Help with my first amplifier

Discussion in 'Amateur Radio Amplifiers' started by W5KV, Oct 14, 2018.

ad: L-HROutlet
ad: l-rl
ad: abrind-2
ad: Subscribe
ad: L-MFJ
ad: Left-3
ad: Left-2
  1. W5KV

    W5KV Ham Member QRZ Page

    Interesting. Thanks for the tip. I was trying not to 'push my luck' so to speak on the 110v circuit. My electrical runs in this house are fairly short though. No dimming of the lights or interference with anything, but I have yet to transmit on the antenna outdoors. Fingers crossed I don't cause interference. Maybe I should start using the name 'Dude' when i'm on the radio ;)
  2. NQ1B

    NQ1B Ham Member QRZ Page

    Yes, I agree with others here who said you should convert to 240 volts as soon as you can.
    W5KV likes this.
  3. WA7PRC

    WA7PRC Ham Member QRZ Page

    Without doing anything, the SLOW T/R relay in the SB-220 will toggle into TX mode AFTER your TS-590S produces RF output. This is known as "hot switching" (you don't want that). You should either not use VOX (fone) or Semi Break-in (Morse), or correct the problem. The BEST plan is to change the SB-220's 3PDT relay to FAST vacuum relays, or add delay in the rig. Page 53 in the TS-590S Instruction Manual "LINEAR AMPLIFIER CONTROL" tells you how to add 25ms delay.

    Aside from being slow, the OE relay has contacts that become oxidized (and then intermittent). Jim W7RY offers a PCB (link) that drives more reliable vacuum/reed relays that are FAST and will never oxidize. You also get electronically regulated and switched bias.

    If you look at the 3-500Z datasheet (link) closely, 3-500Zs like HV above 3000V (better IMD3). In CW/TUNE, the voltage is below 3KV. Some folks hard-wire the amplifier in the SSB mode, and use the CW/TUNE switch to enable/disable T/R control.
    W5KV likes this.
  4. W1QJ

    W1QJ Ham Member QRZ Page

    I hate to continue to repeat myself but I guess the word is not "out there" as well as the voodoo magic science is. The CW/SSB switches in any of the many vintage amps like the SB-220 are simply passe' at this point in time. They were only put there for legality reasons and nothing else. Since the power regulation changed AFTER these amps were minted there is no longer a need to switch the HV from one lower setting to a higher as noted by CW TUNE/SSB. I don't want to go into the specific reason for it but suffice to say there is nothing to gain by using a lower plate voltage on any mode. Use the higher voltage at all times and adjust your drive level to keep the output in the save zone for the mode being used like would be the case of any new amplifier you would buy today. In the case of these amps that do have these switches, the switch can be abandoned for the original purpose, the power supply hard wired for the higher plate voltage and the switch re-purposed for a more useful task. Higher idle current is more desirable for SSB operation and for CW the idle current can be reduced. The switch could be re-purposed to change the operating bias between SSB and CW if desired. This would be unnecessary if you are NOT a CW op, in which case the switch could now be used as a bypass or stand y switch. If you are a CW op and want to lower the idle current then use it as an operating bias switch.

    As Bryan pointed out above, W7RY makes a wonderful QSK board that works very well in the SB-220. Be advised, if you are not savvy on just how the amp works you may get over your head with trying to add the QSK mod. The instructions provided assume certain knowledge you may not have. I have had a few discussions already with hams needing assistance with this mod. On one occasion I resorted to video conferencing to guide one ham through the whole modification. That was fun.
    W5KV and KK4RSV like this.
  5. WA7PRC

    WA7PRC Ham Member QRZ Page

    IMO the limiting factor is the OE HV transformer. At about 600VA continuous, it's just not capable of enough current to support high power + high duty cycle (for very long).
    That's surprising. The documentation Jim @W7RY sent me in email is very good.

    IMO, Jim also needs to stop using the "QSK" term. At first, hams think it's useful only for Morse (it's not). While it's fast enough for full break-in Morse, the relays will quickly reach the 2 million operation specification. The big benefit is no longer "hot switching" the input, and no longer oxidized (and intermittent) relay contacts.
    W5KV likes this.
  6. W7RY

    W7RY Ham Member QRZ Page

    Jim W7RY
  7. W5KV

    W5KV Ham Member QRZ Page

    Much to learn about amps this young one has.

    Thank you all for the input. Printing this off & using it to refer to. Thank you for your time in the explanations, I truly appreciate it!

    WA7PRC likes this.
  8. N0OHL

    N0OHL Ham Member QRZ Page

    Last edited: Nov 10, 2019
  9. N0OHL

    N0OHL Ham Member QRZ Page

    W1QJ says in an earlier post --" Remove the resistor on the blocking cap to the cathode of the tube, go right from coax thru cap, no resistor. "

    I am not sure where in the circuit this is at ??? I too am cleaning up an old SB-220 and the suggestions in this post seem very appropriate.

    Thanks for any help -- on this "Blocking Capacitor"
  10. W9WQA

    W9WQA Ham Member QRZ Page

    working now,great. do nothing in a hurry. i would take readings and dont change tuning. then if you do change some parts do one at a time and repeat the initial readings in between.
    if you take all the advice you got all at once and it dont work right you wont have any idea which "improvement" caused the failure. ask me how i know... no rush.
    N0OHL likes this.

Share This Page