First Amp Recommendations

Discussion in 'Amateur Radio Amplifiers' started by N3AP, Jul 4, 2019.

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  1. N8FVJ

    N8FVJ Ham Member QRZ Page

    If you have $900, a used Ameritron AL80B is the better amp vs the AL-811/A:L811H and produces over 800 watts PEP. I seen the AL80A sell for $600 and is also superior to the AL-811/AL811H. Do not buy the AL-80 as it has design issues.
     
    KW6LA and KE0EYJ like this.
  2. KM1H

    KM1H Ham Member QRZ Page

    Many if not most AL-80's were recalled to solve those problems and the 80A included those fixes.

    The 80A has a marginal transformer when pushed or the filter caps become leaky but the 80B version will fit....barely.

    Many prefer to remove the 80B "Dynamic ALC" which is just another name for EBS. Here is one discussion from the past.
    https://www.eham.net/ehamforum/smf/index.php?topic=39672.0;wap2
     
  3. W2WDX

    W2WDX Subscriber QRZ Page

    I really like the ol reliable Heathkit SB-220 types. Tubes are still readily available (and will be for some time), they are fairly rugged and forgiving, can run on 120VAC if that's all you have (requires soft-start of some ilk) and are especially easy to service, with many parts and mods available.

    If you want something high-end, I also use and recommend an Alpha 8410 manual tune. A monster.

    Not a fan of auto-tune tube amplifiers. (SS amps are different things). I don't need to be that frequency/band agile, and I know how to tune manually quickly.
     
  4. K4MJA

    K4MJA XML Subscriber QRZ Page

    My vote goes to Elecraft's KPA500. It is small and light (for an amp), has an app to use it in remote session, which I do. ~30 W input will give you all 500 W. It works great! It can be ordered as a kit -- saves some $$ and I did; was joy to assemble. It is more $$$ compared to some tube amps, but the price is competitive compared to other solid states.
     
    Last edited: Jul 16, 2019
    N4XRD likes this.
  5. KM1H

    KM1H Ham Member QRZ Page

    There is a lot of good to be said about the SB-220 and SB-200 family. Still reasonably priced for nice ones since so many were sold, and simple enough to overhaul if needed by those not afraid of that sort of work. Those needing a lot of work often appeal to those with the skills. I see on various forums that even new hams are realizing that those amps and construction manuals were designed for beginners as well as those with various levels of prior knowledge. AND thousands are still on the air. No 160M if that is wanted but work on 17 and 12.

    Unlike the AL-811's they werent designed to be as cheap and shoddy as possible along with the sloppiest assembly in the US....and didnt cause years of dissension on the internet about poor reliability from new. I quit working on them since most owners didnt want to pay the going labor rates. I wonder who fixes their cars.

    The AL-80A is getting long in the tooth especially in the PS where the filter caps are developing leakage and should be replaced along with the carbon composition parasitic suppressor resistor. A HV glitch resistor should be installed to minimize/prevent damage from an internal tube arc. The transformer has almost no reserve and often short from the added current of the caps which does not show on the panel meter. The Heath SB-1000 is almost a clone with even a less hearty transformer. The good thing is that the AL-80B one will fit...barely in both...but it does. Rather than use the kluge bracket Ameritron includes I drill new holes and the finished job looks like it belongs there and not rolled over on its side!!:cool::D

    Whatever works.
     
  6. N8FVJ

    N8FVJ Ham Member QRZ Page

    For some reason some Hams like to talk about the cheapness of the Ameritron AL-811 series of amplifiers. There is nothing cheap about the Ameritron AL-811 series amplifiers. And, like many under 1000 watt amplifiers the Ameritron AL-811 series uses a 'receiver type' variable load capacitor. So does the SB-200.

    The Ameritron AL-811 amps do not have the tuned input issues like the SB-200 and has 160 meters included. They also tune 17 & 12 meters as indicated on the band switch. The Heathkit SB-200 has a 21 lb power transformer and the Ameritron AL-811 series amplifiers has a 19 lb transformer. The Henry 1KD amplifier used a 17 lb power transformer. The 19 lb and 21 lb transformers supports 800 watts PEP out.

    The AL-811 three tube produces 450 watts PEP output and the four tube AL-811H produces 600 watts PEP output with 811A tubes. (Ignore the Ameritron AL-811 & AL-811H ratings of 600 & 800 watt PEP output as the 811A tube life will be shortened). The only quality 811A tube left are the old RCA 811A that costs a fortune and the Russian G-811 that are $16 each in NOS and reported to be still providing full power out after 20 years use. Switch to three 572B tubes and either amplifier produces 800 watts PEP out with 65 watts drive. A fourth 572B tube is not needed.

    The Heathkit SB-200 needs rebuilding and a keying interface as the keying circuit is 130 volts or enough to damage the electronic keying in your transceiver plus needs rebuilding at times of the upper band tuned input. This is not my statement, but the statement of others. (I have owned a SB-200 amp and rebuilt it). The AL-811 amplifiers do not need rebuilding nor an keying interface as the amplifiers use 12 volts DC on the keying circuit. The tuned input works flawlessly. The AL-811 and Heathkit SB-200 cost about the same used.

    *****So, you can completely dismiss KM1H's statement of the AL-811 amplifiers being cheap.*****
    I find it somewhat appalling some make false statements about products that are not true plus to add to the insult do not produce any product themselves for the Ham community at all.

    Now, the Heathkit SB-220 is an amplifier worth rebuilding unlike the SB-200. The tuned input works correctly and yes, it still needs the keying interface. But, the amplifier uses a pair of 3-500Z tubes that are available new and are of quality reported to have full output after 10 years use. The amplifier produces 1200 watts PEP out. The filament transformer soft starts (current limits) the 3-500Z filaments. If you have rebuilding skills, I recommend the SB-220 and a lot of SB-220/SB-221 are for sale for $800 already rebuilt.

    Of course the Ameritron AL-80B is a better amp vs the AL-811 series and cost about $300 to $450 more. Three 572B tubes costs $150, so for the power output the AL80B becomes a better deal over a few years due to poor 572B quality tubes that lasts only a few years. And, new Cetron 572B tubes are getting too expensive. The AL-80B amplifier produces an easy 800 watts PEP out, some report a 1000 watts PEP out. It has a 26 lb transformer that easily supports 1000 watts PEP output.
     
    Last edited: Jul 17, 2019
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Well, by now probably more AL-811s and 811Hs have been sold than SB-200s.

    If used gently, they certainly work.

    Built-in protection mechanism: I've worked on several AL-811s and they all had failed tubes, but not one had a failed transformer. The tubes fail first!:):p
     
  8. N8FVJ

    N8FVJ Ham Member QRZ Page

    Unfortunately no one makes a new quality 811A tube. But, the 'old school' Russian G-811 are of quality, but supplies will be exhausted. Perhaps China will step up and build a quality 811A as Shuguang has the talent. The Ameritron AL-811 series of amplifiers rate a 4.5 out of 5 with 356 reviews on eHam. That says something about the quality.

    One Ham's review of the SB-200

    At a minimum, expect the following potential repairs:

    1. New power supply board with new capacitors, diodes, resistors and metering resistor string. Harbach makes a drop-in replacement kit that actually improves on the original.
    2. New electrolytic capacitors under the RF deck
    3. New carbon-comp resistors throughout
    4. New TX relay
    5. New tubes
    6. Input network retuning (on rearmost band switch wafer) – it often shifts on 10 and 15 meters after 40 years, reducing power output to a trickle (you’ve done this before, right?). You will probably need to order a variety of 500 volt, silver-mica caps to do this. They are not cheap.
    7. New output bandswitch wafer (call Harbach or ask on the on-line forums – hard to get), often destroyed by poor tuning/loading, bad SWR match or too much sustained power output causing a cascade failure.

    Then there are the inevitable “Mods” done to these amplifiers – some necessary, some poor and all pretty much undocumented. Consider that quite a few SB-200s have been converted to 6 meters (where they don’t work terribly well) or changed to use a single (often Russian) pentode power tube in a process that can never be duplicated nor reversed easily, or “converted” to cover the WARC bands at the expense of performance on every other band. It’s not that every mod is bad, in fact some are brilliant. But how do you know? The unknown “golden screwdriver” that made them has often passed on to a better place. And then there are the many safety, compatibility and stability mods discussed on-line, some of which are needed and many of which are dangerous. How do you decide? Hmmm.

    Well, in general, the following mods really are needed for compatibility and safety, IMHO – but you need to decide for yourself:

    1. Perform a soft-key mod to convert the 120 volt keying input on the SB-200 to a few volts at a few milliamps, letting a modern solid-state radio key the amp without damage. If you can’t “roll your own”, Harbach makes a nifty soft-key kit for the SB-200 that is a real time saver. Just do it. And its backwards compatible with older tube rigs that expect high voltage keying. If you don't do this mod, at least use an external buffer interface relay or box that does the same thing - several manufacturers make them.
    2. Swap out the funky RCA RF input jack for something that is positive locking, like an SO-239 or female BNC jack, otherwise the cat and you will have a shocking and possibly smoking experience when Mittens pulls the plug on your next DX QSO. I DO NOT know what the engineers at Heathkit were thinking when that made an (audio-standard) non-locking RCA jack a high-power RF port standard for their equipment. Bad engineer! Bad! Go to bed right now!
    3. If you plan to use the ALC input with a modern exciter, look up the Heathkit factory bulletin that recommends installation of an 8.2 volt zener clamping diode to avoid damage to your solid-state rig. And put it in.

    Mods that may be useful and at worst are harmless:
    1. “soft-start” mod that reduces inrush current (and stops the lights from dimming) when the amp is turned on. Harbach makes a nice kit for this. Not needed, but nice to have.
    2. Back to back meter protection diodes. A replacement SB-200 meter is hard to find, and if an HV resistor fails the resulting voltage and current can destroy the meter. This rarely happens, but if it does, you’ll probably wish you’d sprung for the $1 meter protection diodes.

    Mods that are likely unnecessary and may be problematic:

    1. Replacing the power supply caps with units having twice or more capacitance. Just don’t do it. The resulting inrush current will dramatically increase, possibly popping the circuit breakers every time you turn the amp on, and certainly increasing stress on the amp.
    2. Adding a “glitch resistor and fuse” to the HV line. This on-line legend will likely react too slow during a fault to prevent damage, or will cover up a more serious issue, will fail itself during an event, and will add impedance to the critical power supply to the tubes – never a good thing for performance. Your choice, though.
    3. Modified anode resistors/inductors and other mods to “improve stability” and guard against VHF self-oscillation. Some of these suggestions and mod kits are harmless while others actually degrade the stability of the SB-200, whose gain falls off so rapidly above HF that its stability is quite good to begin with. Caveat Emptor.
    4. Bias scheme modifications, anything that changes the tube type, or the power transformer (dramatically) and anything that adds new bands. These usually result in an un-maintainable amp, or causes unexpected/degraded behavior, or even “It’s dead, Jim” syndrome. Plenty of posts about this on-line.

    So… that’s why the SB-200 gets two stars and not five, in the 21st century.
     
    Last edited: Jul 17, 2019
  9. W5LZ

    W5LZ Ham Member QRZ Page

    No matter what amplifier you have/get, not pushing it to it's limit is a very good idea. Most amateur amplifiers are sort of over rated. Having a 'stiffer' power supply is a biggy, but that can get expensive (not to mention heavy). One thing to keep in mind especially with tube-type amplifiers is how much, and how 'common' are the tubes? Eventually, you will be replacing them, mistakes happen.
    Output power depends on the frequency/band in use. They are not all the same. Typically, the higher the frequency the less output. Unless the thing is really, really over-built, power drops off (think power supply). That happens with solid-state amplifiers too, by the way. Has to do with how the tube is designed to start with.
    I've had several amplifiers at one time or another. I tend to look for one that can provide my power requirements (realistic or not), how cheap they are (biggy), and general reputation of who builds the thing. They've run from an SB-200 to a TL-922. Probably the 'best' all-round amplifier has been an AL-80B. A 3-500 is just more 'robust' than an 811 or 572B. Costs a bit more, but I think they are worth it. Another biggy is that they are still in commercial service so are going to be around for a while. Then you get to factor all those characteristics against $$$. [If you're rich enough not to pay attention to that, how would you like to adopt me??]
    I have learned what little I know about amplifiers by making mistakes. NOT the smartest way of learning anything, but...
     
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  10. W2WDX

    W2WDX Subscriber QRZ Page

    I find it really easy to over drive 811 or 572 based amps, especially when you are new to amplifiers. And most that were built have marginal power supplies.

    I do like going with a pair of 3-500 tubes, as long as the supply is up to the task. Plus you won't be looking for a power upgrade anytime soon. The SB-220's have just enough supply, but they can be upgraded especially the main transformer. P Dahl (Hammond) still has a new one that has twice the current capability as the original. Just bought one last fall. Not cheap though. I just put one in my HL-2200 and it really made a difference to IMD, as well as output slightly. The voltages stay very stiff even under full load. Temps are lower as well. I did upgrade the entire amplifier, with soft-start, new regulation and bias, and B+ filters. Still cost much less than buying a similar dual 3-500 amplifier from Ameritron, and much better IMO.
     

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