Helix DSP Repair

       This DSP was sent to me for repair. Its remote out does not work.

       This is also a good chance to see how well it is designed and built.

The DSP on my bench.

Control inputs and analog outputs.

Analog and digital inputs.

A few screws and we're in.

It is a one board assembly. Everything is mounted to the main PCB.

Back of the PCB is clean and there are no parts.

DSP and DAC chips.

Processor chip for control.

Powersupply section is well laid out with generous capacitance spread throughout.

Analog sections are well laid out. There are pots for each input channel.

Only these two MC33079 quad op amps are for the output. Inputs are fully discrete.

B+ is protected by a resettable fuse.

All terminal blocks are pluggable types for ease of install.

Remote output is controlled by a BCP59 PNP transistor without any current limiting/protection. A few cents here with another polyswitch could have solved this problem.

Part is removed and pads cleaned.

Surprisingly, I found an exact part from the junk bin to repair the unit.

Remote works!

       Parts are well laid out. There are a few parts in the input and output paths so there is little need for mods. For possible mods, I would be looking at replacing the output op amps and the output electrolytic caps. Besides those, I would probably leave the rest alone.

Page created and copyright R.Quan ©15 Jan 2017.