Hello!

I have a Drake TR4C and R4C receiver, and noticed there are no injection cables available for this setup as there were for the T4XC and R4C twins.

I know there is an RCA cable (each) for mute, speaker, and antenna. Am I correct in assuming that the VFOs won't track together because of this lack of injection cabling?

Or am I missing something?

Thanks
Scott N1IA

I have been using a TR4310 for about 40 years and can advise you that the correct keys for the set screws are as follows:

Type: Allen keys /Hex keys

Sizes needed

For PBT, RF-Gain and VFO knobs size 5/64”

For the small knobs like Mode, Rit, AF-Gain use size 0.050” / 1.27 mm

These keys can be found in any well equipped hardware store. Personally I use sets made by ”Bondhus” ?(US made) and Arndt(origin unknown).On Ebay you can get a suitable set for USD 18:27, se enclosed link:

73 de Jan /SM5MRQ

Gregory,

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I believe this type to be that which I need for the mode switch on the TR4310. Seems it's no longer listed on the EHC website though.

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The data I found on it here:

says, 'Two 4-40 UNC set screws'. I'm guessing that the set screws require a very small, imperial ('freedom unit', in the US - HI!), hex-type wrench. I have one that I reckon is the correct size and that I've used on knobs for Atlas radio, but darned if I can find it right now!

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Regards,

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Mark, G4FPH.

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Good job, Jim, I'm happy you solved it with no further defective parts. Keep the group posted on your progress.

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Dave

Hi Dave. Just wanted to let you know that was the problem as I now have 10.00 VDC although I will check it at the back panel as they say to do in the manual. I don't know why I did not see that earlier. Guess I couldn't see the trees for the forest hi hi. I really appreciate your help. Now maybe I can start work again on trying to get the transmitter working. I initially?had a bad output transistor so bought a matched pair and replaced?them but it still did not work. Then I found a bad transmitter mixer transistor and a burnt?resistor?as the transistor had a collector to Base short and it did the resistor in. Replaced the transistor and the resistor and that one failed and it was the same part number. So have go back and check that out. I noticed I down't have hardly any audio in the speaker too. Lots to keep me busy. Thanks again Dave.

Southeastern VHF Conference?2025 Announcement &?Call For Papers

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Dave I just measured the Base to Emitter voltage on Q404 and it is 7.92. I think I found a problem as it seems that the diode is not connected to the pot. I am going to remove the board again and check on the bottom. Will get back to you after I do that. Also here is the same scan with voltages written on it. Again I thank you so much for your time and help.

Jim, the fact that the voltage on pin 4 does not change at all bothers me. There should be a volt or two swing with the pot. It makes me think its divider network is open somehow. Check the resistors and that diode should have a 0.7V drop across it. The voltage at each junction in the divider network should NOT be 7.20V.

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Dave

I just replaced what looks to be the same connector on my R4C with a chassis mount DIN connector.? It fits in the same holes with no alternations necessary.? The mounting holes are slightly wider spaced in the DIN connector, but if you use 4-40 screws, they will fit with no drilling/filing.??

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73, Floyd - K8AC

Jim, is the voltage on pin 5 also 7.2V? At 7.21V output, the voltage on pin 10 should be around 5.05V and you have 5.3V. Is Q404 good? What is the voltage B-E on it? How about the voltage on its collector?

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You replaced the regulator with a known good new one? Dave

Thanks to all for the comments and suggestions. I'll be getting the set in a couple of days and will report back.

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73, Steve G8GSQ

Hi Dave. The voltage on pin 4 is 7.20 VDC and no it does not change turning the 10 volt adjust pot. Pins 11 and 12 both have 13.68 VDC and Pin 10 has 5.397. No transistors get warm or hot. Does that help?

Jim, what is the voltage on pin 4, and does it vary at all with the pot? What is the voltage on pins 10 and 11? Is the pass transistor getting warm at all?

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Dave

I am waiting for a new BFO crystal for my TR7 so in the meantime I am working on my TR5. The 10 volt power supply failed when I turned it on a?week or so ago. I have checked just about everything I can on the board. I have replaced the 723 regulator chip and a couple transistors and checked diodes etc. The problem seems to be that the adjustment?pot does not adjust the output voltage at all. I am at 7.21 volts and can't seem to change it any. I have added a blown up section of the schematic for the circuit. Many thanks for any comments.

It’s a possibility, so bear that in mind. ?If you’re only off by a frequency that can be adjusted with knob-slipping or moving the fiducial, I’d leave it alone.

Spline / Bristol used on these knobs ?

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It’s always worth a go. I get about 70% success. That fact that you’re seeing something happening with them is encouraging.?

Beware, it's 17 msecs for that drake clunker to operate.? The xcvr needs a 20 msec delay....to give the mech relay in the L4B a head start.? ?I remember ordering an identical 3PDT? from I think Mouser or Digi key, but that was 15 yrs ago.? ? The relay that CTR engineering sells is better suited for the L4B. It's available with a 24 vdc coil.? ?Consists of a small board with a 8 amp? DPDT relay that does the input and cut off bias.? The 2nd 8 amp? DPDT relay has it's contacts wired in parallel, and is used for the 1.2 kw output.? Both relays are sequenced correctly when going from RX to TX..... and also when going from TX? back to RX.? ?It's also faster at just 4-7 msecs.?