DP/ XR71 not working

[Tahabns1]

Hello everyone
i need some help. I already finished MY xr71 since 7 months ago.
after i connect the coil still give me sounds and the RED LED turn on (12V 1.25A lithium).
I have coils 470uh to 1mh and 2,9R to 3,5R
I'm using IRF840 dumping R=680R 1W
AND THE IRF840 GETTING TOO HOT WHEN I TOUCHE IT, THE SOUND LAGS.
Any solutions for me

[kt315]

good topic with yet one problem. check diodes in power line VD8 VD9. DO NOT DESOLDER THEM.
check in board. if they burned mosfet will be too hot.

[Tahabns1]

Thank you Kt315 to be here for us.
cheking the VD8 VD9 (1N414
i have reading 7.0V in between them so i think they are O.K

[kt315]

7.0V in between them

[Tahabns1]

Thank you Kt315 to be here for us.
cheking the VD8 VD9 (1N414
i have reading 7.0V in between them so i think they are O.K

It was a mistake. I SWITCH ON the dp (irf is surely burned since yesteday ) i found 0.7V between VD8 and VD9 (1N4149) so they are OK i think so

[kt315]

without MOS-FET, set o-scope probe in GATE point. you must see a signal TX PULSE, width must being changing in range 120-500 usec by pot PULSE WIDTH.
frequency 100 Hz.

[Tahabns1]

Can i use another way i don't have o-scope?

[Carl-NC]

You really need an oscope to troubleshoot circuits. My suggestion:

1. Measure power supply voltages without the coil connected, make sure they are correct.

2. Measure power supply voltages with the coil connected, make sure they are correct. I suspect you will see something wrong here.

3. Without the coil connected, look at the TX timing pulse on the gate of the FET switch. For this, you need an oscope.

4. Alternative: cut the trace from the transmitter to the preamp, see if the transmitter will run all by itself without getting too hot.

[pito]

Can i use another way i don't have o-scope?

https://www.sillanumsoft.org

[ivconic]

Why oh why people try to protect PDF documents??
KM1667?? WTF!
Protection removed, translated to English!
Just for fun: https://drive.google.com/file/d/1g2Z...ew?usp=sharing

[Tahabns1]

Thanks every one to be here, thank you M.KT, thank you M.Carl, thank you M.PiTO and thank you M. IVCONIC.
first of all ..
i have disoldred the FET
- checked on all POT, R And C and IC
*found that Problem in Ic555 (changed it)
* R18 12K (REPLACED 120K)
AND Resistor between the + and LF357 is 120k (REplaced 12k)
the FET still good i checked it with RLC meter.
for further work i will change dumping R by 2.2K instead of 680ohm then add the VD "STT" that have been recommended by KT to DRAIN and add direct wire between the SOURCE and the - off power supply.

[kt315]

thank you Ivconic. did you installed the soft on your PC? is working?

[ivconic]

Yes. I downloaded executable one, not installation.

https://www.sillanumsoft.org/Download/VASilviaBETA.zip

[ivconic]

Without dedicated hardware; the software uses audio card In/Out on your computer.

[daluka]

KM1667??

KM1667 che contiene il convertitore PCM 2902 e che viene da noi fornito già montato in SMD
KM1667 which contains the converter PCM 2902 and which is supplied by us already assembled in the SMD