On Thu, May 15, 2025 at 07:28 AM, Ryan Wesolowski wrote:
the output from IC405 and IC406 are not any stronger P2P then the input but the signwave is distorted on the output.?
The reason I suspect that ic405 and ic406 are bad is the fact there is no difference in gain between the input and output.
Like Stan wrote before, it looks like IC405 and IC406 are in overdrive state but not broken. It would be the first time reading about broken ones or find this when repairing a QMX(+).
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Please check these voltages using your DMM:
For Q508 in RX mode the voltages are at S 0 V, at G around 3 V and at D near 0 V.
IC402 pin 9 should be around 2.5 V and depending on the active BPF one of the pins 10, 11, 12 and 13 should be the same.
IC403 pin 7 and 9 should be around 2.5 V. Pin 2 and 14 should be around 1.6 V. Using your oscilloscope you should see there (2 and 14) the LO signal with low at 0 V and high at 3.3 V (or so).
To repair QMX(+) I had to replace Q508, IC402 and IC403 already.
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Could you show please screen shots from Terminal - Hardware tests - RF filter sweep and Test ADC I/Q for a lower band and a higher band?
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73 Ludwig
