Harbach sb 200
07.07.2020 | by Gashakar
Soft start. Control grid. Tuning cap. Input circts. Ant relay. More mods. HV plus. Input tuning. Extra fan. This model, first marketed aroundstill features in many amateur stations. I recently bought a used one on-line at a reasonable price. That remains risky, so the first thing checked here were the transformer and the meters, which were found OK.
The cabinet showed its age but there were no dents or deep scratches. Replacements for their parts can usually be found. The design called for the V supply in the amplifier to energise the amplifier antenna relay through a contact on the PTT relay present in the valve transmitters of the day.
Heathkit SB-200 & SB-201
Modern SSB transceivers have no such relay. That problem will be addressed. After a good cleaning and check-up all looked presentable again.
The two B valves turned out to be as good as the pair I had from another amplifier. The cabinet is a bit like a suitcase, with a lid opening upwards. The internal height is mm, but unfortunately, in the compartment where the two valves are horizontally mounted, the height is only mm, insufficient for GUB or GSB without a lot of mechanical work. GI-7Bs would fit but I doubt these would produce more output than the originals.
I decided to make such changes, possibly with new components as were required to make the amplifier fully serviceable.When you subscribe, you receive only messages for the product you have subscribed to.
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Heathkit SB-220 & SB-221
Reviews Home. Old but proven design, easy to work on and upgrade. They can be had for typically, with or without upgrades. Well build but with the Harbach upgrade options, etc. Tuned input, you can get the WARC bands also tune off the appropriate band for that.
Runs around or so watts out key down, typical for the A amps but the B's are a bit more robust. Great mid level amp, and increasing output to 1KW doesn't buy you much in a pile up.
So, the SB is either a great starter in Amps for your shack, a great back up, a great daily amp. Recently I acquired a Heathkit SB which is in great condition for its age.
All the recent Harbach Mods done. This SB easily does the watts it is rated at. This amplifier is very clean inside. My plans are to run the unit about half the rated power which is about all I need. By doing so the Amplifier will probably out live me, hopefully another 50 years. I also snagged two new B's which I have safely put up in the closet out of harms way.
It is like the other posters here have said, if you have the chance to snag one of these amplifiers you should. They are easy to work on and maintain. If you are not afraid of high voltage this could make for a nice project. A great piece of history that does its job and runs as cool as a cucumber I acquired my SB before I had my ticket and completely rebuilt it while studying for my General.
It was a complete toaster for super cheap and came together easily. This amp is a power house performer.
Easy to use, inexpensive to maintain.During this time I will be unable to process and ship order due to my injuries. I am sorry but I have heal up before I can get back in the shop.
The PC boards come with the wire connection terminals pre-staked and soldered to the PC boards. Complete step by step instructions are also available for download from the website. This all-in-one board installs in the power supply in the original mounting location. It features all new resistors, diodes and capacitors on a newly-designed double-sided PC board. This all-in-one board installs over the bottom of the transformer like the original, but has all new resistors, diodes and capacitors on a single PC board.
The PCB is pre-assembled and tested and includes a new 3-wire line cord and new safety AC line bypass capacitors. This all-in-one board provides a soft-start, soft-key and user adjustable biasing for the Drake L-4B amplifier. The board is assembled and comes with all necessary mounting hardware, miscellaneous parts and wiring. Search our Site. Product Categories.
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Shopping Cart.The Heathkit SB amplifier has been around for years and many are still in use. I rebuilt my Heathkit SB that I obtain from e-bay. This one was in bad shape but the price was right. It was dropped, bad tubes, and definitely been used. I slowly rebuilt the amp and got it fully functional. Refer to their website. I went ahead and modified my SB according to his website and followed most of his recommendations. The following items are what I wanted to accomplish with these modifications:.
I give him all the credit. I am impressed with the stability of the amp and have not had any issues. The modified SB schematic diagram is shown below. This board may still be available from Jackson Press. Here is the meter switch wafer detail. This needs to be modified per the schematic above. I had to had a 24V power supply for these relays since the original used V. Your email address will not be published. Notify me of follow-up comments by email. Notify me of new posts by email.
This site uses Akismet to reduce spam. Learn how your comment data is processed. The following items are what I wanted to accomplish with these modifications: Tube Protection.
Fuse the high voltage to reduce catastrophic failures. Soft Start to limit the primary in-rush of current and slow the rise of anode voltage. This protects the filaments and rectifier diodes and permits the use of a lower current primary fuse. Stability Change amplifier key to support modern radios.QRZ Forums.
I have a SB with the Harbach mods including the soft key module. KO1LSep 3, What are you using for the and the ? You can't just connect it as it will burn up the relay in the Use a Ameritron ARB or such type of switching. WN2CSep 3, W7UUU likes this. Hi Use a outside relay to key the SB as the rather high voltage of the sb relay might be a danger to use straight from the IC If you just use a 12v relay that you key with the ic tx ground, then you can key the sb with this relay.
I made plenty of TX ground devices to switch remote equipement with any rig I had. Also my homebrew noise-canceler is switched with TX ground, and ofcourse my amplifier. PA1ZPSep 3, Once upon a time Heathkit issued a service bulletin on how to modify the ALC by adding a zener diode, to limit ALC voltage and make this ancient amplifier work better with solid state rigs.
In lieu of making this modification, I'd just leave ALC unconnected and back off IC drive input to the SB to limit output to about watts on voice peaks.
IC-7300- Heathkit SB-200
You can probably go to W on 20M, less om 10M. Its not a great idea to push the amp too hard. K6BRNSep 3, WD4IGX likes this. WN2CSep 4, Between the soft key module and a isolation cable I think the relay problem is covered, I think leaving the ALC disconnected and backing down the drive is probably the best idea. KO1LSep 10, Not sure if this thread is still alive but I thought by installing the Harbach soft key you eliminate the need for the keying interface with 12 volt supply.
I was under the impression that the need for anything else other than the rca cable connection from my the send jack of the radio to the antenna keying jack on the amp was supposed to be sufficient ALC being optional. Any input on this is welcome. W9ANWJul 13, It's fine, just don't bother with the ALC. With my old Yaesu I used to use a relay box that I built to key the amp but I don't need it now and my Flex can key the old amps anyway. It will key fine with the Harbach board, no sweat.
Just don't hook up the ALC, like the guys above said. W9ANW likes this.QRZ Forums. I am picking up a Heathkit SB from a fellow Ham this evening. I am wondering if it is possible to add bands to this amp. I am thinking I would like to add 17m and 12m if possible. Anyone know of a source for this information? A google search came up empty with the exception of adding m. Just set the bandswitch to the nearest band and start playing with the knobs.
Think 30M works on the 20M position, and 17 on the 15M position. But it tunes up great and plenty of output. I would just add some labels as to where the tuning hot spots are and the bandswitch positions. Didn't hafta mess with the input coils. Also, U have run outta bandswitch positions.
W0BTUFeb 20, Last edited: Feb 21, W0BTUFeb 21, Thanks for the responses. Good to know that I should be able to get it to tune up on the other bands without modification. I'm not going to bother with the m conversion.
I did check out Harbach's other mods and may consider the new power supply module and soft start kit once I see how well everything works and what problems there is with the amplifier. I finally got around to powering this amplifier up today.
No smoke so that's a good sign. Still think I will change out the power supply board for one of the Harbach ones just to make sure the supply remains stable. The HV Voltage is right at V and held steady so that should be good. I didn't hook it up to a radio yet so still not sure how it will react under a load. Just watch the grid and plate current, and keep an eye on the tubes. You need to raise the hinged lid to see them. My lid stays propped up all the time, so it runs cooler and I can see the tubes.
The anodes should only show color after running it for awhile at maximum on CW, and they should never glow beyond a dull red.
Orange plates are too hot. I replaced them with Svetlanas a couple of years ago. Last edited: Mar 19, W0BTUMar 19, One other thing I did notice is that the socket for the light in the meter is melted and deformed a little.
Looks like someone put too hot of a bulb in it. Guess I'll have to start hunting around for one of those. Also tha fan has been swapped out and a larger computer type fan has been installed.Heathkit SB Rebuild. As a hardware Engineer, over the years I have worked with high voltage and high current devices so I have a healthy respect for this type of hardware.
I then pulled the tubes and boxed them for safe keeping. Then I gave the unit a complete checkout for signs of arching and burnt components. Finding none, I then removed the knobs, meter, and front panel and started the cleaning process. With all of the parts on order I set out to clean the chassis and case. Light soap and hot water is all that is needed to clean the knobs and hinged case. The hinged case was a little dirty from 47 years of use but had hardly a scratch on it, no repainting needed.
I decided to leave the radio in the original HeathKit turquoise green colors as it was painted at the factory as the paint is in such nice condition. I also like to keep a working antique looking original. I do admit a nice Black Chassis and face panel would look nice too….
Knowing that over the last 47 years since this unit was assembled that there must be modifications and improvements made I set out on the web to research it. One of the best places to start looking for any project like this is to look for a Yahoo Group. This is where the experts and newbies can be found.
Here you can find the real experts on these old tube amps. In my quest to learn about what can be done to restore this old amp I found a company that supplies modern replacement kits for improving and fixing older model RF Amps. While I was making the order, I also purchased the 2 replacement electrolytic caps that are used separate from the high voltage supply.Harbach sk220 soft key
The Yahoo group experts recommended upping the size of the electrolytic caps used in the Harbache Electronics PM kit to something a little larger. This should help add the extra filter capacity for high voice peaks.
I specked and purchased the caps from Digikey Part Number: P I had fund much of the same information while searching the net, but it was worth the cost to me as the document was well made, printed on good quality paper and overall a nice document with all the information in one place. To clean the electronics compartments I started using spray electronic cleaner, but it was going to take more than just a few cans to do a good job so I opted for option B. I took out a midsized paint sprayer and filed and adjusted it for spraying Acetone.
Using a brush and rags I would spray, brush, and rubbed the years of grime away. I was careful around sensitive areas like the transformer as its paint is acetone soluble. Any other part that I thought might be sensitive like plastic I removed prior to cleaning. After the Acetone wash, I used a lubricated electronic contact cleaner for all pots, and switches. I wanted to make sure the rotary band switches and the rotary meter function switch were both clean and lubricated. Next was the reassemble process.