Search found 78 matches

by davef
Wed Aug 19, 2015 8:37 am
Forum: DSO138
Topic: Sellers reported selling FAKE DSO138 kits
Replies: 70
Views: 275460

Re: Sellers reported selling FAKE DSO138 kits

Have you read through Banggood's forum posting?
http://forum.banggood.com/forum-topic-61279.html?page=4
by davef
Wed Aug 19, 2015 8:35 am
Forum: DSO138
Topic: Sellers reported selling FAKE DSO138 kits
Replies: 70
Views: 275460

Re: Sellers reported selling FAKE DSO138 kits

Now that is interesting. I believe that the voltage at TP25 and at L1 vary depending on the actual value of L1. If you put your finger on the probe can you pick up AC hum floating around your workbench?

Did you contact Banggood about the fake board?
by davef
Mon Aug 10, 2015 7:56 pm
Forum: DSO138
Topic: Q1 Exploded
Replies: 5
Views: 7470

Re: Q1 Exploded

Check your board first http://www.jyetech.com/forum/viewtopic.php?f=18&t=511 . Seems that wrong value inductors are either common or a fact of life on the counterfeit boards. You would need an inductance meter. If you do have a counterfeit board perhaps the easiest option is to buy the correct v...
by davef
Mon Aug 10, 2015 11:11 am
Forum: DSO138
Topic: Q1 Exploded
Replies: 5
Views: 7470

Re: Q1 Exploded

Are you sure you have a "real" DSO138? Check the value of L2.
by davef
Wed Jul 29, 2015 7:28 am
Forum: DSO138
Topic: Test is not square
Replies: 13
Views: 16880

Re: Test is not square

Glad you are making progress. The test signal should be OK in AC or DC, but you have to be able to adjust the vertical position and to be able to reduce the sensitivity enough to get the whole waveform on the screen. A good "shotgun" technique is to re-solder ... in your case the input/ana...
by davef
Tue Jul 28, 2015 7:12 pm
Forum: DSO138
Topic: Test is not square
Replies: 13
Views: 16880

Re: Test is not square

3mA? Is that the current drawn by the DSO138. It should be around 130mA. I'd suggest, seeing as we can't determine that the test signal point is working going back to the 10VAC source from your transformer and working with that as a test signal. Are you able to the Vpos alignment with no input signal?
by davef
Tue Jul 28, 2015 10:30 am
Forum: DSO138
Topic: Test is not square
Replies: 13
Views: 16880

Re: Test is not square

:? :roll: :cry: Well, there can only be an open track from pin 17 (TESTSIG) on the uP to the end of R26 or a short on this track. Do a close visual inspection to confirm pin 17 is soldered to the PCB track and that there are no shorts on the track to R26. R26 could be open and/or you have shorted pi...
by davef
Tue Jul 28, 2015 8:55 am
Forum: DSO138
Topic: Test is not square
Replies: 13
Views: 16880

Re: Test is not square

Test signal ... if it is not on TESTSIG end of R26 you have microprocessor problems. You will need another oscilloscope to look for it. How about measuring all the other voltages around the board. When you had the 10VAC source on it what amplitude do you read on the screen, even though you can't see...
by davef
Mon Jul 27, 2015 10:34 pm
Forum: DSO138
Topic: Test is not square
Replies: 13
Views: 16880

Re: Test is not square

Sorry, I didn't realise that you were trying to look at the built-in test signal! Well, either the test signal is not on the test output or you have some issues in your input circuit. I was also confused by the top waveform. If you expecting 50Hz and getting that waveform what timebase setting are y...
by davef
Mon Jul 27, 2015 7:29 pm
Forum: DSO138
Topic: Test is not square
Replies: 13
Views: 16880

Re: Test is not square

Can you display the built-in test signal?