Pioneer TX-720 Tuner Discriminator Zero Adjustment

[craigsc]

Hi Folks,

Based on some searching I need to adjust the discriminator zero voltage on my TX-720 but I can't find a service manual online. Anyone have the manual or point me in the right direction for the adjustment procedure?

Thanks.

 

[rcs16]

And why do you think the discriminator needs adjustment?
I do not have a schematic, is it close to a tx-710, using a PA3001-A?
Basically you measure across the ref pin and the agc pin, adjust the lower slug for 0VDC. I am not 100% sure, I would have to check the service manual or another model using the same quad detector to be certain.

 

[larryderouin]

Rick Stout has the manual for sale. http://www.stereomanuals.com/man/rep/pioneer/pioneer_manuals_tx-500_xx.htm This is a repop. Rick's repop's are usually a lot better than originals as he cleans them up (extraneous marks, pixels, etc.) and Binds them with Multiple clamps/clips and uses re-inforced tape on the binding edge. I've been getting his repop's for 10 years and never had a bad one. AND they are clean and clear enough to blow up the schematic page(s) to a poster size. Makes it easier on old eye's. Office Depot or Staples can make posters for about $5.00. NOTE FOR RCS16. The 720 manual also covers the TX-7000 and TX-720L(Japan only).

 

[craigsc]

The tuner continuously scans in FM or AM. You can make it go up or down but it never stops. Another thread with the same symptoms had a discriminator adjustment as a fix. Thanks for the link to Rick Stout's site Larry. Will be picking up the manual and hopefully fixing the tuner.

 

[rcs16]

All you have to do is look inside to see what discriminator it uses. Attach a pic.