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Author Topic: Drake TR-4C is silent  (Read 4399 times)
N9DO
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Posts: 55




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« on: July 13, 2011, 08:50:14 AM »

I have  nice, (not museum quality but nice) TR-4C xmtr. It was given to me from a SK's estate and has worked perfectly until now. I seldom use the rig but yesterday I turned it on and it didn't make a sound of any kind. I turned every knob and checked and rechecked connections, antennas, etc. After 10 minutes or so I heard a sound from the speaker and turned the VFO up and down to find a signal. I finally found a station on 20M very, very weak, that was the only thing I heard on any band. I'm not that well versed on tube rigs and have little test equipment, so I'm wondering if anyone could point me in a direction to try to get the rig speaking again? No doubt I probably will have to have someone knowledgable on tube rigs to fix it for me.
Thanks,
George N9DO
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AC5UP
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Posts: 3864




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« Reply #1 on: July 13, 2011, 09:40:44 AM »

Considering the age of the radio and lack of regular use my first suspicion would be a dirty bandswitch or relay in need of cleaning. Exercise the headphone jack, too. Might want to open it up to check for cobwebs (you'd be surprised at what I've found under a chassis) and re-seat the tubes. Look around for burned resistors, leaky caps literally oozing 'stuff' and anything else that looks not-good like a tube that doesn't light up.

As for the exact symptom you described... Perfect example of what happens when the IF section calls in sick. Years ago I had an FM tuner that went deaf as a post overnight. Turns out the plate voltage for the three 6AU6's in the IF ran through a single 10k two watt carbon resistor that had smoked. Replaced the crispy critter with a five watt part and happiness returned. Easy fix, yours could be similar.

As a general rule if there is noticeable hiss the IF is alive. 1st mixer or VFO could be blotto, but a healthy IF amplifying nothing will have an elevated noise floor. If the audio amplifier went bad a simple bit of signal tracing will test it. This doesn't happen very often but like an incandescent light bulb a cold tube filament can open up when power is applied. Give it a good visual exam and you might surprise yourself at what you discover...............
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K6LO
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Posts: 226




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« Reply #2 on: July 13, 2011, 11:09:37 AM »

Give the RCVR/TCVR switch on the left side a few toggles.  When the contacts oxidize the receiver can get quiet or stone deaf.

73,

Luke
« Last Edit: July 13, 2011, 11:14:10 AM by K6LO » Logged
NK6Q
Member

Posts: 202




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« Reply #3 on: July 13, 2011, 11:01:45 PM »

Since the rig was given to you, you might consider investing in it and sending it out to Jeff Covelli for servicing.  That's what I did with a TR-4Cw I purchased about a year-and-a-half ago.  Sure, the unit was working when I got it, but it sure works a whole lot better after Jeff worked his magic on it.  It's my main rig and I love using it.

Check out the comments about Jeff's work in the "Review" section (he's gotten a perfect 5).  Jeff is super-knowledgeable about Drake rigs and his rates are very reasonable. 

And, no, I'm not Jeff's brother-in-law.

Bill in Pasadena
NK6Q
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K8AXW
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Posts: 3828




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« Reply #4 on: July 14, 2011, 09:24:02 AM »

As one who grew up with "tube" equipment may I suggest.... get the tubes checked!!  Tubes do get weak and also simply give it up.  You might have to call a few TV repair places.... if you can find one.....check with some old hams, like me.... and see if they have a tube checker. 

If the tubes are OK.... then you can get into more involved trouble shooting!
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KE3WD
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Posts: 5689




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« Reply #5 on: July 14, 2011, 05:01:41 PM »

Tube checking is okay, but I'd recommend spraying out all the controls and switches first, given the stated history of storage they are likely dried out and corroded. 


73
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K8AXW
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Posts: 3828




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« Reply #6 on: July 15, 2011, 09:15:55 AM »

3WD:  You're absolutely correct!  My opinion was based on how George described the problem.  Twisting and turning knobs and pushing buttons usually provides some kind of noise in the speaker if they're dirty or intermittent.  He's talking like 'dead!'  Sounded to me like a tube gone south on power up.

My policy whenever I obtain or service a piece of gear is to clean the switches first and if it has tubes, check them just to find out if they're good, weak or bad.  Said another way, I do both, not one or the other.
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KQ6Q
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Posts: 976




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« Reply #7 on: July 20, 2011, 12:25:41 PM »

Remembering tube-era troubleshooting - tubes - all should be lit! If not, replace the dark ones. If there is a Voltage regulator tube, it should be glowing blue-purple. If it's not lit, the dropping resistor that feeds it has failed - replace it! Some basic troubleshooting with a VOM - and eyeball under the chassis for charred components - should find the problem. Also - if the power supply is external, same troubleshooting there, and look for fuses, and check them.
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KA5N
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Posts: 4380




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« Reply #8 on: July 20, 2011, 02:18:03 PM »

This tranceiver has a separate power supply.  Have you checked to see if it is plugged in to AC power?  Have you checked to make sure the power cable from the power supply is securely plugged into the transceiver? 
Sometimes the simplest thing is the problem.  The AC outlet in the house may be defective or the breaker blown.  The power cord might be defective.  Something may have come loose in the cable wiring. Who knows? 
I am sorry but it doesn't sound as if you have any troubleshooting ability at all.  Do you have a local ham friend who can help? 

Good luck and 73
Allen
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KE4VBG
Member

Posts: 220




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« Reply #9 on: July 23, 2011, 03:27:56 PM »

George

There is a #12 lamp located beside the Antenna relay that is used as a fuse. It could be shot. I have seen this before.

Doug KE4VBG
« Last Edit: July 23, 2011, 03:35:29 PM by KE4VBG » Logged
N4UE
Member

Posts: 292




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« Reply #10 on: August 02, 2011, 04:06:31 PM »

Been there, done that several times with my Drakes!!! I vote for Luke's suggestion (K6LO) that bloody switch. I finally made up a batch of 'protectors' to prevent the switches from being moved when moving the radios around.
These are simple radios to work on. Come back to this group with your results.......

ron
N4UE
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WB0CJB
Member

Posts: 38




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« Reply #11 on: December 06, 2011, 11:03:24 PM »

Unplug the #12 antenna fuse lamp and clean the pins on it. My TR4C had that same issue and after trying everything else I cleaned the pins on a whim and that fixed it. Good luck!!

Paul WB0CJB
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