troubleshoot A15 mk2

Arjo

Hi you all,

I'm busy with my A15 but at the bridge rectifier I measure 522V instead of 298V, I can not find a bad link before this accept that at pin 13/14 I measure 258V instead of 230V.
Could this be a fault in br1 or c32 or tr1 or did I f*ck up somewhere? :-\

Thanx
Arjo

Arjo

Nobody?!

I redid the solderings today until br1, now I meassure 233 at pin 6/2 (wrote the wrong pins in the post before) so that's good.
But now the most wierd thing, at the BR1 I now meassure 796V !!!!!!!!!

Any sugestions of what it can be? all is welcome

Arjo

Arjo

O damn I'm such a beginner, had the multimeter wrong

Now I meassure 246V instead of 298V, sounds a bit better but is still wrong.

Arjo

eBernd

Hi,

did you measure the mains voltage (AC!)? Is it 230 V AC?

If it is obviously lower, then you can't get the right voltage behind the rectifier.

Bernd

Arjo

Hi Bernd,

I did measure that and it is 230V (and checked again), so it should be good.

Thanx
Arjo

Arjo

I'm at a loss now.

Voltage are still to low and I can't find the problem.

I turned the amp on and DAMN!!! the thing is LOUD, I can only open the volume a verry little bit (I have the amp connected to the speaker of my 100w H&K attax 100).

Channel 1 is bad, when I play it buzzez like the bass is to loud, channel 2 is better, sounds great but too loud.

I have got no clue what to do?

Arjo

Arjo

No one who can help ?

Arjo

Finally back online!!!

I just moved into my new house, so now I finally have time again to play!!!!!!!!!!

Today I took my A15MK2 out of the box again to try it. When I play on it I can't open the amp too much because it begins too make a cracking noise on both channels.

Annyone tips where I should look.

I haven't found my multimeter yet so I haven't checkt everything yet.

Arjo

eBernd

Hi,

when you find your multimeter - and the schematic with the voltage values - measure all the voltages including the mains voltage at that time and post them...

... and then we'll see...

veel geluk!

Bernd

Arjo

I've measured some things tonight and most things are about 20% less then they should be.
And some things are more
At tr1 @ pin 6/2 is 242v instead of 230V and
V5 @ R51 I measure 100mv instead of 35mv or less ???

At BR1 its 250v instead of 298v
R59 its 228v instead of 290v
C26 its 206v instead of 262v
C33 its 40v instead of 53V

And I've measured some more but all is less, I will go on another night because I'm getting a bit confused and that's no good.

perhaps someone already has an idea?

Arjo

MAD

Hi Arjo,
most important is the wrong voltage at R51. If your measured voltage is right, the cathode current would be 100mA, this would harm your tube pretty soon! So please check, if the voltage is measured correctly and R51 has the right value! If this is the case, change V5 and V6 with each other and check, if the wrong voltage is still there.
Regards,
Martin

eBernd

Hi,

it looks as if you don't know what you're doing...:)

Zitat

R59 its 228v instead of 290v

At which side of R59 (C28 or C29)?

Zitat

V5 @ R51 I measure 100mv instead of 35mv or less

That's a worse thing, it means that you run the power tube with 3x of the recommended current - they won't do that long without damage.:o
Is the plate already glowing red inside?

BTW: you have also to measure the voltage across R52 that equals the current through V6.

But first: Check - without inserting V5 and V6! - the voltage range of the bias voltage at connection R45-R46. Is it in the range of -19 to -24 V ?

You should also use another DVM and compare the measured values with the values from your own DVM.

And once again: Voltage values without mentioning the actual mains voltage doesn't make much sense.

Bernd

Edit: Oh, Martin was faster! But at least our opinions seem to be the same.:)

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