Amplituner Daewoo DV-115 - nie włącza się

Witajcie.

Dostałem amplituner Daewoo DV-115 z wciśniętym do wewnątrz gniazdem słuchawkowym. Urządzenie włączało się a czy było sprawne? Tego nie wiem.
Otwarłem je, zamontowałem gniazdo na miejscu (nic nie było złamane, tylko wyszło spod śruby). Nie wiem co mogło się stać, wszystko jest podłączone tak jak było ale amplituner teraz nie włącza się. Kompletnie nic, jakby nie dostawał zasilania.
Może ktoś pomoże sprawdzić co może być nie tak, a co za tym idzie co mogło się stać?

R706 = 1,5V
C705 = 0V
D727 cathode to GND = 0V

I noticed that the input of IC702 is 13V and the output is 0V. It's some kind of fuse. Can I short it for further trials?

matic написав:Before connecting power supply to the machine measure the resistances to ground on both pins of diode D727.

anode=3,3k
kathode=no reading, as if a circuit break (i have front panel disconected)

After connecting the front panel on the D727 I got:
- anode: 3.3k
- cathode: 165k

I am waiting for the fuses to reach me to replace the IC702.

I don't understand one thing. The MUTE_B + signal from the motherboard comes out via the D727 diode. When I set the multimeter to the continuity mode, I have a direct connection between the D727 cathode and the MUTE+B pin in the CP711 connector (or at least where it should be). As my DV-115 is a version without a mic board, I don't have a CP711 connector, but a CP712. D727 has no connection to any pin in CP712. So where does the resistance on the D727 cathode come from when connecting the front panel? I am browsing and looking at the service manual and schematics and can't figure it out.

matic написав:I don't understand what is strange here. The diode D727 and connector CP711 are on the same board, so there should be connection between them according to the schematic.

I understand that. I mean the next part.

matic написав:Signal "MUTE_B+" is also connected to the DSP board with a wire from connector CP503 to CN503.

Okay. When I measured the resistance on the D727, I had the front panel connected (CP903->CP903, CN901->PN902, CN904->CP712), but not the DSP board. So where do these 130k on the D727 cathode come from?

CP712 have only +5.6V, D-G and VFD signals.

-=edit=-

matic написав:IC702 is damaged and needs to be replaced.

matic написав:Replace the chip IC702 with a 630mA fast acting fuse (F 0.63A).

So I did. I decided to run the motherboard itself without any additional circuits or the front panel. I measured 5.6V signal on the CP712 connector and it turned out that only 4.92V is there. I thought that, propably, it is not the front panel shorting but something else.

I looked closely and it turned out that I have not disconnected one PCB yet -
PCB REGULATOR.



After disconnecting it, the voltage jumped to its 5.6V. Interestingly, after reconnecting it is still 5.6V. There is also 5.6V on the anode of D905, and 4.8V on the cathode.

We are looking far while there is no voltage on the CP703. So if I am not mistaken the main transformer power supply. In fact, I have already checked the R707, Q702, D707 and the RY701 relay, but maybe it should go back to the beginning and go through it again? Maybe you will mark me or describe what voltages (more or less) I can expect on these elements? My measurements are as follows:

Here are the voltages I measured:



Those on the R703 are measured with the ST / BY button pressed and not pressed.

In both cases, this voltage is 0V.

matic написав:Measure the resistances to ground on pins 29, 30, 31 of IC904.

29 - 17kΩ
30 - 17,2kΩ
31 - 17kΩ

matic написав:Measure the voltages to ground on both pins of diodes D904, D905 (both are located on the front panel board).

D904 - anode = 5,57V, kathode = 4,86V
D905 - anode = 5,57V, kathode = 4,79V

matic написав:Do you have an oscilloscope?

Unfortunately not

matic написав:Measure the voltages to ground on pins 29, 30, 31 of IC904.

All three = about 0,1V (considering my multimeter it could be 0V)