Issue with scheme Line Voltage Inducer in Adapter

[MOLOKO]

Hi everyone!

I want go to online, but it's imposible at this moment to buy allready ready "Dreamcast Live USB Modem", becouse I'am live in country in which there is no delivery. (Even if they were available for sale)

So I'am making my own USB Modem with Line Voltage Inducer in it.
I'am using this scheme:

I'am using Original DELL RD02-D400 with MT3608.
Capacitor- 1uF-50V
Resistor - Resistor 390 ohm
In general, I assembled everything according to the diagram above.

But, I when I try and dial a connection on my Dreamcast, it says “No dial tone” or “No answer”.
I tried use Pi4 and VirtualBox on my PC - same issue, adapter showing two green lights, but dosn't work.
Also I tried swaping Modem in Dreamcast (I have two of them)

I measured it with a multimeter voltage on the wire, and it really does convey ~18 V (18,20-18,35)

I have no ideas right now, maybe someone could suggest what else I can try?
I tried to look at the logs in Pi4, but there is practically nothing there.

UPD: - I am attaching a photo of the assembled adapter.



The adapter itself - is working because it always shows up as a modem when connected to a PC or VirtualBox

[megavolt85]

I'am using this scheme:

Erase it from your computer and never use it, all that can be done with this scheme is to burn the modem

[MOLOKO]

T

I'am using this scheme:

Erase it from your computer and never use it, all that can be done with this scheme is to burn the modem

xQPEc5K_RAg.jpg

Thanks for anwering! I changed scheme, like on your screenshot.
It's a still same problem. Two green lights, and no answering.





What I can do next?

[megavolt85]

Unfortunately, after the incorrect connection, it is now difficult to say what went wrong.

[MOLOKO]

Unfortunately, after the incorrect connection, it is now difficult to say what went wrong.

This schematic has already been used to create modems.
I know like a two real people, ho made it like this and it's working.

For proof, Here are their photos


I can assume that the board just gets very hot with this connection, but it's working.

What voltage should be from the output of the converter? 18-19 V?
And what is the voltage on the wire RJ-11 itself?
How to get full logs and status of what is doing DreamPI?
Do you have the correct assembly diagram?

[megavolt85]

This schematic has already been used to create modems.
I know like a two real people, ho made it like this and it's working.

If I were you, I wouldn't listen to the nonsense of that idiot DreamcastFANPro, this scheme can't work, the last person who assembled it according to this scheme contacted me with the same problem as you, but he was luckier than you and his modem survived.

[MOLOKO]

This schematic has already been used to create modems.
I know like a two real people, ho made it like this and it's working.

If I were you, I wouldn't listen to the nonsense of that idiot DreamcastFANPro, this scheme can't work, the last person who assembled it according to this scheme contacted me with the same problem as you, but he was luckier than you and his modem survived.

At this point, I don't agree with the fact that the modem burned out.
First - the adapter responds completely adequately at Win/Lin
Second - the contacts were shorted on one track! They couldn't "short" the whole board itself. They were definitely on the same track. It was like something short circuit, but the path is intact, there are no other components on it. There is nothing to burn even in the event of a short circuit, except the track - and it is intact.



But I already agree 99% that the scheme is wrong.
I don't know how it works for my "comrades".

I discussed the issue with colleagues at work who were involved in telephony back in the 90-20s years.
At this moment, my theory - that the path (Leg) to RJ11 - is not cut completely. I need to cut it more deeply.

Or I need to connect "minus" from DC-DC board to "plus" wire going to Leg RJ11.

Beouse of that, It supplies voltage on cable with RJ11 - but does not change it when the line is addressed.

I used this scheme becouse - it's like the only thing that exists in whole internet. You don't have any different resources. I can rephrase this - I used this scheme not because life was good
And in general, it is possible to order a new modem. But is there a normal scheme then?
The person you helped earlier - he simply moved the wire from the positive to the connection between the capacitor and the resistor (like me)? and did it all work for him?

[megavolt85]

[MOLOKO]

Снимок экрана от 2025-03-17 13-08-55.png

Слушай, забавно получилось, только сейчас понял, что ты на русском тоже общаешься.

В общем, по твоей схеме, собрали на макетке данную врезку в кабель - и всё заработало!)
Причем достаточно долго гоняли, проверяли, раз 10 ребутали - всё без единого лага.







Стали реализовывать данную схему через сам модем - не работает.
В чём причина, и куда понять, не понятно. По разному пробовали, даже просто собирали эту же схему без макетки, паяли от +/- врезку в кабель напрямую - тоже не работает...

Сейчас решил собрать через макету как и было до этого - опять не работает. Но не похоже, что плату добил, ибо симптомы 1 в 1. Чувствую что в какой-то глупой мелочи причина..
Новый модем, на всякий случай, закажу пока есть возможность.

Может быть у тебя будут идеи ещё какие-то?
Я пока попробую поменять модуль MT, и саму банку с резистором.

[megavolt85]

попробуй поднять напряжение до 20 вольт