eHam Forums => Boat Anchors => Topic started by: WD8AJY on August 01, 2011, 09:18:05 AM

Title: Drake TR-3
Post by: WD8AJY on August 01, 2011, 09:18:05 AM
I have an older TR-3 SN 796. My problem is the S meter will not go above S5. I have found 3 bad resistors in the IF. All the manuals i have do not match this radio. Does anybody have a manual for this older radio or any idea what is the problem Thanks. Bob WD8AJY

Title: RE: Drake TR-3
Post by: W5RKL on August 03, 2011, 09:31:50 AM
Did you look at bama website?



Title: RE: Drake TR-3
Post by: WD8AJY on August 03, 2011, 10:55:54 AM
yup i looked at every web sit i could find.

Title: RE: Drake TR-3
Post by: KA5N on August 03, 2011, 12:01:26 PM
Take a look at

The S meter reads the AVC voltage and so if the zero set pot is flakey or any of the resistors in the circuit are off value you will have problems.  Also the meter on this model is an upright type and there may be something interferring with the physical movement of the meter or the bearing might be bad.

Anyway the S-meter is the least important thing in a receiver and I would rather have a rig that worked perfectly except for the S-meter than have a great working S-meter and rotten receive.

Good Luck

Title: RE: Drake TR-3
Post by: VE3EFJ on August 03, 2011, 07:34:04 PM

My experience is mostly with the TR4, but the TR3 isn't that different. This might help some.

The LV B+ is critical to the S Meter. I think its supposed to be around 265V. Also, so is the -ve bias voltage since it drives the AGC amplier.

I've seen some bad S Meters in my day. You can test the S Meter by swapping in the plate current meter. They are both the same 5 ma movement. I've helped folks with this exact symptom on a TR4 and in both cases it was the meter. I am assuming that the problem is not alignment or vacuum tube related.

Testing the resistors is a wise move since at this units age resistors can age 100% higher.


Title: RE: Drake TR-3
Post by: WW3QB on August 04, 2011, 07:49:22 AM
There is a TR-3 manual online at

Title: RE: Drake TR-3
Post by: N3WAK on August 10, 2011, 10:33:27 AM
Bob--There's a Drake "technical" net you could check in to, to ask about your TR-3.  Sundays at 4pm EDT on 7.238.  Jeff, WA8SAJ, Evan, K9SQG, Mark, WB0IQK, and Ron, WB4HFN, are among the Drake experts you will find there, and they're happy to give you advice about fixing your rig.  73, Tony N3WAK

Title: RE: Drake TR-3
Post by: W5RKL on August 10, 2011, 11:46:57 AM
Your problem could be caused by gassy tubes. Most tube testers will not test for gassy tubes. You can use a volt meter (11meg VTVM) and measure the grid voltage on both side of the
grid resistor. A gassy tube will have a more positive voltage on the grid side of the grid resistor then on the other side of the grid resistor. Gassy tubes will affect the AGC gain control
voltage which will affect how the S meter works.

73s Mike

Title: RE: Drake TR-3
Post by: AC5UP on August 10, 2011, 12:02:24 PM
Gassy small signal tubes may have a blue corona visible on the inside surface of the glass. A slight blue glow inside the plate area is usually OK and very common with HV and power tubes, but on a small signal tube there should be no color on the glass when operating. If you have the same tube number used in two different sockets and one has a blue tint, swap the tubes. If the corona stays with the same tube it's probably gassy, if the corona stays with the same socket it probably isn't.

The getter should be a near-perfect silver color with no trace of white or red around the perimeter. A black perimeter is OK and some getters have an amber tone to them, but otherwise no creamy white or rusty red around the edges.

Title: RE: Drake TR-3
Post by: K6LO on August 13, 2011, 06:29:02 PM
In re reading your post, I recall that my old TR4 has a lamp fuse in the rx  path. When the base oxidized a few years back sensitivity suffered til I cleaned it with an eraser.  I do not know if the TR-3 has that fuse or not.  Worth a check.



Title: RE: Drake TR-3
Post by: WW3QB on August 15, 2011, 05:17:34 PM
A frequent point of failure is the TR relay. A dirty contact will cause a lot of attenuation. If you have the open type of relay, as I did, you can try cleaning it. But I found mine impossible to clean and replaced it with the closed type of relay used in the TR-4. There is a kit to do the replacement available on eBay. I did it and it made the difference.