WHAT??? ANOTHER SB-220????!!!!!!!!!!!!!

Discussion in 'Amateur Radio Amplifiers' started by WA6MHZ, Jul 31, 2017.

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  1. WA6MHZ

    WA6MHZ Subscriber QRZ Page

    Yes, the ALPHAs are the AMPS to have, if you have 5 to 10 grand to drop!!!

    Meanwhile, we began the modification
    first we will put in the 10Amp breakers
    20170823_082901.jpg
    I still have the soft start between the breakers and the rest of the circuit
    20170823_103846.jpg
    So we plugged it in and tested the new breakers.
    BLAM!!!!!!!!!!!!!!!!!!!
    WTF??
    OH It is that stupid SHORTING BAR I forgot to disable.
    Well we tested what would happen if a Tube shorts. The breakers didn't blow, but what did blow were the 5A Fuses on the SOFT START PCB. Luckily we had more 5A fuses in the stockroom. Not sure what good 10A breakers will do if the Soft Start has 5A fuses. Maybe the 5A fuses should really be 10A. Though the W7RY docs say to use a 5A fuse.
    Replaced those and tried again with the Shorting plate bypassed.
    This time........
    20170823_090900.jpg
    OK we are ready to proceed.
    Time to YANK the relay, but lets look at it first
    20170823_091009.jpg
    lets look closer
    20170823_091021.jpg
    The wires were removed and identified where they go.
    Then I went to W7RYs Photobucket to try and look how he did it. The pix were there, but I couldn't see them very well. They were all thumbnails and they wouldn't expand to a full sized pic without buying an account and paying dearly!!! RAT BASTARDS!!!!!

    I took a screen capture of the page and got a few ideas. One thing they do is use a fine copper strap between the coax and relay contacts. This is most needed as we don't wanna strain the contacts connectors. In most cases they changed the output coax from RG-8 to a finer LM-240 sized coax. I don't have any of that, so I will use the existing RG-8 and the copper strap.
    Continued later as we make progress. Still waiting on the Mouser parts to populate the board.
     

    Attached Files:

    AF6LJ likes this.
  2. WA9SVD

    WA9SVD Ham Member QRZ Page

     
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  3. AF6LJ

    AF6LJ Ham Member QRZ Page

    I have been wrong before.
     
  4. W0AAT

    W0AAT XML Subscriber QRZ Page

    Sad they lost another ship... saw the news story... Sig is thinking of packing it in before he becomes a statistic. That is one of the most dangerous jobs on the planet
     
    AF6LJ likes this.
  5. AF6LJ

    AF6LJ Ham Member QRZ Page

    Sad indeed..
    All it takes is a rogue wave, a boat loaded with crab pots, and the crew asleep.
    The man on watch is helpless.
     
  6. WA6MHZ

    WA6MHZ Subscriber QRZ Page

    Today the MOUSEYWOUSER parts came in and it is time to build the boards!!
    The relay board went together fast, but one cap was left unstuffed. It was labeled C11. After I built both boards I had one cap left over. a 33PF MICA so I figured that might be the unknown cap. I installed that which goes from the NO terminal on the input relay to ground.
    Here is the Input board
    20170824_103708.jpg
    note there is no reference to C11 or C13 on the supplied schematic.
    And now on to the QSK board
    One error in the schematic seems to be the value of R21. Schematic calls out 68K, but parts list says 1K. since this drives the base of Q4, I decided the 1K was a better choice and loaded that.
    Another discrepancy is C9, which is labeled a 500Pf, but the parts list calls out a .01uF. I used the .01

    I had to tear out the just installed SOFT KEY BOARD, so that was a waste of money for my friend. Maybe he can sell it on Ebay and recoup the lost $20 or so.

    20170824_114448.jpg
    The little relay board is mounted right next to the vaccum relay on the mounting bracket.
    OK we looked around for a convenient place to mount the QSK board and found an ideal spot right next to the Tube socket. In fact I used the 1 tube pin (grounded) for a ground connection to the QSK board. The power transistor is mounted right next to it. I did have to drill 2 more holes in the chassis but not a problem
    20170824_123729.jpg
    All the wiring is routed from under the board down to where it goes. The RF module wouldn't be so easy.
    I used the existing hole where the relay came out of and using a big fender washer, mounted it there.
    The input coaxes were routed to the relay board and then the wire from the NC contact routed over the vacuum relay I used a 16 gauge stranded wire the contacts on the vacuum relay didn't want to take solder, even with FLux. I hope they are OK
    Now before I hear a great OUTCRY on the output coax, realize it is going to REPLACED saturday with some coax Sue has. RG-142. This stock RG-8 is just ridiculout. SO never mind the wire going to the NO contact and to the RG-8.
    I then neatly tied up everything with tie wraps
    20170824_132953.jpg
    20170824_133003.jpg

    OK!! once we get the output coax it will be time to reinstall the tubes and try it. Adjusting the bias is going to be tricky, as you can't lay a SB-220 on it's side while operating. I have to slide the whole works to the table edge and then access the pot from underneath. Then adjust it for the idling current..
    (continued)
     
    NZ5F likes this.
  7. AF6LJ

    AF6LJ Ham Member QRZ Page

    For setting the bias you can turn the amp upside down for a short time while setting the bias.
    If I am wrong someone please correct me.
    Looks good pat.
    I like the relay bracket work that is nicely done.
     
    NZ5F likes this.
  8. WA6MHZ

    WA6MHZ Subscriber QRZ Page

    I just downloaded the SB-1000 manual and WOW!!
    www.radiomanual.info/schemi/ACC_PA/Heathkit_SB-1000_assembly_user.pdf
    Heathkit WISED UP!!!!
    Even though it has only ONE 3-500Z, they got the power supply correct!
    What they do is supply 2 sets of fuses (NO Circuit Breakers)
    10A for 220, 15A for 120!
    Clipboard01.jpg
    notice that the wiring is correct this time!
    also notice they don't run the whole works through the delicate power switch, they use a contactor for switching the AC (Just like in the HP-226!!!)
     
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  9. AF6LJ

    AF6LJ Ham Member QRZ Page

    There is also a bridge rectifier.
     
  10. WA6MHZ

    WA6MHZ Subscriber QRZ Page

    I don't see the bridge rectifier, maybe its for LV circuit. The HV is about the same as the SB-220.
    They looked into the future when designing this and Foresaw the HP-226!
     

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