Syntor Low Band Poor Sensitivity

[Mogman]

I have a low band Syntor X9000 that has very poor receiver sensitivity, I was chatting with the local Motorola shop service manager and he said it was very common for the input filter coils to get corroded and simply cleaning them would fix the issue, he loves to "pull my leg" and most of the time I can bust him but this time I am not sure as living on the third coast makes this plausible but the radio came from the mid-west, anyone had this issue?
Thanks

 

[jim202]

I have a low band Syntor X9000 that has very poor receiver sensitivity, I was chatting with the local Motorola shop service manager and he said it was very common for the input filter coils to get corroded and simply cleaning them would fix the issue, he loves to "pull my leg" and most of the time I can bust him but this time I am not sure as living on the third coast makes this plausible but the radio came from the mid-west, anyone had this issue?
Thanks

I believe that there are several service manuals available on the Syntor X9000 on the repeater builder site. Been a while since I looked, but think they are there.

I would take a gander at the TX output power and see what you get. That will confirm the path between the radio connector and the PA. I have never found one that couldn't be brought back to good sensitivity with some fins adjustments except one. It lost a voltage regulator controlling one of the mixers. Never did fix that one. Just kept it for parts.

The other thing you can do if you get desperate is to locate a Syntor X and just swap the board with the PROM for the one in the Syntor X9000. The rest of the radio is the same. They are a good source of parts. Most people don't want them because the prom they use is no longer available.

 

[Mogman]

OK I will give that a look, I was assuming (probably incorrectly) he was talking about the high pass filter in the receiver front end, as you said if it is the harmonic filter the TX power should also suffer, it will take a couple days to get the present project off the bench and re-test the LB radio.

 

[com501]

If this is in the ham and, and the radio is good in the commecial portion of the spectrum, check the noise blanker tuning.

Otherwise, look at the PA front end near the antenna. If it has a bad diode or any of the components in and around the antenna switching circuit are bad, chances are the PA output will be good but no RX sensitivity due to the circuit failed in the TX direction.