High Gid Current

Discussion in 'Amateur Radio Amplifiers' started by NE7X, Jun 5, 2011.

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  1. NE7X

    NE7X Ham Member QRZ Page

    Tom W8JI wrote:
    1.) Tom does NOT have a zener problem unless he wired it like Henry shows. Henry drew the zener backwards.

    Yes I do have the zener wired the way the schematic shows. Cathode goes to meter circuit and Anode goes to filament xformer center-tap and tube filaments.

    Is it wired backwards?

    73s, Thomas NE7X…
    http://ne7x.com
     
  2. W1QJ

    W1QJ Ham Member QRZ Page

    Tom JI says the schematic shows it backwards, if that is true then you must turn it around.
     
  3. NE7X

    NE7X Ham Member QRZ Page

    I reversed BIAS D1 zener connections (opposite to schematic), cathode to filaments and anode to meters.
    When I powered on after about 3 seconds I heard a “tink” tinny sound, no smoke. SSB mode, I keyed, no drive and the Ig meter read 50ma and the Ip meter read 100ma. I un-keyed and powered off the amp. These reading look much better. However 50ma Ig still should be zero.

    My first though was the “tink” sound maybe the zener blew. It checks good, however I found D105 (100v zener) in the HV supply dead shorted.

    Any idea why D105 shorted? Is this because I have the meter circuit wired on the low side of R109 or is there something else going on in the HV supply? Looks like D105 goes to the ALC circuit in the amp. I do not have ALC connected to my workbench transceiver. What would cause D105 to blow?

    73s, Thomas NE7X…
    http://ne7x.com
     
  4. K9FV

    K9FV Ham Member QRZ Page

    Awwww Please Tom - don't go. We NEED your expertise around here. You and several of the others carry the technical load for the group.

    73 de Ken H>
     
  5. W8JI

    W8JI Ham Member QRZ Page

    OK, you fixed the error in the Zener. That was Henry's mistake in the drawing. Cathode should go to the relay and filament CT. Anode to F1. Opposite what they show.

    You still have a meter problem. I'd bet D105 has been bad a while. I've only worked on two or three of them, but I recalled D105 is a goofy system that stresses parts. It unequalizes the capacitor voltages. I do not think it is a good design to stick D105 where it is. That is why I told you to measure C111-112 junction to ground for resistance. :) My suggestion is, if you do not use ALC (you probably don't) just disconnect R113 from C112 and R108.

    Nothing you might have done would make D105 pop, unless you shorted R113.
    Did you do all of this, and what are the results?

    4.) Measuring from filament pins to chassis and zener to chassis with RF deck unplugged should be open.

    5.) Measuring from junction of R117 and 118 to F101 should be 0.2 ohms.

    6.) Measuring from junction of R117 and 118 to positive of plate meter should be 0 ohms.

    7.) Measuring from chassis to F101 should be .4 ohms, RF deck plugged and unplugged.

    8.) Measuring from the positive end of C112 to chassis should be high resistance with slow charge to bleeder value. (never mind this, it was to check D106 and you said it is bad. Disconnect R113 in all further tests. It is a goofy circuit anyway.)

    9.) Measuring negative of grid meter to chassis should be zero ohms.


    73 Tom
     
  6. NE7X

    NE7X Ham Member QRZ Page

    Update

    I reversed/rewired BIAS zener D1 so the cathode connects to filaments and anode connects to meters. (Per W8JI the factory schematic is wrong). However now when I power on the amp (not keyed) D105 (100V zener in the HV supply) blows dead short

    I just happen to have a 100V 5 watt zeners in my junk box. I replaced the shorted zener, power on the amp and “POP” the replacement blew. So before I replace it again, I need to identify why.

    Here is the link to the schematic.
    http://ne7x.com/henry/Henry-2K-classic-manual.pdf

    Any suggestions what to check?

    73s, Thomas NE7X…
    http://ne7x.com
     
  7. NE7X

    NE7X Ham Member QRZ Page

    W8JI
    QRX, let me make the measurements as you suggested.
    I will post the results here within the next hour.
    Thomas NE7X...
     
  8. W1QJ

    W1QJ Ham Member QRZ Page

    Everybody, the schematic I am looking at that NE7X provided seems to be yet wrong again! The way I see it the antenna relay as shown would be in the transmiting position when the amp would be off and with the relay energized in transmit the relay would be in the standby position. Look at it. That would make the the circuit backwards for the self bias resistor that would notmally be shorted out in transmit to be in circuit on transmit. If someone would wire the relay as shown it would be just the opposite as it should be. Look at it and see if you agree, or am I crazy?
     
  9. K9ASE

    K9ASE XML Subscriber QRZ Page

    I thought it was just me. but I'm just watching this thread because it goes along with the studying for Extra
     
  10. NE7X

    NE7X Ham Member QRZ Page

    W1QJ, you are correct, TR schamatic is wrong

    W8JI, The following measurements were taken using an analog VOM meter in both polarity directions.

    4.) Measuring from filament pins to chassis and zener to chassis with RF deck unplugged should be open.

    Correct, all show open to chassis ground.

    5.) Measuring from junction of R117 and R118 to F101 should be 0.2 ohms.

    Correct, .2 ohms

    6.) Measuring from junction of R117 and R118 to positive of plate meter should be 0 ohms.

    Correct, 0 ohms

    7.) Measuring from chassis to F101 should be .4 ohms, RF deck plugged and unplugged.

    Correct, .4 ohms (plugged and un-plugged)

    8.) Measuring from the positive end of C112 to chassis should be high resistance with slow charge to bleeder value. (never mind this, it was to check D106 and you said it is bad. Disconnect R113 in all further tests. It is a goofy circuit anyway.)

    I removed D105 (since it was shorted) and R113. These two components are no longer in the circuit.

    9.) Measuring negative of grid meter to chassis should be zero ohms.

    Correct, zero ohms.


    Comments:

    With D105 and R113 removed, I tested the amp. When keyed, no drive, Ip = 100ma and Ig = 50ma (was 300ma before). The Ip of 100ma matches my 2K-4 and 3K-A. Also the tubes now when keyed no drive, DO NOT turn hot red like before, they now have a very light soft rose pink color just like the 2K-4 and 3K-A. So by reversing D1 bias zener it appears to have resolved 99% of the issues. I tested the amp and it loads/tunes perfect, full KW out with about 90 watts drive. Only issue, the Ig meter still pegs when driving it with more than 30 watts.

    So at this point I agree, there is still something not correct in the Ig metering circuit. Since the schematic was incorrect for D1 and TR, there is a good change the metering wiring is also incorrect. It’s really tuff trying to fix electronics when following schematics which have wiring errors.

    I have the metering circuit wired 99% to the schematic, the 1% difference is where I have tied to R109. Currently I have the metering circuit connected to the low side of R109. As a test, I connected it back to the high side and the Ip meter pegs and the Ig meter goes backwards. So I believe the low side is the correct way.

    So assuming the amp is actually now working and the meter circuit is causing the Ig meter to peg (Ip meter circuit is working OK), what wiring changes can we make to the Ig meter circuit to keep it from pegging? Maybe change R117 or R118 values? Could the schematic have these two reversed? Maybe R117 is .2 ohms and R118 is 30 ohms? Maybe different R values or a different wiring configuration?

    One final comment, I really appreciate everyone here on this forum helping me troubleshoot this amplifier. Without everyone’s collaborated thoughts and positive motivation, I may have given up like the guy who did which I purchased this basket case from !!! Thanks to everyone who helped, I will have a very sweet and cosmetically good looking Henry 2K-Classic to enjoy.

    Thank You !!!

    73s, Thomas NE7X…
    http://ne7x.com
     
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