6v DC Wall adapter introducing thin black lines into video signal

technical questions/help
1

Hi guys,

I have a composite glitch effect unit that originally runs on 4 AA alkaline batteries. I’m trying to change the power source to a 6V 2A DC wall outlet adapter. I tested the power adapter, confirmed the voltage was correct and soldered the positive and negative wires to the positive and negative wires attached to the battery compartment terminals (positive to positive, negative to negative, de-soldered it from the battery compartment terminals, and covered the exposed wires with slip on wire sheathing).

The unit works as it had but now some thin black lines have been introduced to the video signal. Just looking to see if anyone has experienced this and if they had found a solution. Wondering if this is due to noise interference and could be resolved by adding a ferrite clip to the power wire.

I can add examples of the issue or wiring if necessary.

Thanks in advance

2

it’s to do with the PSU introducing noise. You might improve it with a ferrite core, but it’s advisable to use a different adapter. The device likely uses 5v if it’s powered by 6v battery.

Check for a 5v regulator inside the device. If it uses one (LM7805) then you can use a higher voltage psu. (only up to 9v is advisable though).

This would give you more options to find a noise free supply.

I used a laptop PSU for an audio effect, it worked great. But a different laptop supply made a high pitched whine all over the audio.

3

Thanks for the information. Unfortunately there’s no MOSFETs, only some BJT transistors, KSP2222A, KN2907, KSP2907A.

I think looking for an alternative power supply like you suggested is still best. I’m going to look around for 6v options.

4

ok right it’s making the necessary supply voltages with transistors and not voltage regulation.
Yes try to find something which produces stable 6v supply, something a bit more upmarket : )

5

Definitely, Thanks again for your input.

1 Like
6

Most welcome I’m happy to offer any more suggestions if you are stumped. I can recommend drawing out the schematic of the components where the battery power comes in, this REALLY helps with understanding of the part of the circuit you are dealing with. Especially if you don’t get anything at the start! : )
The problem with 6v is I think anyway, it’s kind of a consumer device voltage level, so there are not many supplies at 6v (everything I have is 5, 9, 12, 4.5, 3.3 or combos of).

If you look at the components making the supply (after the battery) then you can see if you can safely feed it a higher voltage, thus giving you more scope to choose from in PSU. For instance, my Zoom H4 takes 9v. But you can give it 12v no problem at all, because the components can handle it. (not always the case, which is why you need to check - some devices won’t boot with over voltage)