Re: [Drakelist] Drake 2B
Joe - you may want to check out Garey's CD service manual for the 2B at: http://www.k4oah.com/Drake_new7/2-B.html 73 - Dino KL0S On Jun042011, at 2346 PM, Joe Connor wrote: Today, I picked up a very beat-up Drake 2B at a garage sale, and I need some help and advice: 1. The set works well on 80m and 40m but does not seem to work well on 10m, 15m or 20m. What should I be looking at to diagnose the problem? Am I correct in suspecting the crystals for those bands? (For the record, I had to replace the 6U8, which had lost vacuum, and I have to replace the 6BF6, which tests bad). I used a signal generator and could get a signal through on 10m, 15m or 20m only intermittently. I tried several different 6U8s. 2. Eventually, I would like to use this receiver for SWLing. Can anyone recommend a source for crystals? Anyone have any extras for sale? 3. Are there any other known issues with the 2B or any suggested mods that I should be aware of? 4. Are there any diagrams showing the numbers of the the coils and transformers used for alignment. For example, the manual says to adjust L-9 as part of the crystal oscillator alignment. How do I know where L-9 is? As always, thank you for your advice and guidance. Joe Connor ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Drake 2B
Man, you are quick, Dino. I was typing the very same thing as I saw your message. You just can't beat Garey's CD's for answering Drake questions!!! Also, Joe, for intermittents, I would suggest checking the bandswitch on the 2B. DeOxit on the contacts, or at the very least work the bandswitch several times to clean the grime off the contacts. They play a big role in the workings of the set. A drop in each tube socket hole is a good idea as well. 73 and good luck with your find, Don, WB5HAK___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] Fwd: Drake 2B
Ops, forgot to send to the list in case others are interested. Begin forwarded message: From: Dino Papas k...@cox.net Date: Jun 05, 2011 0859 AM EDT To: posta_libero radioradi...@libero.it Subject: Re: [Drakelist] Drake 2B Sure, Garey has a CD available for the TR-4 as well: http://www.k4oah.com/Drake_new7/TR-4.html 73 - Dino KL0S On Jun052011, at 0857 AM, posta_libero wrote: ciao i have a drake tr4 is possible have a service manual for this? you know ? thanks giuseppe italy ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] Inproved audio amp for R-4C
Does Sherwood or anyone offer an improved audio amp for the R-4C? Does the new amp draw more current? ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Inproved audio amp for R-4C
www.sherweng.com and the link for R4C kits is on the home page. 73, Don, WB5HAK ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] Drake Items
I have the following items available, shipping extra: Sherwood AMP-4 audio amplifier upgrade for R-4C: $30. Two available, used perfect condition. Sherwood R-4C 600 Hz 1st I.F. Roofing Filter, new never installed: $90 Sherwood R-4C Two-filter switching with PC board RF relays with sockets, new never installed: $80 Sherwood R-4C Custom Front-Panel AGC/First I.F. filter switch, new never installed: $70 Drake R-4C 1500 Hz filter, used: $50 Drake R-4C 500 Hz filter, used: $50 Drake R-4C 8 kHz Stock Roofing Filter: $25 Will trade either the 1500 Hz or 500 Hz filter for an INRAD R-4C 250 Hz filter. Paul, W9AC ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Inproved audio amp for R-4C
On Sun, 5 Jun 2011 13:13:08 -0700 (PDT), Neil M Califano wrote: Does Sherwood or anyone offer an improved audio amp for the R-4C? Does the new amp draw more current? Velleman offers an audio amp kit that is very close to the Sherwood design. It's a hi-fi amp, so the circuit should be tweaked (change one or two caps) to limit it to communications bandwith, but it's considerably cheaper. Current drain hasn't been a concern since the stock class A amp is disabled in the process, but it should be done in conjuntion with the established power supply mods. http://www.sherweng.com/ham.html#kits http://www.vellemanusa.com/us/enu/product/view/?id=350529 73, -Jim -- Ham Radio NU0C Lincoln, Nebraska, U.S.S.A. TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time! Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime. HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/ http://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] (no subject)
Am I the only one who is getting lots of duplicate posts from the list ,(same sent times??? May be my stupid mail program?? Bud W0HG ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] Sherwood and Inrad
Does Sherwood manufacture their own crystals? Is Inrad a separate entity? ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Inproved audio amp for R-4C
Yes. Look them up. Have had one installed for 15 + years. David Assaf, III W5XU -Original Message- From: drakelist-boun...@zerobeat.net [mailto:drakelist-boun...@zerobeat.net] On Behalf Of Jim Shorney Sent: Sunday, June 05, 2011 6:51 PM To: Drakelist@zerobeat.net Subject: Re: [Drakelist] Inproved audio amp for R-4C On Sun, 5 Jun 2011 13:13:08 -0700 (PDT), Neil M Califano wrote: Does Sherwood or anyone offer an improved audio amp for the R-4C? Does the new amp draw more current? Velleman offers an audio amp kit that is very close to the Sherwood design. It's a hi-fi amp, so the circuit should be tweaked (change one or two caps) to limit it to communications bandwith, but it's considerably cheaper. Current drain hasn't been a concern since the stock class A amp is disabled in the process, but it should be done in conjuntion with the established power supply mods. http://www.sherweng.com/ham.html#kits http://www.vellemanusa.com/us/enu/product/view/?id=350529 73, -Jim -- Ham Radio NU0C Lincoln, Nebraska, U.S.S.A. TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time! Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime. HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/ http://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.449 / Virus Database: 271.1.1/3683 - Release Date: 06/05/11 18:33:00 ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] Duplicates
Bud, It must be your mail program or something. I'm not getting duplicates. 73, Don, WB5HAK___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] Drake TR-4C V7
Hello All, I recently acquired a Drake TR-4C SN 39893. On removing the top cover, for a tentative inspection, I discovered that V7, the RF Amp, had been changed from a 12BA6 (Remote Cutoff Pentode) to a Telefunken 12AU6 (Sharp Cutoff Pentode). According to the RCA Receiving Tube Manual both tubes have similar operating voltages. Also, NJ7P Tube Database lists the 12BA6 as a preferred substitute for the 12AU6; I wonder if the reverse substitution holds true? The TR-4C does receive but, as the circuitry was designed using a Remote Cutoff Pentode, is the use of a Sharp Cutoff Pentode degrading the performance of the Rig ? Should I replace the 12AU6 with a 12BA6 or leave well enough alone? E.N. Lurch in 'Fundamentals of Electronics' Third Printing, Aug. 1961; p.83/84 illustrates the differences between Sharp and Remote Cutoff for the 6AU6 and 6BA6 tubes. The graphs on p. 84 show quite clearly what happens but, as an amateur, the significance eludes me. I assume the Drake designers chose a 12BA6 over a 12AU6 for valid reasons. Any comments please. Bob ZL2AAQ ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Drake TR-4C V7
On Mon, 6 Jun 2011 14:22:07 +1200, jeffers...@xtra.co.nz wrote: The TR-4C does receive but, as the circuitry was designed using a Remote Cutoff Pentode, is the use of a Sharp Cutoff Pentode degrading the performance of the Rig ? Should I replace the 12AU6 with a 12BA6 or leave well enough alone? The following discussion of remote vs. sharp cutoff just came over the R390 mailing list. Although it specifically addresses the R-390 IF deck, the concepts are the same: quote I wrote: The 6BA6 is a remote cutoff pentode, meaning that it takes a relatively large negative grid bias to cut off plate current. The 6AU6 is a sharp cutoff pentode, meaning that its plate current cuts off with a much smaller negative grid bias. Remote cutoff tubes are generally used in stages with AGC control, to provide a proper linear AGC action. In any case, all of the tubes on a common AGC bus should have the same cutoff characteristic, so the IF gain is distributed properly between the stages. To elaborate a bit: With 100 V on the plate and screen a 6AU6 is cut off with a grid voltage of -4.2 V (all tube parameters, voltages, and currents mentioned in this post are approximate). Cutoff is defined on the datasheet as a plate current of 10 uA or less. In typical operation, the 6AU6 with 100 V on plate and screen operates at 5 mA with a grid voltage of just over -1 V and a transconductance of 3900 umho. The transconductance does not change radically with grid voltage around this operating point, although it does change very rapidly between cutoff (-4.2 V) and the vicinity of the operating point (-1 V). A 6BA6 with 100 V on the plate and screen is cut off at a grid voltage of -20 V. Right away we see that it is intended for a different use: in this case, cutoff is defined as a transconductance of 40 umho, not as a particular plate current. In typical operation, the 6BA6 with 100 V plate and screen operates at 10.8 mA with the AGC wide open (or nearly so), also with a grid voltage of just over -1 V, and a transconductance of 4300 umho. However, it is designed to be used throughout the range of grid voltages, not just at one operating point. The transconductance of the 6BA6 changes smoothly with grid voltage, from around 5000 umho with a grid voltage approaching 0 to less than 10 umho with a grid voltage of -30 volts or so. Plate current never really does cut off -- the transconductance just gets lower and lower as the grid goes more negative. Because the amplification of a tube is directly related to its transconductance, we see that the 6AU6 is intended to maintain its amplification near a design value with reasonable changes about its nominal operating point, while the 6BA6 is intended to be a variable gain amplifier, with the gain input on the same element as the signal (i.e., the grid). (There are other possibilities -- gain can be varied by changing the screen voltage of a pentode, or one of the other grid potentials on a multi-grid tube, or changing the effective cathode resistance, for example by using a differential pair of tubes, or lots of other ways.) What does this mean for a radio's IF chain? The grid bias in AGC'd stages is set by the AGC line. Let's assume that a radio has typical AGC (for tube radios) that runs around -1 or -2 volts wide open on band noise, and reaches -15 V or more when it is hit with a lightning crash or your neighbor fires up a kilowatt to call the DX station you are listening to. Let's also assume you have your AGC set to Slow, just so we have time to analyze what is happening (it works the same with fast AGC, just ... well ... faster). Your neighbor just stopped transmitting, so the AGC line is recovering from -15 V or more. As it rises, the gain of the remote cutoff amplifiers increases smoothly, and the band noise (with that buried DX signal) also rises until the AGC stops it at a grid voltage of, say, -1 volts. Now replace one IF tube with a 6AU6. As the AGC line recovers from -15 V or more, the gain of all of the AGC stages except that one increases smoothly. When the AGC line reaches -6 volts, the 6BA6 stages are operating with a transconductance of 500 umho -- about 20 dB less than their maximum gain -- but the 6AU6 stage is still solidly cut off, and passing no signal. So, the IF as a whole is still doing nothing because no signal gets through the 6AU6 stage. By the time the AGC voltage reaches -4.2 V, the 6BA6 stages are up to a transconductance of 1000 umho -- within 12 dB of their maximum gain -- and the 6AU6 stage is just starting to pass signal (if that stage were another 6BA6, it would be operating within 12 dB of its maximum gain, too). So the IF as a whole is still doing essentially nothing. Then, over the next 2 V or so of AGC potential, the 6AU6 suddenly catches up and then passes the gain of the 6BA6 stages. The net result is that even with just one sharp cutoff tube, the useful AGC range has
