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An SB-220 needing lots of attention

Discussion in 'Amplifiers' started by Dmans, Jan 3, 2022.

  1. Dmans

    Dmans Sr. Member

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    All,
    I have undertaken another long term project. It started in early September and is nearing the finish line now. A local operator I have done work for in the past brought me a Heathkit SB-220 in original but very dirty, neglected and homely condition. (I felt a little sick seeing it for the first time.) Operating condition unknown. He came by it through another local operator who purchased and built the kit while he was living and working for an oil company in Venezuela around 1970. The original owner/builder of this amplifier is in his 90's now and is thinning his collection.
    The amplifier has its original set of Eimacs in it and includes the original Heathkit assembly manual with the Eimac warranty card stapled to the inside of the back cover. Interestingly, replacement parts and parts prices at the rear of the assembly manual show replacement Eimac 3-500Z tubes priced at $47.00 each. (Another sick feeling!;))
    I have taken many pictures of this rebuild/rehab and will eventually get to the point where I can organize and post them to this thread. For now, I will post a few here for your entertainment.

    Day 1, as received.
    IMG_1777.jpg
    A peek in the RF Compartment reveals 30 or 40 years of Pall Mall grunge-hence the sick feeling!
    IMG_1742.jpg

    This is why the Grids should be directly grounded.
    IMG_1747.jpg
    Original Rectifier/Metering board with signs of previous repairs.
    IMG_1787.jpg

    Did I mention that it was dirty?
    IMG_1741.jpg


    As I get the pictures uploaded and sorted/organized on my computer, I will post updates.

    73
    David

    (Airsick bags are not provided by the Author of this thread!)


     
    Robalo, NightThumper, NZ8N and 3 others like this.

  2. Moleculo

    Moleculo Administrator
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    Thanks for letting us follow along!
     
  3. Dmans

    Dmans Sr. Member

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    Foolish me, I thought a thorough wiping down would be all "Big Bertha" needed. Little did I realize a complete tear down and then cleaning and acid etching panels was required.
    IMG_1748.jpg
    Getting a little closer now. Ever seen a Gold Plated 10/15 Meter coil in a Sb-220? Thank the Pall Mall gods for this!
    IMG_1796.jpg

    It was a good thing I had an ever vigilant supervision for this adventure.
    IMG_1932.jpg
    Under chassis cleaned and going back together. This shot shows the grid grounding approach. A flat strap of copper soldered to the tube socket grid pins and attached to the chassis.
    IMG_1860.jpg
    Not out of the woods yet. More work to be done.
    IMG_1877.jpg
    IMG_1878.jpg
    That is all I have for now. Stick around. It gets deeper.

    73
    David
     
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  4. Robalo

    Robalo Well-Known Member

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    i love to see restoration on those amps.(y):);)
     
  5. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    That will help keep the "Ice Shanty" from freezing up.

    Good job!

    Fun to watch - gland to see this being done, but still a "labor of love" - good to see a passion being put to good use.
     
  6. AudioShockwav

    AudioShockwav Extraterrestrial Admin
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    Looks good, I used to restore old shortwave radios when I was younger and it is nice to see old stuff live on.
    Thumbs up.

    73
    Jeff
     
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  7. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    Sometimes the "Gold plating" is what preserves the tuning - the oils in the residuals of the smoker's paradise are sometimes permanently etched in glass (tube envelope) - hope this can be freed of such a result.
     
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  8. Dmans

    Dmans Sr. Member

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    Some of the goals for this project was to clean it up (obviously!) check it out thoroughly, replace aged capacitors, ensure good connections, apply any updates or correct some known weaknesses and to provide the owner with some longevity (of an already 51 year old amplifier!!). There is much written about the amplifier since its inception/creation and lots of reading was done on this since I have never personally touched an Sb-220 before.All of the research paid off I believe and a strategy to meet the goals above was developed.
    The owner has a new Yaesu FT1200DX he will be driving the amplifier with. So anything it takes to make the amplifier "play well" with the Yaesu was high on the modification list.
    A couple of these items are listed below.
    • Flat "pass thru" SWR
    • Flat "Keyed Thru" SWR
    • Solid/low resistance S0239's and coax cable
    • Lowest possible chance of Parasitic oscillation
    • No or very low Flyback current from relay
    Of course these few items "spawned" a few other modifications along the way.
    • A replacement for the 1970's (flat cable) power cord, outlet connector and cord grip to the chassis
    • Protecting the unobtainum power switch and meters
    • Protection for the Filament transformer (for 220V primary operation)
    • Something other than sheetmetal screws in the chassis (that take a flat blade screwdriver and lots of patience)
    And the reaction to this laundry list of my other (more watchful) Supervisor below
    IMG_2298.jpg

    An order was placed to Harbach Electronics including the FB-220, RM-220, SK-220 and SS-221. I believe these are a good start to meet some of the above goals.

    The FB-220 was built and installed first. In reality it was installed about 3 times.
    IMG_1825.jpg

    The RM-220 was built and set aside (for the final installation of the FB-220 o_O)
    IMG_1819.jpg
    And followed by the SK-220.
    IMG_1821.jpg
    For those that have not dealt with W8CQ before, his boards are excellent and his service is even better!

    My thoughts were to test the amplifier on 120V and when everything was solid to switch it over to 220V and install the SS-220 at that time.

    Before installing the new filter board, more cleaning was done (not sure it will ever be done at this point).

    I had to remove the gold tarnish from the 10/15 meter tank coil. Wright's Silver Cream and 10,000 Q-Tips knocked that out real easy like!:( I hope the Wife doesn't need to polish any silverware anytime soon.

    IMG_1891.jpg

    The Rear wafer section (output) of the bandswitch was next. Below are the before during and after shots.
    IMG_2025.jpg
    Soaking in Vinegar with dissolved table salt.
    View rece.jpg
    And the final product.
    View rece-2.jpg

    Another installment coming in the future.
    I thought I just heard the Wife mention something about silverware. Hope it included using it not polishing it!

    73
    David
     
  9. Low_Boy

    Low_Boy Sr. Member

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    Wow very nice neat work. Too bad I am afraid of amplifiers. It looks like a fun job.
     
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  10. Dmans

    Dmans Sr. Member

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    Just a couple of "out with the old-in with the new" pictures.
    IMG_1827.jpg
    IMG_1824.jpg IMG_1834.jpg
    The fan was disassembled, cleaned and tested for 24 hours on a makeshift test stand. It did require shimming the shaft with a nylon washer and a drop of 3 in 1 oil.
    IMG_1734.jpg
    IMG_1735.jpg
    And finally mounted to the chassis using rubber washers and fender washers on the inside and outside of the rear panel for a more secure grip on the expanded metal panel.
    IMG_2105.jpg
    IMG_2106.jpg
    Stay tuned........
    73
    David
     
  11. Ranch55

    Ranch55 Sr. Member

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    hello David,
    would this be the amplifier that David has been telling me about ?
     
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  12. Dr_DX

    Dr_DX Well-Known Member

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    Wish they had the SK-220 back in the 80's when I spot welded the reed relay in my IC-735 using a SB220...
     
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  13. Dmans

    Dmans Sr. Member

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    Indeed it is Steve!
    I'm hoping to get it in the "On-The-Air" testing mode this weekend. These 65-70 hour work weeks are killing my hobby!!

    73
    David
     
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  14. Dmans

    Dmans Sr. Member

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    Below shows what I referred to as the "flat cable type" power cord.
    IMG_2300.jpg

    Above cable was chucked in favor of this type cable and cord grip. (No hole enlargement was necessary.)
    IMG_2305.jpg

    With this type of plug on the end. (When it does go 220V input)
    IMG_2303.jpg
    Since the face plate was so nasty and cleaning it without removing the lettering was impossible a custom face plate decal was ordered from Gammaray Graphics ((y)-Good People to deal with!)
    Your eyes are not deceiving you. That is not a blemish in the lower left corner of the decal. The owners call sign was added to it in 1/2" tall white letters. I don't feel comfortable advertising his call sign. If he wants to do that, that will be on him.
    Trust me though, the decal is perfect. Proper preparation was the key. The face plate was stripped of all paint and scrubbed down with a fine grit Scotch-Brite pad until all imperfections were removed. The decal went on better than I expected since I can't draw a straight line with a ruler!!
    sb220panel.jpg

    Yes an "Operate/Standby" switch was added. ( Heathkit purists-Please save your hate mail. I know the tubes are "Instant On" tubes but sometimes you just want to run barefoot and save the Power switch that is made of Unicorn Farts or something like that!)
    Below was being tested with a 5 volt power supply. there was much discussion between me and the owner about LED bulbs to replace the #47 incandescent bulbs. So that was also being tested at the time.
    IMG_2301.jpg


    You are not being deceived again. That is a Bi-color LED. IMG_2302.jpg

    Until next time.

    73
    David
     
  15. Dmans

    Dmans Sr. Member

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    I think the need for cleaning has been covered enough except to say that Windex and 91% flavored alcohol is your best friend here.

    On to bigger things. In keeping with one of the goals of making "Big Bertha" friendly to the owners Yaesu, I measured pass through SWR or Stand By SWR however you view this.
    Firstly the input coax was from 1970 and the output coax from 1970. Time to update these.
    The input and output connectors were a loose center pin fit and they were from 1970!
    They were replaced with Teflon insulated S0-239's. No magic here. Just a picture to confirm their rattiness.
    IMG_1740.jpg
    IMG_1743.jpg
    These are the new S0-239's installed.
    IMG_2318.jpg
    The input coax cables (there are 3 of them) were some crappy looking RG-58U and had to go. First run is from input S0-239 to the relay. (In standby mode this is directly connected to the output terminal of the relay and to the RF out S0-239)
    Second run is from the relay to the front wafer of the band switch and is active in transmit mode.
    Third run is the output of the front band switch wafer to the cathode pin(s) of the 3-500Z's.
    All 3 of these were replaced with RG-316 Teflon insulated coax cable. Good for 1000 watts (If you believe the datasheet). This should be plenty stout for 100 watts input per Heathkit specs.
    (Red circle shows 2 of 3 of these.)
    IMG_1860_1.jpg
    The output from the relay to the RF Output S0-239 was changed from RG-8U to RG-303 Teflon insulated coax cable.This cable is advertised (per Datasheet) as 9000 watts at 10Mhz and 2000 watts at 150Mhz. Should work fine for Bertha.

    RG-303 visible here
    IMG_2316.jpg
    I have more to add to this part but my "Picture Interface" (Google) to get pictures from my phone to computer is whacked out. So this will be continued at a later date.

    73
    David
     
    Shadetree Mechanic and NZ8N like this.

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