Aleph3 recap

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#22
No problemo! My mind was just playing dumb on me. I was always thinking the wrong one that ZM referred to. Some people in other rare disciplines (not mine) use m for micro, hence the confusion.

I only noticed on the darkened spot after I took the photo with flash light. I was wondering what was going on there. Thanks for the explanation. I will take a good look later.

So is that patch under NTC thermistor still good and only re-solder is needed? Why would that spot accumulate heat?

Thanks for the good info. I am learning.
 
#23
grimberg said:
I have bought Elna Silmic II from this site: Handmade Electronics Indexpage

If it is not too much trouble, please post more pictures as you take your Aleph 3 apart. That kind of image is hard to find.
Click to expand...

Thanks for the link. That was where I found out of here.

I certainly can post more photos later if this is not against any rules. And it is quite a job to take out all the necessary screws without a good Allen wrench in my lab.
 
#25
Thanks, ZM. I'll check on it. I have also seen some metal clips on transistor to assist heat dissipation. Would it be good idea to put something like that on NTC if it was so hot? I'll also take an IR measurement next time to see what's the operation temperature of it.

It seems 22mF are very common and anything above that is more expensive and much less choices (for size and spec). Anyone has good sources to recommend?

Thanks!
 
#26
Thermistors will run in excess of 100C. Be careful not to touch it while it's on! 🙂

What are the dimensions of the filter caps. (Height and Diameter are the important ones...)
There are going to be a good number of choices from Digi-Key and Mouser.
 
#27
digikey

part No. P6895-ND for 22mF/25V
P6921-N for 22mF/35V
P6898-ND for 33mF/25V
P10012-ND for 33mF/35V

check by your self - maybe I didn't found cheapest ones

panasonic 22000uF/25V - Google претрага
panasonic 22000uF/35V - Google претрага
panasonic 33000uF/25V - Google претрага
panasonic 33000uF/35V - Google претрага

in any case - my (as always :clown: ) modest opinion is that this amp is well worth spending money on even much costlier caps ; not Audiophool ones , but decent ones with decent price
dunno - maybe Papa can tell what they're using these days in PL products
 
#28
Thank you both!!

6L6 said:
Thermistors will run in excess of 100C. Be careful not to touch it while it's on! 🙂
Click to expand...

Wow! that is super hot. Does the design of that NTC requires to reach that temperature to work correctly? Will putting on mini-heatsink on it distort its functionality? That seems to be safer for the PCB board.

Zen Mod said:
digikey

part No. P6895-ND for 22mF/25V
P6921-N for 22mF/35V
P6898-ND for 33mF/25V
P10012-ND for 33mF/35V
Click to expand...

Yes, I checked Digikey and Mouser but was using 40V as the minmum rating. I guess that I can relax a little bit. The original Panasonic caps has 25V rating anyway.

It seems that I can only use the "through hole" and "snap in" types with that board. The snap-in has two leads for mechanical mounting and I just snip off those, right?
 
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#30
I just use the IR thermometer to take the temperature on the NTC. Actually the temperature on NTC was abut the same as the 22mF caps. However, the square pad where the black wire connected to was as hot as 240F. That temperature quickly rose up or drop down when I turn on or off the amp.

That 240F seems to be too much. I suspect that the pad was bad so the resistance across the pad was too large and hence very hot spot there. Maybe I should jump a wire from black to yellow wire and to the leg of NTC (to bypass the pad) just to see if my theory is valid?

Or whatelse could be the issue for such high temperature on pad? And is OK to keep running it like that?

Thanks a lot for your keen eyes and help!!
An externally hosted image should be here but it was not working when we last tested it.
 
#32
OK, I'll resolder it when the caps come in.

Bear with my ignorance, why is that pad so hot? I don't think the heat came from the NTC. It seems to be from the pad itself.

Oh, this is no burden to a senior research engineer at all. This is just a hobby. I only need to get my feet wet. I just plan to dig out my microelectronic textbook to have some fun. And you had enough fun already. 🙂

Thanks a lot for helping!
 
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#34
That make sense to me and was what I suspect. Maybe the pad can use some mini heatsink later.

And I do feel some 22mF cap a little budged at the top. Thanks a lot for all the help. This give me motivation and some expectation to restore this Aleph 3, if it already sound so good at current state. 🙂

You and others are great guys here and fun to talk to. :up:
 
#40
not that there's anything wrong with replacing all the caps in your amp, but if you want to save a few bucks you might try replacing the small caps first and see if that solves your problem. the smaller DC blocking caps in the signal path will cause a loss of low end when they start going bad, which sounds like the problem you started describing. when the big filter caps in the power supply go bad it will cause hum and buzz problems in your audio due to ripple appearing on the power supply rails.

-Joel
 
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