Heathkit SB 220 Linear Amplifier refurbishment 

Years ago I built a Heathkit SB220 amplifier. Things went well during the kit building. When I got finished with it, it was time to fire it up and test it out into a Heathkit Cantenna dummy load. I got plenty of RF through bands 80-15. On 10 meters I got only the power the Kenwood 820 put out and nothing more. I checked and re-checked all the wiring but gave up and took it to the local Heathkit store. The store manager told me to bring it back to the test bench for testing. The technician set it to 10 meters with a wattmeter to a dummy load. Instead of tuning up the radio in steps as you did in those days he cranked the radio up to 100 watts and started twisting the tune and load controls on the ampflier. The two 3-500Z tubes started to get red hot and then white hot, then the parasitic chokes on top started to smoke! I told the manager to have him stop as he was burning up the ampflier tubes. At that time they were $ 180 each! He told me the repairman knows what they are doing and we sell the kits in front and that is all that counts. After several letters and phone calls I got two new tubes and somehow they found what was wrong with the amplifier. When asked they did not know. I had build a number of Heath Kits and about half of them had mis-labeled capacitors or errors. It’s no wonder some people call them Greif Kits. I am still running the amplifier to this day and that was 37 years ago.

I always enjoy your videos. Please bring us more projects!

Nicely done. I wouldn't even sweat not having the second tube. 800W is a gracious plenty. That's a 1.5 S unit increase. The second tube will only add another 3db or half an S unit for a total of 2. For the money that 3-500s cost, it's not worth it. Heathkit realized this, and the SB-1000 was the result.

Great video, another 220 back to life.

What a change, beautiful work.

I have 3 of these amps and I just love them.

Nice work. I love the front panel.

Nice work

Thanks so much for making this video on the Heathkit SB-200, you made it look like a walk in the park. This is just what I need for my ham shack. I hope I can locate one and restore it back to it's glory. You made me a subscriber. Oh by the way, I love the video on your 56 Oldsmobile Delta Rocket 88, Awesome! :-) 73, K6GRH

Nice video!

Good basic low cost re-furb Pete. It sure hummed on the modified sine wave ! This shows clearly that you don't have to spend money on Harbach boards to get your amp going. two notes fyi.. swapping in the nichrome wire parasitic traps is good cheap insurance for these amps, by far the most important mod on can and should do. When you increase the value of capacitors in a capacitive input power supply ( here) the PIV increases...this can have consequences at the input end. And the inrush current becomes larger also. The heath design is superior to many...and very worthwhile to invest time and money in as you have done. My orphan SB220 will get the treatment this winter. Nice video w6wuh. 73

The "blown-up" choke was, more likely, due to a grid-to-filament short; 3-500Z's were/are known for this, and Heath bought a whole bunch of faulty tubes back in the 1970's. I built several of these amplifiers in the 1970's, and I recall exchanging tubes -- no questions asked -- when those chokes went up in smoke at initial turn-on.

I've never been a Ham, didn't care to take the test. I was owner of an AM Daytimer for a little over 27 years. Learn alot from two Consultant Engineers that I was working on those rigs myself. I had a Collins 20V-3 that I loved, but to stay on, I had to buy a Harris (Gates One) in 1997. For back up, I had a 1948 Gates BC-250GY. We were able to build an internal resistor network to kick the power back to 5 watts for pre sunrise operation and the audio bias stayed perfect! My wife and me owned the property of the little studio and tower site. We sold the building and property. We just turned in the license to the FCC and I retired from that. I play around with Part 15 AM stuff non since I'm disabled.

When that choke goes up in smoke, there is almost certainly a "grid-to-filament short" in the associated tube. Mind you, I'm only about 25% into the video.

I am trying to find parts to build an amp similar to the SB-220 or ALS-80B. The HV Variable caps are hard to find and HV transformers are pricey! I have a chassis that came out of some Satellite antenna control equipment that is very close in size to Heathkit one. Just want to have some fun building a homebrew 3-500 AMP.

I just bought a Heathkit SB 221 today at a local club auction for $200. I am new to the hobby (4 months) and I am very excited to own my first amplifier. The previous owner was there and said that it works and produces 400 watts with 80 watts driving it. Being new to the hobby, I do not plan on messing with it until I can find someone to help me who knows what he is doing. I don't want to kill myself or damage my Icom IC-7300.

I'm working on a SB-220 for a friend. Any idea what would cause the R3 resistor to burn out on the meter board? Obviously, I'm not charging anything for this except that he buys parts. I just put together a new metering board and a new HV caps/resistors board. I'm just trying to figure out what could have caused the R3 resistor to burn out, so it doesn't happen again. Also, just found that the Plate Voltage/Grid meter is open too (probably burnt internally).

I like to remove the transformers, clean and paint them. Makes the interior look great.

Excellent video! I just bought an SB-200 that has two Harbach upgrades. I haven't fired it up yet because I'm waiting for an Ameritron keyer interface and an antenna tuner that can handle the power output. Did this amplifier have an RCA socket for the RF input? If so, did you leave it that way, or did you put in an SO-239 connector?

Very good restoration, just wondering where you get your replacement Heathkit panels from please? Is someone manufacturing them to order? Best, John, Wellington New Zealand.

Two things I see - 1. Lots of cold solder joints, 2. Don't use Carbon comp resistors replacements! I have hundreds of those brand new in parts drawers. I tested a number of them, and found my 5% (gold band) industrial carbon comp resistors

I would hate to have to pay to replace the HV transformer in that, but then an MOT would probably work if you bypassed the voltage doubler. What are the two 1% resistors for?

Great job Pete!! I am just a little confused on something. I thought that tubes like the 833, 3-500z, 813, exc, needed dc on the filaments to prevent hum in the output signal, and this amp and others I have seen use ac. Is there something I am missing? Thank you for reading and giving another amp a few more decades of life.

Hello, Pete- any chance you have the part number of that 5.1 volt Zener--Im rebuilding one of these presently, Thanks KC2WTS

ok Pete it was the one from little diode- I thought you ordered it.. Thanks

Hello. I am working on getting my SB220 back on air, and would like to replace that 20uF cap also, but am not sure what voltage it needs to be... I know that many suggest 2x max, but that would make it a 180V cap....

why are there so many diodes on the power board, are they for different voltages?

Great video, but the audio level is very low. Common to many videos. If you suddenly raise your voice I have to turn down my audio. Thanks for a informative video.

Does anyone build anything with 2C39As anymore?

Hello Pete Great great video. I have some problems with my old QRO HF 2000. I have contacted QRO Technologies via email. Even 2 times. But nobody seems to care. First, the QRO HF 2000 is a great amp and I'm sure Ray Connin would not wait long for an answer. Problem 1 is: As long as the amplifier is on Stanby mode, everything is fine, as soon as I switch to operate, the reception of the transceiver drops dramatically. Problem 2 is: as soon as I turn on the amp, the tubes glow hot without tx !! I turn off the amplifier to protect the tubes. I would appreciate it. If I get an answer, an opinion or a solution to my problems. Regards, Ozer

good work, should have.done some mods like a direct grd on grids, no chokes.

woukld like to buy the sb220 supply board

Some serious iron in that thing

Not a big fan of tacking solder joints, more of a hook and loop to make it look clean.

Pete, Great job on this amp rebuild. I am rebuilding one myself that will be my back up amp. I have a couple of questions for you. First, the bias zener, can you give me the part number so I can order one from Littlediode as well. I want to upgrade from the 10 watter. Secondly, I have seen in some other repair videos, that the by pass caps and chokes on the grid circuit have been removed all together, and the 3 grid lugs on each tube just hard grounded to the chassis. Is there a reason, not to do this?

Sorry I actually typed sine wave, darn spell check

Where did you get the black knobs?

was that inverter pure since wave?

Why don't you use a variac?

Your audio is very low. I am running my audio wide open & it is still very low. I agree with the gentleman who said to ground the grids. Your brother in the Lilac city will get much use from it.

did a chipmunk take a crap in side it

Be glad to purchase if you would sell, thanks much

I would ground the grids like Collins and drake does .there are many vids on youtube😅 to show how, bbi is one .take your time and learn as much as you can and be careful 3200 volts is very dangerous.have fun I did 73

I would had sprayed it with Lysol, let it sit for twenty minutes, then wiped it up.

Should have directly grounded the grids.