Re: Magneto voltage limiter
The challenge with LEDs is that to take advantage of both positive and negative half cycles, a full rectifier is necessary. And a full wave rectifier would create a new ground separated from the chassis leading to cut the regular ground (chassis) connection from the concerned pin of the LED and bringing a new wire from the rectifier's ground.
Why a huge capacitor? Thermal inertia of incandescent lamp should smoothen any low rev flickering.
Agree. Also the reverse voltage between base and emitter...
Pierre95
Senior Member
Last Activity: 03-09-2021, 06:57 AM
Joined: 02-05-2016
Location: Bezons
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Re: Magneto voltage limiter
After a few weeks of involvement on other tasks, I tried designing my own AC limiter.
Top wave form shows an amplitude modulated sine wave which is representative of the variable output AC voltage from the magneto. The signal changes from 0 to almost 50V peak to peak. The output signal (bottom) never goes above ON Zener + ON diode voltage (6,8V+0,7V). The zener and diodes maintain the voltage on the base so that when the voltage on emitter goes above the limit the transistor starts acting as a resistor which forms a voltage divider with...Leave a comment:
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Re: Magneto voltage limiter
Thanks to all of you.
Firstly, there is no battery at all, only the unregulated magneto output. As the stock version is missing indicators, I already designed a regulator circuit driving an astable multivibrator tuned to approximately 1Hz for the blinking to take effect.
Indicator lights are LED, which helps saving power for front/rear lights and the horn.
Each element (Front light, rear light, indicators, horn) takes the power from one wire, the other being moped's frame. This prevents usage of full wave...Leave a comment:
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Re: Magneto voltage limiter
Sorry could a moderator please move the thread to General Electronics Technical Discussion, seems more appropriate.Leave a comment:
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Magneto voltage limiter
Hello,
I recently had some ride on my old moped. After a few miles the front light-bulb burned-out. This is typical issue with those unregulated AC magneto outputs. The bulb is designed for 6V.
Some mopeds are equiped with 2 Zener diodes limiting the output voltage from the magneto.
As both front and rear lights connect directly to the magneto, adding zener diodes would globally limit the AC voltage, which I don't want because the magneto also supplies voltage to indicator lights circuit and horn buzzer and both work better with higher voltages value.... -
Re: Connecting an external display to oceanic le-32z4 mainboard
Thanks for the provided links.
The one from aliexpress may work, HDMI being labelled as output and LVDS as input. Less sure about the other from Amazon as the configuration is more typical of the video coming from the connectors at the bottom, and being output onto LVDS.
Both are quite expensive.
There maybe a way for activating composite video on scart, but as I cannot see what is displayed, I cannot manage to seek the menus.
There are 4 jack connectors,...Leave a comment:
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Connecting an external display to oceanic le-32z4 mainboard
Hello,
This is more a "hack" related question than a troobleshooting thread:
I have a TV with dead display but the mainboard which delivers LVDS signals still functionnal.
I would like to reuse the TV board as digital tuner and output the picture on an external display:
A first approach could be to connect a pannel directly to the LVDS connector but that would require disassembling a computer's display for providing access to the LVDS connector.
A better approach would be to connect the TV board to the display through HDMI,...Last edited by Pierre95; 11-05-2019, 04:01 AM. -
Re: Toshiba 40L3433DG backlight OK but no picture
Resistance between HVIN_12V and VIN_12V is arround 74K in one direction of measurement and 60K in the other direction but the value increases slowly as if some capacitor were involved.Leave a comment:
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Re: Toshiba 40L3433DG backlight OK but no picture
Please find attached the sequence of pictures for the whole TCON....Leave a comment:
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Re: Toshiba 40L3433DG backlight OK but no picture
Thanks for clarification! And I guess VIN_12V gets switched by RT6905 through GD? Is the switching operation initiated through an I2C command sent over the SDA SCL lines or does it start automatically?
I don't see any transistor which may act as Q109 in the proximity of RT6917 on my TCON. Maybe it is actually implemented within RT6917. There is a transistor labelled Q1 but it is located near ICK1 (see attached picture)....Leave a comment:
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Re: Toshiba 40L3433DG backlight OK but no picture
Please find attached connexion routing for HVIN_12V.
As I understand from your schematics, HVIN_12V is issued via pin 46 (LX1) and fed through L104 to generate actual HVIN_12V.
As per my understanding, there is not only a coil between VIN_12V and HVIN_12V as HVIN_12V is generated by RT6905 from VIN_12V.
There may be something that prevents HVIN_12V from being activated.
Or is LX1 an input? Not easy to understand how it works without 6905 or 6917 datasheet....Leave a comment:
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Re: Toshiba 40L3433DG backlight OK but no picture
You may have posted #24 while I was editing post #25. I will have detailed reading of the attached documents you provide, and recheck VIN_12V's fuse and see how it connects to HVIN_12V.Leave a comment:
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Re: Toshiba 40L3433DG backlight OK but no picture
That could be caused by the caps themselves or internal RT6917GQW failure.Leave a comment:
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Re: Toshiba 40L3433DG backlight OK but no picture
There are 4 caps between AVDD and GND. Is that one or several caps are partial shorts creating the 74 ohms resistance or is this value typically of the AVDD output?
Interesting reading...Leave a comment:
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Re: Toshiba 40L3433DG backlight OK but no picture
I don't have VDD, VGH, VGL or maybe they use different naming. What do VDD, VGH, VGL stand for? Maybe I can find some equivalency with different naming.
I have VON, L_L, L_H but they are close to the LCD bias IC so most likely not involved with RT6917GQW.
I read 74 Ohms between GND and AVDD (independently of multimeter's connection direction) and 11,24 KOhms between GND and HVIN_12V for one direction and 14 KOhms for the other direction.Leave a comment:
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Re: Toshiba 40L3433DG backlight OK but no picture
As you suggested budm, I took several measurements on the TCON when TV is ON. I read:
HVIN_12V: 0,17V
AVDD: 0V
VCC_1.8V=0V
VCC_1.15V=0V
VCC_3.3V=0V
Only VIN_12V (provided from the mainboard) is correct. The IC located between the coils labelled 220 is RT6917GQW from Richtek but I cannot find any spec sheet for it. Even Richtek website doesn't provide any reference to it. I only managed to find RT6908 datasheet.
If those voltages according to the labels near...Leave a comment:
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Re: Toshiba 40L3433DG backlight OK but no picture
Yes backlight is ON and yes I've got to the T-CON board which has an unusually wide shape (see picture)....Leave a comment:
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Re: Toshiba 40L3433DG backlight OK but no picture
I took measurements directly on the TCON and for each pair, signals are as shown on the attached pictures which are for the TX_1_0_N/TX_1_0_P pair but other pairs show similar signals, except for the 2 clock pairs which are with no intervals (see 2 other pictures).
And as you suggested R_J, when I depress a menu button I see changes in the displayed signals which most likely means changes in the displayed picture.
The clock signals are lower in amplitude as compared to the data signals.
...Leave a comment:
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Re: Toshiba 40L3433DG backlight OK but no picture
Here are the measurements of voltages on the 2*6pins PSU connector:
TV in standby mode (red LED):
12,11V- -12,11V
5,42V- -12,11V
0V - -GND
0V- -GND
2,24V- -GND
0,22V- -GND
TV ON (green LED):
12,11V- -12,11V
5,38V- -12,11V
0,28V- -GND
3,30V- -GND
0V- -GND
23,4V- -GND
White fuse on the TCON is OK (12V on both sides)
I also took measurement for several mainboard voltages...Leave a comment:
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Re: Toshiba 40L3433DG backlight OK but no picture
I also noted there is no change in picture apparence when the main PCB is disconnected from the TCON which most likely means the mainboard doesn't produce any video signal at all.Leave a comment:
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