Digitech Oscilloscope - Page 1
Forum section: electronics / repair

author: SGRocker
author_rank: Newbie
timestamp: February 07, 2025, 11:33:09 pm
content: Hi,I'm new here . A member of another forum suggested i go here for help . The problem is with a Digitech Oscilloscope QC1924 . I bought it few years ago and after 13months it developed a fault i can't find. And The shop (Jaycar) have been zero help , simply didn't wan't to know about it .Members of the other forum have been very helpful but they don't seem to know much about Oscilloscopes .The forum is mainly about Valve amplifiers,The problem is that the sine wave has bunched up to to right side of the CRT and won't move across to the left. I have checked for dry joints, checked all pots are doing what they should . The horizontal control will move the sine wave only about 6 mm from right to left. The Jaycar circuit doesnt seem to match the PCB. There are numbers on the PCB that arent on the circuit . As in section 5 or section 1 etc. I know about as much about oscilloscopes as i do about frogs !! My thing has always been Valve amplifiers for guitar and playing in bands. Yep i need a little guidance. If anyone is familier with this particular Oscilloscope , any help be very much appreciated.

author: ledtester
author_rank: Super Contributor
timestamp: February 07, 2025, 11:53:51 pm
content: Quote from: SGRocker on February 07, 2025, 11:33:09 pmCan you post a picture?

author: SGRocker
author_rank: Newbie
timestamp: February 08, 2025, 03:05:30 am
content: Hi , yes i'll try to post photos i've taken.

author: SGRocker
author_rank: Newbie
timestamp: February 08, 2025, 03:13:03 am
content: https://imgur.com/a/C8LHjIZ

author: indeterminate
author_rank: Regular Contributor
timestamp: February 08, 2025, 03:45:37 am
content: Have a look for the horizontal deflection circuitry on the schematic.and see if the supply voltages are correct.Bad electrolytic capacitors are the first thing i would be looking for.

author: SGRocker
author_rank: Newbie
timestamp: February 08, 2025, 10:15:18 am
content: Thank you , one of the issues i have is i have no idea where that section of the circuit is. And as i said earlier not even sure the circuit jaycar sent me matches the scope. No mention of the model number on the circuit.i'll check voltages much as possible tomorrow and also check capacitors with ESR meter. Whatever failed it was very quick.SG

author: Sorama
author_rank: Frequent Contributor
timestamp: February 08, 2025, 10:28:27 am
content: maybe you should have a look at this topic:https://www.eevblog.com/forum/testgear/digitech-qc-1922-oscilloscope-schematic/

author: SGRocker
author_rank: Newbie
timestamp: February 09, 2025, 05:49:36 am
content: Thank you Sorama.A friend actually sent me the QC1922 circuit but its a different scope , earlier i think. Interesting to notice comments by others that its not a very good scope.Few hints what to check also. The fuse blowing at start up theory is possible and one i'll check out. If that checks out ok i was thinking to follow the wires from the horizontal control and check parts around the area where the wires connect to the circuit board, as i have no other idea what section to search .As others in that previous article have said about theres may have been a demo model and been repaired before , i notice the solder joints on the horizontal pot lugs are terrible , even the wires are ragged.Thank you SG

author: indeterminate
author_rank: Regular Contributor
timestamp: February 09, 2025, 06:02:46 am
content: the second page of the schematic is the horizontal sectionyour scope will be very similar