Re: [Drakelist] Drake C-Line, Transceive switch on T4X-C, Changing signal strenghts
Chuck - First ... It is normal for the gain of the receiver and transmitter to vary slightly with the position of the transceive switch. That said, the basic fact is that the INJection and the CARrier OSCillator signals are what is patched between the two units. The CAR OSC signal is at 5.645 MHz, and is not likely to be a problem as it is the same on all bands. The INJ signal however, is 11.1 MHz above the dial frequency, and on the higher bands is in the 30 - 40 MHz range. The _capacity_ of the INJ cable is critical, and the original cable has a TOTAL capacity of 60 pF, including connectors. This capacity is connected across the tuned circuits of the input and output amplifiers, and so has a greater effect as the frequency goes up. My _guess_ is that: 1. The 160M band differential MAY be an effect of the narrower bandwidth of the T-4XC on the higher bands. The original version didn't like to go below about 1850 kHz. Changes were made in the second version to stretch this down to 1800. Question. When you recorded the 5 dB difference were you well below 1800 kHz? 2. The other bands WILL vary around whatever band and frequency you did your alignment on. When this occurs, are you able to return the gain to nominal by peaking the PRESELECTOR, or RF TUNE controls? BOTH controls must be peaked, and be close to each other in frequency. After 50 years of servicing and using these radios, I have yet to find a pair that did NOT vary from RCVR to XMTR control in TRANSCEIVE to some extent. As a matter of practical fact, 5 dB difference in a received signal strength is almost NEVER noticeable due to the excellent AVC. One last thought. IF your Preselector or First Mixer tubes are weak, making the PreMix signal level marginal, it would have an effect on this problem. 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 4-B, C-Line TR-4/C Service Supplement CDs www.k4oah.com Chuck Pool wrote: Hi to all: When switching between RCVR and XMTR, by using the Transceive switch on the T4XC, received signal strength remains constant (the same) on some bands while others bands produces a drop or gain is signal strength. I am using the calibrator as the received signal with the AGC set to fast, 50 ohm dummy load selected then antenna selected for comparison. Some times it is the XMTR that has higher received signal strength. Some times the RCVR has stronger received signal strength. And, some times both rigs have identical received signal strength when selecting between RCVR and XMTR, via Transceive switch on T4XC, on different bands. i.e. 80 meters has produced no difference in received signal strength when switching between RCVR or XMTR. i.e. 160 meters produces 5 db stronger received signal strength when T4X-C Transceive switch is set to RCVR. The received signal strength is 5 db less when XMTR is selected. I have tried different types of injection cables, went through a careful alignment of both radios (while both were connected together) and still there is no uniformity between the bands in received signal strengths when switching between RCVR and XMTR. Why is this? Any suggestions on how to obtain uniformity in received signal strengths on all bands when switching between RCVR and XMTR via T4X-C transceive switch? 73, Chuck Pool - AA5WG ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] TR4C, RV-4C VFO, AND AC4
I'm trying to determine what my TR4C, RV4C, and AC4C is worth. Yea I know what the market will bear however I don't want to give it away and need to feed my family. I intend to list them on Craigslist instead of PAY-BAY so any help would be wonderful. They are in great condition and look very good. I've tried to hold on to them through our State Furloughs and financial problems, but I'm now at the point it can't be helped. Thank you Drake List, John, WA6HYQ. ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Drake C-Line, Transceive switch on T4X-C, Changing signal strenghts
Chuck - First ... It is normal for the gain of the receiver and transmitter to vary slightly with the position of the transceive switch. That said, the basic fact is that the INJection and the CARrier OSCillator signals are what is patched between the two units. The CAR OSC signal is at 5.645 MHz, and is not likely to be a problem as it is the same on all bands. The INJ signal however, is 11.1 MHz above the dial frequency, and on the higher bands is in the 30 - 40 MHz range. The _capacity_ of the INJ cable is critical, and the original cable has a TOTAL capacity of 60 pF, including connectors. This capacity is connected across the tuned circuits of the input and output amplifiers, and so has a greater effect as the frequency goes up. My _guess_ is that: 1. The 160M band differential MAY be an effect of the narrower bandwidth of the T-4XC on the higher bands. The original version didn't like to go below about 1850 kHz. Changes were made in the second version to stretch this down to 1800. Question. When you recorded the 5 dB difference were you well below 1800 kHz? 2. The other bands WILL vary around whatever band and frequency you did your alignment on. When this occurs, are you able to return the gain to nominal by peaking the PRESELECTOR, or RF TUNE controls? BOTH controls must be peaked, and be close to each other in frequency. After 50 years of servicing and using these radios, I have yet to find a pair that did NOT vary from RCVR to XMTR control in TRANSCEIVE to some extent. As a matter of practical fact, 5 dB difference in a received signal strength is almost NEVER noticeable due to the excellent AVC. One last thought. IF your Preselector or First Mixer tubes are weak, making the PreMix signal level marginal, it would have an effect on this problem. 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 4-B, C-Line TR-4/C Service Supplement CDs www.k4oah.com Chuck Pool wrote: Hi to all: When switching between RCVR and XMTR, by using the Transceive switch on the T4XC, received signal strength remains constant (the same) on some bands while others bands produces a drop or gain is signal strength. I am using the calibrator as the received signal with the AGC set to fast, 50 ohm dummy load selected then antenna selected for comparison. Some times it is the XMTR that has higher received signal strength. Some times the RCVR has stronger received signal strength. And, some times both rigs have identical received signal strength when selecting between RCVR and XMTR, via Transceive switch on T4XC, on different bands. i.e. 80 meters has produced no difference in received signal strength when switching between RCVR or XMTR. i.e. 160 meters produces 5 db stronger received signal strength when T4X-C Transceive switch is set to RCVR. The received signal strength is 5 db less when XMTR is selected. I have tried different types of injection cables, went through a careful alignment of both radios (while both were connected together) and still there is no uniformity between the bands in received signal strengths when switching between RCVR and XMTR. Why is this? Any suggestions on how to obtain uniformity in received signal strengths on all bands when switching between RCVR and XMTR via T4X-C transceive switch? 73, Chuck Pool - AA5WG ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] Rubber feet?
I recently acquired my first tube radio station. A TR-4/RV-4/AC-4. Everything seems to work as it should. My question is one only a rookie would ask, and I'm sorry to ask but I have looked everywhere I can find, without any luck. Should the AC-4 have rubber feet on it? Mine does not and when I put it inside the RV-4 I have a vibrational hum that is not acceptable. Thanks KB8NXO -- The law, in its majestic equality, forbids the rich as well as the poor to sleep under bridges, to beg in the streets, and to steal bread. - Anatole France ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Rubber feet?
Ok. Thanks all. I did not know the AC-4 was securely mounted to the chassis of the RV-4 with screws. I was just sliding it in there. I see I have the threaded type mount power supply. I also see that the feet on the RV-4 are nutted. So I'll try to screw the RV-4's rear feet into the bottom of the AC-4. That is two mount point short I know. BTW. I read this all day long and am learning a lot, fast. Thanks again. Kb8NXO -- The law, in its majestic equality, forbids the rich as well as the poor to sleep under bridges, to beg in the streets, and to steal bread. - Anatole France ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Need 02 Digital Control Board for R7[A]
Dave - I have no knowledge of the R7 board and don't have the schematic for that, but did recently do some work on my TR7 digital control board and will tell you what I found. Excuse me if I go over some stuff you already know. U201 is simply a BCD to Decimal decoder. On the TR7, two sections of the bandswitch produce a 4 bit BCD code by grounding various of those 4 bits. All four are tied up with 10K resistors on the digital control board. These 4 bits can be accessed on the TR7 at pins 1-4 of the second board position on the motherboard (that's where the digital control board is). There's absolutely nothing unique to Drake in this case - the BCD to Decimal converter (MC14028B in my case) converts the 4 bit input to a one-of-8 decimal value and pulls one of the output pins low for each unique value. The first two bits, identified as Q0 and Q1 on U201 are NOT used in this case as the possible BCD values don't translate to those decimal values. I had a need to be able to sense the bandswitch position, and produce a single bit output, so I needed a device to duplicate the U201 function on a new board using Pins 1-4 described above as input. While MC14028B is long obsolete, I found no shortage of BCD to decimal converters when I went looking at Mouser and Jameco. The problem was the truth table (published for the TR7 on page 2-7 of the service manual I have - mine does not show a version using a Prom). Some of the converters outputted the decimal value by holding a pin high, others by holding it low (ground). I found a TI IC that pulled the pin low, but then found conflicting info on another datasheet for the same device. I finally ended up calling Jameco and talking to one of their tech people (try that at Mouser!) and he steered me to the correct datasheet and the device did indeed pull the output pin low. The truth table in the datasheet matched the one in the TR7 manual perfectly, with the exception I already mentioned - the TR7 doesn't produce the decimal values 0 and 1. The cost of the IC was something like 27 cents. My new board, which uses the converter to select the proper PIN diode attenuator for the PA input, works perfectly using the scheme. I'm guessing that the outputs from both versions of the TR7 board (with and without PROM) are identical, but can't venture a guess on the R7 board. I don't know if the pinout for the MC14028B, Prom, and my converter IC are identical. I used a 7445 BCD to decimal converter IC and Jameco shows only the expensive TI version on their site, but the very inexpensive version from other vendors is available and the pinout is the same. If you think I may be able to help you further, don't hesitate to contact me. The digital converter board outputs are very easy to check with just a VOM, so if someone has an R7 they could open up, they could check those for you. 73, Floyd - K8AC ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] R-4A Notch trouble
Hi My R-4A project is puzzling me. It sounds ok, but when I go through the adjustment procedure I'm puzzled. The book says thet the tuning of T7 andT10 is quite broad. For sure, I can't get a maximum at all. And the notch will not work. There is absolutely no response to any setting of the notch controls. I have tried to replace the tubes with known good ones - no difference. I have measured the notch coil, seems good (only ohms resistance). I have not tried to adjust the core of the notch control for fear of doing something wrong. It would be very strange if it should be out of tune. Where should I start? 73s de Karl LA1CU la...@nrrl.no --- No trees were harmed in the sending of this message, but a lot of electrons were terribly inconvinienced Do not print this message unnecessarily! ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Rubber feet?
Not sure that will work, if memory servers, they may be different threads. The original screw in feet of the AC-4 (shorter than the RV-4 feet, they were just half-rubber balls attached to screws) were to be used to hold the AC-4 in the RV-4/RV-4C/MS-4 cases. Loren - WA3WZR On 1/15/2010 11:44 AM, Richard Palmer wrote: Ok. Thanks all. I did not know the AC-4 was securely mounted to the chassis of the RV-4 with screws. I was just sliding it in there. I see I have the threaded type mount power supply. I also see that the feet on the RV-4 are nutted. So I'll try to screw the RV-4's rear feet into the bottom of the AC-4. That is two mount point short I know. BTW. I read this all day long and am learning a lot, fast. Thanks again. Kb8NXO No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.725 / Virus Database: 270.14.142/2623 - Release Date: 01/15/10 02:35:00 ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] R-4A Notch trouble
Karl - Three things. One, the IF must be aligned properly, i.e., on frequency. Two, NOTCH is VERY narrow. It's easy to go right past it if you turn the knob too fast. Three, the NOTCH ADJUST control on the right side of the chassis must be adjusted as well. These two must be adjusted alternately for the best notch. 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 4-B, C-Line TR-4/C Service Supplement CDs www.k4oah.com Karl Henrik Laache wrote: Hi My R-4A project is puzzling me. It sounds ok, but when I go through the adjustment procedure I’m puzzled. The book says thet the tuning of T7 andT10 is quite broad. For sure, I can’t get a maximum at all. And the notch will not work. There is absolutely no response to any setting of the notch controls. I have tried to replace the tubes with known good ones – no difference. I have measured the notch coil, seems good (only ohms resistance). I have not tried to adjust the core of the notch control for fear of doing something wrong. It would be very strange if it should be out of tune. Where should I start? 73s de Karl LA1CU la...@nrrl.no ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Rubber feet?
The TR-4 has 6 rubber feet (sorta). On the rear there is one in each corner and in the front there are two stacked in each corner. This raises the front to an angle. The RV-4 has rubber feet in both corners up front that look very similar to the ones on the TR-4. And in the rear corners there are the half rubber ball feet. I was told the SK who last owned this station, ran the power supply out side of the case. The AC-4 is without feet. So it looks like I'm just a couple of power supply feet short. The power supply has no real vibration to the touch. But putting inside of the RV-4 without feet and having it rest in the nutted studs from the half round feet on the rear of the RV-4 creates a vibration that sounds like AC hum. This is still new to me and I will take care of this rubber footing when I do a maintenance cleaning (it needs it) next month. Thanks for the information. I now know how it was meant to be. Rick KB8NXO -- The law, in its majestic equality, forbids the rich as well as the poor to sleep under bridges, to beg in the streets, and to steal bread. - Anatole France ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
