In some ways this is a laudable goal because it keeps vintage equipment in use, helps newcomers to understand older technology and demonstrates how far ham radio has come in terms of technological progress. Having long been a fan of the amateur radio equipment manufactured by the R. The guidelines that follow are not meant to discourage collection, repair, restoration and operation of this gear but rather to point out some of the possible pitfalls and areas of frustration that may prove discouraging to the unsuspecting neophyte. In this age of "instant gratification" it is folly to expect that every piece of older, tube-type radio gear is going to be ready for "on the air" use without some kind of TLC by its latest owner.
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Crystal filters used in the TR3 are held in a metal box under the chassis. Based upon the behavior of the filter and the age of the unit, I suspect that the filter used in the TR3 is composed of discrete crystals.
The TR4any are single conversion transceivers. The reason for two filters is to not have the transmit frequency shift between the sideband selection. The second IF frequency is at 50 ohms. It would of been so nice if the TR7 etc took R4C crystal filters, but noooooooo.
It looks like this was purposely done in the TR7. Early model R4C receivers have only one trim pot for setting the S meter zero. Replace this cap with a pf. Ensure it is no higher than Ensure all tube shields are in place. R4C Intermittent Crystal Calibrator The mounting screws for the blanker brackets are held by two 4 sheet metal screws from underneath the chassis.
One of these is a short screw. Ensure that this screw is positioned for the plate near the chassis edge towards the back of the receiver. A normal length screw will short the calibrator when the calibrator is seated down. The S meter will increase in reading when this filter is selected.
The difference could be as much as 20 db indicated. While it may be annoying, it is not an indication of reduced sensitivity so long as you can get a noise peak from the preselector as outlined further in the text.
Make a a 50 kHz network of a 10 mH choke and pf capacitor in parallel. Add a. Install this network from pin 7 of V6 to ground. This should be the plate pin. Lead dress for this mod can be critical and is noted by an increase in audio hash and hum.
My own experience is that this change seems to do little, but it does no harm either. It causes a lot of heat to be generated, distorts, and has terrible frequency response. Some minor updates can be made by changing C detailed elsewhere that will provide improvement. An LM could be mounted on one of the support brackets for the noise blanker or, if you build a circuit board for it and use ground lugs ala Drake, you could use the 2 audio output transistor mounting screw holes.
Some folks have used the LM and this chip will provide a bit more audio output. Commercial users of this chip should not have this problem, but home constructors using the LM should be aware that the LM is a high gain, high current and high output linear audio power amplifier. I had one in an R4C that I had purchased and I removed it. If your receiver has this after market change, you may wish to make some of the changes - particularly the C value change if your receiver is stock.
Bypass the Sartori audio filter and see which you prefer. It is not a good design. The 2 resistors at the right hand edge of the board get very hot and will eventually cook the circuit board.
Drake does this all the time in their equipment and it is a terrible design philosophy. Once you replace the audio stage, the low voltage supply will climb and you can use the EP as a pass transistor or install an electronic regulator.
There is another mod circulating that uses the filament supply as a voltage boost for the low voltage line. Do not do this mod and if your receiver has had this change I strongly recommend you remove it and revert the supply to original. This mod cures nothing and actu- ally generates as much, if not more, heat.
While this does work and does reduce hum and noise considerably, it also creates a lot of additional heat from the regulator. Oakville, Ontario, These folks do small - read single - quantities and have historically dealt with amateurs since Day 1. The crystal specs are different between these two applications.
The TR4any uses overtone crystals. Band range crystals are interchangeable between the entire R4any and T4any and even between the receiver and transmitter. CW Operation If you intend on operating the 4 line on CW only, service life of the 6JB6 finals may be extended by turning the idle bias down to the point that the PA cathode current meter just moves. Please do not run SSB at this setting. Be a pal. R4C LM I enclose this for those that wish to experiment a bit.
For those that want to solve this problem using commercial avenues, Sherwood Engineering offers an audio kit, or they will upgrade and service the receiver as per your requirements. The National LM is near perfect for this application and will, together with the voltage regulator change, clean the audio and reduce current consumption.
This program is evaluation software only - you can load it up under DOS and view and print enclosed schematics. This version of SKEM demonstrates a lot of potential. A lot of input gets wiped out to fix an earlier mistake. All electrolytics have -ve terminal on the ground unless stated otherwise.
Observe good wiring practices, as this is a high gain, high current and high output IC. None of the parts are especially critical except perhaps the 2. If all you have is a 4. Instead of a 2. Value changes such as this will not stop the circuit from working.
Much the same applies to the voltage regulator changes. Remove the audio output transistor and socket from the R4C. You could mount it on brackets right where the original transistor was. If you do this, simply connect the volume control center pin to the 4. Output from the LM through that uF coupling cap goes to the headphone jack where the black wire is. I suggest you build the circuit on Radio Shack perf board and run it stand alone from a seperate 12 volt supply.
If more gain is required, you can increase the value of the 2. If the ratio of the and 2. And loudly! Parts layout is not critical so long as you keep in mind that this is a high gain, broad band power amplifier. You may as well use the EP as it was intended - as a regulator. Remove R from the circuit board. Remove CR18 and CR Remove C Connect a Cathode going to base, anode to ground. Zener diodes make very smelly firecrackers.
The above changes make a useful difference in the R4C audio and will clean it up nicely. You need to make both of these changes at once. The LM needs clean DC to operate from. The regulator change for the pass transistor will not work with the stock audio amp because it draws too much current. This is simply not true. What an LM is prone to do, though, is oscillate at super audio frequencies.
You may not hear the oscillation, but you will hear its effect on the normal audio frequencies. That is why there is considerable bypassing in the above design. Included SKEM files:.
Mezirisar Google [Bot] and 4 guests. So to be clear are you not seeing anything at pins 1 and 7 of V8? Share Drake R4B manual Share this link with your friends, publish within popular social networks or send it via email. You should hear each IF frequency in the general coverage receiver. I have measured the voltage on all the tubes and pin 1 v3 seemed to be the one that was out the most, it is supposed to be Guaranteed by Mon, Jan 7.
Drake R-4B Manuals