Re: [Drakelist] R-4A PTO, Round 1
Shh, Jim, don't tell the Feds or they will outlaw it :-) 73, Don ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] R-4A PTO, Round 1
On Tue, 5 Jul 2011 18:37:35 -0700, Richard Knoppow wrote: >While Freeze Mist or its clones, have gotten >expensive they are still available. You don't need much. Canned air can be used as freeze mist, just hold the can upside down. 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
Re: [Drakelist] R-4A PTO, Round 1
Steve - OK. Well that's more likely to be a Zener or cap problem. Perhaps bad solder. The brown mica caps are just NP0 mica's. They are still being made and available. The TC caps, (the white, tubular ones,) are no longer made, and unfortunately the color codes are not consistent. Some tubulars used in some PTOs don't appear to be TC caps, but it's possible that they are. You can still get ceramic N750, N1500, etc., caps, they look just like regular disc ceramics, and of course are also still available in NP0 as well. They are fairly rugged, although the 'tube' is glass, and can be broken. If your troubleshooting points to one of those, I would suggest photographing it in place, (some are hanging in air!,) so you can attempt to replace it in the right place. The PTOs were originally set up by several 'Grandmothers' who would sit and talk about their Grandchildren or bridge club while 'doing their voo-doo' on them. No one seems to know just what they did, but like most RF stuff there was probably a bit of 'magic' involved. I haven't had to work on many, most were bad Zeners, and a couple with bad FETs (bipolar in the "A"), and some bad solder. If you remove the cover _Carefully_ and are careful to not disturb any of the physical components, again, some of which stick up in the air?, I have yet to destroy one!. I have been keeping my eyes open for a defective one that I could experiment with to try and determine just how they were done, but so far no luck. I don't want to tear up a good one, as they say, 'they ain't making them like that any more'.! :-) 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 Steve Wedge wrote: The frequency jumps when stopped and gets worse when it's fully warmed up. Re the "dog-bone" caps: can these be replaced by silver mica units? Or do they have a temperature coefficient that's different? I would still love to get a working PTO to swap in so I can not fear wrecking this one. Thanks, all, for your help. I'll probably rip it apart again shortly. 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. Date: Tue, 05 Jul 2011 12:30:58 -0400 From: Garey Barrell To: drakelist@zerobeat.net Subject: Re: [Drakelist] R-4A PTO, Round 1 Message-ID: <4e133c42.6030...@mindspring.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Paul brings up a good point. Does the frequency jump when tuning, or even when stopped? ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] R-4A PTO, Round 1
- Original Message - From: "Steve Wedge" To: "Drake List" Sent: Tuesday, July 05, 2011 5:52 PM Subject: Re: [Drakelist] R-4A PTO, Round 1 The frequency jumps when stopped and gets worse when it's fully warmed up. Re the "dog-bone" caps: can these be replaced by silver mica units? Or do they have a temperature coefficient that's different? I would still love to get a working PTO to swap in so I can not fear wrecking this one. Thanks, all, for your help. I'll probably rip it apart again shortly. Steve Wedge, W1ES/4 I think maybe there is come conclusion jumping as well as frequency jumping. Before shotgunning parts I may be helpful to see if its possible to isolate the problem a little. If it appears to be temperature sensitive the approach is to use alternative applications of freeze mist and a heat gun. While Freeze Mist or its clones, have gotten expensive they are still available. You don't need much. Its also worth seeing if there is an intermittant solder joint or other connections. Just poking at the solder joints with an insulated stick may find the trouble. I am not sure about the dog-bone caps in the Drake, most I've seen were ceramic caps of some sort. They may be temperature compensating caps but those also come as ceramic cased units with axial leads. Silvered mica caps in resonant circuits can cause jumping and warbling. The effect is known as scintillation. Its caused by oxidation of the silver coating. That should not happen but does due to various causes. Its mostly found in the older style of cap in a molded Bakelite case. Dipped capacitors seem to be free of the trouble or perhaps just are not old enough. Of course voltage variations will cause jumping. Zener diodes have been pointed out as a possible cause. It may be possible to monitor the output of the Zener on an oscilloscope which will show any variation instantly. Again, the alternate application of heat and cooling may show up a bad guy. A caviet about Freeze Mist or similar, the cooling will tend to condense moisture from the air. The moisture can cause leakage paths which can not only mask the problem but disable many circuits until it evaporates. So use the spray with some caution. Also, check for poor ground connections. They can become intermittant too. Check all this stuff before firing up the soldering iron. As far as a mechanical instability that is something else you may be able to find by poking around with a wooden stick. -- Richard Knoppow Los Angeles WB6KBL dickb...@ix.netcom.com ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] R-4A PTO, Round 1
The frequency jumps when stopped and gets worse when it's fully warmed up. Re the "dog-bone" caps: can these be replaced by silver mica units? Or do they have a temperature coefficient that's different? I would still love to get a working PTO to swap in so I can not fear wrecking this one. Thanks, all, for your help. I'll probably rip it apart again shortly. 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. Date: Tue, 05 Jul 2011 12:30:58 -0400 From: Garey Barrell To: drakelist@zerobeat.net Subject: Re: [Drakelist] R-4A PTO, Round 1 Message-ID: <4e133c42.6030...@mindspring.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Paul brings up a good point. Does the frequency jump when tuning, or even when stopped? 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 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] R-4C Cabinet Bumpers
With all the R-4C work going on here, I have managed to loose (or break and then loose) the two small top cabinet bumpers located at the top rear of the R-4C. These are black in color, flat, and are press-fit into the back top lip of the chassis. Anyone have a pair to sell or is the OEM still selling them through a distributor? Tnx! Paul, W9AC ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] TR-7 Off Frequency (1Khz)
Hi Brian, On Tue, 05 Jul 2011 13:26:33 -0400, bjon...@mindspring.com wrote: >Finally I >remembered my freq counter (keeps track of my 10Mhz frequency standard) >so I hooked the drake up to it directly and threw a 1W cw tone at it and >was off by 1Khz (i.e the DR7 displayed 14.2140, but the counter showed >14.2150) (flipping over to the RV75 results in the same result) A subtle, but important, distinction is that the TR-7 shifts the *transmit* frequency from what the dial reads on CW. It seems that the majority of the import rigs shift the recieve frequency. Thus, the DR-7 readout will be around 800 Hz off from your frequency counter in CW transmit. IIRC, this is not true for AM, so try an carrier in AM mode. >So my first question is: >When trying to use WWV to determine receive frequency, what is the best >way to do so? Apparently how I have been doing it for years is >incorrect! What I usually do is set the PBT to center, RIT off, and adjust for zero beat with WWV's carrier in SSB mode. This is easier if done during the periods when WWV does not transmit audio tones. You will need to turn the volume up as you approach zero beat in order to hear the beat note better. Use the strongest WWV you can find. I'm curious as to how you were doing it that you think is incorrect? >Question number two: >If both my transmit and receive frequency are off the same amount (1Khz) >is there an adjustment on the DR-7 that will allow it to display >correctly (My first glance through the service manual did not reveal any >way, but I thought I would ask the experts here) or is that something >that would have to be fixed through an alignment of the TR7? (or at >1Khz off is it better to just tape a sticky note to the table reminding >me to add +1?) The only adjustment that could possibly cause a TX/RX shift problem here is the RIT center pot on the parent board. Otherwise, your RX and TX are the same as the signals come from the same source. There is no seperate reference for the DR-7. You rig may need to have the RIT center adjusted, and/or a frequency alignment of the oscillators. This is not a hard thing to do, but you do need a sensitive counter to read the oscillator signals. First, check the +10v adjustment; if it's too far off, it will need to be set to 10V and you may need to touch up the AGC/S-Meter adjustment. Then you will adjust the 40 MHz, 13.695 MHz, and 8.05 MHz, in that order. That should get you there, but it's a good idea to check the fixed passband adjustments while you are at it. They are almost always off a little. Follow the adjustment procedure in the service manual, without skipping any steps, and you should be fine. I've found that it's a good idea to isolate the counter probe from the signal under test with an as high in value (carbon) resistor as you can use and still get a stable reading, as the load of the counter can shift the oscillators a tiny but (probably not enough to be concerned, but I'm picky). This seems to be most apparent on the 40 MHz. 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] TR-7 Off Frequency (1Khz)
Long story short: What prompted this was trying to troubleshoot my dad's rig (SGC2020) on the air (there was a question about what frequency he was actually on)... we could not seem to meet up on the right frequency. Finally I remembered my freq counter (keeps track of my 10Mhz frequency standard) so I hooked the drake up to it directly and threw a 1W cw tone at it and was off by 1Khz (i.e the DR7 displayed 14.2140, but the counter showed 14.2150) (flipping over to the RV75 results in the same result) Now I *think* my receive/transmit frequency are both off, because I have had no troubles making qso's (worked 9 of the 13 colonies during the contest this past weekend before I learned of the problem), and if only one was off, I would have to work a split, which I have not had to do) So my first question is: When trying to use WWV to determine receive frequency, what is the best way to do so? Apparently how I have been doing it for years is incorrect! Question number two: If both my transmit and receive frequency are off the same amount (1Khz) is there an adjustment on the DR-7 that will allow it to display correctly (My first glance through the service manual did not reveal any way, but I thought I would ask the experts here) or is that something that would have to be fixed through an alignment of the TR7? (or at 1Khz off is it better to just tape a sticky note to the table reminding me to add +1?) Thanks & 73, Brian KD4UYP ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Drakelist Digest, Bias current Low
Fred - The first thing that comes to mind is that ONE of the PA tubes is DEAD. You can check by measuring the voltage across R32 or R33 in TUNE. Other possibilities are an open Screen or Cathode resistor (R30, 31, 32 or 33) Another possibility is that the HV power supply (AC-4), isn't. The HV should be about 650 VDC at full load (0.340A), and about 700 VDC at no load. Low Screen voltage on the PA tubes can also cause this. Both are voltage doubler supplies, so a single diode or cap failure can result in ~ half voltage. These voltages can be measured at the underchassis shield beside the PA area. The rearmost feed through is the +650 VDC and the middle of the five is the +250 VDC. The capacitors of these supplies are well past their expected life, and should be replaced either individually or wholesale with the Heathkit shop AC-4 kit. 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 fjmel...@aol.com wrote: //Bias and plate current is low on Drake B Line. Adjustment on back of AC 4 is turned up full. Plate current is only .210 mills. Bias is .04 on plate meter.// // // // /Any ideas where to start to look for a cure./ // // // /Thanks / // // // /73 de Fred WD8ADG / ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] R-4A PTO, Round 1
Hi Joe, NOW I understand---thanks for the clarification. I *think* those style of capacitors are called "tubular" temperature-compensating types---but the design is so very old I don't think they're even manufactured anymore...? My first "fix" with my PTO was traced to a bad solder connection with one of the silver micas in the oscillator tank. But I think my best bet here is to again dis-assemble by T4X PTO, & thoroughly clean all of the "sliders" with isopropyl alcohol & Q-tips. I found that the last bit of frequency "squirreliness" could be moved about the dial by my "probing" the grounding yoke of the PTO with a long chop stick, poked through the vent holes of the top cover of the transmitter...and yes, my PTO does have the extra grounding braid soldered into it. So maybe a good thorough cleaning of the "slides" will fix my issue...?I don't know at this point. But I AM fast becoming convinced that, just as the pressure "wheel" used in the PTO / dial drive of the Heathkit "SB" series was the Achille's heel of that marque, the PTO is THE potential "major pain" in Drake stuff! ~73~ de Eddy VE3CUI - VE3XZ On 2011-07-04, at 7:08 PM, Joe Pyles wrote: >> The dumbbell capacitor in mine was across the coil in the PTO can. The >> capacitor is a small, tubular, and white, with colored markings on it. The >> wire leads are wrapped around the ends of > the tube and it looks like a small dumbbell. > > Joe KC9LAD > >> >> >> Hi Joe, >> >> Are you referring to one of the silver mica capacitors in your reference to >> "dumb bell" cap, or a bypass / disc ceramic capacitor...? >> >> Also, was this cap right inside of the PTO can itself, on the PTO circuit >> board...? >> >> I'm very seriously contemplating swapping-out ALL of the discreet components >> in the oscillator portion of the PTO of my T4X (I'll leave the parts in the >> buffer stage alone)---I guess this is called the "shotgun" approach, but I >> was just oh-so-very frustrated the other day when the frequency started to >> act "squirrely" again in that T4X of mine that I began to think the >> "...unthinkable", i.e. take my Icom 751A transceiver with me to future >> junkets to the summer cottage, & leave the Drake Twins behind...!!! >> >> ~73~ de Eddy VE3CUI - VE3XZ >> >> >> * >> >> >> On 2011-07-04, at 6:32 PM, Joe Pyles wrote: >> >>> I have a TR-4CW /w//rit when I got it the PTO would jump in frequency after >>> the radio got hot. After removing and installing the PTO several times I >>> found that one of the dumbbell ceramic capacitors had a hairline crack >>> and as it heated it would become intermittent. I replaced the cap and have >>> had no problems since. >>> >>> Joe KC9LAD >>> >>> At 05:29 PM 7/4/2011, you wrote: Steve, No doubt others with more experience will jump in. I've recently pulled more than a half-dozen PTOs in the last week. The first one takes a bit of time to think through but the info on WB4HFN's website is excellent. After the first trial, subsequent removal of the whole assembly with dials can be performed in about 5 minutes. I found that with the PTO sitting on a bench, and interconnected with RG-174, I could much more accurately analyze problems and performs maintenance on the units. Removal of the entire PTO is a "must" if you want to inspect the bottom of the PTO's circuit board. I have an angled dental mirror but it's no substitute for PTO removal. Anyway, once the PTO is out, you should be able to confidently and easily determine whether the problem is electrical or mechanical. The Zener helps to stabilize line voltage variations. If the PTO is "jumping," I would think it may be a mechanical problem -- or perhaps the issue where the PTO "braid fix" will help. Either way, I would try to pull the PTO and at the same time, perform maintenance on the bearings, clean the dials, etc as long as it's open and accessible. Paul, W9AC - Original Message - From: Steve Wedge To: drakelist@zerobeat.net Sent: Monday, July 04, 2011 3:33 PM Subject: [Drakelist] R-4A PTO, Round 1 I finally pulled my R-4A out of its place on my operating desk and got the covers off. As I was undoing the nuts in preparation for PTO removal, I noticed that there was a 10V zener on the small board that the wires from the PTO connect. I also noticed that one end was broken but still touching its connection. A couple of things come to mind. First, the schematic and comments I've heard from others on this list strongly suggest that the zener sh
Re: [Drakelist] R-4A PTO, Round 1
Paul brings up a good point. Does the frequency jump when tuning, or even when stopped? 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 Paul Christensen wrote: Steve, No doubt others with more experience will jump in. I've recently pulled more than a half-dozen PTOs in the last week. The first one takes a bit of time to think through but the info on WB4HFN's website is excellent. After the first trial, subsequent removal of the whole assembly with dials can be performed in about 5 minutes. I found that with the PTO sitting on a bench, and interconnected with RG-174, I could much more accurately analyze problems and performs maintenance on the units. Removal of the entire PTO is a "must" if you want to inspect the bottom of the PTO's circuit board. I have an angled dental mirror but it's no substitute for PTO removal. Anyway, once the PTO is out, you should be able to confidently and easily determine whether the problem is electrical or mechanical. The Zener helps to stabilize line voltage variations. If the PTO is "jumping," I would think it may be a mechanical problem -- or perhaps the issue where the PTO "braid fix" will help. Either way, I would try to pull the PTO and at the same time, perform maintenance on the bearings, clean the dials, etc as long as it's open and accessible. Paul, W9AC ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] R-4A PTO, Round 1
Steve - Yes, it's quite possible that the internal Zener is 'sorta' conducting. They often fail in this way. The internal Zener is 10V. Cold spray is often helpful in isolating the troublemaker. How MUCH is the frequency shifting? Other parts that can cause these kinds of problems are the capacitors, most often Dur-Mica (brown dog-bone) type, and are np0 types. The white tubular capacitors are temperature compensating caps, so care must be taken in replacing them. 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 Steve Wedge wrote: I finally pulled my R-4A out of its place on my operating desk and got the covers off. As I was undoing the nuts in preparation for PTO removal, I noticed that there was a 10V zener on the small board that the wires from the PTO connect. I also noticed that one end was broken but still touching its connection. A couple of things come to mind. First, the schematic and comments I've heard from others on this list strongly suggest that the zener should be inside the enclosure. Second, if that's true, then a previous owner tried to correct my "frequency-jumping" problem by installing the zener externally to the enclosure to avoid the extra work. Could it be possible that the zener inside the enclosure is still behaving erratically and intermittently conducting at some voltage below that of the external zener? I haven't pulled the receiver back off the desk (arh...) yet and wanted to get a general opinion. Am I right in assuming that this zener - which was installed on the back-side of the little board - was added on? Steve Wedge, W1ES/4 ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] WTB: L4B & L7 power supply boards or rails
Fellow enthusiasts, Perhaps you've done the upgrade for the power supply used on the L4B and L7 linear amplifiers by installing the Harbach Electronics or Heathkit Shop boards. If so, you might be wondering what to do with the old, unused boards and/or rails. I have a need for some of those rails (the metal strips with an offset bend at each end used to mount the power supply boards to the case) and would like to buy some if they are excess to your needs. I'll buy a board with rails attached if need be. Just let me know what you have and the price including shipping to 45434. Enjoy using those Drakes and don't forget the Drake nets. 73, Evan, K9SQG ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
