Philips PTV800, Service Manual

Page: 71 / 567

Two Tuner Models (ASG053, & 54)
Tuner 1
1. Use the VCO and AFT adjustment procedure described under Single Tuner Models for
alignment of Tuner 1.
Tuner 2
1. Cut the shield break points around IC201 and the IF Circuitry (see zone K-5). Peel back
the top cover of the shield to gain access to the internal circuitry.
2. Short Test Points 16C, & D of the Varactor Tuner Module (see zone J-1, bottom view).
3. Short Test Point 23A (Pin 13 IC201) to ground (Shield around IC201 is good).
4. Connect a DC Voltmeter to Test Point 7A (Pin 18 of IC201).
5. Turn the set on and record the voltage reading from Test Point 7A (typically 4.5 to
5.0Vdc).
6. Turn off the set and remove shorts from Test Points TP16C, D and 23A
7. Connect the Coincidence line at the collector of Q207 (jumpTP47, zone J-6, on top of
board) to +5Vdc line on the tuner.
8. Apply a local broadcast signal (air signal) to the antenna terminals and turn the set on.
9. Select the Cable Tuning from the menu system. Select channel 36 or some other high
band inactive cable channel.
10. While still in the cable mode, select your local VHF broadcast channel. The Tuning
System will attempt to tune three times and then lock on to the FCC assigned
frequency.
11. Adjust the AFT Coil (L219) to obtain a reading of +6.6Vdc (+/-25mVdc) at Test Point
TP2A.
12. Adjust the VCO Coil (L 220) to obtain the same DC voltage reading at Test Point TP7A
that was noted in step 5 of this adjustment procedure.
13. Remove the jumper from the Coincidence line.
14. Verify this adjustment by changing between the high band (inactive cable channel) and
your local VHF broadcast channel (ensure that the local broadcast channels lock in
quickly).