QH 40 A - into an Icom IC-R71E HF Receiver
Referenz - Installation of a QH 40 A crystal heater into an Icom IC-R71E HF Receiver
Following, few details of installation of the QH40A into an Icom IC-R71E HF Receiver.
1. As there’s no 8 - 12VDC voltages points around, a TA78L10 10 VDC/100 mA Positive Voltage Regulator is needed to drop 13.7 VDC available to 10 VDC, avoiding possible damages to the QH-40 A
2. IMPORTANT NOTE: A drop resistor is not reccommended, in order o avoid voltage variations !!!
3. I spread some silicon paste on the QH40A and the Crystal Face, to allow heat to be better transferred to the crystal enclosure surface.
Procedure for the mod:
- Locate the PLL Board on the left side of the receiver
- There’s an area on the PLL Board where the main PLL crystal X1 is located. In that area you could install the original Icom CR-64 TCXO option. The drawback is that that option is no more available, and used, really expensive.
- It’s necessary to remove the PLL card carefully removing wire harness (socketed) and two grey coaxes, with slide in plugs. There are six screws holding the board to the cabinet.
o One yellow wire goes to the Main Unit, and it’s single pin socketed. Be careful to unplug it.
- There’s a wire jumper to solder in order to bring 13.8 VDC on the trace with the purpose of powering the CR-64 (in our case it’s ok for powering the Crystal Heater QH40A). Pls refer to the User’s Manual and/or to the b/w picture attached herebelow.
- Cut with a cutter the the trace powering the CR64 Option, leaving a space of 1 mm, then drill 1 mm hole each side of the trace, possibly close to soldering isles.
- Drill a 1 mm hole in the GND area wherever you’re confortable with the shape of the Regulator pins.
- Mount a TA78L010AP Positive 100mA Voltage Regulator following this pinout:
o PIN1 (Input) goes in the hole corresponding to the Isle where Added Wire Jumper arrives
o PIN3 (GND) goes to the GND hole
o PIN2 (Output) goes in the hole corresponding to the Isle where CR64 would be powered ( in our case where a red wire goes to the left soldering isle of the QH40A )
- Re-adjust Frequency Calibrator Trim (it is located on the bottom of the receiver)
o (do that after 15’ of Burn-In)
Note: Measurements of the DC Power out of the regulator was 9.92 VDC very stable, and the Crystal Quartz Frequency went stable just after 3 minutes.
Enjoy your mod !
Roberto – Milano