Tag Archives: Heathkit SB-200

KA9EAK QRO – Update

Back in October I purchased a Heathkit SB-200 amplifier. The pictures in the original post show that it was a bit dusty from sitting for quite some time but otherwise it was in good shape and best of all it was not modified through the years. I purchased the Harbach updates but they largely have sat waiting for time to build, install, and test them. With time off for the holidays I was finally able to complete the work and I got the amplifier on the air yesterday afternoon. All appears to be well. Voltages and currents are where they should be in addition to no smoke or loud noises.

SB-200 HV

SB-200 HV

With 55 W of drive from my TS-590SG I am seeing a peak of 500 W on 40m SSB which is just where I wanted to be. I’m not interested in pushing the amp to its limit. The first contact with the amplifier was Frank, WA3RSL on 40m SSB late in the afternoon. I started the contact with the amp off and finished with it on with a nice and noticeable signal improvement as reported by WA3RSL. Frank has the same radio and also an amplifier so it was nice to walk through bringing it up with someone with the same radio and experience with using an amplifier with it. Second contact was Scott, K3IVN with a good signal report as well on 40m SSB. Later in the evening I was able to contact ZS6CCY on 40m SSB with a 59 report after only a few calls in a messy pile-up with a fair amount of noise and QSB followed by YV5AL, HI7MC, and J6/NY3B all with relative ease and great signal reports. I was happy with the investment.

I had purchased the power supply board, soft start, keying interface, and cooling fan updates from Harbach Electronics. Once they were all built and installed I brought the amp up on my Variac and there were no surprises and the high voltage looked good at 2250 V. The last step was to build the interface cable for the TS-590SG. Thankfully Kenwood provides the DIN connector with the radio and JG1VGX provided a very nice explanation of all of the possible ways to connect the TS-590 and TS-990 radios to amplifiers.

Here are some before and after pictures of the amplifier:

SB-200 top view

SB-200 top view

SB-200 Bottom view

SB-200 bottom view

In addition to the JG1VGX site referenced above I also found the following three sites helpful for this project:

http://www.crompton.com/hamradio/heath/sb200/sb200.html

http://blog.kotarak.net/2008/03/sb-200-part-1.html

http://www.wlwaters.com/id37.html

While there is some more testing to be done across a few more bands I’m very happy with the results thus far for the amount of money invested. In 1964 an SB-200 went for $200 which inflating the dollars to today is about what I have in this amplifier. I essentially purchased approximately one S-unit which is all that I set out to do and I learned a lot along the way which is much more valuable than the S-unit.

1964 SB-200 ad

1964 SB-200 ad

 

Advertisements

KA9EAK QRO

I’ve always run a 100W or less station until now:

Heathkit SB-200

Heathkit SB-200

As my antenna situation is improving I can hear more and work more but I can’t consistently break a big pile-up with 100 watts so I started looking for a little help in the form of an amplifier. Obviously there are a lot of choices but I’ve always liked the SB-200. It’s reasonably well regarded and there is a small cottage industry for parts and upgrades. There were a fair number of them sold from 1964 to 1978 resulting in a pretty good flow on the used market at any given time and it gives me the amount of power I want for a reasonable amount of money.

After watching the various equipment posting sites for a wee bit I found a nice clean one that is all original. No hacks, no mods. It’s a little dusty from sitting for some amount of time but it’s all there including the original Cetron 572B finals.

Original tubes

Original tubes

Old power supply board

Old power supply board

While I fully intend to do the various Harbach mods. when it arrived I wanted to make certain that the power transformer was functioning so after a thorough visual check for potential problems I brought it up slowly on a variac and there was no excitement. It powers up fine, all the secondaries are functioning and the high voltage was 2100 V which is OK but a little low. No big deal as it will get a new power supply board which should largely solve that problem.

The next step was to place an order for the Harbach mods. I chose to do the power supply module, the soft start, the soft key, and the fan upgrades. Within a several days of my order the Harbach parts arrived in the mail.

Harbach mods

Harbach mods

The problem is that Fall is rapidly progressing and we are now three weeks out from Thanksgiving and it’s not uncommon to have some snow by then so outside work has taken precedence over the SB-200 project. I’ll have some time off work through the holidays to build the Harbach mods and get the SB-200 on the air. It will be nice to have around on occasion and I look forward to operating with it.