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Author Topic: Drake 2C: 1 Great Band, 4 Dead Bands  (Read 1874 times)
K3ZL
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Posts: 132




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« on: March 06, 2013, 05:41:19 PM »

I got a Drake 2C off eBay.  On 80 meters it is excellent in all ways. Everything including the calibrate works perfect.  But on 40 through 10 meters it is dead.  On those bands I hear what sounds like atmospheric noise, but no signals detected, Antenna preselector does not make any difference.  I can barely hear the calibrator.   I noticed one on eBay recently that was described as good on 80 and 40, and nothing else, maybe a similar problem.   Just wonder if any of you have an idea as to where to start looking for the problem.  Any ideas appreciated. Tnx
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G3RZP
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Posts: 4718




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« Reply #1 on: March 07, 2013, 02:45:19 AM »

Didn't the 2C use an  80 meter tuneable IF and crystal controlled converter in front of it for the other bands? Memory of the 2C is fading........But if that's the case, then the tubes in the converter section are their assoiciated circuitry is where to start looking. I take you have at least the schematic?
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KA5N
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Posts: 4380




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« Reply #2 on: March 07, 2013, 05:31:37 AM »

Someone may have removed the crystals leaving those bands dead.  Or the transistor
oscillator may be bad or the power for it is missing.  The manual is available on BAMA free of
charge (photocopy).  At least with one band working, you know that most of the circuitry
is working.  Normal troubleshooting should resolve the problems (if the crystals are missing
they may be a bit hard to find, but various manufacturers will supply identical crystals at
a reasonable cost).

Allen KA5N
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KE3WD
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Posts: 5689




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« Reply #3 on: March 07, 2013, 05:51:45 AM »

Or bandswitch contacts might just be a bit dirty...
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K3ZL
Member

Posts: 132




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« Reply #4 on: March 07, 2013, 08:04:58 AM »

Great suggestions from all.  I will find a manual and and get into it.  Cheers to all, tnx.
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KC9UNL
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Posts: 17




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« Reply #5 on: March 17, 2013, 04:44:46 AM »

Would Suggest that you remove the 2C from the case and remove each tube one at a time and spray contacts with a contact cleaner, i.e. deoxit.  Also clean the bandswitch with deoxit.
Then see what you have.  Make a list of all the tubes in the 2C. They are 12BZ6,12AU6,12BE6(2),12BA6 The rest are semiconductors. Replace one tube at a time or do all at one time. It should work. But, I would guess that this will get you up an running.

Curt   KC9UNL
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K1TWH
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Posts: 103




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« Reply #6 on: March 18, 2013, 12:25:50 PM »

From the front of the 2C, on the left side , there is a slide switch to select the external crystal for auxiliary coverage, or the internal crystals for 40-20-15 & 10M.    Make certain the slide switch is in the normal position (not towards the little crystal socket).   Tom  WB1FPA
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W9GB
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Posts: 2626




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« Reply #7 on: March 18, 2013, 01:39:01 PM »

Keith,

90% of Troubleshooting with an HF receiver, that you are not familiar with, is to run through the schematic.
Schematics provide the Visual Blueprint for the Radio Technician to perform repairs.
This will narrow the specific areas to test when receiver is on the electronics workbench.

Drake 2-C Receiver Schematic with specific Power (Voltage) and RF Signal paths highlighted IN COLOR.  
The RF signal path is in GREEN, starting at upper left of Schematic diagram.
http://bama.edebris.com/download/drake/2c/2C_1B.jpg

NOW, based on your reported observations,
I would focus a VISUAL EXAMINATION (magnifying glass may help) in the PRE-SELECTOR
 and the BAND SWITCH wafers (S1A and S1B).  Does it operate properly?
Corrosion or Breakage of those bronze/copper conductive fingers can cause issues you reported.

As suggested by Tom, WB1FPA earlier, IF the NORM/AUX switch is in wrong position --
 Below Pre-Selector in schematic, then the XTAL OSC. (Q1) does not operate
to provide the OSC frequency for the MIXER (V2) to receive other bands.
« Last Edit: March 18, 2013, 01:49:57 PM by W9GB » Logged
K3ZL
Member

Posts: 132




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« Reply #8 on: March 18, 2013, 06:47:11 PM »

Would Suggest that you remove the 2C from the case and remove each tube one at a time and spray contacts with a contact cleaner, i.e. deoxit.  Also clean the bandswitch with deoxit.

Curt   KC9UNL
Curt, you nailed it.  Works great on all bands.  Man, that Deoxit is high at Radio S.  There must be a better source online. But it did the job.  Thanks, Keith
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