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Old 6th November 2012, 09:54 PM   #1271
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Quote:
Originally Posted by Zen Mod View Post
see

view from top , of course
I used 1, 2, 3 for jfet1
but went wrong when I used 4, 5, 6 (instead of 5, 6, 7) for jfet2!

Time to heat up the soldering iron!

Can I have fried the second jfet or should it be ok?
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Old 6th November 2012, 09:58 PM   #1272
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they're tough little buggers

whatever - it's easy to make Idss test when it's unsoldered
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Old 6th November 2012, 11:43 PM   #1273
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Default Lament of a desoldering newbie ...

I have been kicking myself for the last 2 and a half hours but am getting nowhere.

Ah, desoldering
I knew it would not be easy

I have left one jfet in (it was soldered correctly) but tried to get the other one out whole. No such luck.
I ended up cutting/snipping the jfet out (I had left the leads quite long so they should be long enough for re-use) but now have small pieces of the leads in the holes ... and can't get them out
I have used a sharp pin, tried heating with the iron, used wick, ... you get the point. You are probably laughing , because this is such a newb problem.
There is a lot of desoldering info on the web, but nothing I can see that I can use or have not already tried.

I am going to bed
Try again tomorrow. Any suggestions?

Thanks,

Albert
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Old 6th November 2012, 11:47 PM   #1274
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add some solder to any side , and you'll heat it easier

grab one side of pin with tiny pliers or tweezers , heat , pull

that's routine thing

having solder sucker pump is must , when you're messing with tiny parts
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Old 7th November 2012, 09:51 PM   #1275
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Two of the three holes are open far enough that I can see light through them. One is not open enough to mount anything yet. How to open it further?
I tried to push a diode-lead through the hole while heating the other side, but only end up bending the diode leads

The third hole is completely blocked. There is no lead/pin left to grab! What do I do? Buy a very thin drill? Or is there another way?

Sorry for these questions, but I have no idea what to do.

Thanks,

Albert
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Old 7th November 2012, 10:02 PM   #1276
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use a solder sucking pump.
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Old 7th November 2012, 10:04 PM   #1277
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Quote:
Originally Posted by AudioSan View Post
use a solder sucking pump.
I tried but it did not budge. I think with the 3rd hole a piece of the lead/pin is jammed in the hole.
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Old 7th November 2012, 11:18 PM   #1278
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add some solder , so you can heat it easier and suck with pump

or use solder wick

or use sharped graphite pen (bleistift) - heat with solder while pushing pen's tip through hole

graphite will not melt and will not cold solder
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Old 8th November 2012, 12:35 AM   #1279
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Default Left channel working!

Thanks everyone, Zen Mod in particular, for helping me out with this! Much appreciated!

I finally got the third pin out and was able to put the original jfet back in (using the correct holes this time). I now have the left channel back on the heatsink and could not wait to switch it on! I was hoping the rough handling of the pcb and components during my desoldering debacle had not damaged anything and was amazed it is working properly! Incredible how much abuse these things can take!

Rail voltage slowly drifts about 200mV around 27.6V DC and DC offset at speaker output (inputs shorted) is slowly coming down from 56mV to 41mV (after 15-20 mins). Heatsinks quite warm. Will test temperature tomorrow.

Time to go to bed, I think.

Tomorrow or Friday I will take out the right channel and try to do this desoldering stuff a bit better Then I hope to connect the right channel and if everything works out I hope to have glorious sound.
I cannot wait to compare this new ḧome "built, butchered and built" Aleph J to my original Aleph 3. Will keep you posted.

Thanks again everyone!

Good night

Albert
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Old 8th November 2012, 05:40 PM   #1280
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Default Right channel also working

Hi guys,

Wanted to let you know that the second channel is also working. Removing the second jfet was a lot easier than the first and after putting it back into the correct holes, remounting the pcb onto the heatsinks, reconnecting wires (am I glad I used connectors and did not solder the wires to the pcb!) I turned the amp on.

I measure 41.5mV DC at speaker output after 45 mins and with inputs shorted.
Rail voltage has dropped under load from about 30V DC (no load), to 27.6V (left channel only). With both channels it is down to 25.3V. Is it normal that it drops that much?
I have a Fluke 179 and thought I might be able to get some info on the AC ripple by setting the DMM to V AC. I get a reading of about 100mV. Is that OK?

The amp is producing quite a bit of heat! The amp does not yet have feet (the bottom is flush on the desk), so air circulation around the heatsinks is not optimal.
I have checked the temperature and the hottest spot on the heatsinks (after 40 mins; exterior of cabinet) is about 59 Celsius. Ambient is about 26, so about 33 above ambient.

Now I will just let it run in for a while and I hope to be able to listen to it tomorrow or over the weekend.

Not bad for a first ever poweramp build!

Thanks again!

Albert
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