Trust GXT-38 Niestabilne zasilanie

Witam,
Zabrałem się za naprawę swoich głośników
GXT-38. Głośnik basowy (w którym mieści się cała elektronika) stracił ciągłość zasilania. Po podłączeniu pali się czerwony przełącznik, natomiast zielona dioda pulsuje.
Po rozebraniu i sprawdzeniu zasilania otrzymałem dziwne wyniki. Zamieszczone na zdjęciu.

Na pierwszej cewce miałem stabilne 310v.



Jak się domyślam to nie problem samego transformatora impulsowego, ale czegoś w układzie co powoduje zwarcie prawda?? Tylko nie mam pojęcia jak sprawdzić ten transformator.

Arni wrote:Na pierwszej cewce miałem stabilne 310v.

Hello!
Is there a stable 310V on this big 400V capacitor when the transformer is soldered to the board?

Arni wrote:Jak się domyślam to nie problem samego transformatora impulsowego, ale czegoś w układzie co powoduje zwarcie prawda??

Yes, this issue is probably not related to the switching transformer.

Arni wrote:Tylko nie mam pojęcia jak sprawdzić ten transformator.

Impossible, you can only check with an ohm meter if the windings are not in open circuit, but this transformer is not damaged almost for sure.

Don't forget to discharge this 400V capacitor before touching the primary circuit.


Measure the resistance to ground on two highlighted points.

matic wrote:Hello!
Is there a stable 310V on this big 400V capacitor when the transformer is soldered to the board?

Tak ma stabilne 310V, gdy jest wlutowany w płytę.

matic wrote:Impossible, you can only check with an ohm meter if the windings are not in open circuit, but this transformer is not damaged almost for sure.

Don't forget to discharge this 400V capacitor before touching the primary circuit.

W takim razie co powinno być kolejnym krokiem??

Pomiędzy punktem oznaczonym "GROUND" do masy 0ohm
Pomiędzy punktem "2" do masy >20k

Arni wrote:Between point marked "GROUND" to mass 0ohm.
Between point "2" to mass> 20k

Check the picture again - two points are indicated by arrows. If the resistances on both points are high (in kΩ range), post a clear pictures of whole board from both sides.

Also measure the voltage to ground on both points indicated in post #2, when the speakers are turned on. Check, if both voltages are stable.

when power is UP
whats more...

I requested two measurements.
What do you mean with "poza skala"? Is it 0V, or do you get "OL" or "1 ." on the meter display?

Mean between this two point is is displayed "1" when I try to get Ω.
There is from 0v to 13v betweend this two points (not stabile at all)

Arni wrote:natomiast zielona dioda pulsuje

How fast does the LED flashes? About one flash per second, or faster?

matic wrote:How fast does the LED flashes? About one flash per second, or faster?

somthing about 2-3time per sec

Replace the highlighted three electrolytic capacitors (don't measure them, just replace):

matic wrote:Wymień wyróżnione trzy kondensatory elektrolityczne (nie mierz ich, po prostu wymień):

done, but :
at first green diode dosent start at all
after 2-3 times green diode started but now IT is about 5-10times pre sec

whats more, when the diode not started there were 320v on both points that I show
ON BOTH NOW WAS 320v

(It could be my fault because I used not new elements but from OLD PC)

Ok i make mistake, everwhere I put 1µF, now I changed it for right. This mean 1x1µF 1x4.7µF 1x22µF, and now it is this same like before

Measure the resistance to ground on point "A".
Measure the voltage to ground on point B. Check, if the voltages is stable.

A-->GROUND 30 Ohm
B-->GROUND 14V-15V I is stabile but somthimes it is 14v somthimes 15v

Remove the coils L43 and L44 from the board and remeasure the voltages to ground on the picture from post #2.

A----->GROUND 30 Ohm
B----->GROUND 1V I is stabile
Greend diode is not working

Arni wrote:A----->GROUND 30 Ohm
B----->GROUND 1V I is stabile
Greend diode is not working

I requested the voltage measurements on two points from the picture in post #2.

0.02v
edit:
not exacly it is started from 29V and goind down until this dont reach 0.02v

with coils but after changing capacitors there was 1v-2v

Measure the voltage between pins 1, 2 of optocoupler IC6.
Measure the voltage between pins 3, 4 of optocoupler IC6.