Mine are not so high, they measure 22x40mm ; here was the link where I bought it : https://fr.aliexpress.com/item/Free-shippin...08.0.124.KGRgpw
After, I don't know if they are "real" or not ! Could it be an old series ? Or as you expected, they could be contrefacted ?!?

This post has been edited by rsseco: Aug 24 2016, 10:08 PM

My terms are wrong ? Sorry.
But my thoughts are true to say marked side is - pole ? So, normally I always put the Black - pad on this side to have the normal behaviour of the diode, or am I completly wrong ?
Are some of my measurments totally wrong then ?

What should I do next ? Could be I must buy some other capacitors if they are "false" ones ?

EDIT :The fault can be mine too, as I want to buy as cheap as I can... I do it this way, as I doesn't want to spend too much in case my repair will not work.
I know it's a risk by having some bad quality product, and it's a dilemma : Low price = bad quality = perhaps repair will not work because of that ; instead of more expensive = best quality = can work better !
If I was sure to be able to repair it by myself, I would buy things of higher quality, of course !
Because usually, I always buy the best things...

This post has been edited by rsseco: Aug 24 2016, 11:04 PM

OK, I will check this with only Q3 and Q4 soldered. Do I need to try with only one first or can I put the twice together ?

And how will we find what ?

No, values fluctuated to fast ! I can try the "A-Hold" mode of the multimeter

This is not what I already done yet ? Or you mean with some IRF740 in place ? Or in the order you wrote it : first V(G-S) and then V(D-S) ?

I don't know what to say, the "-" sign appears sometimes...

OK. And so could be my IRF740 too... and perhaps what I doubt before, could be faulty or fragile too (that's why they broke as easily ?!? ; and could confirm my guess about why 2 IRF740 broke as before, only one was really out of order).
But, my fluctuate values without any IRF740 in place could reveal any other problem anyway ?

In fact, I don't know which was OK at the first time, as I remove twice at a time to check them. I only know one was defective and the other no
To remember :
Yes and no ! In fact, I've done it by putting the black pad as you wrote me before.
You can see it on this picture (S is written in black, D and G in red) ; I've tested it this way.

Okay, G seems to be written in black... but in fact, it's red !

I have an additionnal cap leaving (as I bought 5) ; should I try to replace C59 in order to see if I have stable value ?

Hi !
Sorry for the delay, but with these hot summer days, not very easy to do some checks !
By the way, here are the new checks of today !
I re-check Q3 and Q4 completly again.
Q3 S->D : 152V, no more fluctuating !
Q3 S->G : 283V

Q4 S->D : 148V
Q4 S->G : 280V

C59 : 157V but decreasing slowly

I wanted to re-check Q2 and Q1, but on Q2 I ripped the red probe between G and D and what should happen, happened ! Shortcut, electric arc and Q2 explodes !

For the other 2, I already threw them away...

But I don't understand why this time I haven't no more fluctuating values !? ! So next step is to replace Q2, then Q3 ?

Hi !
Sorry for the delay, but with these hot summer days, not very easy to do some checks !
By the way, here are the new checks of today !
I re-check Q3 and Q4 completly again.
Q3 S->D : 152V, no more fluctuating !
Q3 S->G : 283V

Q4 S->D : 148V
Q4 S->G : 280V

C59 : 157V but decreasing slowly

I wanted to re-check Q2 and Q1, but on Q2 I ripped the red probe between G and D and what should happen, happened ! Shortcut, electric arc and Q2 explodes !

For the other 2, I already threw them away...

But I don't understand why this time I haven't no more fluctuating values !? ! So next step is to replace Q2, then Q3 ?

You are maybe right, it was perhaps not 280V but mV. I probably have not read well !

Edit : but, if it's mV, you have said it's too low too, so where is the matter now ?

This post has been edited by rsseco: Aug 30 2016, 03:49 AM

Hi, here I am again !

So, here's the results of tests you asking me to do :



In conclusion, for diodes, all seems to be fine/OK.

For Q6, I first done the test with the multimeter, as shown on the next picture :

The value gaves me 199 to 197. I don't know what it means. If I place the PNP in other way (E on C and C on E, it gaves me 0)
Then I measure it with the diode function, and the result is shown in the first picture.


Question : if these values are correct, should I not rebuy some "real" capacitors ? It could be simply - are they seem to be fake ones - that they are the main problem ?

For the 280V, as said before, I think I've just read it bad (must be mV as the first check)

OK, what should buy finally ? And where ?

We come again to my dilema : as I'm not sure it will work after all the replacements, I'd not like to spend a lot of money.
On one hand, I'd like to repair it, but on the other hand, I'm not ready to replace every component if it's not necessary.

At the beginning, I was exited to began the repair process ; but with the time, I'm disappointed not able to found the problem. And more, as my capacities in electronica are limited.

If you haven't no more idea from where's the matter could be (beware, it's not a reproach, I'm very happy you help me until now), I will try to reset all the components and do a new try !

This post has been edited by rsseco: Sep 5 2016, 07:56 PM

Hi !

I'm back and happy new year !
So today, I decided to re-assemble my S750 again after a sooo long time !
I soldered back all the diods, PNP, changed the 3x IRF740, and let's go to the testing :

- No heatshrink mounted, powered on with CN4 and CN5 unplugged : OK
- No heatshrink mounted, powered on with CN5 plugged and CN4 unplugged : OK
- Same thing, but I pugged CN4 too (twice are now plugged) : and here something went wrong (heard a "pffff" noise and fuse blown)

So it could be one of the amplifier board which are defective ? I know I didin't take off the glue on these boards, perhaps that could be the wrong thing ?

I take a short look to find what could have blown (the "pfff" sound) but didn't find something yet. Perhaps another capacitor ?!?

Any ideas ?

Hi,

It's good to read you again !
No, I haven't replaced any other capacitors (only the 470uF ones). As wrote before, I wanted to repair the set as costless as possible... I need to know how much it will cost me to replace all of them, but I hope it will really be repaired after that.

Today, I visually check the upper Amp board ; nothing to notice.
But on the power board, I notice that the C70 was a little "bumped" on the top (the same cap which had exploded as the set died) ; I removed the protection, but didn't found any electrolite leak. Maybe the "pfff" sound could came from it even so. On the back of the board, the + pole of C70 is wonky, so I think it cames from here.

I will try to buy genuine Capacitors first, as you found that mines were faked.