Sansui QSD-1 Calibration

[crhastre]

Does anybody have knowledge of, or access to the factory calibration procedures for the QSD-1 decoder? I don't see anything in the service manual pertaining to this.

I recently had to replace one of the HA1328 ICs in my unit and I'd like to check the calibration to make sure the circuit is adjusted for the new part.

 

[Bonzodog]

Don't remember where I got this, or know how accurate it is.

Sounds reasonable thought.

 

[Bonzodog]

As I remember, I removed F-2465 and F-2464, and aligned F-2463.

Then I inserted F-2464 and removed F-2463, and aligned F-2464.

Then I inserted F-2465 and removed F-2464, and aligned F-2465.

Then I replaced F-2464 and F-2463, and all three boards were aligned and working well.

 

[Bonzodog]

I would be very careful adjusting VR01 on the Power Circuit Board.

If the pot is noisey, voltage spikes could kill the other boards.

Perhaps you should remove the other boards, exercise the pot, adjust for 25 volts, re-insert the boards, and adjust for 25 volts again.

(I think I hijacked your thread.)

 

[crhastre]

No worries there! I had to take out the power supply and rebuild it separately first. The previous owner had blown up TR01 by running the unit on 120V (it's the Japanese unit designed for 100V).

What did you use to generate the the tones for calibration? I have a function generator that can easily produce the necessary tones except for the 180 degree out of phase tone. I think I could create that by using an inverting op-amp circuit, but would the phase delay caused by the op-amp stage cause too great of a differential for calibration?

 

[Bonzodog]

I have an Iso Max that has polarity switches on each of the transformer outputs.

I “Y” the output of my function generator or oscillator and feed both of it’s inputs.

Handy box when you need to check absolute phase.

An inverting op-amp circuit should be so close as to make no difference at any audio frequency. Just require some power. Transformers are nice as they are passive.


View attachment Jensen IsoMax CI-2RR.pdf