Re: [Drakelist] My Drake at Field Day
Years ago, I participated in a Field Day, back when the Kenwood TS940 was fairly new. The Kenwood was to be our primary rig and I brought my "old" TR7, more as an afterthought, to be a back up rig. As you might guess, the Kenwood had trouble and we ended up operating the entire weekend on the Drake. Still have that Drake and it still chugs along. His Kenwood is long gone. 73 Lee WB6SSW ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] My Drake at Field Day
Someone was wondering why they hadn't heard a report yet :) I got my pictures from our K0KKV Field Day into the hands of the web admin tonight, and they are up here: http://k0kkv.org/gallery/index.php/Club-Events-and-Activities/Field-Day/Field-Day-2011 Featured prominently in several shots is half of my 7-Line. 966 total Qs on the Drake over the weekend, and at least one first-time "contester", Heather KB0BXA, got a taste of quality. The Drake accounted for 89% of the total voice Qs for the weekend (not counting GOTA, VHF, and some 40-odd Qs on KT0K's 40 Meter station). With 40 Meter CW added in, we had over 1700 total Qs for the weekend - not bad for our small little operation. The TR-7 performed flawlessly, of course. A shot of me running on the Drake can be found in KD0MXI's pics, if you really want to damage your eyeballs 73 -Jim (any wisecracks about Heather looking better in front of the TR-7 will be heartily agreed with) -- 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
Re: [Drakelist] TR-4C Bias Adjustment
Garey , Richard I, et al Since I am the student here, I can only be Richard II. I measured the resistance of R45, in circuit with the relay pulled. I'm not sure that made any difference. It measured 2.4 ohms on a Fluke 179. Since it is difficult to adjust for MAX or MIN on a DMM, I changed to a Simpson 260 (I know, maybe not too accurate). Then set SIDEBAND X, MODE X-CW cranked in some XMTR gain and tuned PLATE for MAX on the PLATE CURRENT meter (because tuning for MIN didn't work). Max reading on the PLATE CURRENT meter again occurs about mid-range and falls off on both sides. The PLATE METER read 200 mA and the voltage on R45 was 0.46 VDC. Since R45 measured 2.4 ohms from before, the calculated current is about 192 mA. Close to the 200 mA on the PLATE METER. Then I tried tuning PLATE for MIN voltage on R45 with the Simpson. I could not tune to MIN, there was a MAX value about mid-range and it falls off on either side of MAX. The voltage on R45 was very close to 0.46 VDC, the same as above. Again, the calculated current was about 192 mA. Plate current or RF output? I checked the slide switch on the LOAD control. I took resistance measurements in each position and it seems to be working. I added a little DeOxit. I looked at the circuitry for RF output on the relay board ( I have most of Garey's Drake CD's). If the problem is in there, it is going to be a real pain to get to. I hope someone comes up with the "Golden Screwdriver" solution. When I was working, our solutions were "Silver Bullets". Of course, that was before the price of silver skyrocketed. Richard II - Original Message - From: "Garey Barrell" To: "drakelist" Sent: Wednesday, July 13, 2011 1:42 PM Subject: Re: [Drakelist] TR-4C Bias Adjustment Richard Knoppow wrote: - Original Message - From: "Garey Barrell" To: "drakelist" Sent: Wednesday, July 13, 2011 6:19 AM Subject: Re: [Drakelist] TR-4C Bias Adjustment Richard - I don't recall a C73 reference.? Possibly C74, which is the Cathode lead feedthrough? Rats, I thought we might be on to something. The fact that the meter reading peak results in The other Richard I think. C-73 was my blunder from looking at the TR-4 schematics. Obviously the TR-4C has considerable differences. I meant to find a point where the collective voltage drop across the cathode resistors could be measured independandly of the panel meter. My idea was not to get a precise reading but only to see if the current there behaved normally, i.e., dipped at reasonance. The peaking of of the meter when adjusting plate tuning sure suggests its looking at output not plate current. Maybe not a bad switch but it could be something in the wiring there. At any rate an RF amplifier just can't behave the way the meter says its doing. I have enountered bad slide switches but not many, it can't be discounted with something as mysterious as this. It could be something as simple as a solder butch or something having been mis-wired in the past. The idea is to isolate the problem and I think using an independant meter would help. There has been a lot of tail-chasing over this problem and I am afraid I made it worse by making a fundamental mistake, that is making an assumption, in this case that the two versions of the TR-4 were mostly similar. My only excuse is that I am on a medication for the after effects of Shingles that makes me a little dumber even than usual. Richard - Unfortunately, I don't have medication as an excuse! I did have low blood pressure after rehab this morning, does that count?!? :-) C74 would be a reasonable place to measure the drop across R45 to check for a dip coinciding with maximum output. I was trying to set the BIAS voltage correctly by measuring across the Cathode resistors, and the resistor's values, 'accurately'. Richard came up with ~ -50 VDC, which I'm afraid could result in over-dissipation of the PA, -60 to -65 is more typical for 100 mA. THIS RF amplifier _MAY_ behave just as described, (max output and max current coinciding,) with 'some' PA tubes and/or improperly adjusted neutralization, by oscillating on its own. Yet another problem is that this transceiver has NEVER worked for this owner, so a 'golden screwdriver' may yet turn out to be the problem!! 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs ___ 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
[Drakelist] R4 medium wave
Will the R4 series tune medium wave(1-1.5 Mhz)with the appropriate crystal? There is a close band setting for 1.5-3.0 and the preselector seems tune that low. Signals in this range are very strong after all. I don't want to buy an expensive 1.0 Mhz crystal and discover it won't work. Thanks. ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] R-4A PTO, Part Deux
Hi Steve: THe PTO that I have worked on have a diamond shaped hole in the coil end coverfor the back end of the brass shaft and are not tight at all. Shaft just kind of rides there. However, ANY slight movement of that end will cause a frequency abberation. If there is any type of build up of debris or gunk there, or inside the coil between the form and the metal slugs stacked on the shaft, it will make the shaft bump and create a jump. I generally pull the whole shaft assembly and clean it thoroughly with lacquer thinner or similar--even some fine wet or dry 400 grit could be used. Also clean the square hole well with some thinner or 99% iso alcohol. What you want is a low friction dry sliding condition at the back end. Be sure the brass rod is not coming in contact with the housing and there can be no relative motion between elements or shield back there. I use a dry spray lube that is like graphite powder on the shaft but dry works just as well. NEVER any type of oil or grease or non-drying cleaner/lube. Of course, any free play in the FRONT bearings or slider will do the same. I assume you have cleaned and lubed and re-set the shaft end-play bearing? THat adjustment is a hex thru the back end of the coil base. It should be baled off and then adjusted in (tighter) JUST until there is no endplay. The difference between good and poor on this adjustment is a praction of a hex flat. Perhaps a couple of degrees on the set screw. But it makes all the difference. Hope this helps some. I have completely field stripped several Drake PTO assemblies in the last year and haven't lost a single patient yet! Just take your time. Curt KU8L Steve Wedge wrote: I pulled the pto out and removed the cover (of course, this meant pretty much disassembling down to the chassis to get it out!). There was no zener inside -it had been clipped out. I couldn't find any obvious bad parts using a stereo microscope, so I re-flowed the solder on the board wherever I could and I moved the external zener onto the B side of the board and soldered it in. It seems more stable but it's still jumping a little. I've noticed I can get it to jump frequency when I wiggle the brass shaft that holds the slug. It also jumps some when I wiggle the cover. How loose should that brass rod be with respect to the hole in the end of the coil? There's definitely some free play there. Steve Wedge, W1ES/4 To be is to do - Socrates To do is to be - Plato Do be do be do. - Sinatra All my computers have my signature with various pearls of wisdom appended thereto. ___ 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
[Drakelist] R-4A PTO, Part Deux
I pulled the pto out and removed the cover (of course, this meant pretty much disassembling down to the chassis to get it out!). There was no zener inside -it had been clipped out. I couldn't find any obvious bad parts using a stereo microscope, so I re-flowed the solder on the board wherever I could and I moved the external zener onto the B side of the board and soldered it in. It seems more stable but it's still jumping a little. I've noticed I can get it to jump frequency when I wiggle the brass shaft that holds the slug. It also jumps some when I wiggle the cover. How loose should that brass rod be with respect to the hole in the end of the coil? There's definitely some free play there. Steve Wedge, W1ES/4 To be is to do - Socrates To do is to be - Plato Do be do be do. - Sinatra All my computers have my signature with various pearls of wisdom appended thereto. ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] TR-4C Bias Adjustment
Garey Barrell wrote: Richard Knoppow wrote: - Original Message - From: "Garey Barrell" To: "drakelist" Sent: Wednesday, July 13, 2011 6:19 AM Subject: Re: [Drakelist] TR-4C Bias Adjustment Richard - I don't recall a C73 reference.? Possibly C74, which is the Cathode lead feedthrough? Rats, I thought we might be on to something. The fact that the meter reading peak results in The other Richard I think. C-73 was my blunder from looking at the TR-4 schematics. Obviously the TR-4C has considerable differences. I meant to find a point where the collective voltage drop across the cathode resistors could be measured independandly of the panel meter. My idea was not to get a precise reading but only to see if the current there behaved normally, i.e., dipped at reasonance. The peaking of of the meter when adjusting plate tuning sure suggests its looking at output not plate current. Maybe not a bad switch but it could be something in the wiring there. At any rate an RF amplifier just can't behave the way the meter says its doing. I have enountered bad slide switches but not many, it can't be discounted with something as mysterious as this. It could be something as simple as a solder butch or something having been mis-wired in the past. The idea is to isolate the problem and I think using an independant meter would help. There has been a lot of tail-chasing over this problem and I am afraid I made it worse by making a fundamental mistake, that is making an assumption, in this case that the two versions of the TR-4 were mostly similar. My only excuse is that I am on a medication for the after effects of Shingles that makes me a little dumber even than usual. Richard - Unfortunately, I don't have medication as an excuse! I did have low blood pressure after rehab this morning, does that count?!? :-) C74 would be a reasonable place to measure the drop across R45 to check for a dip coinciding with maximum output. I was trying to set the BIAS voltage correctly by measuring across the Cathode resistors, and the resistor's values, 'accurately'. Richard came up with ~ -50 VDC, which I'm afraid could result in over-dissipation of the PA, -60 to -65 is more typical for 100 mA. THIS RF amplifier _MAY_ behave just as described, (max output and max current coinciding,) with 'some' PA tubes and/or improperly adjusted neutralization, by oscillating on its own. Yet another problem is that this transceiver has NEVER worked for this owner, so a 'golden screwdriver' may yet turn out to be the problem!! 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist Yes..the whole PA going into oscillation could do that as you described although I've never seen a Drake PA do that on 40M or below. It would also be weird if it was oscillating on tune and also had near zero bias current at idle. I have seen badly oxidized meter switch contacts but they always seem to just mess up the RF out mode, not the PA current. Anyway..sounds like the right track. PS...make sure it is the PLATE control for the dip and not the the LOAD control during tune-up. Getting this in reverse will really skew the result! :) Curt KU8L ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] TR-4C Bias Adjustment
Richard Knoppow wrote: - Original Message - From: "Garey Barrell" To: "drakelist" Sent: Wednesday, July 13, 2011 6:19 AM Subject: Re: [Drakelist] TR-4C Bias Adjustment Richard - I don't recall a C73 reference.? Possibly C74, which is the Cathode lead feedthrough? Rats, I thought we might be on to something. The fact that the meter reading peak results in The other Richard I think. C-73 was my blunder from looking at the TR-4 schematics. Obviously the TR-4C has considerable differences. I meant to find a point where the collective voltage drop across the cathode resistors could be measured independandly of the panel meter. My idea was not to get a precise reading but only to see if the current there behaved normally, i.e., dipped at reasonance. The peaking of of the meter when adjusting plate tuning sure suggests its looking at output not plate current. Maybe not a bad switch but it could be something in the wiring there. At any rate an RF amplifier just can't behave the way the meter says its doing. I have enountered bad slide switches but not many, it can't be discounted with something as mysterious as this. It could be something as simple as a solder butch or something having been mis-wired in the past. The idea is to isolate the problem and I think using an independant meter would help. There has been a lot of tail-chasing over this problem and I am afraid I made it worse by making a fundamental mistake, that is making an assumption, in this case that the two versions of the TR-4 were mostly similar. My only excuse is that I am on a medication for the after effects of Shingles that makes me a little dumber even than usual. Richard - Unfortunately, I don't have medication as an excuse! I did have low blood pressure after rehab this morning, does that count?!? :-) C74 would be a reasonable place to measure the drop across R45 to check for a dip coinciding with maximum output. I was trying to set the BIAS voltage correctly by measuring across the Cathode resistors, and the resistor's values, 'accurately'. Richard came up with ~ -50 VDC, which I'm afraid could result in over-dissipation of the PA, -60 to -65 is more typical for 100 mA. THIS RF amplifier _MAY_ behave just as described, (max output and max current coinciding,) with 'some' PA tubes and/or improperly adjusted neutralization, by oscillating on its own. Yet another problem is that this transceiver has NEVER worked for this owner, so a 'golden screwdriver' may yet turn out to be the problem!! 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] TR-4C Bias Adjustment
Mark - Yes, they do develop oxidized contacts. However in this case that type of failure would not present as being 'stuck' in one position. When Richard checks the items in my last message we'll have a pretty good idea what's happening! Thanks for contributing! 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs Mark Nace wrote: I have had two separate issues with this switch. Deoxit and working back and forth a few times solved it. 73 Mark N5KAE *From: * Garey Barrell ; *To: * drakelist ; *Subject: * Re: [Drakelist] TR-4C Bias Adjustment *Sent: * Wed, Jul 13, 2011 1:19:27 PM Richard - I hate losing all our previous information on this message... My fault. Just keep the other one. Adjusting the BIAS control while measuring the voltage across each of the Cathode resistors is ok, but you also need to measure the resistors, preferably with a DMM. Even one ohm either side of 15 on one or more resistors (likely, often more) can throw you off. I don't recall a C73 reference.? Possibly C74, which is the Cathode lead feedthrough? Rats, I thought we might be on to something. The fact that the meter reading peak results in maximum RF OUTPUT sure sounds like the OUTPUT function of the PLATE meter. Measure R45 with your DMM. Should be 2 ohms, but measure as accurately as you can. Then measure the voltage across R45 while adjusting the PLATE control. This voltage should _dip_ (minimize) coincidentally with maximum RF OUTPUT. Calculate PLATE current using measured voltage and resistance of R45. If this is normal, then we have confirmed that we don't have an oscillation as Al suggested yesterday, and the problem is strictly with the meter circuit. The meter circuit is very simple, just confusing the way it's drawn. To measure PLATE current, R45 is in series with the Cathodes of the PA tubes, and the meter, with R13 (up on the LOAD control shaft switch) in series, measures the VOLTAGE across R45. To measure RF OUTPUT, a voltage divider of C161 and C162 samples the RF OUTPUT, which is then rectified by D9, integrated in C163 and the resultant positive voltage is applied directly to the meter. Slide switches are pretty simple, and not prone to shorting. Check the wiring around the switch to ensure that there aren't any shorts, and ensure that the switch slider is actually being moved by the LOAD control shaft. It certainly appears that the meter is reading RF OUTPUT rather than PLATE current, and this can be confirmed by the R45 measurements above. What band are you testing on?? I normally troubleshoot on 40M. 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs Donley wrote: > Completed tasks. > > Adjusted bias control until 0.5 VDC across cathode resistor, equals 33 mA, three resistors in parallel equals 100 mA total bias current. Bias voltage is -55 VDC at this point. No bias current measurement on plate current meter (actually has been just a slight wiggle all along, but nothing more than a half pointer width wiggle). > > C-73 is not a feedthrough, what point should be measured? > > The LOAD control spring is intact and functioning. > > In tune procedure, PLATE control does not dip, it is maximum about mid-range and reduces to near zero on either side of peak. > > LOAD control pushed in or out, peak occurs about mid-range and falls off on either side of peak. > > Is this pointing to the RF output slide switch circuit, possibly a shorted switch? > > > > - Original Message - From: "Richard Knoppow" <1oldle...@ix.netcom.com > > To: >; "drakelist" > > Sent: Tuesday, July 12, 2011 10:26 PM > Subject: Re: [Drakelist] TR-4C Bias Adjustment > > >> >> - Original Message - From: "Garey Barrell" > >> To: "drakelist" > >> Sent: Tuesday, July 12, 2011 6:36 PM >> Subject: Re: [Drakelist] TR-4C Bias Adjustment >> >> >>> Richard - >>> >>> This is what I referred to in my last message. There is no "adjusting pot" on the TR-4C, but the meter is switched from Plate current to output meter. That's why I said to push and pull the LOAD control a couple of times. There should be a hairpin shaped spring on the LOAD control shaft that pushes the LOAD knob OUT for PLATE current reading and you PUSH it IN for RF OUTPUT reading. >>> >>> 73, Garey - K4OAH >>> Glen Allen, VA >> >>That's obviously a differenc I missed between the TR-4 and TR-4C but the idea is the same. If the meter is stuck reading output it could behave as described. That's why I suggested an independant measurement of cathode current. If he gets a dip there but not on the meter the switch is probably no good or something else is causing the meter to read output all the time. >> > ___ Drakelist mailing list Drakelist@zerobe
Re: [Drakelist] TR-4C Bias Adjustment
Curt Nixon wrote: Donley wrote: Completed tasks. Adjusted bias control until 0.5 VDC across cathode resistor, equals 33 mA, three resistors in parallel equals 100 mA total bias current. Bias voltage is -55 VDC at this point. No bias current measurement on plate current meter (actually has been just a slight wiggle all along, but nothing more than a half pointer width wiggle). C-73 is not a feedthrough, what point should be measured? The LOAD control spring is intact and functioning. In tune procedure, PLATE control does not dip, it is maximum about mid-range and reduces to near zero on either side of peak. LOAD control pushed in or out, peak occurs about mid-range and falls off on either side of peak. Is this pointing to the RF output slide switch circuit, possibly a shorted switch? - Original Message - From: "Richard Knoppow" <1oldle...@ix.netcom.com> To: ; "drakelist" Sent: Tuesday, July 12, 2011 10:26 PM Subject: Re: [Drakelist] TR-4C Bias Adjustment - Original Message - From: "Garey Barrell" To: "drakelist" Sent: Tuesday, July 12, 2011 6:36 PM Subject: Re: [Drakelist] TR-4C Bias Adjustment Richard - This is what I referred to in my last message. There is no "adjusting pot" on the TR-4C, but the meter is switched from Plate current to output meter. That's why I said to push and pull the LOAD control a couple of times. There should be a hairpin shaped spring on the LOAD control shaft that pushes the LOAD knob OUT for PLATE current reading and you PUSH it IN for RF OUTPUT reading. 73, Garey - K4OAH Glen Allen, VA That's obviously a differenc I missed between the TR-4 and TR-4C but the idea is the same. If the meter is stuck reading output it could behave as described. That's why I suggested an independant measurement of cathode current. If he gets a dip there but not on the meter the switch is probably no good or something else is causing the meter to read output all the time. At the risk of being redundant or stupid, I'll jump in here and say that while in tune and the plate meter is behaving as you describe (peak and then low either side of that) the meter is more than likely stuck in the RF output mode (load switch not switching as others have pointed out) It would take a pretty messed up system to make the actual plate current respond to tuning they way you describe. If you watch the cathode resistor voltage while tuning, same as while you adjusted for 33mA, I bet you will see a pronounced dip at the point of the peak you see on the meter. Curt KU8L Curt - Generally speaking, you are correct. My last message suggested measuring actual PLATE current with a separate meter to confirm our suspicion that the internal meter is in fact measuring output power rather than cathode current. However, this type of behavior, 'PLATE' meter peaking coinciding with maximum RF output is in the case of an oscillating PA. This is most often the result of either weird, off-brand PA tubes, or misadjusted neutralization. Based on what we have eliminated so far, it's looking more and more like a metering problem. Unfortunately, we have already established that the transceiver has NEVER worked for its present owner!! Richard is tasked with checking and verifying the meter switching involved per my last message. 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] TR-4C Bias Adjustment
- Original Message - From: "Curt Nixon" To: "Donley" Cc: "Richard Knoppow" <1oldle...@ix.netcom.com>; ; "drakelist" Sent: Wednesday, July 13, 2011 9:43 AM Subject: Re: [Drakelist] TR-4C Bias Adjustment At the risk of being redundant or stupid, I'll jump in here and say that while in tune and the plate meter is behaving as you describe (peak and then low either side of that) the meter is more than likely stuck in the RF output mode (load switch not switching as others have pointed out) It would take a pretty messed up system to make the actual plate current respond to tuning they way you describe. If you watch the cathode resistor voltage while tuning, same as while you adjusted for 33mA, I bet you will see a pronounced dip at the point of the peak you see on the meter. Curt KU8L Thank you Curt, that is a much clearer statement of what I was trying to say. C-73 is a mistake, its the part designation for the TR-4, not the TR-4C. The idea was to find a suitable place to measure the same thing as the front panel meter is _supposed_ to be seeing with an external meter. The exact value of the voltage is not important only that is dip at plate resonance. If it does it confirms that there is a problem with the meter switching or wiring. -- Richard Knoppow Los Angeles WB6KBL dickb...@ix.netcom.com ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] TR-4C Bias Adjustment
Donley wrote: Completed tasks. Adjusted bias control until 0.5 VDC across cathode resistor, equals 33 mA, three resistors in parallel equals 100 mA total bias current. Bias voltage is -55 VDC at this point. No bias current measurement on plate current meter (actually has been just a slight wiggle all along, but nothing more than a half pointer width wiggle). C-73 is not a feedthrough, what point should be measured? The LOAD control spring is intact and functioning. In tune procedure, PLATE control does not dip, it is maximum about mid-range and reduces to near zero on either side of peak. LOAD control pushed in or out, peak occurs about mid-range and falls off on either side of peak. Is this pointing to the RF output slide switch circuit, possibly a shorted switch? - Original Message - From: "Richard Knoppow" <1oldle...@ix.netcom.com> To: ; "drakelist" Sent: Tuesday, July 12, 2011 10:26 PM Subject: Re: [Drakelist] TR-4C Bias Adjustment - Original Message - From: "Garey Barrell" To: "drakelist" Sent: Tuesday, July 12, 2011 6:36 PM Subject: Re: [Drakelist] TR-4C Bias Adjustment Richard - This is what I referred to in my last message. There is no "adjusting pot" on the TR-4C, but the meter is switched from Plate current to output meter. That's why I said to push and pull the LOAD control a couple of times. There should be a hairpin shaped spring on the LOAD control shaft that pushes the LOAD knob OUT for PLATE current reading and you PUSH it IN for RF OUTPUT reading. 73, Garey - K4OAH Glen Allen, VA That's obviously a differenc I missed between the TR-4 and TR-4C but the idea is the same. If the meter is stuck reading output it could behave as described. That's why I suggested an independant measurement of cathode current. If he gets a dip there but not on the meter the switch is probably no good or something else is causing the meter to read output all the time. -- Richard Knoppow Los Angeles WB6KBL dickb...@ix.netcom.com ___ 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 At the risk of being redundant or stupid, I'll jump in here and say that while in tune and the plate meter is behaving as you describe (peak and then low either side of that) the meter is more than likely stuck in the RF output mode (load switch not switching as others have pointed out) It would take a pretty messed up system to make the actual plate current respond to tuning they way you describe. If you watch the cathode resistor voltage while tuning, same as while you adjusted for 33mA, I bet you will see a pronounced dip at the point of the peak you see on the meter. Curt KU8L ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] TR-4C Bias Adjustment
I have had two separate issues with this switch. Deoxit and working back and forth a few times solved it. 73 Mark N5KAE___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] TR-4C Bias Adjustment
Richard - I hate losing all our previous information on this message... My fault. Just keep the other one. Adjusting the BIAS control while measuring the voltage across each of the Cathode resistors is ok, but you also need to measure the resistors, preferably with a DMM. Even one ohm either side of 15 on one or more resistors (likely, often more) can throw you off. I don't recall a C73 reference.? Possibly C74, which is the Cathode lead feedthrough? Rats, I thought we might be on to something. The fact that the meter reading peak results in maximum RF OUTPUT sure sounds like the OUTPUT function of the PLATE meter. Measure R45 with your DMM. Should be 2 ohms, but measure as accurately as you can. Then measure the voltage across R45 while adjusting the PLATE control. This voltage should _dip_ (minimize) coincidentally with maximum RF OUTPUT. Calculate PLATE current using measured voltage and resistance of R45. If this is normal, then we have confirmed that we don't have an oscillation as Al suggested yesterday, and the problem is strictly with the meter circuit. The meter circuit is very simple, just confusing the way it's drawn. To measure PLATE current, R45 is in series with the Cathodes of the PA tubes, and the meter, with R13 (up on the LOAD control shaft switch) in series, measures the VOLTAGE across R45. To measure RF OUTPUT, a voltage divider of C161 and C162 samples the RF OUTPUT, which is then rectified by D9, integrated in C163 and the resultant positive voltage is applied directly to the meter. Slide switches are pretty simple, and not prone to shorting. Check the wiring around the switch to ensure that there aren't any shorts, and ensure that the switch slider is actually being moved by the LOAD control shaft. It certainly appears that the meter is reading RF OUTPUT rather than PLATE current, and this can be confirmed by the R45 measurements above. What band are you testing on?? I normally troubleshoot on 40M. 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs Donley wrote: Completed tasks. Adjusted bias control until 0.5 VDC across cathode resistor, equals 33 mA, three resistors in parallel equals 100 mA total bias current. Bias voltage is -55 VDC at this point. No bias current measurement on plate current meter (actually has been just a slight wiggle all along, but nothing more than a half pointer width wiggle). C-73 is not a feedthrough, what point should be measured? The LOAD control spring is intact and functioning. In tune procedure, PLATE control does not dip, it is maximum about mid-range and reduces to near zero on either side of peak. LOAD control pushed in or out, peak occurs about mid-range and falls off on either side of peak. Is this pointing to the RF output slide switch circuit, possibly a shorted switch? - Original Message - From: "Richard Knoppow" <1oldle...@ix.netcom.com> To: ; "drakelist" Sent: Tuesday, July 12, 2011 10:26 PM Subject: Re: [Drakelist] TR-4C Bias Adjustment - Original Message - From: "Garey Barrell" To: "drakelist" Sent: Tuesday, July 12, 2011 6:36 PM Subject: Re: [Drakelist] TR-4C Bias Adjustment Richard - This is what I referred to in my last message. There is no "adjusting pot" on the TR-4C, but the meter is switched from Plate current to output meter. That's why I said to push and pull the LOAD control a couple of times. There should be a hairpin shaped spring on the LOAD control shaft that pushes the LOAD knob OUT for PLATE current reading and you PUSH it IN for RF OUTPUT reading. 73, Garey - K4OAH Glen Allen, VA That's obviously a differenc I missed between the TR-4 and TR-4C but the idea is the same. If the meter is stuck reading output it could behave as described. That's why I suggested an independant measurement of cathode current. If he gets a dip there but not on the meter the switch is probably no good or something else is causing the meter to read output all the time. ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
