Racal RA17 - 100 kc/s Filter Commissioning - UK Vintage Radio Repair and Restoration Discussion Forum

BackToTheLab · 20th Aug 2018, 8:22 pm

Hello boys and girls,

As you may recall if you are RA17 fans, I have been rebuilding a Racal RA17MkII for some time now, and have shifted my focus to the IF strip which lacked sensitivity somewhat.

After finding that most of my anode resistors and way out of spec, and that most of the "Hunts" capacitors had gone open circuit, I decided to do a full rebuild. Initial results are encouraging, although I now find myself unsure regarding the 100kC/s alignment instructions in the service manual.

Section 6.2(a) states that a sig gen at 100kc/s should be attached to V16 pin 1 (grid), and that C191 should be adjusted for max indication on the meter. I have done this and I see that on my set 430mVrms provides a 100uA deflection on the meter.

The service manual states that the required input should be 320mV - is this peak, peak-to-peak, or rms? Is this value the meter setting, emf, p.d.? I can't find any reference in the service manual as to what this voltage level actually is...

Is the value of 430mVrms that I have obtained acceptable? I was brought up on transistors, with the occasional foray into valve technology, and I have no feel for what is right and what is not on this technology... Perhaps I need to grow a beard...

Note that I have measured the anode, cathode, grid, screen and heater voltages of V16 and these are all now spot on following my rebuild....

Any suggestions would be greatly appreciated...

Best regards,

Peter

20th Aug 2018, 8:22 pm	#1
BackToTheLab Retired Dormant Member Join Date: Jul 2018 Location: Cheltenham, Gloucestershire, UK. Posts: 7	Racal RA17 - 100 kc/s Filter Commissioning Hello boys and girls, As you may recall if you are RA17 fans, I have been rebuilding a Racal RA17MkII for some time now, and have shifted my focus to the IF strip which lacked sensitivity somewhat. After finding that most of my anode resistors and way out of spec, and that most of the "Hunts" capacitors had gone open circuit, I decided to do a full rebuild. Initial results are encouraging, although I now find myself unsure regarding the 100kC/s alignment instructions in the service manual. Section 6.2(a) states that a sig gen at 100kc/s should be attached to V16 pin 1 (grid), and that C191 should be adjusted for max indication on the meter. I have done this and I see that on my set 430mVrms provides a 100uA deflection on the meter. The service manual states that the required input should be 320mV - is this peak, peak-to-peak, or rms? Is this value the meter setting, emf, p.d.? I can't find any reference in the service manual as to what this voltage level actually is... Is the value of 430mVrms that I have obtained acceptable? I was brought up on transistors, with the occasional foray into valve technology, and I have no feel for what is right and what is not on this technology... Perhaps I need to grow a beard... Note that I have measured the anode, cathode, grid, screen and heater voltages of V16 and these are all now spot on following my rebuild.... Any suggestions would be greatly appreciated... Best regards, Peter