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Pearl Two
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Old 20th October 2017, 04:09 AM   #2801
6L6 is offline 6L6  United States
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If you have the schematic with the voltages, start testing the board.

Black lead on Gnd (your yellow wires or the bare wire where your PSU gnd connects to the board, and red lead at the various test points, set to DC volts. Look for anything off by a few volts.
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Old 20th October 2017, 09:52 PM   #2802
naturallmystic is offline naturallmystic  United States
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Things looked pretty normal voltage wise until I got to Q3. The E leg is 11.5volts and the C leg is .1mv, so Iím guessing I zapped that guy while removing or replacing the linear voltage regulators. I did catch myself without my wrist strap on a couple of times, perhaps thatís the cause. Having read all the posts in the Pearl Two and Building a Pearl Two threads I ordered extras of ZTX450 power transistors which I will be replacing tonight. 🤞
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Old 21st October 2017, 02:50 PM   #2803
naturallmystic is offline naturallmystic  United States
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Pearl Two is up and running again and even better than before! After replacing Q3 it still didn’t measure out so I went back to Q1 which was dead. Either it was dead before and I neglected to measure it or I killed Q1 while replacing Q3. With both replaced the Pearl Two is sounding better than before I messed it up! Prior to changing Q1 and Q3 there was a slight hiss in the left channel (which I was unfairly blaming on my 300b Audio Nirvana amp, by the way this is an amazing sounding 300b amplifier), which has miraculously disappeared! Troubleshooting was actually fun.

Again, thank you so much to everyone for every post before me! I’ve learned some things with this project, which is great in itself, and it has given me the confidence to build an Aleph J. This is because of others willing to share information, their time, and effort. Starting with Nelson, Wayne, and Jim and including that person that made a single comment that turned on a light bulb for me, all of the participants. Also thanks DIYAudio store, it is great to have the resource!
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Old 21st October 2017, 03:03 PM   #2804
Russellc is offline Russellc  United States
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I think you will find the Aleph J easier than the Pearl 2.

I guess I was lucky, my Pearl 2 fired up right off and worked fine with no zapped 3310 or anything. Other than normal precautions, I used no static wrist devices, just a solder gun.

I want to install the cap that seems to zero and stabilize the offset, but I hate messing with something that works....

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Last edited by Russellc; 21st October 2017 at 03:05 PM.
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Old 21st October 2017, 04:20 PM   #2805
naturallmystic is offline naturallmystic  United States
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Russellc I hear you on not messing with a working Pearl. I should have installed the heatsinks from the beginning but in the end I’m really happy to have had the troubleshooting experience, especially since it turned out so well. You sure posted some helpful info and questions so you too are on the ‘grateful you are here list’. Thank you.
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Old 21st October 2017, 07:16 PM   #2806
Russellc is offline Russellc  United States
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Well, thanks but I'm still a babe in the woods with all this...There is a reason I ask so many questions!

I can Id parts, follow a schematic and solder fairly well. I would never have built all I have built (such that it is, many are WAY ahead of me) without the knowledge and patience of members here.

The internet and digital cameras have really been a giant help to the whole diy community.

Russellc
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Old 27th October 2017, 01:56 AM   #2807
Eric is offline Eric  United States
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Scott: Great to hear that you solved your problem! I've been tied up with work lately and a little behind on messages. I was going to suggest looking at your regulators again as well as some of the other more sensitive transistors.

Russell: doing the mod to remove the DC offset is worthwhile. It was pretty easy to accomplish and moved a "floating" few mV of offset to a rock-steady 0.0mV.

The next mods that I want to try are adding Salas' shunt regulators and replacing some of the 0.1uF film caps with some NOS Russian teflons. This might be a trick, though, as the Russian teflons are HUGE caps. I'll need some way to strap or glue them down.
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Old 27th October 2017, 08:49 AM   #2808
jackinnj is online now jackinnj  United States
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Quote:
Originally Posted by Eric View Post
The next mods that I want to try are adding Salas' shunt regulators and replacing some of the 0.1uF film caps with some NOS Russian teflons. This might be a trick, though, as the Russian teflons are HUGE caps. I'll need some way to strap or glue them down.
The noise performance of P-2 is excellent and i could see no improvement when i removed the Nat Semi regulators and fed the circuit with +/- 24 Superregulators.

If you are planning to tweak the design, adjusting the RIAA component values gives the best bang for the buck.
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Old 28th October 2017, 08:33 AM   #2809
jackinnj is online now jackinnj  United States
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and you might want to compare those honkin' big Russian Teflon caps with some C0G MLCC leaded or surface mount ceramics. 10 of them will set you back $11.14 at Mouser. These were very favorably reviewed in a Linear Audio article several months back.
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Old 28th October 2017, 01:09 PM   #2810
Wellerman is offline Wellerman
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I have always wondered what effect Idss in the quad in the first stage has. Does a quad with higher Idss have more gain?
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