Re: [Drakelist] TR7 acting strange
Garey, Even thought I had spontaneous healing of my TR7 per our e-mail discussion, I opened up the rig and did some voltage tests. Rig in SSB, all boards installed. Pin spec measured 1 -5V -3.43 2 +25 23.3 3 gnd 4 AM 4.99 5 RTTY7.01 6 CW 4.31 7 LSB 6.26 8 USB 3.83 9 DCin13.53 10 +10VDC 10.01 11 +5V 4.90 The 24VDC line stayed solid as I moved the bandswitch and up down buttons. Per the drake service dept alignment procedures, pin 2 should measure between 23.25-24.0. Assuming my meter is accurate, that voltage is very close to being out of spec low. Maybe a weak/leaky C2110? I could not get to the input of U2103 (24V regulator) without pulling the DR7 board. Pulled it and installed probes and then reinstalled the DR7. Input to the 78c24 was at 27VDC immediately after turning on the rig, and then climbed to 32-35 volts w/i about 10 seconds. As I recall the 7800 family of chips need 2 volts to regulate, so I think input is w/i spec even at turn on. When switching the bandswitch, it made the input voltage move, but never under the 32 volt level. Caveat, using a DVM so it may have spikes that I was not seeing. After this, I pulled the DR7 and replaced it with the service kit jumper logic board. Basically had the same results with it in place of the DR7 board. TNX es 73, Ron --- On Mon, 1/25/10, Garey Barrell k4...@mindspring.com wrote: From: Garey Barrell k4...@mindspring.com Subject: Re: [Drakelist] TR7 acting strange To: Ron wd8...@yahoo.com Date: Monday, January 25, 2010, 9:56 AM Ron - Definitely sounds like marginal VCO locking. The bands from 160 - 20M will all wander around 17 MHz. 15 and 10M bands will wander around 34 MHz. An open AUX-7 position will result in an unlocked VCO, as will pushing the FIXED RCV button in. First step is to check that +24V DC supply bus. That is the most likely cause of this, i.e., random, occasional, loss of lock on both PTOs. Certainly there are other possible causes, but that little transformer core is a problem, and the super glue that Drake used to put it together is letting go (after only 40 years or so). Easy fix, just glue it back on. 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 4-B, C-Line TR-4/C Service Supplement CDs www.k4oah.com Ron wrote: Garey, I started to look at the TR7 last night. First was to see for sure what was going on frequency wise. Turned it on, 80 meters, where I had left it and it was fine. 2.5 then 1.5 wondering 17xxx.x 1.5. Back to 80 meters fine, and of course everything else was fine too. So then I went back down to 2.5 and 1.5, they too were fine now. So I thought maybe temperature or time. Could not get it to fail after several hours. Got to playing and went to aux settings. They were fine with the band light lighting if I was not in the correct band. Then I went to an open aux location and got wondering 17xxx.x. I can not remember it that has always been that way or not. Looks like it could be correct given the block diagram of the rig in my head. So I know it sounds like VCO/PLL issues, which voltages are most likely. But, is there anything in the bandswitch that exercise might cause to clean up? Or am I in for what looks to be a PITA intermittent? Also, I have looked for how my TX is open. The motherboard out of lock trace is not cut, and the Q9001 collector on the DR7 board seems in tack. Maybe I just missed how they defeated Q9001. Is there something with the aux board that also somehow opened the TX? I thought it was only for the modules in aux, not the whole TX? Thanks in advance. Also thanks for being an anchor for this list. Your knowledge and willingness to share that knowledge is a tribute to the real meaning of Ham Radio. 73, Ron WD8SBB --- On Sun, 1/24/10, Garey Barrellk4...@mindspring.com wrote: From: Garey Barrellk4...@mindspring.com Subject: Re: [Drakelist] TR7 acting strange To: Ronwd8...@yahoo.com Cc: Drakelist@zerobeat.net Date: Sunday, January 24, 2010, 4:40 PM Ron - You may need to recheck your frequencies. ~17 MHz is the target frequency for the Lo Band VCO (through 20M), and 34 MHz for 15 and 10. This is where the VCO's settle when unlocked. First thing to check is the +24V DC supply. This higher voltage is used for the Loop Filter and VCO steering. If the voltage is low, check that E core on the DC/DC converter transformer on the little power supply board. There are other possibilities, but this is a start. Unless the transmitter has been modified, it won't transmit if the VCO is unlocked. 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 4-B, C-Line TR-4/C Service Supplement CDs www.k4oah.com Ron wrote: Got a strange one going on. Finished and 80 meter net and was headed to 40 to listen to the Drake
Re: [Drakelist] TR7 acting strange
Ron, I haven't been following the thread but of the TR-7's that I have owned or serviced the lowest I have seen the +24 volts and not had an issue with the PLL locking up on 14 mhz and higher was 23.6 volts. That's not to say 23.3 vdc is bad, I just haven't yet seen it. The voltage just needs to be high enough for the VCO to work on higher frequencies. The 30 vdc input for the 24 v regulator is derived from the DC inverter Q2104, Q2105, T2101, and associated parts. Some times the powdered core halves of T2101 will separate and lower the 30 volts input. In that case just reposition them and tighten the loop wire holding them or use hot glue to keep them in place. Some power supply boards will have 68 ohm resistors soldered across R2129 and R2130. This may also help to raise the 30 volts from the regulator. I also in one case I replaced C2117 and C2115 with .033 ufd to get the voltage up. Like the 68 ohm resistors some boards have those same capacitors soldered on the backs of the board so I suspect Drake had issues with the design. 73, Gary W8PU http://home.roadrunner.com/~w8pu ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] TR7 acting strange
Gary, great shots of the Drake stations across the years; I had a ball with the TR-33C; I purchased one when they first came out and had it crystalled for the one local repeater and 146.52. I still have it here and put it in service on the outside antenna occasionally and receive great audio reports! (slightly off topic) 73 de W4DLMike Pompano Beach, FL USA - Original Message - From: Gary Poland To: Drakelist@zerobeat.net Sent: Saturday, January 30, 2010 2:05 PM Subject: Re: [Drakelist] TR7 acting strange Ron, I haven't been following the thread but of the TR-7's that I have owned or serviced the lowest I have seen the +24 volts and not had an issue with the PLL locking up on 14 mhz and higher was 23.6 volts. That's not to say 23.3 vdc is bad, I just haven't yet seen it. The voltage just needs to be high enough for the VCO to work on higher frequencies. The 30 vdc input for the 24 v regulator is derived from the DC inverter Q2104, Q2105, T2101, and associated parts. Some times the powdered core halves of T2101 will separate and lower the 30 volts input. In that case just reposition them and tighten the loop wire holding them or use hot glue to keep them in place. Some power supply boards will have 68 ohm resistors soldered across R2129 and R2130. This may also help to raise the 30 volts from the regulator. I also in one case I replaced C2117 and C2115 with .033 ufd to get the voltage up. Like the 68 ohm resistors some boards have those same capacitors soldered on the backs of the board so I suspect Drake had issues with the design. 73, Gary W8PU http://home.roadrunner.com/~w8pu -- ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] TR7 acting strange
Hi Gary - Ron's unit was locking ok except on the top of 10M.. The regulator is specified +/- 1V (+/- 4%) so from what you say, a changed regulator might be in order. The A version is +/- 2%. Your message does bring up a question that I have been pursuing. You mention the wire loop around the transformer as holding the core sections together. It doesn't! :-) The wire loop is wrapped around the lower core half, 90 degrees from where it would be to hold the sections together. The wire is also stripped and soldered together, forming a shorted turn. I think its purpose is to shunt the external field from the transformer, much like the copper band around many power transformers. The other thing that Ron is seeing is that the unregulated 30V is considerably lower (~27V) for the first 10 seconds after turn-on, when it jumps up to 32+. I was wondering if the multivibrator was slow to start, and your mention of the added resistors and/or caps is interesting. For the R-7 they gave up entirely, and used a single transistor oscillator driving a power Audio Amp chip.! Lots simpler 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 4-B, C-Line TR-4/C Service Supplement CDs www.k4oah.com Gary Poland wrote: Ron, I haven't been following the thread but of the TR-7's that I have owned or serviced the lowest I have seen the +24 volts and not had an issue with the PLL locking up on 14 mhz and higher was 23.6 volts. That's not to say 23.3 vdc is bad, I just haven't yet seen it. The voltage just needs to be high enough for the VCO to work on higher frequencies. The 30 vdc input for the 24 v regulator is derived from the DC inverter Q2104, Q2105, T2101, and associated parts. Some times the powdered core halves of T2101 will separate and lower the 30 volts input. In that case just reposition them and tighten the loop wire holding them or use hot glue to keep them in place. Some power supply boards will have 68 ohm resistors soldered across R2129 and R2130. This may also help to raise the 30 volts from the regulator. I also in one case I replaced C2117 and C2115 with .033 ufd to get the voltage up. Like the 68 ohm resistors some boards have those same capacitors soldered on the backs of the board so I suspect Drake had issues with the design. 73, Gary W8PU http://home.roadrunner.com/~w8pu http://home.roadrunner.com/%7Ew8pu ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] What circa tube tester?
I hope this is not off topic. With the use of vintage being used for all Drakes and tube testers, many from the 1940's and before, up to the last ones made, it has become impossible for me to determine what will service my early TR-4. I have spent hours and hours looking up tube testers by type, make and model. I have spent hours squinting at pictures trying to count socket pins. I am burnt out and am looking for help in finding just where to look. I have no idea if post WWII testers even test 9 pins, or if all 7 pins are of the same size. Richard Palmer 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] What circa tube tester?
Richard - First, there are two major types of tube testers. The least expensive is the Emission type which merely applies power to the filament and plate of a tube and measures the current on a Good-?-Bad meter scale. They are slightly better than using an ohmmeter on the filament pins to see if the filament is intact! The more expensive type, the Mutual Conductance type, applies filament and plate voltage and then applies a known AC signal to the grid to measure the actual gain of the tube. The Emission tester will tell you if the cathode is still emitting electrons, and the Mutual Conductance tester will tell you how the tube amplifies _at the single test point and level_ chosen by the tester manufacturer. Neither tells you much of anything about operation at RF. Typically only the latest tube testers will test the Compactron type of tubes (6JB6) without some sort of adapter. One of the better tube testers available is the military TV-7/U family. It doesn't have sockets to test the Compactrons, but someone has made a set of adapters for it to allow it to test the common sweep tubes, like the 6JB6. All the rest of the tubes in the Drake gear are 7 and 9 pin miniature types, which just about any tester made after about 1940 will test. These tubes are all the same size pins and pin circle. All that said, a tube tester isn't all that much help anyway. The only REAL test for a tube is in the circuit you want it to work in. Your best approach to maintaining your Drake gear is to get a couple of each tube type, test them by plugging into a working radio and if they work, put them in a safe place! This is especially true for 6JB6 tubes used at RF frequencies. These tubes were designed for use as horizontal output tubes for TV sets. They operated at almost 16 kHz in that service!! Sylvania, in the early 60's, characterized (tested) some of their TV Sweep tubes such as the 6JB6 for linear amplifier service from 2-30 MHz. The resulting data was used by Drake and several other Amateur equipment makers to develop transmitters that would run considerably more power than those using the 6146, and do it at a lower plate voltage! Add that the sweep tubes were about 1/3 to 1/2 the cost of the 6146, and that a lower plate voltage could be used for higher power output and it was a done deal. The pertinent characteristic was a high perveance, or high currents at lower plate voltages. They were designed to operate 24/7, inside a TV set with 25 other tubes and keep working, so they were able to serve in CW or SSB service at considerably higher power levels than their published specifications.. The catch here is that since the tube was designed to operate at 16 kHz, NOT 30 MHz, not all brands of the same tube type were interchangeable. Operation at 30 MHz requires considerably more attention to internal tube structure such as lead lengths, interelement capacitance, etc. The result was that one manufacturer might make a 6JB6 with considerably higher reactances that worked just fine at 16 kHz, but would make it impossible to neutralize in an HF transmitter without changes in the neutralization circuitry. Add the fact the some of the smaller, even well known companies that put their name on a tube may well have had that tube made by more than one manufacturer, and it gets difficult to say which tubes will work in a T-4X and those that won't. Further complicating the situation is that the RF gain of a tube falls off with decreasing emission, and falls off first at the higher frequencies. 6JB6 tubes in T-4X service will fall off first on 10M, then 15, then 20, then ... Most will continue to put out SOME power on 80 and 40M after 10M output is just about zero. My experience has shown that Sylvania, Zenith, RCA and GE are the ONLY brands of 6JB6 that I have found to work _consistently_. Raytheon, Westinghouse, Standard, and most others are potential trouble. Some work, some don't, depending upon who _really_ made them. By the way, it is NOT a good idea to replace ALL the tubes in a radio at once. Retubing is somehow seen as similar to replacing all your tires. This is not only wasteful of a finite source of vacuum tubes, but can turn a working radio into one that doesn't! Even New Old Stock tubes, all manufactured over 30 years ago, are not all good. So get a few spares for each type, _check them in a currently working radio_, and if they are good put them in your tube stash for a rainy day. 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 4-B, C-Line TR-4/C Service Supplement CDs www.k4oah.com Richard Palmer wrote: I hope this is not off topic. With the use of vintage being used for all Drakes and tube testers, many from the 1940's and before, up to the last ones made, it has become impossible for me to determine what will service my early TR-4. I have spent hours and hours looking up tube testers by type, make and
[Drakelist] T4X-C. Now more output power and no RFI?
Hi to all My T4X-C always put out about 110 -120 watts, less on 20 - 10 meters. On 40 meters there was always RFI problems with our organ. Today, the T4X-C was putting out 150 watts on 80 meters. All the other bands had much more output power too. Amp meter said 400 - 450 mills. 320 - 350 mills is normal for me. 400 - 450 amp mills seems to high? Is it? Now there is no RFI problem on 40 meters. What is going on? Any ideas? 73, Chuck - AA5WG Cedar, Michigan ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
