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sb200 no/low output on 10 meters

Discussion in 'Amateur Radio Amplifiers' started by WX7G, Sep 29, 2019.

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  1. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    AL-80B has a heftier power transformer, but still on AM I don't push mine past about 175W carrier power. Within 2 minutes, the anode is glowing red and after 5 minutes, brighter than that.

    Using a linear amp on AM is never efficient.:p
    WA7PRC and KD2ACO like this.
  2. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    I feel more comfortable running my sb in AM than the AL 80. A big helper fan sitting on top and running really slowly and quietly lets the Heathkit do its job with no tears at 150 watts.

    The AL 80 seems like I’m pushing it at 150 watts. I guess that shedding heat is more of an issue with the Amertron.
    Last edited: Oct 6, 2019
  3. WA2CWA

    WA2CWA Ham Member QRZ Page

    Not sure how you define "hard hours". This SB-200 has been in a number of HF phone contests each year over all these past 50 years. 50 years is a lot of hours and minutes. :)
    And since roughly the mid 90's, Kenwood 599D Twins drove it on AM and since the 21 century, an IC-756 Pro II and Pro III have driven it on AM. I never found AM operating to be "one of the few".
    Repairs included replacing meter lamp and shorted diode in SWR bridge.
    I also have another SB-200 that I bought used, which was built in 1973, that also gets a lot of HF use during contests and it still has original tubes. And, back around 2012 at Dayton, I bought two power supply update kits from Jeff (Harbach Electronics). I have yet to put them in, so power supplies in both SB-200s are still running original components after 50 and 46 years respectively.
    It's like "living on the edge" :)
    For even bigger shoes, I run a Johnson Thunderbolt. This particular one was part of laser experiments in late 50's/early 60's at Bell Labs.
  4. K6BRN

    K6BRN XML Subscriber QRZ Page

    Chris (KD2ACO):

    Yep... that's pretty much how I run mine when it's hooked up to the Kenwood TS-440SAT ( I um... sold the HW-101 at a swap meet). After I put in the Harbach double board with new caps, THAT part of the design runs a LOT cooler. But the tube compartment really can use a good external fan to flush out the hot air. The internal fan seems focussed on keeping the

    Yes, "Push-push" class AB grounded grid amps are about as simple as amps get.

    Well, your was a "goner", so what was wrong with it when you picked it up? Obviously - a LOT!

    So - what have I seen go wrong and helped fix....

    1. Blasted band switch output tank circuit wafer, caused by running to much power (especially on 10M) or into too high an SWR for too long. The band switch wafers in these amps are not very good. And replaing them, even after I've "got it down" is tedious. I've even seen hams who've "Fixed" the switch by sawing it in half to ger it out, then sleeved ir with heat shrink, a crimped (hammered) metal tube or other kludge to get it back together.
    2. "Fixed" band switch that is mis-indexed by the would-be repair tech,
    3. Tubes run so hot they literally sagged in their sockets (I saved a pair - kind of like glass art)
    4. Caps dried out or leaking like sieves or simply open. Power supply, bottom deck, etc.
    5. Input and output network slugs "tuned" into obivion (and slugs gone, paper tubes split) by well meaning newbies with a screwdriver, at the advice of "Elmers"
    6. Sticking meters, smoking solid-state rigs that were connected directly to the key line (ditto for ALC in SOME cases)

    Really - the list is endless. And on-line these amps are promoted as the best bargain going by a lot of older amateurs in pointers to newbies who view these antiques as bargains at $300. Not good advice. Not for them. Consider where amateur radio and technology has gone: Less eduation for amateurs, zero awareness of HV dangers and for modern technology, all low voltage/broadband/low SWR required. What could go wrong? A LOT. And it usually does.

    Glad you are happy with your SB-200. Still having trouble letting go of mine - but it WILL go some day.

    Pete (WA2CWA)

    I'm impressed! When was that last time you changed the oil in your 50 year old car? Are you REALLY telling me that the 50-year old electrolytics in those amps are "Just like new"? Because it's not credible. The amps may be limping along and you may still enjoy them, but they are about at the end of their reliability curve. Good thing you have two - most likely because you already KNOW this. And ham radio with or without an amp is not an essential, anyway. So if they barf up a cap or a tube, its just another fun Sunday project for a retiree. (I USED to be there, darn it! Just didn't "take").

    So next time you advise a new operator to just stroll down to HRO or the nearest swap meet and grab an old SB-200 - first think about the disappointment and danger a person who has zero background in electronics, memorized the test to get his/her ticket and knows nothing about the dangers of HV, will be facing. What IS the responsible thing to do, if you are NOT going to take that person "under your wings" as they try to use or repair that old amp? Maybe its better to just steer them in a safer direction?

    Think about it.

    Best Regards,

    Brian - K6BRN
  5. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Mine was missing its case and bolted to the transmission hump of an ancient car. The sockets were burned and it needed a stripping and re-wire job. Most of the parts are not what it was born with except for the front panel controls. The Cetron tubes are still great but living in Japan right now. I run Taylors that behave exactly the same as the Cetrons did.

    Edit~ Oh yeah, it was cheap! :p
    Last edited: Oct 7, 2019
  6. K6BRN

    K6BRN XML Subscriber QRZ Page


    I have to hand it to you, you really make me chuckle - and I mean that in a light hearted way.

    I'll argue that what you bought RESEMBLED an SB-200, but was more a collection of used and abused parts of uncertain pedigree. A good project. Glad to hear you had some fun getting it back together!

    Regarding cheap... not a virtue to me. Just a necessity for some. Had to live that way growing up. Not ever going back. The "Dark Side" is much better! They not only have cookies - they also have solid state amps!

    Brian - K6BRN
  7. WA2CWA

    WA2CWA Ham Member QRZ Page

    I haven't change the oil in any of my cars for at least the last 30 years. I have a mechanic that does all that.
    Never said the "electrolytics in those amps are "Just like new"". But they have never been changed - no leaky areas, no swelling, no outward signs of immediate disaster.
    "but they are about at the end of their reliability curve" - that's why I bought the two power supply upgrade kits in 2012 :) I'm just slow in implementation.
    I have the second one because I was at an auction bidding on a Heathkit SB-101, SB-610, SB-620, speaker, and external VFO and won the auction bid. When I went to retrieve my prize, I found out that the SB-200 was also included. All this, not bad for $130.
    I retired from the corporate world years ago and became an entrepreneur. Now I work 7 days a week. :)

    I generally don't come in contact with new operators, and even if I did, I would not direct them to stroll down to HRO or the nearest swap meet to buy anything. They need to do their own homework what they are looking to purchase and what they are capable of using and understanding from a technical perspective. And personally, a new operator should never purchase a 50 year old rig unless they fully understand that repairs are inevitable, HV is present, and one wrong slip could be their last.
  8. K6BRN

    K6BRN XML Subscriber QRZ Page

    Hi Pete (WA2CWA):

    Good for you. Why get your hands dirty and strain your back. I'm sad to say that my mechanix days are about over as well, but I do have a well equipped garage and some interesting cars my son and I sometimes putter around with.

    Well, I TRIED to retire "from the corporate world" But it followed me home - and to many other places. So I gave in and then dragged afew good friends back with me. Someone forgot to tell the baby boomers to train their own replacements. (Sigh!)

    Sounds like a wise move. Good way to avoid liability. Unfortunately the on-forum reviews and low-cost promises of 50 year old equipment lures many newbies (and not necessarily YOUNG newbies) into sticking their fingers into it. Literally.

    Enjoy your old Heathkit gear! I certainly did. Now it's on to newer things.

    Brian - K6BRN
  9. W1QJ

    W1QJ Ham Member QRZ Page

    The band switch, both the input and tank switch are the same in the SB-220 ad also the SB-200, I mean exactly the same wafers. The contacts are also the same on the AL-80A, B, SB-1000 and the high power Ameritron AL-800H that easily does 1500-2000 watts output. The band switches that burn up badly in SB-220 and SB-200 amps but don't in an Ameritron AL-800H that can do nearly double the power, doesn't. So it's not really that the switch can't handle the power and is inferior for the job. Sure, some amps have much better and heftier band switches but most of the time Heathkit band switches especially on the 220 and 200 models go bad because of other reasons not related to them being insufficient for the task. There could be any number of reasons why a Heathkit band switch gets burned up. Hams who understand loading GG amps usually don''t ruin band switches in this amps. Most damage is abuse and not insufficient material. Granted better switches are available but not necessary in the right hands.
  10. K6BRN

    K6BRN XML Subscriber QRZ Page

    Try and destroy a cam-and-contact Henry 2K bandswitch - not going to happen, until the cams get brittle and crack due to old age. The circular bandswitch wafers in all the amps you mention are weak - and are that way because it was the most cost effective solution. Not much contact area, not much separation for an HV circuit, OK for careful operators, not so tolerant of abuse. Which is why both MFJ/Ameritron and Harbach do a brisk business selling these wafers and they are often the subject of posts on forums. Always popular at hamfests.

    Brian - K6BRN

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