Heathkit SB-220 Repairs

This is a few pics of a Heathkit SB-220 amp I repaired for a friend. It had a basket full of problems...HV supply was dropping voltage intermittently, band switch arcing, tuned input problems, bias issues, and more. These amps are real workhorses when in good operating condition. Here's a few pics and info on what was wrong with this beast.  

This amp was a mess....I started by breaking it down, and I prefer to work on it with the high voltage safety defeated. DO NOT do this...it's very dangerous, and the voltages / current available in this power supply can easily kill you! 

I pulled out my vintage high voltage probe to poke around in the HV supply...

I started right off by pulling and replacing a bunch of bad parts. Voltage divider resistors from the metering curcuit, RF choke from the grid circuit, blown LV filter cap...

One of the filter caps had literally blown the terminal right off the cap!

You can see the black area around the filter cap terminal in the upper LH filter bank...

I had to use my resistance substitution box to calibrate the HV meter function, those resistors were so far off and the original values didn't really bring the meter into calibration. 

I replaced the bad cap and all of the bleeder resistors. All caps should have been replaced, but I had to stay in the owner's budget. 

The HV curcuit is now working correctly and the meter is in calibration. 

Using the HV probe to double check the supply voltage.

Tweaking the metering circuit to read correctly...

One of the tubes would loose the filament connection from time to time....

The paracytic suppressors and plate connections were also a mess...coating popped off of the resistors in spots, some nasty braid used in the plate circuit, etc. I ripped all that junk out and rebuilt it...

 Winding new coils to install on a pair of new carbon film resistors for plate suppressors...

Plate suppressors all finished and installed...

Warming up and ready to test bias...

Added some silicon diodes to the bias string to get the bias current where it should be. 

Applied a little drive, and found the tuned input to be all buggered up...

Had to remove the front panel to get to the tuned input. One of the silver mica caps was exploded, most always due to over drive. No telling what had been driven into this amp by a previous owner...

Band switch wafer repaired (was arcing) and bad tuned input caps were replaced.

Band switch wafer had arcing contact, way down there. Another tough one to get to for repairs!

I discovered one of the tube filament pins were not making good contact in the tube socket. I removed the springs, cleaned the pin clamps, and resprung the clamping mechanisms. 

The metering switch was also broken. This is the replacement switch I installed...

This is the wafer from the broken metering switch...

 While cleaning up, I removed the knobs and with a little Windex and toothbrush I gave them a good cleaning.

 Driving the amp from a Yaesu FT-101 for testing...

Here it is, all cleaned up and ready to go. This was one of those projects, where the more things you repair, the more stuff you find that needs attention. It has had a rough life and problems were ignored at some point, but now it's back up to speed and running quite nicely. 

Dave WB4IUY
www.WB4IUY.net

Speed-X Key, looking the model #...

 

This is an old Speed-X straight key that was given to me many years ago by friend and ham Peter N4SXG (now SK). It doesn't handle very good, but it is usable. I use it from time to time, and on straight key night, as it does have a special meaning to me. 

I am trying to find an approximate date of mfg, and the model #, if anyone out there should know what it is. It looks like the little cheapie plastic base unit that was sold by MFJ, Radio Shack, Ameco, etc....with a couple of exceptions. Those are:

It has Speed-X embossed into the lever...

It has Speed-X molded / raised in the plastic base, as well as a small raised rib in the base all the way around it's perimeter.  

Pete made a wooden base for it and installed some felt on the bottom of it. When he was alive, he only worked a straight key, and could really hammer this thing. Pete was a Navy CW op and copied on a mechanical typewriter.

Dave WB4IUY
www.WB4IUY.net

My Heathkit HW-101

I originally bought this Heathkit HW-101 back around 1993 from a friend at the Maysville NC hamfest. It had never been on the air, and my friend said they couldn't figure it out. It was originally built back around 1970, wouldn't work, and was put back in the box and stored away. After a little bit of work (assembly problems), it was on the air and playing like a new radio! I took it up to my Mom & Dad's lake house at Kerr Lake in NC, strung up some dipoles, and left it there...until January of 2020. I recently brought it home, and gave it a bit of a checkup, cleaning, and adjustment. It's on the air again, and just as good as it ever was.

Here's a little video after I finished up with a minor facelift on the rig. Receiving an SSB conversation on 40M at night. I have always loved these rigs, and have owned several over the years.

Here, I have the hood up. Tubes cleaned (they cool better when clean), sockets and all controls cleaned and lubricated, several mods done to improve the  SSB reception by increasing the BFO osc level and reducing the IF injection at the mixer. Also replaced a bunch of carbon resistors that had shifted values over the years.

I pulled the inner lower cover and cleaned the band switch. This one also has the CW filter.

Penta Labs 6146's in the PA! I neutralized them using the cold cathode method. I also gave the rig a full alignment and made a mod to improve the carrier injection null.

Cases and face plate cleaned, and looking great for a 50 year old rig!!

Ready to move her over to an operating position in Studio B!

Wired to a non-amplified D-104 mic, the transmit audio sound great and gets good reports. 

A little action on 40m SSB

Dave WB4IUY

www.WB4IUY.net

Wiring the shack...

I've had visitors and webcam folks ask: "What are you reaching under the table top to do?". This was always funny to me for some reason, so I decided to make a post and explain it, as well as my AC/DC power system. First, here's a basic pic of Studio A, my primary operating position. The 8' long main table was built for me back around 1993 by a good friend.

I have various radio gear scattered on 3 tiers of table and shelving. Almost all of it runs on low voltage DC. I have a large, deep cycle battery system in the garage (just on the other side of the RH wall in the photo). Those are charged by a pair of high current DC supplies, and diode switched to provide instant battery backup in case the AC mains are lost. I live in a rural area, and have a whole house generator to keep things powered, and opted to go this route to keep the bulk of the load off of the generator should I be on emergency power. The shack will run a few days like this, with no AC assistance from the generator, if needed. The shack computers are powered through some fairly large battery backup (UPS) systems to keep them online while the AC supply is cutting over from AC mains to the generator.

 

 On the top shelf, just to the right of the lamp, you'll notice a 5 position rotary coax switch mounted to the forward facing edge. This is how I select various HF rigs and a cable that runs out to Studio B, to the various antennas that are brought into the shack. It's an easy reach from my rolling chair :-)

In the pics above, you'll see the AC surge suppressors / power strips I use to power the various AC widgets and computer backups. I have those mounted along the inner rear edge of the table. Notice the copper pipe running lengthwise along the rear underside of the table? That is attached to a 6' copper ground rod, driven into the ground directly under that table. Radios, coax, and other items are all ground through that.

 From the DC supply system in the garage, I bring in a short run of 2/0 automotive battery cable, to a DC power distribution terminal block pair located in the center web of the underside of the table. From there, I connect all of the various DC radios and other devices through fuse blocks. This makes the addition of radios and such pretty easy. Again, you can see the ground bar running along the bottom of the table.

Now, on to "what I'm reaching for under the table". Along the front inner edge of the table, I have 3 antenna switches mounted. I easily reach under the front edge of the table, and select the HF yagi, dipoles, slopers, VHF yagi, 6m yagi, Cantenna dummy load, etc. That keeps my shelving and desk top free of antenna switches and a bunch of bulky cables that's always trying to pull them off the table.

This is pretty basic stuff, and I'm sure there's much better ways to do it, but it's how I do it. Hope that helps someone with their shack layout!

Dave WB4IUY

www.WB4IUY.net

 

Straight Key Century Club

Wow, so glad I found this group. Years ago, I really enjoyed using my straight keys. Over time, I started using my Iambic paddles and electronic keyer for contecting and such, and the keyboard for CW rag chews. I totally forgot how much fun the old keys were. I found this group, dusted off one of my old keys, and jumped in. Lots of fun...my fish isn't what it once was, but it's getting better. Check them out on facebook and on their website at www.SKCCGroup.com 

Dave WB4IUY
www.WB4IUY.net