JYE Tech Forum

Hi
I have AV- is around zero
I measured the voltages for Q1 & Q2 terminals and found ok except the positive terminal of D1
D1 isolated and tested outside and found OK
Can anyone provide us with a waveform signal in the AV- circuit ?
I have another oscilloscope , found the i have around 17 kHz signals
Waiting support
Thanks

Could I ask for help getting my scope to work? The digital side of things is okay; the MCU boots up, the buttons work, the display draws the picture just as it should, and I updated the firmware via ST-Link to the latest version without an issue, but the analog side isn't working. I already tried even replacing Q2, but that didn't have any effect whatsoever.

The board is powered from a 9V battery (actual voltage of the battery is at 8.1V atm)
Here are the most important values I am getting via multimeter:
AV-: 0.662V
AV+: 4.95V
V+ : 7V

Step 1: 0.826V
Step 2: -1.445V
Step 3:
Q2 collector: 5.39V
Q1 base: 6.98V
Step 4: -- this is where things seem to go wrong
D1+: 0.598V
D1-: 1.277V (and rising slowly?!)
Step 5: 0.598V

There are DSO138 and ST-LINK v2. I want to upgrade the firmware using STM32 ST-LINK Utility v4. Error.

HI

I am having trouble as well with the trace on my DSO138.
The trace looks like it has flat lined at the top of the screen.
I am getting 2.88v at v1, 3.38v at v2, .78 at v3 and 1.56 at tlvl.
0.66v at av-, 4.96v at av+, 3.23v at +3.3v and 5.00v at +5v, v+ is 8.54.
TP22 is 3.24v, TP25 is 0.58v.
Any help would be most welcome.

Hi do you sell spare parts as I think my L2 power inductor is suspect?
If not where can I source one?
Cheers

Spare parts are available. Please contact JYE Tech at jyetech@163.com.

I also am having trouble whith my DSO138. Pretty much any signal gives a full spiking read. no matter the settings. if i read the 1khz 3.3v test signal at 1x 1v ac or dc i get a full top to bottom of the screen signal and my AV- is 0.75+ Volts.
I tried to fix it myself but my electronics skills come up a little short.
I followed all the steps up to 4. This is where i got some weird readings.
the Positive side of D1 was -45 Volts. I am not sure whats wrong or where it is. but -45 seems extreme to me.
I hope anyone of you can give me some insight to what part is broken or where a short could be.

Another "troubleshooting" problem:
System works every time when powered from the 9V battery, but it doesn't boot when powered from the 9V from DC-DC converter or from 12V from regular switching DC wall adapter. Amperage is not a problem, I tried even some PC switching PSU which gives quite a lot of power. Voltage is stable at 9V.
Symptoms: white screen, voltage at test points is wrong.
I repeat: everything works from the 9V battery.
I tried putting capacitator between the pins to reduce noise in the DC, but it didn't help.

What can be done? I can't use 9V battery forever.

im having a trouble with my dso 138
it shows trace but cannot see the inbuilt test signal the 1khz and 3.3v
it cannot also read other signals,

lately i see it reads signals below 10mv in AC cpl, but it does not show any voltage at
the upper top right corner?

can you help me with this?
please email me if you have an idea to help me thankyouuu!

Hello! I have the "no trace" problem with my DSO138.
Unfortunately the other trobleshooting-steps did not solve my problem.
I checked all soldering points many times & resoldered some of the components (& changed Q1).

My input voltage is 9,4V (as voltage reference in manual)
I get the following differing voltages:

AV- = -4,2V (instead 5V)
L1 = -5V (instead -8,11V)
V- (TP25) = -5V (instead -8,08V)
V2 = -2,2V (instead 1,66V)

Does somebody have an idea, where the problem could lie?
Thank you for your help!