I am recaping a HQ 129X with red lettering. I have run into two points that I need help with.
The first one is the resistor that goes from VR105 Pin 1 to Pin 3. I can't read the colors on it and haven't found it on the schematic. It measures 1.8K. #2 -- The schematic shows cap #25 at pin 5 of V#5 to be .1Mf and a resistor, #82 of 300 ohms from Pin 5 to ground. The resistor is in the radio and that position,however, there there is no cap present and it looks like it has never had one there. I checked V5 on another rig i have and there is a .1Mf cap on pin 3 of that unit. Both rigs work very well and am wondering if I should change either or both units to schematic spec's. Also checked the resistor on the other unit and can not read that one either.
Mike

That is the first production run and there were a few changes over the years. The VR-105 resistor is 4K 5W and add the .1, to V-5, it should be there.

You can also check the HQ-120 and RBG-2 circuits and see the progression of the design.

Carl

Mike -
Pin 1 on a VR-105 has no connection in the tube. The socket lug is just acting as a terminal strip to support the resistor. So, look for a wire from Pin 1 leading off to the RF, converter, or 1st or 2nd IF stage. Looking at the schematic, your resistor must be one of these: R52, R23, R14, R8 or R2 - all of them 2200 ohms, 1/2 watt.

The photo in Sams shows the .1mfd cathode bypass for V5 located between V5 and V4 - a large, hard to miss waxed paper cap directly under IF transformer T3. If its not there, tack one in and see if you notice an increase in IF gain.

--Chuck

OK, I should have known not to look at a schematic just before going to bed Thanks to Chuck for catching that

Carl

Thank you, Carl and Chuck. Yes you are correct. I think the resistor is R6. A 2200 ohm. However , a interesting turn of events, ALL of the resistors the schematic says are 2200 in fact are 2000 ohms. I replaced them with 2.2K's and I have very strong audio and a very narrow band width and it seems like the filter is on, as there is very little background noise. The AVC/BFO
seem to work correctly. I will do more work on it next week. I think I may have messed up somewhere. Any comments would be gladly accepted.
Mike

Mike -

I'm no expert here but I'm just thinking, provided the radio is "all-original" it may be that the mfr ran short on 2200 resistors but either had or was able to lay hands on a batch of 2000 resistors, and since that's only 10% difference maybe that was considered "acceptable" even if not ideal. Parts substitution on the assembly line perhaps? I know that VW did not have "clean" model year cut-offs... sometimes they made mid-year production switch overs based on availability and other factors, which can really confuse a restorer. I had a 1962 VW beetle that had both the new fuel gauge and the under-dash fuel cut-over valve (a necessity before the gauge was introduced). It's strange to see both on the same car. And yes, it was all original like that from the factory.

Sometimes technical compromises are made in the interest of keeping the line working, or shaving costs, and this might be a possible example of that principle at work.

Glad to know your correction of their "compromise" is working well for you!

The Crystal Selectivity switch in the upper left corner should make a lot of difference as you switch it through its range. In the far left position (OFF) the crystal filter is shorted and leaves you with the widest bandwidth as set only by the IF transformers. The wide position (OFF) is about 6 dB down at +/- 4 KHz. The narrowest position (5) is about 6 dB down at +/- 250 Hz.

If the bandwidth seems too narrow and you are not seeing any change you might have to open up that can and take a look. The wafer switch might have a problem that is causing it to not be rotated by the shaft.

If it IS changing, you might be just dealing with the need for an alignment. As often noted, in these receivers you have to align the IFs to match the crystal even if that is not exactly 455 KHz. Otherwise the crystal filter just acts like a big attenuator.

Curtis Eickerman

In my last post , I stated that R6 was a 2.2ki and I should have said R2. I think R 6 is a 22ohm. Yes Curtis I think the CS switch was in the first position. I have removed the face plate and don"t have many knobs on, so I replaced that one and the background noise seems to be norm. However, and there always seems to be a HOWEVER. Now when I tune a very strong station on the BCB or short wave and I turn to AVC, the audio is almost gone. If I tune a weak station and turn on AVC there is no audio. The BFO is very strong and works well the two times I have tried it. I am wondering if the problem might be around the V1, as I have replaced all of the caps and resistors in that section also. The voltage at 6SJ7 - P 6 is high when I turn to BFO. When in AVC mode, the s-meter shows a very small signal strength with a strong BCB station and you can see it wiggle during the broadcast. I just don't think I have the correct voltage in the AVC mode.
Mike