Luxman L3 problem

[Amapola]

Hi there,

Suddenly on a L3 220v version (with p-2251 power transformer) i had a blown fuse (f001) 1a.

I just changed this fuse 1 time ; and the same...

I checked on the power board ; all transistors are ok expect q407a and q470b. All diodes and bridge are ok.

I decided to put out the q407a and q408a ; and same for "b".

I placed a new fuse of 1a ...and for now no sign of life...

Anyway , after putting light in my brain... if this fuse has blown, the problem comes from before the fuse...so the power transformer

In fact, i've on primary 11ohm

secondary : 1.2 ohm for red wires which supply the rectifier bridge
2.5 ohm for blue wires

Anybody can confirm whom power transformer is out ?

Thanks in advance for light

[sam_sam_sam]

Re: Luxman L3 problem

Here is something you can try unhook the secondary side of the transformer and see if it still blowing the fuse if it does then you have some type of short problem with the transformer

[Amapola]

Re: Luxman L3 problem

Hi,

I desoldered the secondary from the power board ; but for now no sign of life with this power transformer ! When i push "on" , nothing...

In normal work, a power transformer make always a little noise (about 50hz) ; and there 's nothing.

I've also measured the resistance of the primary through the mains plug with switch off "nothing" (there it's normal) and on; I have 11.3 ohm.
But if 11.3 ohms are found in the "on" position, the on switch is ok; true?
So the mistake dont come from the on/off switch...

What do you think about ?

[CapLeaker]

Re: Luxman L3 problem

Only because the fuse blows, doesn’t mean automatically that the problem is before the fuse. That is a wrong assumption.

[Amapola]

Re: Luxman L3 problem

In all case, for now the transformer dont show sign of life ... I mean just the on/off switch with this transformer...

[Amapola]

Re: Luxman L3 problem

In all case, for now the transformer dont show sign of life ... I mean just the on/off switch with this transformer...

I checked the voltage on the secondary , on the blue i have 40v70 and for the 2 red 31v70... I wanted to be sure, in fact the transformer is not dead at least.

But i saw something strange , on the connection face of one of the 2 big caps 6800uf , i saw white marks, as if there had been a start of burnout...( see pics)

On the other cap, there's no white marks ...

[budm]

Re: Luxman L3 problem

So the main AC fuse F001 is no longer blown after you disconnected the secondary windings form the board?
Did you check rectifiers D403 ~ 406 for sure that they are good?
Did you check the output transistors for sure that they are good?
Is the fuse really 1A rating? According to the chart it is supposed to be 3A/1.5A for 'E', I do not quite understand why it shows TWO RATINGS 3A/1.5A

[jons]

Re: Luxman L3 problem

Most likely 3A for 110/120V voltage and 1.5 for 220 as it have switchable mains transformer.

[Amapola]

Re: Luxman L3 problem

Yes the fuse f001 dont blown for now.

But i've the p2251 version of transformer so it's the "s" version (for north european country) am in france ; not the "e" p2250. The "e" is multi voltage selector version.
...and according do the schematics it's really 1A T . Furthermore on the case there's a sticker with mentionned "1A T 250V".

I checked again rectifier diode , all have around 0.480v, and off course all in the same way...and nothing in reverse way. So these rectifiers diodes are ok.

For transistors, like i mentioned in the 1st post, all are ok expect q407a and q408a ( i just saw i made 1 error i wrote q470b instead of q408a ; because q470 dont exist).


In fact, before the 1st time fuse f001 blown, i would check the values of voltages ...So i started with q405a (2sc2235 ebc),for the e leg it was ok but when i would mesure b leg , even if i used clamp test probe with "grip jaws" there was a wrong contact between the base and emitter of the q405a...there was a little spark.
So i turned off the amp, it checked the q405a and it was still good... It was when i turned "on" the amp , this is was the 1st time whom the fuse f001 blown !
For now, if q407a and q407b blown too i dont know why f001 fuse blown and not f002a ( L channel) ; because the f002 was still always ok. For info , f001 was glass fuse (little fuse but glass), the f002 fuses are ceramic fuses (little fuse) and the f401 fuse is in ceramic too (little fuse).
And what happened for the the q407a and q470b ? Maybe there were too weak to support the wrong contact between base and emitter of q405a ?

So for now, i have to wait the calm of covid19 to reach new transistors and maybe news 6800uf capacitors...

On the back on the sticker with serial i saw approx 220v , so in france we have closed to 240v instead of 230v. Can this difference cause the damage ? (maybe) . What do you think about ?

Thanks

[Amapola]

Re: Luxman L3 problem

Most likely 3A for 110/120V voltage and 1.5 for 220 as it have switchable mains transformer.

But for mine i dont have switchable mains transformer... The switchable version is the "e" version p2250 ; mine is "s" p2251 (north europe version)

Furthermore on the case there's a sticker with mentionned "1A T 250V".