Tsebi Projects Forum

The IC-7300 uses an MP7741 audio power amplifier IC in quite an elaborately filtered configuration.

Documents for the IC-9700.

Approved for use in Singapore. The following are the documentation and service manual.

Interestingly, ICOM also uses the LA4425A in the output stages, for example in the IC-718 (pg.16 of attached file). This has been confirmed to exhibit that hiss at zero volume as well.

The FT-DX101MPD, on the other hand, uses the TDA2003 power amplifier chip.

The noise in the output of the amplifier does not change with volume, so it must be inherent to one of these three parts - the M62364FP, NJM2737 or the LA4425A. The NJM2737 is specifically a low noise part so I'm not suspecting it as a noise source at the moment. The M62364 has only 8-bits so it is ...

Most of Yaesu radios appear to employ the same kind of design:- 1. Various audio signals AFOUT, AFOUT2, TONE comes into a 8-bit digital volume control chip M62364FP chip. 2. The output of this chip is mixed without gain using a single NJM2737 op-amp stage. 3. The output of this mix is fed into the L...

1. Install drivers for the CP2105 USB-serial chipset (can be obtained from the Yaesu page) https://www.yaesu.com/downloadFile.cfm?FileID=16755&FileCatID=42&FileName=CP210x%5FWindows%5FDrivers.zip&FileContentType=application%2Fx%2Dzip%2Dcompressed 2. In the radio, select FUNC->Radio Setti...

Even with the voltage increased to 13.8V (actual was 13.7V) and the lowered TX current, we still managed to reach thermal foldback in about 35-minutes of operation. This was shorter than the 45-minute 100% duty-cycle dummy load test, suggesting that maybe SWR is more critical than we had assumed. A ...

Further testing reveals that the repeater will still overheat at 25W output after about 35-minutes of continuous usage. We do not know if this overheating condition has always been happening (for years). All we know is that we have just noticed it - possibly as a result of higher repeater usage and ...

Last night's usage test showed the repeater heating up from ambient and took about 25-30 mins to reach the point where the TX LED started to blink and about five more minutes before there was noticeable power output drop. Work done today:- 1. Checking actual voltage at the radio. When receiving, it ...