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Thread: FT-101E ; low power output--HELP!!!

  1. #1

    Default FT-101E ; low power output--HELP!!!

    Help!!!! This is a Yaesu FT-101E that only puts out about 20 watts on 10, 12, 20 meters, (yes, the 15 meter band has been
    replaced with the 12 meter band) and on the rest of the bands few .5 watts at most, also oscillates on 10 15 and 20 meters when trying to tune sometimes (while oscillating puts out about 40 to 50w, and usually it is the tubes full output power or close to it. so there must be something in the output tuning that I'm overlooking), Therefor I can never get to the neutralizing procedure (even though I have tried different positions on the neutralizing capacitor).

    I have replaced the high voltage caps for the 600 plate voltage supply, all the electrolytic caps in the entire radio, the two 6js6c and 12by7a driver (NOS), replaced C2 100pf neutralizing cap for a 10 pf (this mod should done when American made tubes are used; to compensate for the difference in inner electrode capacitance from the original Japan manufactured brands), have aligned and peaked out all the trimmer caps for all the bands from the crystal to the input of the 12by7a and to its output to the final tubes.

    On the oscilloscope I get a higher reading at the output of the 12by7a across all bands than I get from the final stage, for except 20 and 10 meters (20 to 30 W). I have cleaned all relays and swapped them out with good working ones, cleaned all the wafers on the band switch, mode switch and other switches. Took out the tank coil,cleaned it along with all the parts in the final section and assembled it with the same results. All the silver mica caps within the final stage check out close to their face value on my meter but not exact; as they have tolerances that might vary with temperature under operating conditions.

    I have swapped out all the boards with no results. If anyone has had a similar problem and found the solution PLEASE LET ME KNOW. All the high voltage levels check out OK, and the 6V and 12 volts as well. Perhaps it can be a cap in the driver and final stages that appears to be good, but under working conditions might not; making it very difficult to troubleshoot during TX, due to the high voltage levels in the final stages. I have replaced the coupling cap c13 (80 pf) between the 12BY7A and the 6js6 finals and c104 (80pf) at the very output right before RL-2; which appeared to have been a leaky cap.

    Please contact me at [email protected] if you or someone you know might be able to help. I've spent many days trying to figure this out and I really don't know what to do anymore for except start randomly start swapping out parts from another unit.
    Thank you for reading.
    Jose, W4LXE.

  2. #2

    Join Date
    Dec 2008
    Elgin, Illinois

    Default Re: FT-101E ; low power output--HELP!!!

    Hello Jose,

    Hmmm .... It appears like you've managed to modify your Yaesu FT-101E into a Basket Case of Problems/Failures. I have not read anywhere in your Posting that you have the required Tesr Equipment & Yaesu Service Manuals, Oh but you have mentioned something about having a Golden Dittle Stick and tightening down all of those loose Capacitors.

    Yaesu Service Manuals:

    Did you know that if a transmitter is Self Oscillating or Flying, you will never see Full RF Power Output because the transmitter is covering a multitude of Frequencies above and below the Carrier Frequency. It can be Plus & Minus 30 MHz .... a major headache trying to troubleshoot and locate the defective components! Till you solve the Transmotter's Self Oscillating, Flying or the Power Amplifier's Stage NOT Being Properly Neutralized, you're going to continue to Shotgun Analyze the Failure.

    Hint #1: NEVER ASSUME that NEW / NOS Cannot Be "Bad From Stock" Components!

    Hint #2: NEVER ASSUME that Silver Mica Capacitors Are GOOD Because 99% Of The Silver Mica Capacitors "FAIL" At Higher Voltage Levels!

    Hint #3: Poor and/or Cold Solder Connections On Vacuum Tube Finals CAN Cause Self Oscillation In the RF Driver & Final Power Amplifier Stages!

    Hint #4: In The 1970s & 1980s (Even Today) Amateur Radio Dealers ALWAYS Sold 6JS6C Matched Pairs Of Vacuum Tubes For The Yaesu Products & Big RF 1.5 KW Amplifiers (Using 3-500Zs) Because It Causes LESS Problems With Self Oscillation / Neutralization! The BEST Method For Testing Vacuum Tubes For Gain Emissions Is Either Have A Military Surplus Tube Tester Or Know Someone That Owns One.

    Hint #5: When Ceramic Bypass Capacitors Become Defective, They Normally SHORT And They Can Be Read With A DMM On The Lowest OHM Scale Indicating Between 10~40 Ohms And The Capacitor NEEDS Replacing!


  3. #3

    Default Re: FT-101E ; low power output--HELP!!!

    Hello Dan, thanks for the reply and the info. This unit was in really bad shape when it first landed in my hands. Let me start by saying that the 10 and 15 meter tabs were burned brittle right off the tank. Apparently this rig was used for CB back in its days. I bought 3 pairs of NOS final sets (all from different sellers)of which I have tested in a good working FT-101E and they seem to work OK; about 145W on 80 and 40 and ending with 100W on the top of 10. This has isolated the problem to the this rig itself. There is one thing that might help pin point the problem, and that is that when tuning on any band, even to get out that half watt to the 20 watts on 20 meters, the loading control always has to be maxed out all the way clockwise, as if something was off.
    Sorry about not mentioning the test equipment used. On my bench: Tektronics 2335 100Mhz oscilloscope, a HP 8924C service monitor, a bird 43 , an HP 3478A and a 8000A fluke bench multimeters, Kenwood VT-171 AC Voltmeter, a TENMA 72-6644 function generator/frequency counter , a MFJ-259B, and a BK Precision 820 capacitance meter.
    The only cap so far that was passing voltage (leaky) but did not appear as a short was C104 80pf; the the last in the RF output chain, right after the tank and before the tx/rx relay by the antenna jack. when out of the circuit and connected to a HV source, you can read the source voltage as if the cap was not there, a full bypass of voltage. well I guess I'll continue trying...
    Thank you for the help, keep me in mind if you get any bright ideas!! HI


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