Interesting, a Heathkit SB-240 Linear Amp

[XE1/N5AL]

I had never heard of this amplifier before: Heathkit SB-240 (http://forums.qrz.com/showthread.php?374725-Heathkit-SB240-LInear-Amplifier). According to the seller's story, the product never made it to market and the amp being offered is a "proof build" before it would have gone into production.

[wa6mhz]

Wow, that's quite a story, and it sure sounds and seems to be true. $2800 for it though. Maybe he should put it on Ebay.

[KG4CGC]

He should ask 8 grand at least.

[W3WN]

Yeah. Quite a story.

Paint me cynical; I'm not buying it (neither the story nor the amp) pending further proof. I've heard this story before...

Quite a few years ago, I saw something at Dayton that was billed as a "KWM-4" prototype. Looked like a KWM-2, all solid state, just smaller...

same story, allegedly an engineering prototype, one of only a handful, very rare... but no documentation to back it up, only a story. And it didn't make sense that it would have been developed before the 380-HF / KWM-380, but numbered after it.

I started asking some questions; the vendor told me that if I had to ask these questions, clearly I wasn't interested, so buzz off. Didn't have a camera with me, so I couldn't take a picture.

Anyway... if this amp is really this rare, it would be worth a HELL of a lot more than he's asking for it. And a true Heath collector/fanatic would have snapped it up at the asking price long before now.

[W3WN]

Hmmm.

Here's a picture from LA6OP, who was also claiming, in 2006, that this is an SB-240 prototype: http://home.online.no/~sindtorp/sb240front.JPG

OK... so this is independent proof that the unit potentially exists. Potentially.

Further reading of THIS thread on RadioBanter: http://www.radiobanter.com/showthread.php?t=108608 indicates that there is some dispute as to whether this is a real radio prototype, or someone's kitbashed kludge. At least one poster claims that the "SB 240" had an 8873, not a pair of 3-500's.

Incidentally, it just struck me... LA6OP's unit matches the paint scheme of the SB-104, but this other one from KC8IV? Doesn't. Looks like one of the later units -- which would imply it was out AFTER the SB-1000 amp.

Or am I color blind?

[NQ6U]

It's difficult to tell from photographs but it looks like it might be a re-cased SB 220. Here is a shot of the innards of an SB-220:

http://www.ad4c.us/Amps%20pictures/HEATHKIT%20SB-220/SB-220%20BY%20THE%20TOP.jpg

And here is the one from the "SB 240" on QRZ:

http://i815.photobucket.com/albums/zz79/gyrogeerloose/SB240Inside-1_zps344e1b22.jpg

Although they are not identical, there is a distinct resemblance.

[N8YX]

Anyone compare the metering system with that of an HL-2200?

[N9RD]

Hello I am new to this list but when I read about the Heathkit SB240 amplifier , I joined to put in my 2 cents worth.
The same amp that you guys were talking about showed up in the latest QST.
Well I just want to straighten out a few questions and W3WN hit the nail on the head. The original SB240 was green just like the SB220 and matched the color of the SB104. I had an SB104 and could never keep finals in it.
Now the SB240 is an other animal I have one in service for 20years or more. It just keeps on working like it was new. I got mine from the Heatkit surplus store in Benton Harbor MI for next to nothing. I have a set of graphite anode Amperex 3-500 z's in it and this amp got me all the way to the DXCC #1 honor roll.

One nice thing about the amp is that Heathkit changed the input from the original SB220 to toroids which made it broadband enough to cover "all" HF bands from 80m to 10m. When I needed a little more power on 160, I modified my SB240 for 160. It does not look as pretty as the Amp in QST
(or pictures above) but then It has been used for a long time and was not in storage. I never had to do more than blowing out the dust, changing a few chokes, the output band switch wafers (like all SB220's), and filing off the plate capacitor to remove the molten metal after arcing. It's truly a remarkable Amp. Too bad that Heathkit did not put it into production.
I had mentioned the amp in my BIO in QRZ bur never posted any pictures but I think if I ever get my ham shack cleaned up , I will take some pictures to post.
Juergen N9RD

[W3WN]

Hello I am new to this list but when I read about the Heathkit SB240 amplifier , I joined to put in my 2 cents worth.
The same amp that you guys were talking about showed up in the latest QST.
Well I just want to straighten out a few questions and W3WN hit the nail on the head. The original SB240 was green just like the SB220 and matched the color of the SB104. I had an SB104 and could never keep finals in it.
Now the SB240 is an other animal I have one in service for 20years or more. It just keeps on working like it was new. I got mine from the Heatkit surplus store in Benton Harbor MI for next to nothing. I have a set of graphite anode Amperex 3-500 z's in it and this amp got me all the way to the DXCC #1 honor roll.

One nice thing about the amp is that Heathkit changed the input from the original SB220 to toroids which made it broadband enough to cover "all" HF bands from 80m to 10m. When I needed a little more power on 160, I modified my SB240 for 160. It does not look as pretty as the Amp in QST
(or pictures above) but then It has been used for a long time and was not in storage. I never had to do more than blowing out the dust, changing a few chokes, the output band switch wafers (like all SB220's), and filing off the plate capacitor to remove the molten metal after arcing. It's truly a remarkable Amp. Too bad that Heathkit did not put it into production.
I had mentioned the amp in my BIO in QRZ bur never posted any pictures but I think if I ever get my ham shack cleaned up , I will take some pictures to post.
Juergen N9RD
Juergen,

On behalf of the multitude, Welcome to the Island! Don't forget to let the barkeep know your first one is on my tab.

I was a little floored when I saw that article the other day in QST. This is indeed amongst the rarest of rare birds out there.

Out of curiousity, how did you get yours? The story is that only 10 protoypes were actually built before the company pulled the plug on the project, and allegedly only 3 survive to this day... which would imply yours, LA6OP's, and the one in the article are those three. Might be an interesting story...


...and I'm always looking for newsletter fodder... :twisted:

[N9RD]

Thanks for the welcome to the Island , I will certainly enjoy the first one !

Well I am not sure about the survival story that only 3 made it. Mine may be #4 ?????, no one ever contacted me about mine so they probably don't even know about me. I am not that famous but I will let the QST editor know. As I mentioned above, it came from the Heathkit surplus store at the factory.
We are only 50 miles from Benton Harbor, MI and some hams went up there every Saturday. A friend of mine picked up (2) SB240A's which he peddled I ended up with one all it needed was the tubes. I don't know about the 2nd unit It may have been scrapped or is still around here somewhere but I never heard about it. At least I dont think that it is on the air. I am not even sure when it was 20-25 Years ago ???? Heathkit was selling all kinds of stuff at that time , parts, prototypes etc. One thing I know I will not part with it... BTW just worked Spratley island 9M4SLL on 20m RTTY with it. Could never have done it without my SB-240A

[N2NH]

He might have a point. There are other sources for information on the SB-240 if you do a bing search.

This thread on another page is interesting. (http://rec.radio.amateur.boatanchors.narkive.com/8a3i8Nih/heathkit-sb-240-prototype)

The picture on that thread is different from the one in the OP. This one has SB-104 paint.

Lettering that doesn't look factory made says "2KW Linear Amplifier." (Picture) (http://home.online.no/~sindtorp/sb240front.JPG)

[AE1PT]

Say, does anyone besides me notice the labeling in the lower left corner that says:

HOHMBRU ELECTRONICS

Just checking...

[KC2UGV]

Say, does anyone besides me notice the labeling in the lower left corner that says:

HOHMBRU ELECTRONICS

Just checking...

Just noted that. The first picture appears to be slightly photoshopped too. Note the lettering "Amplifier" (Can't read the rest). It doesn't look properly aligned to the picture. In other words, it doesn't look like it's printed on the unit, but added into the photo.

[W3WN]

He might have a point. There are other sources for information on the SB-240 if you do a bing search.

This thread on another page is interesting. (http://rec.radio.amateur.boatanchors.narkive.com/8a3i8Nih/heathkit-sb-240-prototype)

The picture on that thread is different from the one in the OP. This one has SB-104 paint.

Lettering that doesn't look factory made says "2KW Linear Amplifier." (Picture) (http://home.online.no/~sindtorp/sb240front.JPG)The first link starts off with a post from LA6OP, and continues on with some speculation. It looks like the second link might be a picture of his amp.

Now I'm not afraid to admit being a bit skeptical about these units when this first surfaced, as I explained earlier. But as the stories are coming out, and as they're clearly not contradictory, but all fit together... it's making sense. (Which is not to say that SOME of the "SB-240's" out there might not have been the actual prototypes, but that's another story)

Since they were prototypes, it also makes sense that they might have different paint schemes, or that they may resemble previous models such as the SB-220. Simply put, it's likely that there were older cases & panels either sitting around as spares, or that could be easily reproduced. So why not use them? If they didn't work out in the protoype, and otherwise the rig proceed further towards production, a redesign or two could have happened. And if they did work out, why re-invent the wheel?

[NQ6U]

I was a little floored when I saw that article the other day in QST.

Which issue was that? I missed it completely.

[W3WN]

Which issue was that? I missed it completely.April 2013. And no, this wasn't the "April Fool's" article.

[K7SGJ]

The first link starts off with a post from LA6OP, and continues on with some speculation. It looks like the second link might be a picture of his amp.

Now I'm not afraid to admit being a bit skeptical about these units when this first surfaced, as I explained earlier. But as the stories are coming out, and as they're clearly not contradictory, but all fit together... it's making sense. (Which is not to say that SOME of the "SB-240's" out there might not have been the actual prototypes, but that's another story)

Since they were prototypes, it also makes sense that they might have different paint schemes, or that they may resemble previous models such as the SB-220. Simply put, it's likely that there were older cases & panels either sitting around as spares, or that could be easily reproduced. So why not use them? If they didn't work out in the protoype, and otherwise the rig proceed further towards production, a redesign or two could have happened. And if they did work out, why re-invent the wheel?

Because they reinvented the cart?

[NQ6U]

April 2013. And no, this wasn't the "April Fool's" article.

Okay, thanks. That issue just arrived in this morning's mail, which would explain why I hadn't seen the article.

[NY4Q]

Looks like some dimwit bought it, so there ya go.

I really need to start selling those "Triple Swing Diodes" on FleaBay.

[kb2vxa]

I'm not in any kind of position to judge but something made me wonder.

"During beta testing to disguise the amplifier the front trim strip said HOHMBREW Electronics model SIGNAL 2400EX and was painted a two tone tan and brown color."
Who were the beta testers and why the disguise?

"This however was a limited proof build of only 10 units."
OK, call it a proof build but in the industry they're known as prototypes. If the seller worked for Heathkit why not use industry standard terminology?

Here's the rub, I've done plenty of R&D work and tested prototypes IN HOUSE so why a disguise if they never left the factory? Funny how in house there is plenty of lab standard test equipment calibration traceable to NIST which is the usual requirement to prove equipment meets FCC standards, if it isn't "government approved" the test results are invalid. So what can sending it out into the "real world" prove that lab equipment and a dummy load can't? If you were responsible would you put anything on the air that wasn't properly tested and certified first? If it puts out a load of hash mash and trash yo in a heap o' trouble boy! So why then send already tested and certified equipment out to prove what?

The point is while some of the story makes perfect sense some of it smells a bit funny. It's a well known fact in political, propaganda and advertizing circles that if you mix known truth with lies the whole seems true. It's just sugar coating on a bitter pill, a technique used by the pharmaceutical industry every day. "Just a spoon full of sugar makes the medicine go down." Bottom line here for my 2c worth, there's something fishy in Vichy. Can't prove it so I won't try, just hooked on a feeling, high on believing.............

There's a song for every occasion. (;->)

[NQ6U]

April 2013. And no, this wasn't the "April Fool's" article.

Oh, and by the way, are you going to build one of those 2m Q-Pole antennas?

[W3WN]

Oh, and by the way, are you going to build one of those 2m Q-Pole antennas?Nah. I'm good.

Now the All Electric Tower, that's another story.

[NQ6U]

Nah. I'm good.

Now the All Electric Tower, that's another story.

Agreed. In fact, I want two of those to hold up my 160m flat top dipole.

[K7SGJ]

Nah. I'm good.

Now the All Electric Tower, that's another story.

Maybe with the left over stuff you can build an all electric chair, no?