Darrell Bellerive <[EMAIL PROTECTED]> made an utterance to the drakelist gang ---------------------------------------------------------------------- When I completed my first radio restoration project, an Heathkit GR-81, and announced that my next project would be a Drake 2-B receiver, a few people asked me to post my progress to the mailing list. I will cross post to both the Drake (drakelist@zerobeat.net) and Glowbugs ([EMAIL PROTECTED]) lists. I will also include "VA7TO 2-B:" in the subject for those who would like to filter messages.
I hope that this serves two purposes, first is for me to gain from the experience of others, and learn some tips and tricks and second to document what I have done so that those following me in a 2-B project can learn from my efforts. First of all a little history of my 2-B. I purchased it at the Spokane Hamfest in September of 2007 complete with 2-BQ Q multiplier and speaker. The seller did not know much of the history of the radio, and a quick test at the hamfest showed it received a 40 meter test signal. I paid $275 cash. The radio is in good shape cosmetically and looked fairly clean inside. The receiver immediately went into service as my bedside receiver. I was thoroughly impressed by the audio quality and the selectivity on CW with the Q-multiplier. Hindsight is 20/20 and I wished that I had purchased a 2-B as my first receiver rather than an Hallicrafters SX-140 back in 1975. The 2-B saw regular duty for several months, until one evening it exhibited a loud white noise sound. At that point it was taken out of service and has remained unused. The details on the white noise sound are in this message: http://www.mail-archive.com/[EMAIL PROTECTED]/msg08842.html Last night I pulled the cover off and was surprised to see how clean the inside of the chassis is. It is also a lot easier to work on than I had thought it would be. In operation, the passband control did not seem to line up with the knob markings and I suspected that the knob had been reinstalled incorrectly at some point in the past. Using the information on Garey Barrell, K4OAH's Drake 2-B Service Supplement CD, I was able to confirm that the knob had been placed 90 degrees clockwise from where it should have been and I readjusted it. For a starting reference point I measured all the points listed in the resistance table in the 2-B manual. I was also surprised to see that the measured readings were quite close to those listed in the table. The radio was NOT connected to anything including the power, 2-BQ or speaker, and the controls were set as follows: Preselector: 5 Band: 15 M Power: Off Cal: Off Stby: Rcv AVC: Slow AVC NL: On Detector: Product BFO: On RF Gain: Max (fully clockwise) AF Gain: Max (fully clockwise) Passband: 2.1 kHz and Knob arrow pointed to 12:00 o'clock. Freq: 21.150 Mhz The resistance of pin 3 of V-8 will be altered by the position of the noise limiter (NL) switch. Intially I had the switch off and measured only 346 kilo ohms, rather than the 2.5 mega ohms I should have seen. A quick check of the schematic showed that the switch must be on to reach the specified resistance. The next step was to test the tubes. V-1 (RF amp) and Zenith 6BZ6 - Tested OK V-2 (1st mixer & xtal osc) RCA 6U8A - Tested shorted V-3 (2nd mixer & vfo) RCA 6BE6 - Tested OK V-4 (3rd mixer) Sylvania 6BE6 - Tested OK V-5 (IF amp) Sylvania 6BA6 - Tested OK V-6 (AVC Amp and AM det) Sylvania 6BF6 - Tested right on the line between good and bad V-7 (Prod Det and BFO) Sylvania 6BE6 - Tested OK V-8 (audio amp) Sylvania 8BN8 - Tested OK V-9 (audio output) Sylvania 6AQ5 - Tested just into the good V-10 (Power Rect) unreadable brand 6X4 - Tested OK Crystal Calibrator Sylvania 6BZ6 - Tested shorted 2-BQ Sylvania 12AX7 - Tested OK I had a spare 6BZ6 of unreadable brand that I substituted into the crystal calibrator and also a spare 6U8A also of unreadable brand that I substituted into V-2. So all the shorted tubes have been replaced, but some low emission tubes should also be replaced. The manual specifies a 6U8 at V-2, but there was a 6U8A there. Should this be replaced with a 6U8? I would guess that the 2-B originally came with all Sylvania tubes. Can anyone confirm this? Are there better brands that anyone would recommend for certain tubes or stages? I would like to replace the 6BF6 (V-6) and the 6AQ5 (V-9) with stronger tubes. I am wondering if I should stay with Sylvania brand tubes or if it matters, or if there are better brands to use. Should I even go so far as to replace the non-Sylvania tubes with Sylvania tubes or other recommended brands? I also have a number of industrial tubes and wonder about tube substitution with some of these. Please reply with your comments and suggestions on what you think I should do about the tubes. While I wait for advice on tubes and then source replacements, I will begin work on recapping, replacing the RF and AF gain pots, and cleaning up the knobs and dial. I was fortunate to get a recapping kit, the RF and AF gain pots, and the red window slider knob from Unique Radio Parts before they ceased business. I also have a replacement filter cap from Tom NØJMY (http://hayseedhamfest.com). Please email me any suggestions. 73, Darrell VA7TO -- Darrell Bellerive Amateur Radio Stations VA7TO and VE7CLA Grand Forks, British Columbia, Canada ---------------------------------------------------------------------- Submissions: drakelist@zerobeat.net Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost: [EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net ----------------------------------------------------------------------
