Authored by VE3EFJ4.1 R4C CHANGE SUMMARY
There are many changes previously outlined for the R4C, and it can get confusing. There is a reason for this, for there are a number of alternatives, and what you do depends upon how radical you want to get. This is complicated by the serial number of your receiver. Early model R4C had a lower voltage transformer, and it isn't easy to get the secondary voltage up high enough for a voltage regulator IC. That won't happen unless something is done in the audio section to drop the current consumed by the audio output stage.
-4C Audio Section Summary
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If you want to 'improve' the audio ....
 | C100 Change |
| Bypass the anti-VOX line with a .005 uF |
| Route secondary transformer grounds to the filter caps. The first 2 items may be all you need. |
If you want to improve the audio and limit heat
| EP487 and zener diode regulator/pass transistor |
| C100 change |
| Bypass the anti-VOX line with a .005 uF |
| Route secondary transformer grounds to the filter caps. |
| LM380/LM383 |
And last, if you have a later model R4C ....
| Sherwood audio board and regulator |
| Bypass the anti-VOX line with a .005 uF |
| Route secondary transformer grounds to the filter caps. |
