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Yaesu ft 101E no ALC indication on SSB
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Hello. my first post for a long while so hoping somerone can help me. |
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Hi Peter,
The D2 referred to is the D2 in the ALC circuitry which is located on tag strips in the chassis just outside the PA/Driver compartment - I think this is what you referred to as the D2 in the grid circuitry of V2? However, I don't think that is your problem. The page you referred to in the service manual assumes (although it doesn't say so) that the meter is going full scale to start with and "no ALC indication" means that there is no deflection back from full scale. So, your problem would seem to be with the metering circuit would be my guess. As a start, try cleaning the contacts on the PO/IC/ALC meter switch. The next thing to try would be clean the contacts on the main chassis mounted relay, RL1. The ALC meter signal passes through both of these and if the radio has been sat for a number of years then these contacts may need cleaning. Other things that might stop the meter from being able to be set to full scale on ALC would be a dead Q6 or open circuit/ dirty VR2 on the processor board. The schematic of the processor board later in the service manual shows what voltages you should be seeing on Q6. If you are seeing the correct voltages on Q6 then the only thing stopping the meter from going full scale is VR2 and the switch/relay contacts between the processor board and the meter. You should still be able to check that you get SSB output by tuning the radio and set the mic gain to, say, 3, and then key the radio and check for speech peaks with the radio's meter set to Ic. You should also be able to see RF output on an external power meter. Hopefully you can get the ALC working at some point. Good luck! Peter G4DJB |
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Hi Peter and many thanks for your comprehensive reply!
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I will certainly try your suggestions for the metering fault. However I can get no power out at all using a dummy load (on a separate power/swr meter) with the mic gain turned up to max from zero and whistling into the mic. If it was just a metering problem could I expect to see power out on a separate meter? Maybe the metering is OK and faithfully reporting that there is no power out.? But I stilll don't get any meter movement from zero when switch to ALC. I'm confused! I did think of that relay and removed it for cleaning but couldn't work out how to remove the plastic case! The meter switch works perfectly for the other positions so I'm assuming its OK for the ALC position - but maybe not! I will certainly measure the voltages on Q6 as you suggest. If you're willing will email the results for further comment? Kind regards Peter G0LQU Peter Roberts G4DJB wrote: Hi Peter, |
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Hi Peter,
Okay, so no SSB out even though you have AM & Tune/CW. It still could be a fault with the ALC or dirty relay. You could certainly check the voltages around D2 in the ALC circuit. If C17 has gone leaky (a common fault) then there could be a large negative voltage on the ALC line to the processor board which would shut down the SSB output (ALC does not operate on CW,? AM or TUNE). As for the relay, there is a small cross-head screw on the top of the relay's plastic cover that fixes the plastic case to the metal bracket that holds the relay coil. Remove that screw and it should then be possible to remove the relay's plastic cover. Probably best to start with voltage checks on the processor board around Q6 and the ALC input pin. One other thing you could try is to take/make a short jumper lead and temporarily connect the input to the output on the processor board and see if SSB on Tx works like that. By all means you could email results as I don't often check this group. 73, Peter G4DJB |
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Hi Peter and many thanks for the additional advice. Actually I have decided to have a break from that radio - if anything there are other things not working - when I try to adjust the standing current Ic in "Tune" mode it suddenly jumps to full scale, the pilot light dims, and there is a "crack" sound fro the area of the PA.If I may I'll contact you later when I feel like pursuing this!
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Kind regards Peter G0LQU Peter Roberts G4DJB wrote: Hi Peter, |
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Okay Peter - that one sounds very much like a leaky C13. That capacitor couples the anode of the driver to the grids of the PA and is another of those known weak spots!
I sounds as if your radio does need a fair bit of TLC and I would recommend replacing C11, C13, C131 and C17 - all of these are chassis mounted items on the underside of the radio in the driver/PA area. Whilst there, the driver & PA areas should also be checked to see if any of the resistors there have gone out of tolerance and replace any that have. I have an early 101 and a late 101E and have seen all of the above capacitors go leaky on one or both radios, plus a number of the resistors in the driver/PA area go out of tolerance. 73, Peter G4DJB |
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Thanks again Peter. I'll look into those items. (when I next get the inclination!)
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Peter G0LQU Peter Roberts G4DJB wrote: Okay Peter - that one sounds very much like a leaky C13. That capacitor couples the anode of the driver to the grids of the PA and is another of those known weak spots! |
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