Hi

Just bought a used FT 857, and have discovered that the SSB receiver seems to have at least 40 dB attenuation or what ever it is. I can hardly hear any stations, and S-meter shows low value.
If I change to FM everything works excellent. I do not know the state of the TX, as I am not able to do any communication.

Listening to the weak signal in SSB mode, the same signal is very high when changing to FM

Anyone who knows what this could be?
And where do I get the repair manuals?

Thanks in advance

Ruben

开云体育

The service manuals are available on line and a quick search will find them.
Check the output SSB and if it is weak as well it is very likely that the SSB crystal filter is bad as it is used solely for SSB, both receive and transmit. If the AM is OK transmit and receive this would zero in on the SSB filter CF1004 that would be the most likely place to look. The AM filter CF1005 is switched into the same part of the transmit chain for AM and the same amplifier circuits are used. FM and CW do not use this part of the circuits (as well as I can determine from the block diagram and schematic.?
When you download the service manual and look at the schematic you will find these filters in the upper right hand corner. D1076 and D1078 switch between the two.
At least the CF1005 is very cheap at $0.71 from Yaesu. I don't know about the price for CF1005.?
The output of the receiver chain feeds these two filters directly for SSB and AM. The FM and CW have different paths per the block diagram.
Suggestions here are if you are having almost any problem change the CF1002, 2. and 5 filters. CF1004 gives fewer problems since it is hermetically sealed.
Anyway if you order parts get the filters:
? ? ? ? Yaesu P/N? ? ? ? ? ? ? ? ? ? ? ? ?ID? ? ? ? ? ? ? ? ? ? ? ? ?Description? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?price
1-? ? ? ? H3900543? ?$0.71? ? ? CF1002? ? ? ? ? ? CERAMIC FILTER ALFYM455E? ? ? ? ? ? ? ? ? ? ? ? ? ?$ 0.71? ? ? ? ? ?
1 -? ? ? ?H3900545? ?$0.71? ? ? CF1003? ? ? ? ? ? CERAMIC FILTER ALFYM455G? ? ? ? ? ? ? ? ? ? ? ? ? ?$ 0.71? ? ? ? ??
1 -? ? ? ?H3900542? ? $0.71? ? ?CF1005? ? ? ? ? ? CERAMIC FILTER ALFYM455H? ? ? ? ? ? ? ? ? ? ? ? ? ?$ 0.71? ? ? ? ??
Just so that you will know not everyone would agree with me on this.

So these filters are covering the AM and SSB line, but not in use in the FM line?

From what I can tell that is so, but the actual switching is convoluted and not at all clear to me. Download the service manual and take a look at the block diagram and read the technical discussion.?
I looked at the CF1004 signal with my scope to see that mine was working and my transmit problem seemed to be in the FET amplifier after it.
Others say it is a problem with CF 1002,3, and 5. There are evidently a lot of problems with those crystal fitters and changing them when you are in the area is suggested.
A quick check with your scope should tell you if the CF1004 is passing the signal or if you are losing it somewhere else.

OK, will dust my oscilloscope and have a look at the FETs.

And at the same time I will order some filters, seems to be good idea to change these :)

Nice to have something to do during these dark times :)