Sample Journal Article

Collins Journal
Jan/Feb 2002
Technical Corner

Retrofitting the KWM-2 with a Shield in the Balanced Modulator Section

After obtaining one of these shields from a parts chassis, I can confirm that this retro-fit/add-on is NOT adaptable to older 1N34A diode balance modulator units [pre-1964 models]. The balance modular diode terminations located on Vector E50-H, prevent the use of this shield without major rewiring changes. Therefore, I am abandoning this project. Thank you for taking the time to photograph this shield. My shield is available should one be required for a unit more compatible. Stu, K2QDE

Techniques on Dial Cord Restringing

Thanks for sharing your experience. Here are some comments from someone who has restrung MANY dial cords. (I made my living for 55 years repairing radios). I don’t recall a single instance of a slipping dial cord that couldn’t be fixed without resorting to your method. (don’t get me wrong. If it works for you, that is fine).

The largest cause of slippage is too much load. I always lube the bearings on both ends of the variable capacitor. If the grease has dried and is hard, remove it and put in some new. Lubraplate is great. Also squirt some contact cleaner on the ground wiper. Not only does this reduce friction, but is protection against intermittent operation. I do recall one SX-100 and a couple of another brand also starting with H, that use rubber drive belts (O-rings), that WILL stretch. After a thorough cleaning and lubing, they still slipped. Turning the capacitor by hand revealed excessive friction. Apparently the frame of the capacitor was too tight against the bearings. I had to spring (bend) the frames outward just a little.

For small capacitors, I took a pair of gas pliers and ground a notch on the outside of both jaws. By inserting the pliers into the capacitor (plates closed of course) pull the handles apart. Just a little at a time, until the capacitor feels free but does not have any play in the bearings.

For larger capacitors, I remove the capacitor from the radio and secure it in a vise, and slightly bend the frame with a Crescent wrench. That fixed all three. I also lubricate the pulleys, as a lot of little frictions add up. I also recall a Gonset GSB-100 transmitter with a slipping cord for the dial drum. Again turning it by hand revealed too much friction. After several attempts at bending the sheet metal mounts, I could spin it with little effort.

Another factor is the composition of the dial cord. You mentioned Nylon, which is a slippery material. It is frequently used for bearings. I use only cotton covered cord. I get mine from a sporting goods store. It is sold for fly-fishing as it floats on the water.

Another factor is the size of the cord. It used to be available in several diameters. I have some NOS, made by GC Electronics, that is about twice as thick as fishing line. The larger diameter has more surface area to grip the shaft. I don’t know if it is still available. Ed Richards

Relay Thoughts

I prefer a totally different relay. The original relay was prone to misadjustment when handled for assembly or when touched with tools while working in its vicinity or when the terminals were bent to allow attaching wires. Its an open type of short form telephone style relay. Hand-adjusted at the factory, at one point in early S-line production the Collins warehouse wanted to save space in the bins by removing the relays from their individual cardboard boxes. That was a disaster in production with many relays no longer making contact. The short form telephone relay also has very little contact pressure or contact wipe, which makes it prone to failure in the long run.

The later plug in relay was not much better, still a short form telephone relay, just in a plastic case to protect it from so much external mechanical abuse but still with the failings of low contact pressure and very little contact wipe.

I prefer the P&B KHP series relay, an armature type of relay, it has better contact clearance, better contact wipe, and NO adjustments ever necessary. It does make more noise. There is one with a 110 volt DC coil that works fine. Doesn’t plug into the Collins socket, but wiring to it doesn’t change the contact positions. Sockets are available. It�s not original to the S-line (would have been if I’d been there for that design), I don’t know if there ever was a Collins part number for the one I recommend, but I DO KNOW that relays in that family were used, because I used them. And they had Collins specifications or easily met new Collins specifications. don’t know where one might find the P&B relay internationally. I’ve not tried to buy one lately. But I can look it up in some catalogs:

In P&B, a KHAU-17D11-110 is right. One catalog shows Potter & Brumfield as a division of Siemens Electromechanical Components, another shows Tyco Electronics.

Then there’s the hermetically sealed KHS-17D11-110 (expensive!). And the KHU17D11-110.

And KHAU17D12-110 with silver-cadmium oxide contacts.

Aromat HC4-H-DC110V

Idec RY4S-UDC110V or RY4S-ULDC110V

I have seen similar relays in the ECG (now I presume in the NTE) replacement relay catalog also. 73, Jerry, K0CQ

Using the 6146B Tubes

Most of the older rigs run about 800 volts, or so, with a pair of 6146 tubes under load. You can use either the 6146 or 6146A without any problems. The 6146B is actually a different tube and may cause problems if you substitute it for the original 6146. The only difference between the 6146 and the 6146A is the make up of the heater (“filament”). The 6146B has different interelectrode capacitances, etc. You can “mix” a 6146 with a 6146A, but NEVER mix a 6146B with either a 6146 or 6146A.

If you try the 6146B tubes, make sure and neutralize the final. If the final will not neutralize, then don’t use the 6146B tubes. If it does neutralize, then check it for several days. If the neutralization “drifts”, then go back to the 6146 / 6146A tubes. If the final does neutralize and holds the neutralization, then the 6146B tubes will work fine in that particular transmitter (individual transmitter, the next one of the same model may not be able to use the 6146B).

The problem with the 6146B is that they are very “prone” to “taking off” (spurious emissions, especially in the VHF range) when used in circuits that were not designed originally for them.

You should be taking the voltage reading when in the CW “key down” position so that the final amplifier tubes are drawing the most current. I think that 6K ohm will be way too much. You should have around 750 to 800 volts under load (144 watts input on CW if I remember my HT-37 specifications). Glen, K9STH

Moving the KWS-1

If you just need to slide it around, I bought a set of these Teflon button pads (about 1″ round and a 1/4″ to 3/8″ high but you can get other sizes) that are sold at places like Lowes, Home Depot, etc. They are used to put underneath the legs on furniture and appliances and make things real easy to move around with just one hand. I put them at the four corners of a 3/4″ plywood board cut to match the size of the base of both my KWS-1 PS and my 30S-1 Amp. Now I can move (slide) those two items around real easy. I’ve used these things on cement floors, wood floors etc. About the only place they don’t work is on deep pile rug as the rug drags against the wood. Ray W2EC

Removing the PTO from the 75A-2

The removal procedure was basically simple and if I were to place it in any order it would go like this. The instructions take into account that you have desoldered all the VFO connections to the main chassis and have labeled the wires. Don’t forget to do this! Also remove the 6BA6 tubes from the VFO.

1. Place the bandswitch on the 160M band and turn the tuning knob counterclockwise until it stops. This will give you a reference point.
2. Loosen the screws that hold the Oldham coupler assembly to the VFO shaft.
3. Remove the three screws that hold the VFO to the U bracket.
4. The screw that holds the top of the VFO to the U bracket is connected to an extension in the VFO itself. Remove this extension by carefully unscrewing it.
5. Pull the VFO backwards and pull out from its shaft the section of the Oldham coupling mechanism. The Oldham coupler itself will probably fall from the center of the whole coupler.
6. Now by pushing the VFO toward the front and then moving it upwards in the back you can pull it out CAREFULLY!!

With the VFO out proceed to remove the can and the small metal cover under the tube sockets. The last one is usually soldered at some points so you may have to remove some of the solder.

Under the tube sockets you will find two long and slender brown beauties. These are paper caps C131 and 132 (.01 uF). REMOVE and REPLACE. I used 630VDC rated small tubular polyester caps. Make sure that you place insulation in the new cap leads and cut as short as possible. In my case C132 was totally shorted and C131 leaking badly. After removing the can you will find another one of these beauties connected to L25. REPLACE but be very careful. The connection to L25 is a delicate one.

Replace all covers and remember to resolder the points in the tube socket cover. Use the reverse procedure to return the VFO to its place. The tricky part here is the replacement of the Oldham coupler half that goes into the VFO shaft. You may have to play around a bit but it will fall in place. We are all an inventive bunch.

I tested the radio after the replacements and it came out alive and well. Since I did not move the VFO shaft, I ended up with the original alignment of VFO/Tuning dial. Nonetheless the alignment of the whole set needs to be done as well a repair of a nonfunctional BFO.

Many thanks for all of your help and please add any comments, instructions or critiques to this note. Guido Santacana, KP4FAR

Modifying the SM-3 Microphones

I decided to check over my SM-3 mikes as on the air reports indicated poor quality speech. It is the third one I have owned and all of them have been disappointing. I have concluded that maybe they were never good in the first place.

I stripped the mike insert and matching transformer from the barrel and installed a two terminal Electret mike cartridge. To energize the mike, I then made up a network consisting of a Duracell D type cell, a 4.7K resistor and 10 nf. Disc capacitor. To this network I then attached a few inches of screened cable and an RCA phono plug and connected this to the phone patch socket on my KWM-2. This in parallel with the mike input, of course. Checking on a scope, I had 50 mv P-P on normal speech.

A test call and QSO on 80 meters brought excellent speech reports from three different stations and I am very pleased with the results.

The drain on the D cell is only 250 microamps so I reckon it would be good for at least 12 months even if left connect4ed but of course if the mike is unplugged each time after use then it would probably last for five years (shelf life). Next test will be on my 32S-3. Peter, G3GGK

Correction: Henry Lewis, G3GIQ, is the director of the CRA United Kingdom (UK) Chapter.

FOR SALE/TRADE: Manuals: 75A-1, 32V-1, 75A-4, 32V-2, KWS-1, 30L-1, 30S-1, 51J-4.

WANTED: Manuals KW-1, Johnson Kilowatt, Valiant II, Heath GC-1A, National NC-188, NC-140, NC-155, B&W 6100, Hallicrafters S-76. AL Bernard, NI4Q, P.O. Box 690098, Orlando, FL 32869-0098. (407) 351-5536.

FOR SALE: **** Mechanical Filters ****
Collins F455Y21 / 526 9337 00 455 KHz, 2.1 KHz bandwidth. NOS, checked ok. $120
Collins F455Y21 / 526 9337 00 455 KHz, 2.1 KHz bandwidth. Used, checked ok. $80
Collins F455Y160 / 526 9343 00 455 KHz, 16 KHz bandwidth. Used, checked ok. $60
**** Oscillator ****
CTS Knights JKTO-47 970-2602 — 1MHz ovenized oscillator also bears Collins part number: 292-0308-010. Looks new, w/data sheet. Original cost was $325! now only $50
**** Manuals & Book ****
Collins (original) Manuals
32S-1 Transmitter $50
520 5430 00 Vernier Tuning Knob $5
Amateur Single Sideband by Collins Radio. 1962 Hardbound. Excellent condition; previous owners name in ink on p.106. 143 pages. $50
All of the above plus shipping, if necessary, naturally. Contact: Marv WC6W 310 649 3111 (reasonable hours Pacific Time please) or via:

WANTED:I need a crystal for my S-line, 28.4-28.6. I also need miscellaneous crystals to complete my crystal pack. I have duplicates to trade for anyone that is interested. Let me know what you have. I also need a round emblem for my 516F-2 and a vox relay coil, K1, 972-1353-00 (my contact assembly is OK) for my 32S-3. If you can help, email me at Bill, K3PGB.

WANTED:If you have a damaged, incomplete, or otherwise unusable Collins M2/S-Line cabinet, Please write. I’m in need a top-cover lid. (Don’t care about size or the hinge) –

WANTED: K4ESE, Neill, looking for the modulator deck for a 30K – / 910 862-2938 day, 910 647-6621 night (collect on this number is fine) / Box 10, Clarkton, NC 28433

FOR SALE: KWM-2A WE in Excellent condition w/ PM-2 supply. A few minor scratches near the Zeus fasteners. Realigned, Retubed. All ready to go. Connect Antenna + Mic and you are on the air. Prefer Pick up but would consider shipping. $1290 + Shipping + Packing CP-1 Xtal Pack – clean w/ Xtal puller $195 Call Peter @ 410-295-7064 or Email Located in Annapolis, MD

WANTED: Manual or manual copy for 20V-3. Rolynn K7DFW, 503-728-4157 Oregon.

INFORMATION: Shielding covers for R-390 receiver covers Fair Radio has them @ $49.50 a set –

Collins speaker 312A-1 speaker light:
“Just Bulbs”
136 Broadway
New York, NY
12″ 40w (white/clear) w/out clips: $20