depends which source you will choose - the most suitable to you. And is all pleasure to find what you need in the huge parts database

Best regards,

nAr
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Old 11th September 2010, 11:13 PM   #506
akimo is offline akimo  United States
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Default C9 - Mica okay?

Today's dumb question from a non-engineer:

Is a mica cap the optimal material for C9?

Thanks in advance

P.S. Other dumb question:
My boards came with three packs of 4 of the Toshiba jfets each. I was planning on using one bag for Q6-Q9 for each channel, and then splitting the third bag into the two channels of Q4-Q5. Is this the right approach?
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Old 13th September 2010, 01:59 PM   #507
m2003br is offline m2003br  Brazil
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Quote:
Originally Posted by Rudymay1945 View Post
Guys, just finished the pearl two using Pass boards and I have a problem.

Power supply is in a separate box. It checked out ok. But when I connect it to the circuit chassis strange things happen. On turn on things sound fine but within a couple of minutes the volume fades away.

When I checked out the voltages, the positive supply rail at R4 starts dropping from 24.06 volts to around 5.74 volts in about two minutes. The negative rail goes up to 62.1 volts.

This happens with both boards whether one or both are connected to the power supply.

Any suggestions? I have checked the layout and it looks ok. I'm not a techie so I'm a little lost.

Thanks
Rudy
Hi Rudy,

The power supply schematic on the manual, fig 7, have one error. You need to connect the center line of the 2 bridge rectifiers to the center of C2 and C3.
If it is not your case,
maybe you only forgot to connect the Zero Volt line from your separate PS to Pearl II board (pad2-Ground).

Hope it help.

Marcos
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Old 13th September 2010, 02:04 PM   #508
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Default Pearl Two issue.

Marcos,

Thanks for the info. I did finally discover the error and that fixed my problem.

Sounds wonderful!

Rudy
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Old 13th September 2010, 06:23 PM   #509
nar is offline nar
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Default Suggested PSU layout

Here's a simple layout that can be P2P wired or converted to a board via traditional DIY methods

Dimensions are 3'16" x 2'53" @300dpi
Attached Images
File Type: jpg PSU_Layout.jpg (77.7 KB, 947 views)
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Last edited by nar; 13th September 2010 at 06:47 PM.
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Old 14th September 2010, 08:14 AM   #510
nar is offline nar
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Diode bridges are in standard GBU806 package. I used Digikey part GBU806DI-ND. AC / AC pads are meant for tranny secondaries connection (22 or 24V). C2 & C3 parts are 10.000uF/40V Mundorf M-Lytics caps (25x40mm). There is extra space between caps and diode bridges, in case you would like to mount some heatsinks on the rectifiers. One issue could be the in / out connectors holes sizes + GBU holes size for drilling & soldering though. I might change this in the near future
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Last edited by nar; 14th September 2010 at 08:24 AM.
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