Complete newbie building a 41Hz AMP6

[niiico]

Hi,

I ordered an AMP6 from www.41hz.com and I'm building it with the most carefull attention since I'm a complete newbie in electronics (but I don't like to be told I'm not able to do something )

This is even more difficult to me because I work only with 45 min sessions, 2 times a week.

The first thing I'll remember is : do not buy unleaded silver (4%) solder! It is even more difficult to solder because of the higher melting point! But that's all that I have, so...

It is not yet finished, but it passed yesterday evening the onboard power supply test : I got 21.5 V between C99 leads and 14.61 V between C1819 leads. Hurra !

Since this is the first time I do this kind of stuff (I already made my speakers, you can see them here. The text is in french, photos are international ! ), I'm very happy with this first result.


Here is the test board:


You can see the 39 KOhm resistor in place between C1819 leads for the power supply test:


Some details on the unfinished board:



I have now to solder the chip on the board. I hope to have some good news next week, but I'm still waiting a 10000µF stiffener cap to add in parallel to the C1819.

[phn]

Nice work.

The 45 min sessions are actually a good thing. A common problem is that people try to do too much at once, get tired and make mistakes.

[Pano]

Looking good niiico!

The chip is not too difficult to install, but the legs are always a bit bent - you'll have to straighten them.
If you solder a few pins on each end to hold the chip in place, it will be easier to install the caps that go in the leg holes.

You are right about silver solder, it can be a pain to use. Takes a lot of heat to melt.

The speakers look cool, nice work - C Bo! Ah, the good old "Maison du Haut Parleur". My son lives across the street from the Paris shop. They've been selling Audax longer than he's been alive.

Let us know how they play with the AMP6.

I am also working on a new speaker project that will look much like yours. But he drivers are quite different.
See this thread.

Keep up the good work!

[niiico]

Originally posted by panomaniac
Looking good niiico!

The chip is not too difficult to install, but the legs are always a bit bent - you'll have to straighten them.
If you solder a few pins on each end to hold the chip in place, it will be easier to install the caps that go in the leg holes.

That's exactly what I was planning to do.
The most part of the work will be to wire it for the tests and then rewire it to put it in a box (I'm not yet sure of what case I will take).

BTW, when we are testing the board, there is some energy remaining in the caps and I got beautiful blue sparks by touching the leads (after main plug removal ).

Is there a safe way to discharge the caps (not in my fingers ) without damaging the board?

You are right about silver solder, it can be a pain to use. Takes a lot of heat to melt.

Yes, but I'll use it all because I have 500g of it I should have invest in a solder station with more power than my JBC 40S. When this one will be too old, I'll invest.

About the speakers, the kit is from HP Systemes but you won't find 'em anymore on the site since they've been replaced but the 217X (the Audax speakers don't exists anymore).

[phn]

Originally posted by niiico
Is there a safe way to discharge the caps (not in my fingers ) without damaging the board?

A resistor will do.

[niiico]

Hello,

my AMP6 is now functionnaly finished (I mean... it has no box today but it works ).

Let me tell you...

Last week, I have soldered the chipset and the caps within its legs without any problem. I had just some problems to identifiy the polarity of the diodes and ran out of time to finish it.





This was last week. As you can see, the FETs that drive the leds are in the orientation written on the PCB...

This week, Jan explained on the www.41Hz.com forum that the FETs had to be reversed... As a complete beginner, it took me 45 min at least and one of them is now, how to say... short!

But I did it. I connected also some temporary wires to test it for the first time...



You can see the "shorter" FET...

So... Before to connect anything to the amp, i had to test it doesn't burn when plugged and turned on

I put a 200mA fuse (as Jan advices it), put the amp in sleep mode and plugged it. No smoke, nothing weird. How is the fuse? Burned! $£*# !!

I checked everything twice, put a new 200mA fuse and tested again, watching the fuse while plugging the amp in. Instantaneously burned.

Re-check, re- new fuse, re- plug, re- $£*# !!

Everything looked fine, so I decided to put the final 2 mA fuse instead of the 200mA, ready to unplug the amp if it burned in smoke...

Looking at the fuse while I plugged, I noticed that the wire inside it "bent" a second but stayed in one piece. Nothing seems to be burning or becoming instantaneously hot, I woke up the amp and the green light went on. Ha haaaa, was I on the right way?

I think that the 200mA fuse burned because of the caps asking energy too fast... I hope it is that!

I measured 16mV and -54mv offsets (I don't understand why one is negative...). Looks correct.

Unplug, plug an Ipod, plug some small loudspeakers (my future surrounds), amp on...

Hurra! It plays music!

Here is a view of my "workshop", dedicated, as you can see, to my electronics experiences...



It's time now to find a box, to wire it with the right cables and then to add a stiffener cap as suggested by panomaniac. But I think there is already some good power inside the caps: it takes about 5 seconds to the music to stop after unplugging the amp!

BTW, when I turn off the amp, at the end of the 5s music, the red led lights on about 1 second and then goes off. Why is the red led going on at the end?

You can't imagine how happy I was to make this work at the first attempt!

[niiico]

Originally posted by niiico

Everything looked fine, so I decided to put the final 2 mA fuse instead of the 200mA, ready to unplug the amp if it burned in smoke...

I meant 2A, not 2mA

[niiico]

Speaking (alone) about fuse...

Do you think a 2A slow fuse is "string" enough for the AMP6 with a 80VA transformer?

If I look at the theorical power consumption, it is ok, but in real life, what do you think?

Panomaniac, what fuse do you put in your Octopus Amps (if its not a secret)?

[Pano]

2A slow blow is what I use. 2.5A regular fuse also works.

You are correct, Niico, that the big cap C99 is what was blowing your small fuse. I think that when Jan says to use a 200ma fuse he was thinkning of the AMP3 type boards, which do not have the big cap or the regulated supply.

Congratulations on your amp!

[niiico]

Hi,

I asked the same question to Jan a few days ago (before your answer) and here is the answer :

From support: 21/05/2006 12:24:58

Hi

Power = ((15/1.41)^2)/4*2 = 57VA.

Ipeakmax = U/Z = 15/4 = 3.75A per channel, Imax average(RMS)= 15/1.41/4 = 2.6A per channel. But 5A should be enough. The voltage regulator has built in overprotection at 5A. You can use a fuse on the primary side rated according to the max current of the transformer. 2A on the seconcdary may blow if you turn up the volume...

So, I think there is an error in the formulas on his site and I will buy a 5A (or a little less) slow fuse to protect the regulator