Buying, fixing, and using Round
and Green (and other) boatanchors.
(c) 2002 HHR.
Update: December 2, 2002
In this issue:
Testing and fixing the SB solid state LMO
The SB-304
The previous issue of Heathstuff.
Join the radio investor discussion group.
Reading Heathstuff/Boatanchors. This is a website created for
you to read and reread. The first page links to this one. This
page will link to a future issue, I will update the issues from time to
time as I get more information for the articles. I will also
update the ads and links. This is a little different from reading
a static site.
The LMO is a standalone oscillator. You can run it outboard of the SB-303 with only 3 connections. Ground, +10V, and LMO out, an RCA cable. If the LMO is unstable and only if it is unstable, remove it from the radio, and open the bottom plate (4 small philips screws). Remove the RTTY board, it slides out. You must unsolder the three wires from the LMO.
Use an extender cord to connect the LMO to the mixer. If you feed the LMO output to an analog Oscilloscope or a Frequency Counter. Remember you still need a 47 ohm load.
The LMO tunes from 5.510 to 4.990 mHz. The output should be about 5.0 V Peak to Peak. I've measured 4.8 to 5.2 Volts on a good LMO. The sine wave should look smooth and clear on the scope.
You can listen to it on a general coverage receiver. It should sound like a pure CW note.
If the LMO makes bursts of noise, warbles, tunes scratchy, or drops out of oscillation, it might be a dirty brass spring. The spring touches the rotor of the tuning capacitor. You can see it next to a shield and behind the circuit board.
Another symptom is low signal levels. I've seen 2-3 Volts Peak to Peak. I use a Tektronix TDS 210 digital storage oscilloscope to measure this. In September 2002, I bought a Tektronix 2215, dual trace, 60 mHz, delayed sweep scope for $80 on eBay. It came with the panels for rack mounting. The 2215 is more than adequate for checking the oscilloscope output.
De-Ox-it should fix this LMO problem. Shoot a little De-Ox-it onto the spring and work the tuning shaft. Listen to the LMO, watch the trace, the counter, or listen to the band. It should clear up. If working the control doesn't do it. Make a burnishing tool out of a piece of cardstock and feed it to the rotor hub as you tune the capacitor. The cardstock will show dark lines from the corrosion or dirt. Clean the contact point until the cardstock comes out clean.
Cleaning should stabilize the LMO. I've fixed two this way. These went from stray, random oscillation to absolutely rock solid. They track within spec across the band. I set one on 5.250 004 mHz. I checked the drift with a frequency counter. Through out the day, it drifted about two hundred Hertz as the temperature changed. After 6 days it was back on 5.250.020 mHz. This is outstanding stability for a 30 year old LC oscillator.
You should not have to turn the air trimmer capacitor. If you do, you will have to re-align the LMO, preferably using a frequency counter.
I've seen LMOs with missing shields replaced with duct tape. I replace these with a small piece of aluminum or stainless steel tape; larger hardware stores carry this. Cut the tape to size and press on the LMO to replace the duct tape. I use a concave scissors from "Michaels Crafts" to round the corners of the metal tape.
Review of the AADE digital readout for the SB series.
After the SB-303 is back in spec and aligned. Here are some modifications that I call the SB-304. I do not like to butcher or modify collectable boat anchors but these changes can be reversed.
These tweaks are in addition to my mechanical alignment, De-Ox-it the controls, oiling the moving parts, thorough cleaning of the front panel, interior and knobs, an instrument electrical alignment, and setting the endpoints of the LMO and verifying that it tracks and is stable within spec, checking the audio output by measuring the RMS output at specific frequencies.
Replace the antenna jack with a BNC connector or a gold RCA connector.
Replace the speaker connector with a gold RCA connector.
Add a 10-50 puff cap to the output of the 3rd IF to pickoff the IF signal to a spare RCA connector. Label this "Scope". Use RG-174 or better. Leave enough slack to work on the boards or use a disconnect.
Add a second SSB filter in series with the first. You will lose a little IF gain but an SB-303 is so hot that this mod does not require the addition of a 4th IF amp. The second filter will fit below the chassis next to the "daughterboard".
Pry off the main tuning knob skirt and fill the cavity with lead shot and glue. Be careful to keep the knob in balance.
Replace the feet with 20 mm "sliders" from Home Depot. These come 8 to a pack. You will need new hardware, 1/2 inch 6-32 stainless steel machine screws. 20 mm sliders are superfeet. They do not leave black marks if you stack radios.
If the knobs have blade setscrews replace them with stainless steel Allen setscrews.
Consider replacing all electrolytic caps in the powersupply. I use higher values where possible. These are inexpensive when bought mail order in quantity and smaller than the stock caps. I keep the original caps in a baggy so that if I ever sell an SB-303 to a purist, I can give him the original parts with the radio. Some purists will hollow out the old caps and hide a new cap in it to maintain the original look and feel.
I label the voltage and S-meter controls on the bottom of the chassis with a sharpie pen. A purist can easily clean this off but it makes adjusting the radio much easier.
I am working on an external mini-station console for the SB-303 using a metal speaker. It will contain a passive audio filter essentially a stereo speaker crossover that rolls off the high-end audio at 3,500 Hz. I will add the AADE frequency counter and a small digital clock.
I make the LMO load using a gold RCA plug and a 5% 47 ohm resistor. At the center connector, I put a small loop in the resistor wire by doubling back the lead. This is where I attach a frequency counter for testing or the oscilloscope for monitoring the LMO waveform.
Set the crystal calibrator on frequency and verify that it is stable. Generate a delta chart for the bandswitch crystals.
I spin the metal hairline adjuster knob against 1,500 grit emery cloth and jeweler's rouge to put a chrome-like polish on it. Most of the hairline knobs are corroded.
Socket the crystals for 15 mHz, and two of the four 10
meter band crystals. I replace these with the following crystals:
| Original Band | New Band | Tuning Range | Crystal |
| 15 meters WWV | 17 meter WARC 18.068 - 18.168 | 18.000 - 18.500 | 26.895 mHz |
| 10 meter A | 12 meter WARC 24.890 - 24.990 | 24.500 - 25.000 | 33.395 mHz |
| 10 meter B | CB1-CB40 26.965 - 27.405 | 26.900 - 27.400 (plus overlap) | 35.795 mHz |
15 meter WWV covers a foreign broadcast band. You might not want to trade it for the 17 meter ham band.
Paint the cabinet if needed.
Xerox copy of the SB-303 manual and new reproduction full size schematic.
Plastic feeler gauge and Allen wrench for setting the knob spacing.
Longwire antenna and RCA plug.
Metal case Hi-fi speaker with high frequency rolled off, includes digital clock. Frequency counter optional.
Dec 2002 - I found a nice digital clock for $5.00.
Office Depot is selling "travel alarm clocks". These have buttons
for 16 cities, 12/24 time. Time digits are slightly larger than 1/4
inch. Includes a calculator too.
September 2002, I saw a beater R-390 at the Maryland Hamfest was on the "survivor's assistance/silent key" table run by the F.A.R..
Years ago I took a turn as a rep to the F.A.R., the Foundation for Amateur Radio, which is a regional club of radio clubs.
Among many other activities, the F.A.R. helps widows dispose of radio equipment.
So. Ham-to-ham, if something should happen to you, what happens to your equipment? Does a predator pick it up for pennies on the dollar and sell it on eBay? An arrangement where your survivors get little.
Does your area have a F.A.R. which mans a table at local Hamfests and tries for top dollar (within constraints).
If not, do you have a trusted friend who is knowledgeable enough to liquidate the collection? Do you want it donated to a tech school radio club?
I suggest getting a three ring binder and labeling it "About the Radios" or something like that.
On the first page, write the following in large type:
This is an inventory of my radio and electronic equipment. Each piece of equipment may have a corresponding manual or a ziplock bag of accessory parts. The manuals and ziplock bags are labeled with the name of the radio and its serial number.
This manual explains how to dispose of the equipment.
When you sell or otherwise dispose of a radio, be sure to include the manual and ziplock bag of parts. If the radio is in use, it should be include the powercord and wires connected to it.
Generally, serial numbers are on the back or in the top lid of the radios. If not, there will be a sticker that identifies the item.
Start a page for each radio or piece of equipment as such:
Item: Heathkit SB-303 receiver. Serial Number 123456.
Description: This is a solid state amateur radio receiver made in the 1970's. This unit has 3 filters and has been restored to near showroom condition.
Corresponding manual: Xerox copy on the bookshelf, labeled with serial number.
Accessory parts: Zip lock bag, labeled with serial number.
Other wires: Powercord
Disposition: Sell/give to Larry/donate/whatever.
Maintenance History:
2001 - aligned and replaced powersupply capacitor
2002 - added connection to IF for oscilloscope output
Current valuation at a distress sale: $180.00
Recent sales on eBay:
$200. 2002.
Do not keep this in the computer. No one will find it.
Leave enough space so that you can update the maintenance history and the valuation. Put all the parts baggies in a bin and label it. "Parts Baggies, sell with each radio".
While some of this seems to belong in a Will, you're not
going to keep a Will updated. This binder serves as a working inventory
for you and will help you plan and organize your projects.
Your survivors will thank you for doing this.
Future issues of Heathstuff/Boatanchors will carry articles on the AADE counter, reversable upgrades to the SB series, using a monitor scope with the SB-303, super feet, stainless steel hardware, testing SB-303 #4 the dual cascaded SSB filter radio, the ultimate boatanchor - Signal/One, fixing the SB-104A, No PL in boatanchor HTs, test equipment old and new, the Tektronix digital LCD scope, frequency counters, DMMs, retailers, cleaning boatanchors, crystal calibrator, repainting the green, and more.