I picked up a nice XR-1 on eBay. This was Heathkit's first transistor radio kit I believe. I changed out the electrolytics and fired it up using a Heathkit Power supply set at 9V. I get low volume, i.e. only get 2 or 3 strong stations and the volume is all the way up. I did the standard tracing. I believe I narrowed down an issue but need to understand what is typical since this is my first transistor radio rework.
Here is the schematic for reference:http://louhaskell.com/data/heathkit-xr1-schematic.jpg
I get about 1.5V peak-to-peak of nice modulated IF at the collector of the 2nd IF transistor, pin 3 of the last IF transformer. But I only get about 0.1 - 0.2V at pin 1, which is connected to the top of the volume control.
I measured the winding and got 1.5 ohms on the primary and 5 ohms on the secondary of xfrmr 52-13. Also, moving the slug made very little difference in the peaking of the IF can. Strange I thought. I removed the xfrmr and took it apart since it has the diode and caps inside. The diode is good, the caps seem good?? No loose connections. Just connecting an RF generator at 455kc across the primary and putting a 2.5K resistor across the secondary gives me the same results on a little test bench. SO not sure what is up with this thing.
So.. some questions:
1. Is 1.5V at the collector of the 2nd IF transistor about as much as can be expected?
2. Given the resistance measurements of the primary and secondary, does the xfmr seem like it should step DOWN the voltage by a factor of 5? (true, it has to overcome the 0.2V junction of the diode but I included that in the calculation.
3. Is 0.2V on the volume control good and I should understand why the amplifier stage is not stronger?