Working my way back in time - Drake TR-4

Discussion in '"Boat Anchor" & Classic Equipment' started by K0OKS, Feb 16, 2018.

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  1. K0OKS

    K0OKS Premium Subscriber QRZ Page

    Hey all,

    I got into Amateur Radio because I like tinkering, electronics, and repair. I started with a 7300, then got a Kenwood Ts-820s, which I restored from a broken state, and now I have acquired a Drake TR-4. Soon enough I will have a spark gap transmitter (and lose my license for using it).

    I have the manuals. The circuit is amazingly simple given all it does! I love this older gear I can really wrap my head around.

    I got the AC-4 power supply with it. The whole thing was supposedly working. I got it from a friend who got it from a hamfest. I figured I would start by testing the power supply, and recapping it if the caps are original. I figured I would try to re-stuff the cans in the power supply if I can. The single section ones should be easy, especially if they have the cardboard tubes over them. I have hidden new caps in empty tubes in previous restorations of tube gear (AM/FM and test equipment).

    Is it worth getting the upgrade kit with the new board from the HeathkitShop ? I don't like the way the board mounts so close to the transformer. I wonder if that increases hum, but I know lots of people have used the kit and are happy with it. The Hayseed capacitor kit for the power supply is very pricey; so I am thinking either do my own restuffing/underrigging or do the HeathkitShop upgrade.

    For the transceiver I did go ahead and order the Hayseed multi section can. It just seemed easier and cleaner, and the price was not substantially more than ordering new, quality caps with shipping.

    I cleaned all the band switches and pots (no, I did not spray residue leaving cleaners on them... I have done a bunch of receivers before). I checked all the bulbs, and generally cleaned everything up. The unit is in really nice shape. It looks to have the noise blanker installed as well!

    Anything else I should check on this unit (other than the power supply) before bringing it up on a Variac?

    WB1E likes this.
  2. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    Awesome!! Should you ever want the RV-4 external LMO/speaker, I have a couple of them....

  3. K0OKS

    K0OKS Premium Subscriber QRZ Page

    Thanks for the offer. Mine came with the speaker for the Ms-4 (along with the power supply). But it lacks the CASE for the MS-4. I am not in a hurry to find one, though. I run my radios through a switch (eventually a mixer if I ever build or buy some sort of T/R relay to share the antenna) and into an external DSP and a speaker. So I don't really need the original speaker.

    The Drake is just so cool to look at. Nice build quality, with very pretty construction.

    Looking forward to playing with it.
  4. K0OKS

    K0OKS Premium Subscriber QRZ Page

    Oh, the RV-4 is the remote VFO!! I am still learning about these guys. That would be cool. I have the remote VFO for my Ts-820s, and I use it all the time, even for working split at times.

    That might be quite interesting, I would have to figure out where to put it on my equipment rack.

    Can you do split with it as well?
  5. AD4U

    AD4U Ham Member QRZ Page

    Drake (like all other HAM companies of the time) cut some corners in the design of their rigs. In fact Drake did some crazy things. One is the large resistors that drop HV down to low voltage. This generates a lot of heat. It is amazing the performance of Drake gear compared to most other rigs of the same time. Many rigs of that time had large cases with many more components in the design.

    Two years ago at a hamfest I bought TWO Drake TR4/cw transceivers. Each came with the AC4 PS and MS4 speaker. One of the TR4/cw rigs has the RIT and the rare Drake noise blanker. The other TR4/cw came with the RV4 remove VFO. Both worked perfectly "right out of the box".

    Many HAMs shy away from the old tubes rigs. But a few old timers like me, gravitate to the boat anchor rigs. That is why I have around 60 of them. I enjoy buying rigs now that I only could drool over when I was an new HAM in the 1960's and the 1970's.

    Dick AD4U
    KE4OH and K0OKS like this.
  6. N8YX

    N8YX Ham Member QRZ Page

    If you can find one, the TR-5 is touted as a solid-state TR4CW/RIT - albeit sans AM. Its overall circuit layout is very close.
  7. K0OKS

    K0OKS Premium Subscriber QRZ Page


    Do you happen to know which resistors had issues? I always thought the resistor droppers were pretty primitive. They were used quite a bit in a lot of old AM or AM/FM sets, and I remember seeing one for the first time and thinking to myself, "How crude!"

    They do seem to work, though, even if they were responsible for a lot of caps drying out. I guess transformers windings were expensive, and there were no DC To DC converters :eek:
  8. KK6IYM

    KK6IYM Ham Member QRZ Page

    I have used the re-build kits and also just replaced the capacitors with discrete components. Either works fine. I usually stuff the old cans as that uses less space under the chassis.

    As far as the TR-4, I would suggest you change the cathode resistors (15 Ohm) and the screen resistors (68 Ohm) for the finals. These almost invariably are high. The other resistors that cause problems are the meter shunt (or shunts, there may be an added resistor) and maybe others in the meter circuit. The meter shunt is a 2 ohm. If it is a cement type (TR-3 were cement), then those don't drift up in value, but if carbon--it is probably high. It should be located on a circuit board at the very rear of the radio. What this means is the bias will not be set right. The blue LED's look really cool in the Drake radios. Whatever you do--do not buy these on Ebay. Go to a pinball supply website where they are 38 cents each--not $10 each. Sometimes the relay contacts need cleaning. One of the worst failure points with these Drake radios is the on-off switch. It is not replaceable as it is part of the concentric RF gain, AF gain pots. Because of this, any type of soft start you can add in to the power supply would not be a bad idea.

    N2EY likes this.
  9. K0OKS

    K0OKS Premium Subscriber QRZ Page

    Thanks for the info, Norm. This is exactly the kind of sage advice I was looking for.

    Any reason not to replace those resistors with metal films of the same or higher power rating?

    This soft start method aboutnhalfway down looked pretty easy to me:
  10. KK6IYM

    KK6IYM Ham Member QRZ Page

    Metal film resistors are fine. I use the 1 watt resistors as they are about the same size as the old carbon half watt. The "Phase Two" soft start looks exactly like what would be a good solution for the switch.

    K0OKS likes this.

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