ad: w5yi

Yaesu FL-50 transmitter accessory plug

Discussion in '"Boat Anchor" & Classic Equipment' started by KI7WQH, Feb 27, 2021.

ad: L-HROutlet
ad: l-rl
ad: Left-3
ad: Subscribe
ad: Left-2
ad: L-MFJ
ad: abrind-2
  1. KI7WQH

    KI7WQH Ham Member QRZ Page

    Hey guys,

    So I’m taking a break from the nightmare 101 and trying to get a FR/FL-50 pair going in the meantime. I have the FR running great and I’ve hit a snag on the FL. Just like the ft-101, the FL-50 has an accessory plug in the back (it’s 8 pin though, instead of 11) and in the manual it says it won’t give power to the finals unless it’s in place. I don’t have the plug, but figure it probably just needs to have two of the pins shorted like on the 101.

    I have the schematic, but I don’t feel confident enough to just short some pins until someone who knows what they are doing has a look. I would really appreciate it if someone has a spare moment and doesn’t mind having a look. The octal plug is on the bottom right. C2875A2D-D7AD-4EB5-BF08-338D59565882.jpeg
     
  2. SM0AOM

    SM0AOM Ham Member QRZ Page

    The plug on the FL-50 is of the 11-pin relay style, at least on
    the schematic shown in manual .

    The plug pinout is as follows:

    1. PA tube filament in
    2. 6.3 V AC filament out
    3. 350 V plate out
    4. 175 V plate out
    5. 175 V plate out
    6. -80 V bias out
    7. Phone/CW switch, grounded on CW
    8. Chassis ground
    9. NO aux contact on antenna relay
    10. NC aux contact on antenna relay
    11. 12.6 V AC filament out

    Using the 11-pin socket, then short pins 2 and 1.

    If there instead is an octal socket there which has been put in by a "third party", then all bets are off.

    I would recommend the following approach:

    1. Using a continuity tester, find the pin which goes to chassis ground
    2. Measure all voltages, AC and DC, on the other pins with respect to this pin
    3. Pull out the PA tube and check continuity between the ungrounded filament pin and one pin of the socket
    4. Make a shorting plug between the pin with 6.3 V and the PA filament pin

    73/
    Karl-Arne
    SM0AOM
     
  3. G3YRO

    G3YRO Ham Member QRZ Page

    Yes it normally has the same socket as on the FT101, and wired in the same way.

    Back in the day I put a VFO inside an FL50B . . . and converted it to 160m !

    By the way, I also had a small external Transformer that put 1kV on the PA, which then ran 150W input/75 watts output !

    Roger G3YRO
     
    KI7WQH likes this.
  4. SM0AOM

    SM0AOM Ham Member QRZ Page

    I now recall that it is 50 years ago since I saw an FL-50 "in the flesh".

    It was at an exhibit made by the Swedish importer (SM5KG [SK]) of the Yaesu/Sommerkamp equipment at a district meeting, and it carried a 20% discount from its list price.

    But, alas, no takers.

    upload_2021-2-27_13-28-18.png
    It appears that the FR-50 was somewhat easier to sell.

    73/
    Karl-Arne
    SM0AOM
     
    KI7WQH likes this.
  5. KI7WQH

    KI7WQH Ham Member QRZ Page

    Thanks for the replies guys, I was hoping you wouldn’t say pins 1 and 2! I have an earlier model of the FL-50 (no B) and pins 1 and 2 have nothing connected. Is there maybe a pin on the tube I can trace back to the plug? C63F1DD7-6775-4B90-AFE7-43DF0CECF6DA.jpeg 92C38129-B75B-4BE3-ACB9-4EC43A2B1265.jpeg
     
  6. G3YRO

    G3YRO Ham Member QRZ Page

    [/quote]Is there maybe a pin on the tube I can trace back to the plug?[/quote]
    Yes . . . you will see a thick wire going to the Heater on the 6JS6 valve base . . . follow that back to the socket on the back.

    However . . . as that socket has been replaced, are you sure the Heater voltage isn't already connected directly to the Valve base?

    (the only reason Yaesu made the PA heaters go through that rear socket on most of their rigs was to make it easy for people to use Transverters for VHF/UHF)

    Roger G3YRO
     
  7. KI7WQH

    KI7WQH Ham Member QRZ Page

    Is there maybe a pin on the tube I can trace back to the plug?[/quote]
    Yes . . . you will see a thick wire going to the Heater on the 6JS6 valve base . . . follow that back to the socket on the back.

    However . . . as that socket has been replaced, are you sure the Heater voltage isn't already connected directly to the Valve base?

    (the only reason Yaesu made the PA heaters go through that rear socket on most of their rigs was to make it easy for people to use Transverters for VHF/UHF)

    Roger G3YRO
    [/QUOTE]

    I got 2 of these in Japan from different people and I think they came with this plug out there or they changed them out because both have this 8 pin plug. The Japanese manual I just found for the FL also shows 8 pins, but I can’t read Japanese so maybe it didn’t need the plug? The other FL was heavily modified so I figured I’d get this one working first.

    Looks like the big blue wire on the tube goes right to 12volts on the transformer. I don’t know what it could be though because I hear the relay going (maybe dirty?), the IC meter moves a tiny bit up, and the ON AIR light comes on. I’ve tried using the VFO on the FR and with a crystal and no dice. Not even a blip on my yo-150 dummy load in 6 watt mode or on my station monitor. I tried AM and SSB with mic gain turned all the way up, zero output.

    I wonder if something else needs to be shorted on this plug, I have a FL-50b and they are somewhat different.
    B153E714-74C0-4C1A-A731-2DF7E5F9E288.jpeg
     
    Last edited: Feb 27, 2021
  8. SM0AOM

    SM0AOM Ham Member QRZ Page

    If the socket is wired as in the last schematic, no shorting plug is needed.

    I believe you are in for some serious trouble-shooting.

    First, make sure that all operating voltages are there, and that
    the filament voltages are close to nominal.

    As the PA tube and the rest of the filaments appear to be
    series-connected, a problem or bad connection somewhere in the string may show up as too high or too low filament voltage
    at one or more tubes.

    I would suggest "wiggling" all tubes in their socket just to make sure that the filament voltages are OK. Low voltages look almost identical to "weak" tubes.

    73/
    Karl-Arne
    SM0AOM
     
  9. KI7WQH

    KI7WQH Ham Member QRZ Page

    Well I just ran every tube in the FL through the tube tester and they all came up 100+ and I also made an octal cable out of a broken tube I had had to make sure it was all connected to the FR-50 receiver as per the manual instead of just having the VFO hooked up in case that mattered. Same no transmit. For kicks I hooked up the heavily modified FL and also had no transmit, but that might not mean anything. However it does possibly mean I'm missing a step - can't imagine what it would be though since I hear the relay - bad relays in both maybe? I really hope not because they are hard to get to and soldered in and not just in a socket.

    Open to suggestions. I can't believe how nice the little receiver actually sounds, and even though I think the japanese models might only put out 10 watts, maybe once this thing is working Roger can tell me more about his modified 75 watter.
     
  10. SM0AOM

    SM0AOM Ham Member QRZ Page

    Generally speaking, all trouble-shooting activities and especially "boat-anchor", use the divide-and-conquer method.

    A suggested progression is as follows, assuming that some test gear is available:
    1. Check obvious things, such as burned resistors, blown fuses or missing/severely out of range voltages. Use a tube data manual to get starting points
    2. Since the relay seems to be working, check that the aux contact makes reliable continuity when in transmit mode
    3. In CW mode, check that a carrier oscillator signal with the right frequency that changes with the CARRIER control setting reaches the grid of the transmitter IF stage and that it also shows up in the plate circuit
    4. Listen for the conversion oscillator using a general coverage receiver.
      Or check for its presence using an RF voltmeter, oscilloscope or frequency counter
    5. When the IF signal is present, check that the conversion oscillator is present at the mixer grid, and that it can be peaked by the GRID control
    6. Check for the mixing product in the mixer plate circuit and check that it can be peaked by the GRID control
    7. Check for the mixing product in the driver plate circuit and check that it can be peaked by the GRID control
    8. Check for the mixing product at the PA grid circuit and check that it can be peaked by the GRID control
    9. Check for the correct idling current in the PA stage, and that the current increases with peaking the GRID control
    10. Check for RF in the PA plate circuit and check that it may be peaked by the PA TUNE control
    11. Using a dummy load with RF indicator, check that there is RF output that can be peaked using the TUNE/LOAD controls
    12. Repeat 4 to 11 for each band
    Should any of the steps fail, the circuit has to be examined with respect to first DC operating points, and then for RF of the right frequencies and levels.

    A "completely dead" transmitter may be hard to find the proper path of attack, but starting at the input end and working towards the PA stage usually gives the fastest results.

    The circuit of the VXO in the second schematic looks very suspicious.
    As drawn, it would self-destruct as soon as the switch is placed in the "EXT VFO" position.

    upload_2021-2-27_21-32-40.png

    There should not be any connection between the right-hand switch section and the 6U8 pentode section plate.

    73/
    Karl-Arne
    SM0AOM
     
    Last edited: Feb 27, 2021
    N2EY and KI7WQH like this.

Share This Page