[Ron Ramirez]

Thanks, guys...

Rather than wait until the weekend, I pulled the 225 out this evening, pulled chassis from cabinet, and put it on the bench.

I replaced TR701 with a BC547CTFR from Mouser.

I decided to triple the values of R702, R703, and R704.

Resistor - Original value - Calculated value - Actual value
R702 - 220K - 660K - 680K
R703 - 1K - 3K - 3.3K
R704 - 820K - 2.46M - 2.2M

As you can see from the list above, I used the closest standard values to the calculated values.

I did not replace the 0.47 uF C701 with a larger value - I left the ceramic unit in place that I had put in previously to replace the original electrolytic.

Soldered everything back into place, and performed the first of two tests by carrying the chassis upstairs to my home office desk, plugging it in, plugging a set of headphones into the unit, and turned it on.

Auto Magic worked as it is supposed to!

Next, I carried the chassis back to the basement, put it back into its cabinet, and brought the complete unit back up to my home office.

Plugged in headphones, plugged the until into the power strip and...

Yes! It works properly!

That's right, the tuning meter now turns white and stays white (and AFC stays off) as long as I have my hand on the tuning knob. As soon as I let go, it turns green again and AFC kicks back in.

So, with these slight mods, Auto Magic works as designed.

I'm not going to leave it in my home office - I've already switched my Sherwood S-7900A with a Lafayette LR-3500 that I recently recapped and converted all lamps to LED. When I decide that it is time to switch receivers in here again, I'll bring up the STA-225, knowing that it will work as designed.

That is it for this STA-225. Many thanks to Mike (morzh) for his suggestion of the transistor change and of increasing the values of R702, R703, and R704. It is just what this receiver needed! Thanks also to Mondial, and to everyone else who commented.