September 01, 2022, the last third of 2022.
Fall will arrive in three weeks and the outside temperature today will be greater than 100F. I suspect that for some segment of our great nation the temperature seems as hot as Hell, and we are not talking OAT. (Outside Air Temperature). MAL might be one of those places!
This series on resurrected radios will soon come to an end and likely many are breathing a sigh of relief. Who wants to read about this old stuff? But as I pointed out with the SBE-33 -- it was an extremely sophisticated design.
This will terminate the Resurrected Radios Trek!
As I sit in front of the SBE-33 and "twiddle the knobs", I am really impressed at the late 1950's early 1960's technology. There is some pure genius in this design! Yet when I stack this "prize of old" versus my homebrew SDR transceiver, there is no comparison with today's technology.
The sophistication of today's technology insofar as frequency stability with a readout to one hertz coupled with the signal processing capabilities is astounding! Signals can be narrowed down or opened up without the need for expensive crystal filters -- it is all done in software. The huge bonus is to be able to LOOK across a whole band of frequencies and see the activity. The SBE-33 limits you to about 3 kHz.
Keep in mind that in the 60-year interval between the Wright Brothers at Kittyhawk and landing a man on the moon is the same time horizon between the SBE-33 and the homebrew SDR. No one in their right mind would take the Wright flyer out for a spin today, yet the SBE-33 can be and is being used on the ham bands. Thank you, Faust Gonset!
8/30/2022. 1962 Advanced Technology
Here is a partial schematic of the SBE-33 which
involves 8 transistors. But it is how these transistors are arranged that offers an insight into 1962 Advanced Technology. Keep in mind it was only 14 years prior to this that the 1st transistor became operational!
- Q4 is the Microphone Amplifier
- Q5 is used both on transmit and receive. It is called a Signal Splitter
- Q14 is the BFO
- Q13 is an Emitter Follower feeding the Diode ring which is used both on Transmit and Receive.
- Q15 and Q16 art Pure Art for 1962. Q15 is a Frequency Doubler which produces a 910 kHz Signal. This is then fed to Q16 which can be either a Doubler (1820 kHz) or a Tripler (2730 kHz) depending on what capacitor is switched into the circuit.
- The 455 kHz transmit SSB signal is mixed with either the 1800 kHz or 2700 kHz signal to produce a 22oo kHz IF signal either USB or LSB. That is all done with the diode following the Mechanical Filter. On receive the 1800 or 2700 kHz signal is mixed with the incoming to produce a 455 kHz IF signal into the diode ring.
This was an advanced design, and the question remains just who designed the SBE-33. The Urban Legend has that a group of illuminati did this on a contract basis.
Names like Don Stoner and Lester Earnshaw have been postulated as part of such a group. Maybe Butch Mason and Ed Marriner may have had an oar in the boat too. Butch Mason is the INVENTOR of bilateral circuitry as was 1st used in the Cosmophone 35.
8/29/2022
The Speaker fix continues to hold --so indeed the culprit. My next issue is to find out why there is not full output on 75M. I figure getting it to work on this band will enable a bit of gentle harassing of those hams, mainly with 7 Calls, who know nothing about the law or politics yet speak like the Oracle from Delphi. (BTW that is Delphi in Greece not the State of Indiana.)
8/28/2022
My caregiver duties typically raise hell with any meaningful bench time. So, when a problem comes up it is difficult to resolve with only 15 minutes available every 2 or 3 hours. Yes, that was the case yesterday. After replacing all of the Electrolytic caps it was now possible to do some serious evaluation with power ON.
The SBE-33 would work on Receive and then after a short while go dead. Yet flip it to Transmit and it would output and then on TR would come on in Receive but only briefly. So that was telling and that gets us to Step #5 Read the Tea Leaves.
The first conclusion is that the common and the transmit circuits are working. So that leaves the problem to the Receive only circuits. After several 15-minute sessions I tried something. Nothing coming from the speaker but upon plugging in a set of headphones -- audio output. Pull the headphones and no audio, but it is there on the headphones. The headphone jack disconnects the speaker when headphones are plugged into the jack. I checked the phonejack and it was in good working order so that was not the issue.
That left the speaker as an area to investigate. There is a single wire going to the built-in speaker and the other speaker lead is connected to the speaker frame and the speaker frame is screwed into the font panel. So, the next time it went dead. I jiggled the speaker itself and found the bolts were not tight and that was the source of the intermittent connection. The not so obvious is often the guilty party!
Then the light bulb went ON! The tune switch is on the front panel and is a rotary switch located in close proximity to the Speaker. When you engage that switch you are torquing the front panel, and this causes the intermittent connection to ground of the speaker case. Not so obvious!
Read the Tea Leaves! Indeed, not so obvious, Mary Jo was not wearing any underwear!
8/27/2022
As promised more tribal knowledge about this particular project. Step #1 was to Research the Documentation. Step #2 is to Read and Digest the Information. In the troubleshooting section of the SBE-33 Manual which can be found on the BAMA/Edebris website clear mention is made about the electrolytic capacitors as being an issue for low audio output or low transmitted output. So, you have been warned.
Thus, Step #3 is that you must conduct a visual inspection of the circuit components with particular attention to the Electrolytic caps. Often with the High Voltage caps there is an escape port on the positive terminal -- that will show sign of being blown. Liquid oozing from the cap is another sign. Sometimes the cap will look pregnant. Mark down the caps that show these physical signs. But the old axiom -- one rotten apple in the barrel was never so true. These electrolytic caps are 60+ years old so they all should be replaced! Also look for any discolored Ceramic Caps or burnt/smoked Resistors. Keep notes and I do this by marking the part(s) right on the schematic. In one earlier SBE-33 restoration it was a 0.01 Ceramic Coupling Cap that was the culprit in a non-functioning radio.
Step #4 is to apply voltage to the Radio using a Variac to reform the Electrolytic caps if only to see if there is some basic operation or to sense if there may be some shorts to ground. I took over an hour to apply voltage in 10 Volt increments. No shorts, but low audio output on receive (it does work) and no output from the Microphone amplifier stage.
I had removed the final tubes as they looked smoked. So that removed one possible short to ground and the leaking electrolytic caps are all in the HV power supply -- so no HV was tested or shorted to ground.
As I made the inspection (Step #3), tears came to my eyes as I read the manufacturers of these parts. They were all American companies with plant locations like Nashville, TN and Chicago, IL. The ranks of American Electrolytic Capacitor Manufacturers have been very much thinned! Here are the Electrolytic Caps that were removed. There are 19 in the photo --must be missing one as I thought there were 20
8/26/2022
This is a vintage 1963 Sideband Engineers SBE-33, Four Band, Hybrid SSB Transceiver with Built-in Power Supply and a Collins Mechanical Filter. I bought it for $45. It did not have a case. It was dusty but looked like it was all there. This unit was built in San Francisco possibly by Linear Systems or Raytheon.
[A side note here. Since Raytheon purchased SBE they technically were in the Ham Radio business. The irony today, is that two ham radio equipment manufacturers, Raytheon and FLEX Radio, are jointly producing the next generation SDR based Radio System for the US Air Force. Key -- they made ham equipment before making military radios! ]
This was a huge deal for me. Several years ago, I purchased a "Junker" and thus have many repair parts including the all-important case. Critically important are the many mechanical parts that just are not available anywhere other than with a second parts donor unit. Basically, it was a low-risk purchase. Also, noteworthy because I had worked on previous units, I had a stock of the needed parts. That is the value of buying parts in bulk.
These rigs had unique "bi-lateral" circuitry which pre-dates Bitx transceivers by some 60 years. This is not my first rodeo with the SBE-33 and the most typical problem is the electrolytic capacitors. The built-in power supply used a voltage quadrupler circuit of the mains (shades of the S-38E) to produce 450 VDC for the plates of the 27GB5's. The power output on 80-20M is about 50 watts and slightly less on 15M.
The two critical electrolytic capacitor replacement areas are the low-level audio stages and the power supply. In total there are about 20 capacitors that require immediate replacement. Beyond that are the normal bypass and coupling capacitors.
By the way this radio has selectable sidebands and is done with a single BFO crystal. In a design way ahead of its time, the BFO (455 kHz) is frequency multiplied to 1800 kHz and 2700 kHz. These frequencies are then used in a mixer circuit when mixed with a transmitted signal at 455 kHz produces an IF at 2200 kHz. Whereas on Receive the 2200 kHz IF is mixed with either the 1800 kHz or 2700 kHz to produce 455 kHz IF. A simple Germanium Diode Ring operates as a Product Detector on Receive or Balanced Modulator on Transmit.
For Mobile operation SBE sold a rudimentary inverter that produces 115VAC from 12 VDC. These are hard to find but a modern 400-watt inverter was purchased from Bezos for $24.
In subsequent posts I will outline the additional tribal knowledge steps to bring this puppy back to life! Teaser -- it is working!
One observation -- modern equivalents of parts like 300 Ufd 150 VDC electrolytics are way smaller than their 1960 equivalents. So once all of the replacements are made -- the rig looks barren whereas the 1960 version was stuffed to the gills! It is like a 29A versus a 44DD!
The three larger capacitors are the original units and by each one is the exact same value only modern components. You can see the parallel to the 44D versus the 29A comment! The adjunct comment -- Bigger is not necessarily better -- it is just optics friend!
8/24/2022 Update
While many of my resurrected radios have tubes, I also acquired some early solid-state models such as this Ten Tec Model 540 (Analog Version). I got this radio for about $80, and it had problems with a broken dial string and lacked the pointer mechanism and dial skirt. The front panel looked like someone puked on it.
About 10 years ago I actually did a similar project with a model 540 and converted it to a Model 544, the digital version. That project was a subject of a published article in QRP Quarterly. That Model 540 retrofit to the Model 544 used the AADE VFO display/controller which is no longer available.
So, this resurrection took a slightly different course and cheaper fix. I purchased an in expensive 6-digit counter display (about $15) and made the install. This display had the offsets enabled so that the dial read 0 to 500kHz as was done on some Ten Tec Rigs like the Scout. The band switch essentially set the MHz digits. In the second photo if the band switch were set to 7 MHz then your frequency would be 7.256.5 MHz.
So, the parts added plus just some elbow grease turned this into a 100-watt radio with a digital display. I heard from a friend of a new ham who lacked an HF rig and was barely making enough to live on, so I gifted this radio to that ham. He was so thankful and appreciated having an almost modern rig to use. BTW these TT rigs had some really nice features and this one had the extra 10 Meter crystals, the CW Filters and the Noise Blanker. Now it had a digital display
As promised, I will outline the steps I use to resurrect these older ham rigs and how they can be resurrected and used on the bands today!
STEP #1. Research and Collect data on the radios from the period 1970 to 2000. This is where you turn off the soldering iron and do not look at the eBay listings! What were the most popular rigs during that time period and also look for things that could be gotcha's?
Here is an example of a gotcha with the ICOM IC-701 which was their 1st Solid-State HF rig sold in the US. I saw one in action in the mid-70's and was taken by its small size and many bells and whistles. But with a young family and a mortgage -- just no way to get one.
Fast forward 50 years and I still look but don't buy. That particular radio had extensive use of relays that came into play when you switched bands, and the encoder was state of the art but today -- these relays are unobtanium as is the encoder. So, you need to likely purchase three IC-701's to get one working radio. Thusly, not a good candidate!
On the other hand, the Ten Tec radios are in good supply as was with the Model 540 and are easily upgraded. So, if you are going to look for a Solid-State Resurrection Candidate then bookmark Ten Tec.
The other consideration with Ten Tec is the way they are built with plug in circuit boards which have easily accessible test points and are easily removed for servicing. Yet another bonus is the available documentation, you tube videos and the Ten Tec .io group.
One significant Research resource is the eHam product reviews. This is where I picked up that for the Tempo One it was imperative to replace C55 and C40 otherwise risk smoking your Finals. Use this resource as it also gives you the "ham rating" as to how well this rig was accepted by the general ham population. If the rating from 40 hams is a 1.8 out of a possible 5 then that gives you some clue -- steer clear!
Step #1! Research and Collect Data!
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I have spotted a significant number of bargain radios that can be had cheaply. But they all likely will require intervention to get working. That, however, is the opportunity for you to undertake a radio resurrection. To do this you must have some learning under your belt. Thusly if you want to learn something about our hobby then a resurrection of an old-time radio is a grand start.
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My Tempo One is a great example and another is my KWM-1. I got the KWM-1 which is a late production serial number (S/N 953) for way under market. The advert said works on receive but transmits on a different frequency. Well, I had my suspicions and they turned out to be true. It was a simple tube replacement in the transmit chain. So that radio is worth a lot more now because it works!
There are many .io groups that support these older radios, so you are not flying totally blind. You Tube Videos are another resource. There are even on the air nets that promote the resurrection of these oldies but goodies.
In the next couple of weeks, I hope to outline a resurrection process, so I enjoin you to ride along with me as I share some Radio Resurrection Tribal Knowledge.
Pete N6QW
To Lindsey Graham you might want to focus on your own possible legal problems with the State of Georgia and not predict riots if the FPOTUS gets indicted. The chickens are coming home to roost!