Best AMP for the bang and buck!

[KD0CAC]

That's what I understood , so I will look for 2 amps , a 80B for 160-10 , and some other amp with enough damage to make for a 6m amp .
I am looking for either or both in need of repair condition , to help learn and save some $$$ with my labor , that makes a getting 2 benefits out of one purchase

[KM1H]

Ive converted scores of single 3-500 amps to 6M such as all the AL-80 series, SB-1000, LK-450, Drake L-75 and a couple of low volume brands. A couple are so easy that Ive done 2 in one day or 3 in a weekend.

The SB-200 converts very well to 6 as long as the tubes are good, USA or Chinese, for 700W+ as they are more efficient without the high loss encountered in multi band switching and circuits.

The Chinese 3-500's are still iffy, especially when pushing or exceeding 3000V. At 1800/2500V under load as in a SB-220 they should last a long time on HF and 6M; that is another very simple 6M conversion that takes no more time than a single tube amp.

The Drake L7 will run the same 1200W output power as the L4B since it uses the same PS which is far from wimpy, the L7 doesnt cool the tubes as well but you gain 160M.

For a reasonably priced 2x 3-500 amp Id suggest the LK-500ZC but not the NT version or earlier models such as ZA and ZB unless discounted a bit. Its capapble of 1500W but its better at 1200 and covers 160-10M including WARC. Ive had one since 1986 (company went out of business for reasons not associated with their products) and its still on the original Eimacs. Components used are the same as Alpha, big Ameritrons and other good amps and its easy to work on if needed.

[WA6MHZ]

Think I want to find a 2nd SB-200 or 230. whatever is cheapest, to convert. Or the SB-1000. There is a swapmeet next weekend. CHino Hills had no amps this time.

[WA7PRC]

You can use several of the Russian triodes on 6-meters including the GI-7bT, GS-31b, GS-35b, etc.

Converting the amplifier to use one, or two, of them is pretty easy.

Ditto. They're relatively inexpensive and are good to WAY past 6m.

[AE1PT]

For a reasonably priced 2x 3-500 amp Id suggest the LK-500ZC but not the NT version or earlier models such as ZA and ZB unless discounted a bit.

Carl, I just picked up a 500ZB. The price was right at <$500. What is your objection to the ZB--besides issues I have heard about involving sporadic cooling and solder melting problems?

[W1QJ]

Carl, I just picked up a 500ZB. The price was right at <$500. What is your objection to the ZB--besides issues I have heard about involving sporadic cooling and solder melting problems?

Less than $500 for an LK-500ZB is a super price for sure. I don't know what you mean about solder melting but the cooling isn't the greatest as you say. There were many variations of the LK-500 series amplfiers. I don't think I have seen 2 exactly alike. There was the Lk-500 and then (A) (B) and (C). There were QSK options available also. Some had a step start circuit and some didn't. Some of the models mainly the later "B" models and then the "C" models had a fault board. The amp would kick into stanby with high plate or grid current. There was poor documentation on this fault board and if something went bad you had no idea what it was or what the correct replacement part was. Bypassing it was the easiest thing to do. At the time no other company had any such fault circuits for a 3-500 amp. I suppose they thought they would sell more units touting they had this safety feature. All the Lk-500 amps have noisy fans. One run of LK-500 amps had a Hi/lo fan switch. Not all of them did. The ones that had them, when put it the Hi position you would think you were inside a room with a 747 ready for take off. Be aware, there were a short run of Lk-500 amps that had a similar band switch to that of the SB-220 amp. The amps with this switch usually have the 160 and 80m contacts vaporized. I think every one I have seen except one which I was told was never used had a good switch. Most all other Lk-500's had a similar switch to the Drake L4B. This is the good one and should last a lifetime. The other switch is on borrowed time out of the factory. Well actually the switch isn't that bad it is just that the amp was not engineered correctly for the use of that switch. Give your amp a good inspection and check to see which switch it has. Some LK-500 amps had only 6 filter caps, some had 7. Then. some had 8. Check and see how many you have. The HV runs about 2700vdc on most of these amps. One nice thing about these amps is they have nice vernier tuning dials with log scales. Something the SB-220 really needed. It's got a 12vdc relay with less than 200ma current draw and most SS radios can handle it. I saw one version of the no tune design in an LK-450 which was basically similar on the 500. That was a waste of time in my book. Good for 6 meter conversions along with the one with the SB-220 like band switch. Now what did I forget?

[W6JPK]

I'm recently back in to ham radio and have the AL811..Dx with this little amp is spectacular with just a small 12 foot vertical..You can retube the amp with taylor 811's and spend less then 80 bucks !! It's my vote for the best bang for the buck. My next amp will be the AL80B since it still works on 120V and only uses one 3-500 which keeps tube cost down..Jim

[KM1H]

Carl, I just picked up a 500ZB. The price was right at <$500. What is your objection to the ZB--besides issues I have heard about involving sporadic cooling and solder melting problems?

You stole it Pat, congrats!

The tube sub chassis went thru several changes to get good cooling at the pins, if not there it needs a couple of rows of 1/4" holes along the right side. Ive seen early parts used in later models; nothing got wasted but there was no docs either. Check the tube and socket filament pins for signs of overheating.

My ZC is a late model with step start, 2 speed fan (modified with an air flow temperature sensor), vacuum relay, QSK, ALO board, and external PAC-5 transformer. That was partial payment for consulting work I did, also got a LK-780 which I later sold when the real serious contesting days were over.

Ive always been very involved with the AS line for service, updates and mods as well as 6M conversions. And since Bill Edwards, K4BWC, died Ive taken on a lot of his workload. We were close friends for about 25 years and used to tear up Dayton with Denny Had.

So tell me what you got and maybe some pix so I can make a few other comments or suggestions.

Oh, I did go with an EBM Papst fan for quieter and more flow.

Carl

[WB2WIK]

I'm recently back in to ham radio and have the AL811..Dx with this little amp is spectacular with just a small 12 foot vertical..You can retube the amp with taylor 811's and spend less then 80 bucks !! It's my vote for the best bang for the buck. My next amp will be the AL80B since it still works on 120V and only uses one 3-500 which keeps tube cost down..Jim

IMO the AL-80B is more bang for the buck since it includes a true PEP wattmeter/SWR bridge (lacking on the AL-811), runs nearly double the power, and still does it all in a fairly lightweight desktop amp -- for not that much more money.

It also has the RF-activated bias system which actually works well and reduces idling current/power to zero until you modulate on SSB or key down on CW. Not difficult to implement, but the 811 series doesn't have that and just wastes power and heat.

3dB more power, one tube instead of three, bias cutoff system and integrated wattmeter (which actually works quite well, so you don't need another one) is worth the extra few hundred bucks.

[AG6K]

I have 3 amps now, and all put out about the same power. The SB-200, SB-230 and Drake L7. All run on 110VAC and don't blow the circuit breaker no matter HOW HARD I call. Now, the L7 uses a pair of 3-500Zs, which NORMALLY would be equivalent to a SB-220, but Drake, in their wisdom (or lack of it), undermade the power supply so it is really a 1KW linear instead of 2 like the 220.
...........

 Drake was smart to use lower anode V because more V =s more amplification and that means a greater chance of parasitic-resonance oscillation thanks to a 3-500Z's internal feedback-C. Another solution is to lower the VHF-Q of the parasitic suppressors in order to reduce VHF amplification and thereby improve stabilization. However, back in those days no one had yet figured out how to build better VHF suppressors that would not incinerate on 10m.