TR-3 Repair Notes
15/9/99
All my radio repairs start with a careful cleaning. In case of Drakes (4-line and similar cases, as the TR-3), I use to get both covers off, do a visual inspection for obvious troubles, as burnt resistors, charred wires, loose wires, cold solder joints and so on. Check also special attention to the tubes; sometimes you don't have the correct tube in one or more sockets!. Once done that, I get off the knobs, front panel, tubes, PTO cover, RF tune capacitor cover, power cage, dial lamp assembly, S-meter assembly, ... So the rig (or what remains of it) is as in the pictures:
In this case the chassis was in good shape, showing the usual dark spots here and there. By the way, there are different points of view about what to do with Drake copper chassis spots. I like a bright / like new chassis, but in these cases, I remove the loose dust with a vacuum cleaner and a brush (hint: protect the metal part of the brush support with plastic tape; that way you will save your rig from some scratches) and then I use a metal cleaner/protector (Tarni-Shield, made by 3M) to get some bright and, same time, protect the surface from further corrossion. The results are good enough and you don't ruin the letters on chassis.
In my visual inspection I found a capacitor which has one leg connected, bridging T11 and V11 pin 5, and the other leg unconnected. It seems as a factory made soldering work... In my manual picture, I can clearly see the bridge, but not capacitor at all... But in the schematics, there is C103 which I can't locate in my TR-3 nor in the manual picture. Any idea?. Here you have a close picture. The leg at the upper right is not connected:
One common problem with Drake PTO knobs is that they develop some excessive shaft play, which leads to irregular dial movement. This can be due to the PTO ball bearing adjustment. In this case, you can solve it just by adjusting an allen screw at the rear part of the PTO. The hole to reach the allen screw is shown here inside a red circle:
In fact, my TR-3 had some play at the PTO shaft. I got rid of it by adjusting the mentioned screw and now it is lots smoother than it was. Good!
Another item I like to get really clean is the dial scale. It makes a big difference when you have finished your work with a rig: it looks like new!. I use a piece of old cotton blanket with a bit of water and, if it has any oily dirt, mild soap. If it is not necessary, I don't remove the PTO assembly (as you should unsolder the PTO wires to do that) so I need to clean the dial disk mounted in the rig. It is just a matter of patience and you can get it clean:
16/9/99
Today the work has been mostly cosmetic. First, I have cleaned the power amplifier cage, by means of a bath in water and mild soap (hint: a brush helps to get the dust from the holes. Dry it with a towel and put it in a sunny place (if available!) to get all water off. Or use a hair drier in worse climate ). Then all the aluminum covers (PTO, tubes and RF tune) were also cleaned with Tarni-Shield. Look at the difference among a cleaned and an 'as-is' tube cover:
Other items which you can get shinning are the knob extension shafts, as they are made of aluminum. Other items which can benefit of a metal cleaner are the crystals:
In this picture you can see the whole cleaned chassis, with some items already re-installed:
Now it is time for some electrical work. The T/R relay, as it is open type, should be carefully cleaned to prevent failures. I use a piece of white paper soaked in CRC Contact Cleaner (or your favourite one, as De-Oxit). Manually toggle the relay contacts carefully and put the soaked paper in every contact moving it so the contacts get cleaned:
USB/LSB lamps were also cleaned and put back in place (hint: you should be careful with the black cover position, as it has an opening which could 'leak' some light to the dial if improperly placed).
Some polish paste was applied to the tuning knob to get it to close to new condition (thanks to Andy Wallace for supplying the correct knob!)
18/9/99
Once the transceiver has been carefully cleaned, it is time to put again the front panel, S-meter, knobs, tubes, ... (hint: one good way to keep them stored while you are working on the rig is to use egg holders):
But before putting the tubes, they should be checked. I did it in my Triplett 3444 'Tube Analyzer' (which is in fact a transconductance tester) and got good results for all except for the 6GX6 tube, which had lot of leakage in the heather - cathode interface. Good, as my Excel tube stock file showed no 6GX6/6GY6 at all... So I opened my TR-4C and got the 6GX6 tube on it (which I knew was good). It is also a good idea to put some contact cleaner in the sockets and push-pull the tubes several times to get clean contacts. This will prevent lots of headaches!
Once the tubes, S-meter and dial assembly are back, the transceiver starts to look again as such:
And then the front panel and knobs are added:
Here you have some close views of the baby. It is pretty, isn't it?:
Once here, it is time to hook up an AC-4/MS-4 power supply/speaker combo and a suitable antenna (10-15-20 m vertical).
So now is the great moment... lights off... let's apply power to the rig and...
No smoke!. Fine!!!. Ok, lights on again, the show is over. Let's see if there is anything suspicious. Ok!. And then some noise comes from the MS-4 speaker... I can hear some hams on 20 meters!!!. Hooray!. But yes, the signals are definitely low. I check it with my TS-520S: a S-9 in the Kenwood is a S-1 in the Drake... Hmmmmm...
Let's read the TR-3 manual, technical section. I carefully check the alignment and all seems to be peaked. In fact, the TR-3 still has all the variable coils with a lacquer mark, which seems factory made, and every tweaking attempt is worse that the original setting. It seems perfectly aligned (not bad for a 30+ years old rig!). And the calibrator signal is strong in all bands (except on the two 10 meter highest bands; more on this later). So, what is happening?...
About one hour later, studying the schematic and block diagram, I got an idea. It is so obvious... Some days ago I cleaned the TX/RX relay but... did I a good job?. Definitely not, as touching it with an isolated plastic screw driver I find that signal strength varies. So it is time to remove the power amp cage (which implies removing some other parts) to reach the relay. This time, I use a stronger approach and with some light sanding paper, the contacts are cleaned, carefully but extensively. Now my Fluke 77 gets continuity!. Here you have the culprit:
Cheking all the bands it seems that the two highest 10 meter bands are dead. Changing the crystal oscillator tube makes no difference. The manual alignment is also checked but nothing happens. So I swap the crystals with the TR-4C ones and I got these bands working. It seems that I have two bad crystals (43.0 and 43.6 MHz; any spare around?)
Well, if it receives... what about transmission?. Following the manual advice, I adjust the bias and then load the transceiver in 15 meters (about 120W in the Bird 43). I monitorize my signal in the TS-520S. It sounds good! So it is time to work a DX. After calling CQ somebody reports 5/9 in LU land... It works!!!.
Now I just need to clean the case halves and put them back. Another Drake is again in the air :-)!
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