Help troubleshooting inverter circuit

Thread Starter

ranks33

Joined May 9, 2011
22
Hi All
I Am working on this power supply with an inverter circuit. 5v to -+15v
On Q3 and Q5 gates and source i get the 15v there but nothing on the drains.So that
leave the rest of the circuit with out the 15v.
Any idea what to check?

http://rohmfs.rohm.com/en/products/databook/datasheet/discrete/transistor/mosfet/rtr030n05.pdf
http://rohmfs.rohm.com/en/products/databook/datasheet/discrete/transistor/mosfet/rtr030p02.pdf

http://elektrotanya.com/pioneer_ddj-sx_rrv4382_dj_controller.pdf/download.html

Mod edit: reduced image size.
 

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N11778

Joined Dec 4, 2015
174
Keep in mind I have never trouble shot a P channel MosFet CKT. first one I have seen.

Q3 is a P Chanel MosFet So you need a negative voltage on the gate to turn it on.
Q4 is NOT conducting so the collector is 15v, that is keeping Q3 turned off.
Check for a voltage coming in on the Base of Q4 to turn Q4 on, connecting the collector to ground.
This will turn on Q3 by making the gate negative compared to the source which is +15v.

I think the trouble mite be someplace up stream in the PW-ON Input to the Power Supply.
 

Thread Starter

ranks33

Joined May 9, 2011
22
N11778 you right problem is in turn on circuit.


Roadoggydave

Q4 http://pdf1.alldatasheet.com/datasheet-pdf/view/71118/LRC/DTC124EKA.html

Q8 http://pdf1.alldatasheet.com/datasheet-pdf/view/58996/DIODES/DDTA124TKA.html

The voltage on Q4 base/in is 0.531
It look like 3.3v is the turn on voltage.
If i connect a 10k resistor on the in/base of Q4 to the collector of Q8 the power supply
starts to provide the 15v to the rest of the circuit.

On the collector of Q8 is 4.44v.When i connect the resistor across the two point i get 1.2v on the in/base of Q4
which i guess turns it on? I trace the circuit but was unable to find where the turn on voltage is getting lost.
 

N11778

Joined Dec 4, 2015
174
Your going to have to find where the turn on voltage is getting lost.
Do you have the rest of the schematic?
What is this thing part of the,,,,,, Space Shuttle ???.
 

N11778

Joined Dec 4, 2015
174
WOW I'm dizzy chasing around the print.
FYI you can find stuff in the diagram by searching for it in the pdf viewer of your print.
It Makes it easier to find stuff your looking for.
check the attached print below for some hints.
The SDV signal comes from DA5V at IC36 thru a diode
DA5V originates in the power supply just up and to the left of Q4
Good luck
 

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Thread Starter

ranks33

Joined May 9, 2011
22
Went at it again today.
I see 5v on pin5 of IC 19 and 4.35v on pin4.
The 4.35 volts is on both side of the diode D6 but not on the input of Q7 and Q4.
Do you think i have an open trace or the mute circuit might be my prob?
 

N11778

Joined Dec 4, 2015
174
I searched and looked for PW_ON other places and cant find it anywhere else.
check the continuity between base of Q4 and Q7 should be zero or close to zero.
then check from Q4 and Q7 base to D6 Anode (C38 end) should be zero also.
If its not zero either the drawing is wrong (I suspect not) or we are seeing it wrong or the trace is open.
could also be a bad solder connection around C38 , R24 and D6.
Try putting the 10k resistor from the base of Q4 or Q7 to the Anode of D6 the C38 end,
if 10k is a low enough resistance it should start working.
Again good luck
 
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