ad: elecraft

3-500Z Home Brew problem almost solved and I need ideas.

Discussion in 'Amateur Radio Amplifiers' started by KM6CND, Jul 21, 2018.

ad: L-HROutlet
ad: l-rl
ad: MessiPaoloni-1
ad: L-MFJ
ad: Subscribe
ad: Left-2
ad: K5AB-Elect-1
ad: Left-3
  1. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    ^I agree.

    With a good dummy load, I'd try the amp out on every band it can work. If it works properly on one band and not another one, could reveal a problem with the bandswitch or any number of things.
     
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Forget the antenna, use the dummy load.
     
  3. KM6CND

    KM6CND Ham Member QRZ Page

    Thank You, Silly me can't see this on the drawing.
     
  4. KM6CND

    KM6CND Ham Member QRZ Page

    Thanks again, I've been too careful these days.
     
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    You can't be more careful than using a dummy load! That's about as careful as it gets.:)
     
  6. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    It's not you! :p
    The point I was trying to make is that if the OP gets 800 watts PEP on SSB, this doesn't necessarily mean that he can hold 400 watts carrier for any length of time without burning something... especially if the meters are funky, he's new to amps and subsequently can't tune or load the beast.

    IMO, the easiest way to get this amp in shape would be to make an as-built schematic. In the process, you would learn how it's wired up and go over every connection and examine every component. If it were mine, I would want to peek under the tube socket to see how the grids are grounded, check the shunts and mulitpliers to figure out what the meters are trying to tell me, etc.

    Making a scheme isn't as bad as it sounds. Maybe 2 or 3 evenings with a pad, pencil, and a DVM. It could certainly save a lot of time and money. It would make it easier for the jolly lads here to help out!
     
    Last edited: Jul 24, 2018
    KM6CND likes this.
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Amplifiers like this without fancy digital control circuits (as many "new" commercial amplifiers have) are so simple it's barely worth having a schematic.:)

    I like simple amps. The only "troublesome" commercial amp I've ever owned was the Alpha 87A. Solid as a rock RF-wise; every single problem related to the very complex control circuits, which unfortunately shared the same chassis with the power supply and RF components.
     
  8. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Oh, I agree with you completely! There is something going on with this amp. I figure that if km6cnd decides that it’s worth drawing it out, we’ll find out why it’s not working and he’ll fix it, have a nice amp going, and learn a bit more about them.

    Looking at a picture of the insides of this amp, the three meters are labeled hv, Ip, and Ig. The numbers he quotes don’t ring a bell with me... 5 minutes with a power supply, alligator clips, and a DVM would fix that, and he wouldn’t be flying blindly.

    I like simple too!
     
    Last edited: Jul 24, 2018
  9. KM6CND

    KM6CND Ham Member QRZ Page

    Well folks, I stopped at HRO and picked up the MFJ dummy load / PWR SWR meter. It's really sweet, can mess around with the dummy and flip a switch to go back to the antenna.

    I attached the dummy, switched to 80M on the radio and amp. The dials were nulled, CW mode and 5 watts. I key up and begin to turn the top dial and the cross needles started to move :) yea, I say as I continue to tune up... and then both needles collapsed.

    This amp is so simple in it's construction, it really boggles the mind.
     
  10. N5MEP

    N5MEP Ham Member QRZ Page

    Do you still have a plate voltage indication when the output goes away?
     

Share This Page