EH Scott Radio Enthusiasts

The Fine Things are Always Hand Made

Hello All,

I'm seeking some help with the IF alignment of this set. This is the first Scott I've restored. It is super clean and all original. I've read every post on the topic of Philharmonic XXX alignment. I have the technical service data .pf and the Philharmonic simplified alignment document put together by Norman Braithwaite (very helpful) but I am not getting the results expected.

After replacing all the wax and electrolytic caps and out of spec resistors the radio worked everywhere except the If signal died between the 2nd and 3rd IFs.  A rough alignment using a HP 8645B and a Hickok Traceometer tuned to 465 kHz got the radio working with acceptable gain between each IF stage.  In attempting a proper IF alignment as prescribed by the technical service data and Norman's alignment charts I'm not getting any reading at the IF test point on the Selectivity control.  I've tried different meters to ensure my equipment isn't the problem.  I can measure miliamps at the RF and IF diodes but not at the IF test point of the anti-clockwise lug of the sensitivity switch. I'm hoping someone has some suggestions on what may be wrong.

This set has a few differences from the schematic in Rider's but all differences appear to be original and not modifications made after manufacture.

Cheers,

Scott

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That is about where the IF diode assembly is located electrically. Did you replace the 3 caps inside the IF diode assembly ? an .05 and a pair of .005's as I recall. Check that the resister leads are intact too (not broken).

Is a pain to dismount the IF diode. There is  a coil in there too. 

Yes, I replaced the caps in the RF, IF and Audio diodes and circuit traced the coils and connections. Everything checks out.

Some versions of the Philharmonic had a capacitor between the AVC signal and the selectivity control.  If your set is one of those versions, you will need to move the meter to the AVC side of the capacitor instead of the selectivity control side.

Norman

The capacitor between the selectivity switch and the AVC was the problem.  Thank you for pointing that out. IF, diodes and RF alignment completed.

I will tackle the expander adjustment tomorrow. It definitely improves orchestral pieces, the difference is certainly marked.  I didn't find any information on the adjuster for the tuning eye. It's functional and the internal resistor is within spec but I think it should close fully when tuned to my transmitter that is just a few feet away. I also need to see if I can remedy the speaker rattle when reproducing heavy bass tones. 

This is a fun project and a good workout to boot.

Check if the speaker is off center with regard to the baffle hole. And any thing loose in the cabinet. 

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