Yaesu FRG-8800 No Receive in LSB Only

[KA1CDE]

I have a FRG-8800 Yaesu receiver that works great except in LSB, I have owned this receiver for years, all of a sudden when trying to listen to LSB, I push the selector button, the beep acknowledges I have depressed the LSB button, and no receive.
I can see some signal showing on the S meter, but no a noise out it. Head phones used make no difference, no sound only LSB.

Looking for help and suggestions >>>>

Thanks

Pat

[KO6WB]

What type of service equipment do you have?
An oscilliscope would be nice but do not go out a buy one just for this. A DVM would work. The servie manual is vey handle, provided you capablity underatand needed to complet this task.

[KO6WB]

Okay, so I went off to search from more information and QRZ automatically posted my incomplete post.
But it still hold true. What type of service equipment do you have?
With an o'scope you can see the waveforms and tell what they are doing. But with a DVM you can measure the responses you would need to get. To successfully service the FRG-8800 you will need lots of experiance. See if you can get one of the other amateurs to help. You will also need the service manual and you can get it at http://pdf.textfiles.com/manuals/SCANNERS-S-Z.
BTW if the CW portion of your FRG-8800 works then the problem is in a switch or connection. Check the service manual because I am wrong sometimes, well okay more than sometimes, OKAY OKAY OKAY most of the time. Geeesh hate it when my second personnality pops up:o
Hope this helps
73
Gary

[N0SYA]

Is the lsb bfo xtal used in cw or rtty modes? If so and those modes work that kinda points to the variable cap or inductor used to set the lsb bfo freq. Sometimes a nudge of that cap or a few revolutions can get things going again, but be carefull of tuning the core of an inductor, don't use a metal bladed tool or the core will probably get cracked, and don't push too hard on the core when tuning. You can tune the rig to a wwv freq and set the bfos by ear easily. I had a bfo cap that was really picky and would stop oscillating if set to any but the optimum cap setting, and was slow to start but once set it works as expected.

[KA1CDE]

All I have for equipment is the schmatic and ohm meter/volt meter: I was hoping someone else may have run into something of the same and could help direct me where to find the problem. Looking at the schematic it may be Q44 ?

Pat

[N0SYA]

Link to a service manual?

[KO6WB]

Yeah...I gave that link in posting #3. You have to scroll down to Yaesu FRG-8800 and then move your cursor over to the row the says PDF and clink on it. Works for me.
Hope this helps
73
Gary

[KO6WB]

Pat,
you can do a lot with just a VOM but you need to know what to look for and how the resistance of the meter will effect the readings.
In my previous post I asked if you were able to hear proper operation when you have selected CW. If you can't then it might be Q43 or Q44. You will just have to check them but first check and see if you have CW selected and if that mode of operation is okay.
Hope this helps
73
Gary

[KA1CDE]

Gary,

Yes every other mode works well, only LSB has no sound, the S meter looks like it seeing a signal, when I depress the mode button for lsb, it make a beep indicating it was selected, but no sound.

I have ordered a replace for Q43 and Q44

Thanks for your help.

Pat

[KO6WB]

Pat,
if CW works then it is not Q43 or Q44. It's something else. The problems with trying to fix something over the internet is that it takes a very long time. If you look at the circuitry for the IF amplifier/Detector portion find the connection that has the detected audio out. Now tune to WWV or a local AM station and set the unit to USB. Tune for a beat note. Now with the VOM set to read AC you should be able to measure the detected audio level. Once you have that signal switch over to LSB. You may have to slightly tune a bit off but you should be reading the audio tone at that point just like you did on USB. If you have it there then the problem is after the IF amplifier/Detector.
Try this and see if it's any help. This troubleshooting technic is called the half split method. It gives you a direction to go so it is easier to troubleshoot.
Hope this helps
73
Gary

[N0SYA]

Find tc1001 on the main board and give it a few rotations with a tool while in lsb mode, see if that brings the lsb bfo back.

[KA1CDE]

Gary,

Thanks, I will check it out !

Pat