The Fine Things are Always Hand Made
After quite a while I'm getting back to the AW-12 and I'm hoping I can get some tips on the IF alignment.
Since I do not have any spare IF covers I'll need to drill a hole in at least one of the cans. Before I tried to do that I wanted to see if anyone can provide advice on how to do that without damaging the can.
The other question is has anyone replaced the grommet where the cable goes into the back of the receiver? The grommet has become very hard and is falling apart. Any recommendations on what to use would be appreciated. I'm considering just getting some various size grommets and picking the best fit just to prevent any damage to the cable.
With the repair of the cold solder joint and some minor adjustment to the alignment the BCB performance is now quite good.
The next on the list is the tuning indicator.
When the radio is off the needle is on the left. Once the radio is on the needle moves to the right and then stays stationary regardless of the strength of the station being received. In watching this closely there may be a slight wavering of the needle when tuning through a strong station. From what I can see without taking anything apart is that the needle is bent quite a bit.
Any advice on how this should respond normally, what I might look at next and how to straighten the indicator needle without damaging it ?
Thanks for any info
The meter pointer is indeed quite small, not much bigger than a wire.
In mounted position, the action is lateral. So the pointer is bent down to enable the pointer to cast a shadow on the dial.
With mine, when powering up the radio, the shadow appears from the left and moving right rapidly and comes to rest at the near edge of the broadcast band graphics. Tuning a stronger station, the shadow moves to the left towards the SW scale graphics. A weak station produces little meter action. The stronger the station, the further left the shadow moves towards the SW graphics.
The meter is on a stalk, so adjust the stalk with regard to the dial lamp so the meter shadow plays within the edges of the dial strip.
This is 1932 technology. To improve action, the next model (model Fifteen) added an amp tube to the meter circuit.
Thanks again for the info. I removed the movement and straightened the pointer somewhat. However, there is still no movement of the meter to the left when tuned to a strong station.
One thing thing I can think of to try is to use a signal generator and connect it to the antenna terminal to see if the meter will move and change as the level of the generator is changed. If not I'll have to dig deeper.
Lars - The signal generator idea is good - you can create a very strong signal to see if the meter reacts. As Dave noted, the 12 doesn't have great meter action and Scott added another tube to increase the responsiveness in the 15. Still, you should get some movement on stations, I wonder (since the indicator was bent) if it may be dirty. You can remove, dismantle and clean the meter <very> carefully.
The primary cause of poor tuning meter response is IF alignment. Scott radios are well known for being able to pick up stations even though the IF is not well aligned. In such cases the tuning meter will have anemic operation.
Kent and Norman
Thank you for the quick replies and the information.
Once I have a little time I'll check the response of the meter with the signal generator and after that take a look at the IF alignment.
Just an update:
I finally got around to checking the tuning meter using a signal generator. I connected the generator to the antenna terminal and set the receiver and generator to 700 kc. With the generator at minimum output I gradually increased the output of the generator looking for the meter to move to the left but it did not move at all.
After turning the radio on the meter moves from left to right and stays there. There is no deflection when tuning a strong station or with the signal generator connected.
After I get around to the IF alignment I'll see if I can get a response.
If the meter moves when the set powers up, it is ok. Meter action is not as strong on the AW12 sets but once the alignment is done, you should see some action.
Thanks -- I'll update after I get a chance to do the alignment.