Electronic Repair & Modifications
Latest Rabbit Hole project....Started with adding a line isolation transformer and morphed into a complete circuit rebuild... The original circuit was pretty much a widow maker design, with direct line voltage feed the amp.
3 PCM 41 units in for repairs. These are some of my favourite delays, many fond memories playing with these in feedback.
On the bench is a line mixer with a intermittent right side of the the 2nd output.
Interesting design inside, very late 80's...
This one came in with a loud buzzing and flickering screen...
Got to take a peak inside the M460D...
I am big fan of Rupert Neves stuff, and the Portico Series 5014 widener did not disappoint. Great attention to detail in this box!
The unit had a bad cap in the switchmode power supply filter.
One of favorite units, the 1178 is a very useful tool. This one has an issue when the needle intermittently pins hard right. It took a while to replicate the issue on the bench. It might be a cap, cold solder joint, opamp?
I don't know yet, I am going to start to trace the problem from the output back to the input.
I am getting interested in building a hardware stereo image widener circuit. I have seen a few ideas floating around based on the Middle(M) +Side(S) technique. The basic premise can be summarized into the following equations:
Encoding M and S
Middle = L+R
Side = L-R
Translating that into basic op-amp circuits, the Middle signal could be created with a summing amplifier.