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High Gid Current

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

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  1. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I'd put black tape over it so I didn't have to look at it.

    Plate current on a pair of 3-500Zs hardly matters, anyway.:p
     
  2. NE7X

    NE7X Ham Member QRZ Page

    Something is still not right….not fixed yet……

    Two different scenarios:

    1) With D107/R119 connected to HIGH side of R109
    SSB mode
    Keyed, no drive, Ig meter indicates zero, Plate meter Ip pegs full scale
    When I talk into microphone Ig meter varies with voice, between 0 -250 ma
    Full power output
    Stop talking, keyed, no drive, Ig meter reads zero.
    Plate meter still pegged, tubes running red cherry, until un-key.
    This tells me the tubes are conducting when there is no drive

    2) With D107/R119 connected to LOW side of R109
    SSB mode
    Keyed, no drive, Ig meter indicates 300ma, plate meter Ip reads 100ma
    When I talk into microphone Ig meter pegs full scale, Ip meter jumps to 300-350ma with voice peaks
    Full power output
    Stop talking, keyed, no drive, plate meter back to 100ma, Ig meter at 300ma
    Tubes running red cherry, until un-key.
    This tells me the tubes are conducting when there is no drive

    So depending upon what side I connect D107/R119 to R109, I one meter works and the other does not.
    Also both ways, the tubes are conducting with no drive.

    I checked and rechecked, the meter circuit is wired to the factory schematic. This is driving me nuts. Now I know why the other guy gave up and some me the amp !!! The amp is either haunted or has a curse!

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

    W1QJ Ham Member QRZ Page

    The meter switch, is it push botton? Could there be a short in the meter switch? Also, could D106 have gone again because something is still wrong? With full power drive you did not say what the output was so it could be possible depending on the health of the tubes and output that your readings on gris current are pretty correct when you have zero Ig in idle mode. When amp is in transmit and Ig is zero and goes to 250 300 at full output, that seems normal perhaps. It seems that either the Ip works and the Ig does not and vice versa. SO I wonder maybe the switch? I would not overlook it.
     
  4. NE7X

    NE7X Ham Member QRZ Page

    No matter which way I have everything wired, or which switch is engaged, the tubes are conducing. The tubes should not conduct until drive is applied. Keyed, no drive, the tubes are turning red.

    Yes I did check D106 again, D107 and D105. Lifted one end this time. :)

    I’m thinking maybe the tubes are going into oscillation?

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

    W1QJ Ham Member QRZ Page

    No, I don't think so. The tubes WILL turn red if you have the amp keyed with no drive! Don't forget, when the amp is keyed with no drive you still have idle current about 90 to 100ma per tube depending on HV and bias V. But remember if the tubes have a total of say 200ma in idle, that is HV*(idle curret)= 3500v*.2A= 700watts/2=350W per tube. If the amp is in idle for a short while they surely will start to go red. SO that is normal, the trouble begins if the tubes turn red when the amp is NOT keyed. You are fine, it seems you only have this metering problem. I am wondering about that push button switch.
     
  6. W1QJ

    W1QJ Ham Member QRZ Page

    OMG, You are Tom Boza! Tom, A few years ago you had lots of info about changing the input coils on the SB-200. I have sent loads of guys looking for that on the interent. It seems to have dissappeared. Now I see you have this website, why don't you put a link to that information on your site? Many people are asking for it still! I book marked it a few years ago and indeed it dissappeared. That was a great piece of work and I am sorry to see it go. You should bring it back for those looking for it. I am starting to take a personal interest in this problem with the Henry amp. It seems as though depending on how you wire things, you either get a proper Ip reading or a proper Ig reading but not both correct at the same time. This is why I am suspicious of that push button switch. Can you check the switch out? At this point I would not leave a stone unturned. Interesting fact... A few years back my cousin bought 2 Collins 30S1 amplifiers from a guy down south. One was a Ham version and one was a Military version. The Ham unit worked fine and the military one had a problem that the original ower could not fix, then my cousin bought it figuring he could fix it and make a nice profit on it. Well he worked on it longer than you have been working on this Henry. Like the first owner gave up so did my cousin. He then called on me to have a look at it. I drove to Penna. to stay the weekend with him so I thought I would have loads of time to see if i could fix it. The 2 of us worked for hours on the problem. I checked and rechecked and triple checked and quadruple checked the area in which the problem had t be. Every time I looked I saw the same thing and so did he. When I went back for the 5th check of the same area it was as plain as the nose on my face. This amp had been surgically de-commissioned. Without a trace of eany distrubance (you can usually tell if someone made changes to a commercial piece of equipment) of the original wiring the wiring had deliberately been miswired to make the amp not work. I found the problem on the 5th look at the same small area in question. The problem was to look at that area of the amp you had to lay on your back and look up under the RF deck with a flash light. I found the deliberate wiring change, put it back the right way and the amp came alive. The same thing happened to me years later with a Military version of a 30L1. It was a **MINT** looking unit I bought from an elderly gent whom I saw many times a local hamfests. He said he just had it on the air last week (at the time). I took it home thinking I can plug it in and use it. I did. When I went to key it into transmit the relay would not engage. SO I opened it up to troubleshoot it. I could ground the relay at the relay and put it into transmit but not from the rear panel phono jack. I thought a bad wire? No, so here we go again, I had to remove a sub chassis to get to the back of the phono connector. You know. military units have a red covering on all solder joints. SO when I got to the back of the jack, all looked fine, all solder joints had the red markings and nothing looked molested. Fortunately I know my resistor color code and I spotted the problem right away after a glance at the schematic. Again, we had a surgically de-commissioned unit here. SOmeone, with percision work had removed the series 39 ohm resistor on the jack and replaced it with a 4Kohm. All the red markings were there. I changed it to a 39 ohm resistor and the amp came alive. So, what does this all mean? it seems that military and govenment equipment is decommissioned in this way. Why? I don't know, but you need to be really sharp to find out just what they did. Now, you got to know that the old man was not telling the truth about using that amp just last week. I'll bet he tried to fix it and could not find the problem. Eventually this amp will get to working right. Keep digging Tom. Oh, check that push button switch eh?
     
  7. K2XT

    K2XT Premium Subscriber QRZ Page

    I have run across that also Lou. I got a 30L1 1.5 years ago in an estate. It was found in the basement workshop. I don't remember the details but it was in the wiring of the relay and I said there is no way whatsoever that amp ever could work that way. It was something like the input was wired to the output and the amp was never in the circuit. And yes, the little red paint was there too. Fixed it, installed new caps and it worked perfectly. I asked the owner who was in a nursing home at the time why he was working on his 30L1 and he couldn't remember. Now you know there is no way that amp ever left a Collins factory that way ! But I think I know why that happened. If an amp is dead and has some time on it maybe the military would decide to not bother fixing it and put it in the surplus pile and the unscrupulous technician could buy it for scrap prices. I saw this happen once at AT&T. A lab was being cleaned out and stuff could be purchased by employees, for fair prices, say $100 for a printer. I later found out a guy would do things like remove a cover off of a printer, store it in his desk. Then when they put prices on the printers they marked the one that had been tampered with way down, to maybe "$10 As-Is." He bought them, and later took the cover home to re-unite it with the printer. Clever guy. I wonder if he is out of jail yet !
     
  8. W8JI

    W8JI Ham Member QRZ Page

    Tom,

    If you have an accurate schematic and description including parts values it will be pretty fast to find the problem. After all, there are probably dozens or hundreds of that particular model that work fine.

    Wipe the idea of an oscillation out of your mind. It isn't anything that mysterious or esoteric. It just sounds like you have a metering circuit problem.

    Usually when someone is stumped like you are, it is because the schematic is wrong or they are just overlooking something.

    73 Tom
     
  9. NE7X

    NE7X Ham Member QRZ Page

    Thanks for everyone being so patience and helping me troubleshoot this issue. Fixing someone else “basket case” can be changeling and hard, all bets are off. No telling what the other guy did.

    Here is where I am today:

    Amplifier BIAS and meter circuits are 100% wired to the factory schematic (see link to manual, pages 22 & 24)
    Per schematic. R119/D107 wired to high side of R109
    I did find one shorted diode (replaced)
    As requested, I did ohm out the meter pushbutton switch and it appears to check OK. However its wired in circuit so there may be a false reading.
    The amp does put out full RF
    When I power on, no key, the Ig meter moves negative (backwards) -10ma and Ip meter reads +100ma. Both meters move slightly off zero.
    The tubes do not appear to be turning red when not keyed.
    When I key (SSB no drive) Ig meter returns to zero and Ip meter pegs full scale.
    When I speak into the microphone, Ig varies between zero and 250ma, Ip meter is pegged full scale. Full RF power output.
    When I key (SSB no drive) after about 30 seconds, the tubes start turning red.
    I also removed F101 to take Ip meter out of circuit, same issues, just Ip meter has no movement.

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

    When I wire R119/D107 on the low side of R109 (which is the way it was wired when I acquired the amp), Ip meter works perfect, does not pin and I get nice dip (400-600ma) when tuning and I do not get the -10ma reading on Ig meter when not keyed. However when I key no drive, Ig meter reads 300ma, then when I speak into the microphone the Ig meter pegs full scale. The tubes still are turning red when keyed, no drive.

    My thoughts:
    When I wire R119/D107 on the low side of R109, it appears both Ig and Ip meters are giving me correct readings. The 300ma Ig when keyed, no drive, I believe is a true reading and should not be there. If I subtract the 300ma from the total, Ig would be correct. Whatever is causing this 300ma when keyed, no drive, is also causing the tubes to turn red (conduct).

    What could be causing 300ma Ig when keyed, no drive?
    When keyed no drive, should the tubes be turning red?

    My assumption, the tubes are turning red, keyed no drive, because of this 300ma Ig.

    Currently everything wired to the factory manual. I have been informed by others, Henry manuals and schematics have been known to have errors. So since I have the amplifier wired to the schematic, this “could” be the root cause of my issue. This could also explain why the meter circuit wiring did not match the schematic before I re-wired it. Henry Radio no longer supports these amplifiers, so I am on my own.

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

    W1QJ Ham Member QRZ Page

    FWIW....I think when you get the proper Ip reading and the 300ma grid meter reading is when you have everything wired correctly. I think you may have a bad tube. Do you have another set of tubes you can try? It seems either way you hook it up you have either a negative reading or a 300ma reading. Neither reading is good in the idle mode. I thinking a bad tube or tubes. Also, THE TUBES WILL TURN RED IN IDLE MODE WITH NO DRIVE, BOTH TUBES ARE DISSIPATING 350 WATTS EACH IN IDLE MODE SO THEY WILL TURN RED WITH NO DRIVE.
     
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