Re: Another TR-3 s/n 1329
¿ªÔÆÌåÓýThe TR3's 100Khz calibrator signal can be checked at pin 1 of V7.If your scope can display the frequency of the signal, connect the scope probe (probe initially set to x10) to pin 1 of V7. Turn the calibrator ON and if the calibrator signal is there, the scope should display the sine wave and 100Khz frequency. If the signal at pin 1 of V7 is low, switch the probe to x1. I found my TR3's calibrator top be right on 100Khz. Loss of receiver quite often is caused by the VFO not working. My TR3 had no receive and with the calibrator turned ON, I heard a very low level tone (SIDE BAND set to "X"). That tone did not change when tuning the TR3's VFO. Measure the voltage at the positive terminal of? C145B (see picture below). There should be "+250VDC". If you don't see +250VDC at C145B positive terminal, check R111 3.3K 1/2W resistor. R111 connects between the top of the 2 small PC board to the right of can capacitor C145 and next to the audio transformer. R111 is 3.3K 1/2W, color band Orange/Orange/Red with Silver 10% tolerance. If R111 is open then there will be no B+ to V16 6GX6 (Product Detector/BFO oscillator) and to both stages of V18. Lost of +250VDC to the Product Detector/BFO oscillator will result in loss of receive. Measure voltage at C145A, you should see regulated +150VDC (see location of C145A in the picture below). 73 Mike W5RKL On 5/21/25 4:28 PM, n4buq via groups.io
wrote:
I had a constant tone when I engaged the Calibrator in my TR-4. It can be caused by the carrier oscillator not being set properly. Barry - N4BUQI find myself with another TR-3 that I was not expecting. I arrived at my Hamvention booth Saturday morning to find a TR-3 sitting there. A fellow booth person who is local to Dayton brought it to me and said $50. I wasn't looking for one but said OK. He said he hasn't looked at it in about 15 years and remembers that it does not work. I have confirmed that it does not work! At least no snap, crackle, pop or smoke when powered up. Tubes and meter lights do light up. Audio is low to start and after 5 minutes there is almost no audio. No change in noise when the RF tune knob is rotated on any band. RF gain does work and s meter responds higher as gain is turned down. When put in CAL position there is a constant low frequency tone everywhere on any band. No RX signals anywhere even with my TS590 at 100 watts into a dummy load sitting next to it. When put in X-SSB to tune there is no plate current on any band. I am using the same power supply as I do with my other TR-3 so that should be OK. Time to open it up and look at the tubes first and go from there. Your thoughts, suggestions and guidance are appreciated as always. Dave, KC3AM |