That is definitely the way to do things...incredible. What software are you using to parse the signal & generate those graphs?

Have you ever gotten a flat result out of a RIAA preamp circuit?

As far as restoring the Beomaster 1000, I was planning on replacing most, if not all the caps, using the notes above by Die_Bogener, and cleaning/lubing the switches. Also checking for any notorious transistors.

If anyone else has improved the preamp ( or any other part of the unit ) I was hoping there was documentation somewhere to reference.

Not planning on messing with tuner alignment though as I don't have the tools or knowledge, but any electrolytics in there might get replaced. Depends how it works.

 

I do have a sine generator and a scope although I have never used them. Maybe by the time I get this rebuilt I'll try analyzing some parts of the circuit like that. Fascinating!

 

And thanks! Great food for thought

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What software are you using to parse the signal & generate those graphs?

I use a dedicated audio analyzer and use the software included with it. Prices and quality of audio analyzers vary greatly. Testing with general purpose test equipment and post processing the results is also a viable alternative. The price and quality of the general purpose equipment also varies greatly. What is more important than the price/quality of the particular equipment is that one understands the limitations of it and uses it accordingly.

Have you ever gotten a flat result out of a RIAA preamp circuit?

Everything is flat if you zoom out enough. Nothing is flat if you zoom in enough. I don't worry that much about the "flatness" of vintage equipment. The "tonal coloration" of the old equipment is part of the charm that makes it interesting. I concentrate more of having the left and right channels match.

Maybe by the time I get this rebuilt I’ll try analyzing some parts of the circuit like that.

I try to repair the equipment just enough to get it working reliably. This usually consists of fixing the broken solder joints on the edge connectors, ensuring that the power supply voltages are correct, and adjusting the bias currents. I then do a baseline performance test (i.e. the "before" test). You can learn quite a bit at this stage. Sometimes this test reveals a specific issue that needs to be fixed. Other times, it reveals that a 60 year old piece of equipment is remarkably close to its original performance specification. It is much easier to do the "before test" before you swap all of the capacitors ;-). Glitch  

Great tips, thank you for the explanation!