Search found 8 matches

by Hextejas
Sun Mar 11, 2018 3:02 pm
Forum: DSO138
Topic: Trying to display a sine wave
Replies: 4
Views: 5862

Re: Trying to display a sine wave

It's working now. I resoldered a few joints and adjusted the sensor so as to handle a smaller voltage.
The sensor was set at 1v whereas the signal was about 1.5mv.
All is well.
by Hextejas
Thu Mar 08, 2018 2:31 pm
Forum: DSO138
Topic: DSO138 troubleshooting - No AV- (no trace)
Replies: 97
Views: 274246

This doesn't make sense.

My readings are: V+ = 8.35 VC2 = 6.22 VB1 = 8,14 And the testing procedures say this: Step 3: Check voltage at Q2 collector (Vc2) and voltage at Q1 base (Vb1). Vc2 should be around 6.4V and Vb1 around 8.3V. My voltages are correct according to the above. 3 ) Vb1 is very close to V+. This case indica...
by Hextejas
Thu Mar 08, 2018 11:59 am
Forum: DSO138
Topic: Trying to display a sine wave
Replies: 4
Views: 5862

Re: Trying to display a sine wave

Have you tried changing the input selectors switches for different sensitivities? Can I assume that you can hear this tone easily on a pair of headphones? If so, have you a good connection from your sound source to the 'scope? Thank you Dave, and yes to all 3 of your points. Have you been successfu...
by Hextejas
Wed Mar 07, 2018 11:56 pm
Forum: DSO138
Topic: Trying to display a sine wave
Replies: 4
Views: 5862

Re: Trying to display a sine wave

I see there have been a few members viewing my thread.
Would you be so kind as to download the 1k Hz tone and see if your DSO 138, scopes it accurately ?

Thanks
by Hextejas
Wed Mar 07, 2018 4:54 pm
Forum: DSO138
Topic: Trying to display a sine wave
Replies: 4
Views: 5862

Trying to display a sine wave

The test square wave works perfectly and I am trying to look at a 1k Hz sine wave from this site. http://www.mediacollege.com/audio/tone/download/ And using this procedure https://www.circuitspecialists.com/blog/how-to-observe-audio-with-an-oscilloscope/ And nothing shows on the screen. But a straig...
by Hextejas
Wed Jan 10, 2018 5:57 pm
Forum: DSO138
Topic: My DSO 138 won't work
Replies: 4
Views: 5775

Re: My DSO 138 won't work

Hooray, it works !

When adjusting, the C6 trimmer, it didn't seem to do anything. Is that normal ?

Thanks
by Hextejas
Wed Jan 10, 2018 4:35 pm
Forum: DSO138
Topic: My DSO 138 won't work
Replies: 4
Views: 5775

Re: My DSO 138 won't work

Have you done Step 2 A? That's the one where you check the 3.3V at TP22 and short JP4 if the voltage is OK. The 3.3V powers the microprocessor which puts pulses into R40 to drive the voltage inverter. Your readings indicate you are missing this signal. Well tp22 is ok but I forgot jp4. Let me do th...
by Hextejas
Tue Jan 09, 2018 2:38 pm
Forum: DSO138
Topic: My DSO 138 won't work
Replies: 4
Views: 5775

My DSO 138 won't work

The screen comes on but it is white.
Some of the readings are
V+ 8.28
V- .218
AV+ 4.9
AV- .793
VB2 base 0
VC2 collector 8.29
VB1 base 8.29
D1+ .213
D1- 0
R40 0

Please tell me what to do.

Regards