Re: uBitxr4 audio distortion fix
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we will probably have to increase the emitter resistors in that case too. The other option would be to use slightly higher bias voltage rectifiers like the 1N4001s.
On Fri, Jun 29, 2018 at 4:17 PM, Raj vu2zap <rajendrakumargg@...>
It was too much! Q72 started to get hot but not Q73. Means they are not
Iq went up almost 100mA. So I used a pot where 47 Ohms seems
What may work that instead of these diodes use the same transistor BE
Then just two may work, need to experiment on this.
At 29-06-18, you wrote:
What if we use three diodes
On Fri, 29 Jun 2018, 13:35 Raj vu2zap,
- Got back to town and plugged in the uBitxr4 and found the audio
- Poking around the finals I found that the two diodes D15 and D16 gave
only a drop of 1.2V total
- but the final transistors needed more like 1.5V. i.e. 0.75v
- I simply cut the track between D5 and D16 and soldered a 100 ohms
multiturn preset as shown
- in picture below. (Preset leads used is center and one side)
- Start with the two soldered connections of the preset set to ZERO
- Power on and tune to a station at low volume and slowly increase the
preset till the audio
- becomes clear. In my board the RX power consumption increased by 25mA
at the best sound.
- Just check and see that the output transistors are not getting
- My board sounded great with 47 Ohms between D15 D16 and I run at
13.6V. If you run at the
- same supply voltage then you can try a fixed resistor. For 12V supply
you could try a higher value
- like 56/62 or even 68 Ohms.
- Raj, vu2zap
- Bengaluru, South India.
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