Video Scope fried with 12VDC from faulty power supply?

A few years ago I got the old versions of the Black & White Video Scope and the Rhythm Scope. I used a power supply which lets you dial in the voltage. Mine was set to 9V (center positive), but both Scopes didn’t work. So I measured the voltage of the power supply with a multimeter and it read 12,4V!!!

According to the manual now my units are damaged. On visual inspection of the PCB I couldn’t see any physical damage. I’m pretty capable of SMD soldering, but have only limited knowledge of electronics (dangerous combination, I know). Does anyone here know, which specific component(s) might be damaged? What can I do to repair it myself?

Sorry to hear this. Have you tried a different power supply?

Thanks @chrisk. Yes I’ve tried a different power supply. Didn’t make any difference unfortunately. I’m waiting for a converter I ordered yesterday to bring composite video to VGA to rule out the AV input on my beamer. Will report back then.

So, I tried the composite-to-VGA-converter and at least I got some visuals – and some quirks:
Black & White Videoscope:
Most visuals are very distorted, more than I remember.
Response to audio is functional, but I have to give it really high levels (something like 10Vpp minimum).
Rhythm Scope:
Visuals are ok, but no response to audio input at all, and Random Mode not functioning at all.

Thanks for the update. It appears that both units’ audio inputs appear to have been damaged by the incorrect voltage but their programming is working fine**. It is probably worth replacing the op amp IC that receives the audio prior to sending it to the microcontroller.

(** the Rhythm Scope’s Random Mode is triggered by the audio input so if the audio input is not functioning, the randomization will not occur.)

Here is the IC:

The specs are:

  • Manufacturer: Texas Instruments
  • Manufacturer Part Number: OPA2342UA

These are two good suppliers:

Hey @chrisk !
Thank you very much for your quick reply :star_struck:
Replacing these opamps should be easy. Luckily I am putting together a mouser order at the moment anyway, so your message came spot on :smiley:
Definitely worth a try. Will report back in a couple of days.