[drakelist] RE: audio waveform has warble/hum on it!
Guess what; I just pick up a TR-7 last week and I heard that voice warble on it too! Ever so slight, but I heard it. I checked into the Drake technical net over the weekend and no one on the net heard of that problem. The more I listen to the TR-7, the less noticable the warble, maybe it's dirty switch contacts and just the fact that I'm exercising them helps? Tom Laird W9QI Moline, IL. On Behalf Of [EMAIL PROTECTED] OK, my TR-7 is getting back in line to what it left Ohio many years ago. I have been listening pretty critically on the receive and it seemed on SSB like there was a slight warble on the audio. When going to CW it was harder to hear but still there. (I listen to 35+WPM so maybe I couldn't hear it.) Went to the Calibrator and it seems like the 25kHz calibrator signal is jumping up and down (in voltage) slightly, maybe +/- 3% or so on the scope. Audio-wise it is hard to hear but.. it is there - warbling ever so slightly. There is also some sort of other signal in the background. The other signal is much lower in frequency, maybe 60Hz? but the same amplitude! The scope seemed like it had problems syncing... Any thoughts on this? Frank KG9H
[drakelist] Drake Items For Sale
I have the following Drake items for sale: Nice MS4 speaker$55 Very Nice MS4/AC4 speaker/pwr supply$145 DC4 supply WITH Drake matching cable$85 Thank you...W2AO [EMAIL PROTECTED]
Re: [drakelist] RE: audio waveform has warble/hum on it!
Each time I had the warble on a receive, especially noticeable on a cw or calibrator signal, the cause was the 10 volt regulator card contacts being slightly oxidized. I pull the card, after removing the heat sink nut and bolt for the pass transistor on the side of the case of course, and clean the pins and all contacts. Replace the card and check the 10 volt rail. Rock the card a bit while listening to the calibrator tone. If you care to experiment, adjust the pot on the top of the board and you will hear the tone shift as the 10 volt supply is varied. (VCO is run off of this supply) That has worked a few times for my TR-7 down here in humid south Florida. Good luck, Mike W4DL - Original Message - From: Laird Tom N To: Frank Krozel ; drakelist@www.zerobeat.net Sent: Tuesday, December 12, 2006 8:26 AM Subject: [drakelist] RE: audio waveform has warble/hum on it! Guess what; I just pick up a TR-7 last week and I heard that voice warble on it too! Ever so slight, but I heard it. I checked into the Drake technical net over the weekend and no one on the net heard of that problem. The more I listen to the TR-7, the less noticable the warble, maybe it's dirty switch contacts and just the fact that I'm exercising them helps? Tom Laird W9QI Moline, IL. -- On Behalf Of [EMAIL PROTECTED] OK, my TR-7 is getting back in line to what it left Ohio many years ago. I have been listening pretty critically on the receive and it seemed on SSB like there was a slight warble on the audio. When going to CW it was harder to hear but still there. (I listen to 35+WPM so maybe I couldn't hear it.) Went to the Calibrator and it seems like the 25kHz calibrator signal is jumping up and down (in voltage) slightly, maybe +/- 3% or so on the scope. Audio-wise it is hard to hear but.. it is there - warbling ever so slightly. There is also some sort of other signal in the background. The other signal is much lower in frequency, maybe 60Hz? but the same amplitude! The scope seemed like it had problems syncing... Any thoughts on this? Frank KG9H
Re: [drakelist] AC-4R upgrades
Hey, thanks for the tip! I just checked the vertical ceramic load resistor and it is open, just like yours. Last night I decided to just replace all the electrolytic capacitors under the chassis (and the diodes as well). Before clipping out the old parts, I took voltage measurements so I'd have a baseline to test against after replacing the capacitors. The HV seemed unusually high at 854 vdc. The open load resistor probably explains that very HV. Thanks, Tom On 12/12/06, Donnie Garrett [EMAIL PROTECTED] wrote: Tom: I have one of the early AC3 supplies that used a HV choke. Garey K4OAH and I had a lot of discussions about its design some time back after I discovered the ceramic 25W load resistor was open. You better check yours to see if its OK. It will still operate but the no load HV will float very high with an open load resistor. I was never able to find an exact replacement at the time I needed it so I installed a 25W wire-wound resistor in a vertical fashion with a small bolt running through it. Somewhat similar to the original setup. I choose a 25K 25W instead of a 15K to reduce the heat dissipation produced by the resistor. The 25K still loaded down the HV and was near the same as was prior with the original 15K 25W resistor which seems to regularly fail due to running it at or near it's maxium wattage dissipation. Also one last thing, If I recall the HV winding on this early choke version AC3 was higher than the later AC3 and AC4's that didn't use the HV choke. Seems I temporally jumped across this choke just to see what effect it had on the HV and if I recall correctly the HV jumped up in voltage considerably, and was then out of speck and was near the max voltage ratings of the 2 HV caps. (No Good) I would appreciate your findings on the HV secondary windings if you don't mind. Too put it quite frankly I don't care for the early model AC3 choke type supply due to these issues. The only nice thing about this model is that all the caps mount on the underside of its chassis. This AC3 supply now serves as my test bench supply and is not used in my station. Hope this helps, Don / WA9TGT On 12/11/06, Tom Taylor [EMAIL PROTECTED] wrote: I have a number of Drake A, B, and C twin combos. I decided to upgrade all the power supplies with AC-4R boards. Since most of the caps are now 30 to 40 years old, I don't want to risk a bias supply going out and ruining the finals or some short ruining the transformers. I order a bunch of blank boards since I already had some of the parts. The rest of the parts I ordered from DigiKey. I assembled all the boards at the same time and then started upgrading the AC-4s, one by one. So far, all of the power supplies are different in one way or another and all of them have been modified by previous owners. Here are some examples: #1) A previous owner replace the mid-voltage supplies' capacitors with a bundle of three caps mounted to the upper end the supply. #2) A previous owner replaced the sand resistor below the chassis with two higher wattage resistors mounted to the upper end of the supply. #3) A previous owner replaced one of the diodes in the HV supply. The transformer in this supply has transformer bolts inserted the wrong direction to mount the AC-4R board. Unfortunately, it's not as simple as removing the bolts and inserting them in the other direction because the bolts are just long enough to reach, but not long enough to add the board spacers. #4) This is an AC-3, serial #101. I've never seen a Drake power supply like this. There's a large choke mounted adjacent to the transformer. All of the other parts, including the capacitors, are radial lead caps that are packed underneath the very low chassis. Has anyone else seen an early AC-3 like this? I'm planning to remove the choke and rebuilding the supply just like all of the others since all of the circuitry is now on the AC-4R board. Thanks, Tom N7TM -- WA9TGT / Don Garrett / Muncie, IN Unique Radio Parts www.wa9tgt.com
Re: [drakelist] AC-4R upgrades
Dennis Monticelli [EMAIL PROTECTED] made an utterance to the drakelist gang -- My company makes chips for switching supplies. One important design choice is whether or not to allow the filter inductor to operate in discontinuous mode. This simply means that the current through the inductor is not continous; it runs out of stored energy each cycle as the current drops to zero. When that happens its filtering action is impaired. An old fashioned tube supply with a choke is no differrent even though the frequency is much lower. If the choke has insufficient inductance for the minimum load current, then it will run dry before the next cycle of the line voltage replenishes the energy. Wwhen that happens its ability to regulate the output voltage is seriously impaired and the output soars to 1.4 times the RMS. This is why Gerry recommends that the minimum load represented by the stock bleed resistor be heeded. To paraphrase Gerry, only use choke input supplies when the load current range is relatively narrow; 10:1 is too much. Denny AE6C On 12/12/06, Gerry [EMAIL PROTECTED] wrote: Gerry [EMAIL PROTECTED] made an utterance to the drakelist gang -- What you describe is typical of choke input power supplies. Text books tell us that choke input supplies are better at regulation but that is simply not true if you have a wide ranging dynamic load. Choke input power supplies require a minimum load. There are formulas in the old handbooks to calculate the value of resistance to draw a proper load current. Without a minimum load it would be as if no choke existed (except for its DC resistance) and the filter capacitors will charge to 1.414 times the value of AC rms. In other words, if you have 750VAC secondary the capacitors will charge to over 1,060 volts with no load! With a properly chosen resistor this would be 0.9 times 750 volts or 675 volts. Please note the HV filter capacitors are only rated to 350 volts for a total of only 700 volts. So as you can see, the 10k, 20w load resistor on the output of the HV side of the supply is crucial. That resistor dissipates around 16 watts. Notice that the low end is referenced to +250V and not ground. It should be rated for twice the actual power dissipation or 32 watts. Put it another way, without the load resistor, key up voltage would be around 1kV while key down would drop to about 675 volts. I should mention that the choke has DC resistance which may be a significant contributor to voltage drop. If you draw 450 mils and your DC choke has 50 Ohms of DC resistance, you will drop an additional 22.5 volts across the choke. Also look at the +250 volt side and see that the filter caps are rated to only 300 volts. This is much too close for comfort and is really a very slim margin of safety. Typically the voltage rating of electrolytics is related to the maximum voltage it can withstand for a given numbers of hours at some temperature. Component manufacturers usually try to embellish the specifications and say their caps will take 1000 hours of use at room temperature. But in actual operation ambient temperature will be higher than 25 degrees C and they typically don't say too much about self heating due to ripple current which brings up temperature even more. This is why it is always best to over rate voltage in electrolytics when selecting components. I see that Drake realized this was not a good design and soon changed to a capacitive input supply which is better suited to SSB service, and less expensive. As far as I'm concerned I would avoid the original AC-3 in daily use. You wisely chose to use it on the test bench instead. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Donnie Garrett Sent: Tuesday, December 12, 2006 5:27 AM To: Tom Taylor Cc: drakelist@www.zerobeat.net Subject: Re: [drakelist] AC-4R upgrades Donnie Garrett [EMAIL PROTECTED] made an utterance to the drakelist gang -- Tom: I have one of the early AC3 supplies that used a HV choke. Garey K4OAH and I had a lot of discussions about its design some time back after I discovered the ceramic 25W load resistor was open. You better check yours to see if its OK. It will still operate but the no load HV will float very high with an open load resistor. I was never able to find an exact replacement at the time I needed it so I installed a 25W wire-wound resistor in a vertical fashion with a small bolt running through it. Somewhat similar to the original setup. I choose a 25K 25W instead of a 15K to reduce the heat dissipation produced by the resistor. The 25K still loaded down the HV and was near the same as was prior with the original 15K 25W resistor which seems to regularly fail due to running it at or near it's maxium wattage dissipation. Also one last
[drakelist] tr7
Any input on this tr7 problem will be greatly appreciated: I have a TR7 which has been gone through and realigned etc. Upon removal of the DR7 board and installation of N9OO's blue LEDs - very nice - I reinstalled the DR7. Following this reinstallation, I now have several symptoms. 1. Reduced sensitivityS9 signals now S4 2. Loss of proper filter bandwidths 3. All usb signals readable on usb, lsb and cw mode. 4. Freq. display correct on lower portion of bands flipping to incorrect freq. as tun PTO upward. For instance, in the 3.5 position, the freq. display is correct from 3500 up to about 3750, then flips to 32??, then flips to 14??? etc. as continue to tune upward with PTO. These symptoms have continued through several uninstalls and inspections, and reinstalls. And through the install of a different DR7 board. Something beside the DR7 board has gone haywire. I have inspected the connectors, solder joints, plugs, etc. numerous times and still no joy. The unit was functioning nicely before the DR7 uninstall. Any input will save some hair perhaps. hi Thanks. Mike K5NU
Re: [drakelist] tr7
Jim Shorney [EMAIL PROTECTED] made an utterance to the drakelist gang -- On Tue, 12 Dec 2006 15:57:18 -0600, Mike wrote: The unit was functioning nicely before the DR7 uninstall. Any input will save some hair perhaps. Is it possible that you accidentally bumped one or more of the adjustment pots on the DC-DC converter supply board in the front right corner of the rig? It's so easy to do when messing with the DR7 that it ain't even funny. -- Jim Shorney --.--Put complaints in this box jshorney (at) inebraska.com Ham Radio NU0C Lincoln, NE, USA EN10ps http://incolor.inetnebr.com/jshorney/ -- Submissions:drakelist@www.zerobeat.net Unsubscribe:[EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost:[EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net --
RE: [drakelist] AC-4R upgrades
Gerry [EMAIL PROTECTED] made an utterance to the drakelist gang -- What you describe is typical of choke input power supplies. Text books tell us that choke input supplies are better at regulation but that is simply not true if you have a wide ranging dynamic load. Choke input power supplies require a minimum load. There are formulas in the old handbooks to calculate the value of resistance to draw a proper load current. Without a minimum load it would be as if no choke existed (except for its DC resistance) and the filter capacitors will charge to 1.414 times the value of AC rms. In other words, if you have 750VAC secondary the capacitors will charge to over 1,060 volts with no load! With a properly chosen resistor this would be 0.9 times 750 volts or 675 volts. Please note the HV filter capacitors are only rated to 350 volts for a total of only 700 volts. So as you can see, the 10k, 20w load resistor on the output of the HV side of the supply is crucial. That resistor dissipates around 16 watts. Notice that the low end is referenced to +250V and not ground. It should be rated for twice the actual power dissipation or 32 watts. Put it another way, without the load resistor, key up voltage would be around 1kV while key down would drop to about 675 volts. I should mention that the choke has DC resistance which may be a significant contributor to voltage drop. If you draw 450 mils and your DC choke has 50 Ohms of DC resistance, you will drop an additional 22.5 volts across the choke. Also look at the +250 volt side and see that the filter caps are rated to only 300 volts. This is much too close for comfort and is really a very slim margin of safety. Typically the voltage rating of electrolytics is related to the maximum voltage it can withstand for a given numbers of hours at some temperature. Component manufacturers usually try to embellish the specifications and say their caps will take 1000 hours of use at room temperature. But in actual operation ambient temperature will be higher than 25 degrees C and they typically don't say too much about self heating due to ripple current which brings up temperature even more. This is why it is always best to over rate voltage in electrolytics when selecting components. I see that Drake realized this was not a good design and soon changed to a capacitive input supply which is better suited to SSB service, and less expensive. As far as I'm concerned I would avoid the original AC-3 in daily use. You wisely chose to use it on the test bench instead. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Donnie Garrett Sent: Tuesday, December 12, 2006 5:27 AM To: Tom Taylor Cc: drakelist@www.zerobeat.net Subject: Re: [drakelist] AC-4R upgrades Donnie Garrett [EMAIL PROTECTED] made an utterance to the drakelist gang -- Tom: I have one of the early AC3 supplies that used a HV choke. Garey K4OAH and I had a lot of discussions about its design some time back after I discovered the ceramic 25W load resistor was open. You better check yours to see if its OK. It will still operate but the no load HV will float very high with an open load resistor. I was never able to find an exact replacement at the time I needed it so I installed a 25W wire-wound resistor in a vertical fashion with a small bolt running through it. Somewhat similar to the original setup. I choose a 25K 25W instead of a 15K to reduce the heat dissipation produced by the resistor. The 25K still loaded down the HV and was near the same as was prior with the original 15K 25W resistor which seems to regularly fail due to running it at or near it's maxium wattage dissipation. Also one last thing, If I recall the HV winding on this early choke version AC3 was higher than the later AC3 and AC4's that didn't use the HV choke. Seems I temporally jumped across this choke just to see what effect it had on the HV and if I recall correctly the HV jumped up in voltage considerably, and was then out of speck and was near the max voltage ratings of the 2 HV caps. (No Good) I would appreciate your findings on the HV secondary windings if you don't mind. Too put it quite frankly I don't care for the early model AC3 choke type supply due to these issues. The only nice thing about this model is that all the caps mount on the underside of its chassis. This AC3 supply now serves as my test bench supply and is not used in my station. Hope this helps, Don / WA9TGT On 12/11/06, Tom Taylor [EMAIL PROTECTED] wrote: I have a number of Drake A, B, and C twin combos. I decided to upgrade all the power supplies with AC-4R boards. Since most of the caps are now 30 to 40 years old, I don't want to risk a bias supply going out and ruining the finals or some short ruining the transformers. I order a bunch of blank boards since I already had some of the parts.
RE: [drakelist] RE: audio waveform has warble/hum on it!
I have the same issue with my RV-7 VFO. It is also tougher to turn the tuning knob. I've been told that it needed to be adjusted/loosened from a small set-screw that's accessed from the back of the VFO case. Best Regards, Jim N9WW James E. Chaggaris President PowerOne Corp. 1020 Cedar Ave. Suite 110 St. Charles, IL 60174 Phn:(630) 443-6500 Fax:(630) 443-6505 Web: www.pwrone.com _ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Laird Tom N Sent: Tuesday, December 12, 2006 7:27 AM To: Frank Krozel; drakelist@www.zerobeat.net Subject: [drakelist] RE: audio waveform has warble/hum on it! Guess what; I just pick up a TR-7 last week and I heard that voice warble on it too! Ever so slight, but I heard it. I checked into the Drake technical net over the weekend and no one on the net heard of that problem. The more I listen to the TR-7, the less noticable the warble, maybe it's dirty switch contacts and just the fact that I'm exercising them helps? Tom Laird W9QI Moline, IL. _ On Behalf Of [EMAIL PROTECTED] OK, my TR-7 is getting back in line to what it left Ohio many years ago. I have been listening pretty critically on the receive and it seemed on SSB like there was a slight warble on the audio. When going to CW it was harder to hear but still there. (I listen to 35+WPM so maybe I couldn't hear it.) Went to the Calibrator and it seems like the 25kHz calibrator signal is jumping up and down (in voltage) slightly, maybe +/- 3% or so on the scope. Audio-wise it is hard to hear but.. it is there - warbling ever so slightly. There is also some sort of other signal in the background. The other signal is much lower in frequency, maybe 60Hz? but the same amplitude! The scope seemed like it had problems syncing... Any thoughts on this? Frank KG9H
Re: [drakelist] RE: audio waveform has warble/hum on it!
Tom Evans, AG9X [EMAIL PROTECTED] made an utterance to the drakelist gang -- Frank, Inspect the PTO to see if it has the braid mod. Without it, the frequency can jump around ever so slightly. http://www.zerobeat.net/drakelist/tr7moremods.html Look for (10) -Tom, AG9X On 12/11/06, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: OK, my TR-7 is getting back in line to what it left Ohio many years ago. I have been listening pretty critically on the receive and it seemed on SSB like there was a slight warble on the audio. When going to CW it was harder to hear but still there. (I listen to 35+WPM so maybe I couldn't hear it.) Went to the Calibrator and it seems like the 25kHz calibrator signal is jumping up and down (in voltage) slightly, maybe +/- 3% or so on the scope. Audio-wise it is hard to hear but.. it is there - warbling ever so slightly. There is also some sort of other signal in the background. The other signal is much lower in frequency, maybe 60Hz? but the same amplitude! The scope seemed like it had problems syncing... Any thoughts on this? Frank KG9H -- Submissions:drakelist@www.zerobeat.net Unsubscribe:[EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost:[EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net --
[drakelist] Tr7 - PTO bulb replacement - was DR-7 install
Laird Tom N [EMAIL PROTECTED] made an utterance to the drakelist gang -- I replaced the PTO bulb last night in my TR-7 which constitutes removal of the DR-7 (unless someone knows an easier way?). Removal is somewhat delicate. You need to unplug all the surrounding connectors, remove the braided wire, and the single machine screw near the center of the board. The hard part is lifting the connectors EVENLY to avoid bending the board. I had a piece old copper 12ga. house wire that I bent the end (J-hook) and used that to snake under the edge of the board next to the press-in connectors and; as evenly as I could, leverage up the board. It worked, but be careful - there is another connector near the middle of the board the that you will have to grab the board edges and wiggle it up and out. BTW, the display is part of the board and does not need to be removed, seperately. Re-installation isn't any easier. Getting the display rocked in first and then trying to line the pins up on the bottom side (when you can't see them anyway) is a real chore. The re-installation process depends entirely upon you removing (see paragraph above) it straight up without bending any pins!!! As for the problem below, I would suspect one of two things. A possible crack in the board upon removal (could be a weak solder joint on one of the pin connectors). Or, a bent or mis-aligned press in connector pin on the bottom. Just my 2 cents worth. BTW, the bulbs are #53's (14 volt) the one that was in mine and burnt out was a #47 (6 volt). Tom Laird W9QI Moline, IL. -Original Message- Any input on this tr7 problem will be greatly appreciated: I have a TR7 which has been gone through and realigned etc. Upon removal of the DR7 board and installation of N9OO's blue LEDs - very nice - I reinstalled the DR7. Following this reinstallation, I now have several symptoms. 1. Reduced sensitivity, S9 signals now S4 2. Loss of proper filter bandwidths 3. All usb signals readable on usb, lsb and cw mode. 4. Freq. display correct on lower portion of bands flipping to incorrect freq. as tun PTO upward. For instance, in the 3.5 position, the freq. display is correct from 3500 up to about 3750, then flips to 32??, then flips to 14??? etc. as continue to tune upward with PTO. These symptoms have continued through several uninstalls and inspections, and reinstalls. And through the install of a different DR7 board. Something beside the DR7 board has gone haywire. I have inspected the connectors, solder joints, plugs, etc. numerous times and still no joy. The unit was functioning nicely before the DR7 uninstall. -- Is it possible that you accidentally bumped one or more of the adjustment pots on the DC-DC converter supply board in the front right corner of the rig? It's so easy to do when messing with the DR7 that it ain't even funny. -- Submissions:drakelist@www.zerobeat.net Unsubscribe:[EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost:[EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net --
Re: [drakelist] AC-4R upgrades
Donnie Garrett [EMAIL PROTECTED] made an utterance to the drakelist gang -- Tom: I have one of the early AC3 supplies that used a HV choke. Garey K4OAH and I had a lot of discussions about its design some time back after I discovered the ceramic 25W load resistor was open. You better check yours to see if its OK. It will still operate but the no load HV will float very high with an open load resistor. I was never able to find an exact replacement at the time I needed it so I installed a 25W wire-wound resistor in a vertical fashion with a small bolt running through it. Somewhat similar to the original setup. I choose a 25K 25W instead of a 15K to reduce the heat dissipation produced by the resistor. The 25K still loaded down the HV and was near the same as was prior with the original 15K 25W resistor which seems to regularly fail due to running it at or near it's maxium wattage dissipation. Also one last thing, If I recall the HV winding on this early choke version AC3 was higher than the later AC3 and AC4's that didn't use the HV choke. Seems I temporally jumped across this choke just to see what effect it had on the HV and if I recall correctly the HV jumped up in voltage considerably, and was then out of speck and was near the max voltage ratings of the 2 HV caps. (No Good) I would appreciate your findings on the HV secondary windings if you don't mind. Too put it quite frankly I don't care for the early model AC3 choke type supply due to these issues. The only nice thing about this model is that all the caps mount on the underside of its chassis. This AC3 supply now serves as my test bench supply and is not used in my station. Hope this helps, Don / WA9TGT On 12/11/06, Tom Taylor [EMAIL PROTECTED] wrote: I have a number of Drake A, B, and C twin combos. I decided to upgrade all the power supplies with AC-4R boards. Since most of the caps are now 30 to 40 years old, I don't want to risk a bias supply going out and ruining the finals or some short ruining the transformers. I order a bunch of blank boards since I already had some of the parts. The rest of the parts I ordered from DigiKey. I assembled all the boards at the same time and then started upgrading the AC-4s, one by one. So far, all of the power supplies are different in one way or another and all of them have been modified by previous owners. Here are some examples: #1) A previous owner replace the mid-voltage supplies' capacitors with a bundle of three caps mounted to the upper end the supply. #2) A previous owner replaced the sand resistor below the chassis with two higher wattage resistors mounted to the upper end of the supply. #3) A previous owner replaced one of the diodes in the HV supply. The transformer in this supply has transformer bolts inserted the wrong direction to mount the AC-4R board. Unfortunately, it's not as simple as removing the bolts and inserting them in the other direction because the bolts are just long enough to reach, but not long enough to add the board spacers. #4) This is an AC-3, serial #101. I've never seen a Drake power supply like this. There's a large choke mounted adjacent to the transformer. All of the other parts, including the capacitors, are radial lead caps that are packed underneath the very low chassis. Has anyone else seen an early AC-3 like this? I'm planning to remove the choke and rebuilding the supply just like all of the others since all of the circuitry is now on the AC-4R board. Thanks, Tom N7TM -- WA9TGT / Don Garrett / Muncie, IN Unique Radio Parts www.wa9tgt.com -- Submissions:drakelist@www.zerobeat.net Unsubscribe:[EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost:[EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net --
Re: [drakelist] AC-4R upgrades
Garey Barrell [EMAIL PROTECTED] made an utterance to the drakelist gang -- Denny - Absolutely. However ... The Drake supply in question varies over a roughly 3:1 ratio, i.e., 100 mA idling to ~ 330 mA full load, at an audio rate for SSB or a rate determined by CW keying speed, NOT including bleeder current, which is constant. 73, Garey - K4OAH Atlanta Drake 2-B, 4-B C-Line Service Supplement CDs www.k4oah.com Dennis Monticelli wrote: Dennis Monticelli [EMAIL PROTECTED] made an utterance to the drakelist gang -- My company makes chips for switching supplies. One important design choice is whether or not to allow the filter inductor to operate in discontinuous mode. This simply means that the current through the inductor is not continous; it runs out of stored energy each cycle as the current drops to zero. When that happens its filtering action is impaired. An old fashioned tube supply with a choke is no differrent even though the frequency is much lower. If the choke has insufficient inductance for the minimum load current, then it will run dry before the next cycle of the line voltage replenishes the energy. Wwhen that happens its ability to regulate the output voltage is seriously impaired and the output soars to 1.4 times the RMS. This is why Gerry recommends that the minimum load represented by the stock bleed resistor be heeded. To paraphrase Gerry, only use choke input supplies when the load current range is relatively narrow; 10:1 is too much. Denny AE6C On 12/12/06, Gerry [EMAIL PROTECTED] wrote: Gerry [EMAIL PROTECTED] made an utterance to the drakelist gang -- What you describe is typical of choke input power supplies. Text books tell us that choke input supplies are better at regulation but that is simply not true if you have a wide ranging dynamic load. Choke input power supplies require a minimum load. There are formulas in the old handbooks to calculate the value of resistance to draw a proper load current. Without a minimum load it would be as if no choke existed (except for its DC resistance) and the filter capacitors will charge to 1.414 times the value of AC rms. In other words, if you have 750VAC secondary the capacitors will charge to over 1,060 volts with no load! With a properly chosen resistor this would be 0.9 times 750 volts or 675 volts. Please note the HV filter capacitors are only rated to 350 volts for a total of only 700 volts. So as you can see, the 10k, 20w load resistor on the output of the HV side of the supply is crucial. That resistor dissipates around 16 watts. Notice that the low end is referenced to +250V and not ground. It should be rated for twice the actual power dissipation or 32 watts. Put it another way, without the load resistor, key up voltage would be around 1kV while key down would drop to about 675 volts. I should mention that the choke has DC resistance which may be a significant contributor to voltage drop. If you draw 450 mils and your DC choke has 50 Ohms of DC resistance, you will drop an additional 22.5 volts across the choke. Also look at the +250 volt side and see that the filter caps are rated to only 300 volts. This is much too close for comfort and is really a very slim margin of safety. Typically the voltage rating of electrolytics is related to the maximum voltage it can withstand for a given numbers of hours at some temperature. Component manufacturers usually try to embellish the specifications and say their caps will take 1000 hours of use at room temperature. But in actual operation ambient temperature will be higher than 25 degrees C and they typically don't say too much about self heating due to ripple current which brings up temperature even more. This is why it is always best to over rate voltage in electrolytics when selecting components. I see that Drake realized this was not a good design and soon changed to a capacitive input supply which is better suited to SSB service, and less expensive. As far as I'm concerned I would avoid the original AC-3 in daily use. You wisely chose to use it on the test bench instead. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Donnie Garrett Sent: Tuesday, December 12, 2006 5:27 AM To: Tom Taylor Cc: drakelist@www.zerobeat.net Subject: Re: [drakelist] AC-4R upgrades Donnie Garrett [EMAIL PROTECTED] made an utterance to the drakelist gang -- Tom: I have one of the early AC3 supplies that used a HV choke. Garey K4OAH and I had a lot of discussions about its design some time back after I discovered the ceramic 25W load resistor was open. You better check yours to see if its OK. It will still operate but the no load HV will
RE: [drakelist] RE: audio waveform has warble/hum on it!
I have the same issue with my RV-7 VFO. It is also tougher to turn the tuning knob. I've been told that it needed to be adjusted/loosened from a small set-screw that's accessed from the back of the VFO case. Best Regards, Jim N9WW James E. Chaggaris President PowerOne Corp. 1020 Cedar Ave. Suite 110 St. Charles, IL 60174 Phn:(630) 443-6500 Fax:(630) 443-6505 Web: www.pwrone.com _ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Laird Tom N Sent: Tuesday, December 12, 2006 7:27 AM To: Frank Krozel; drakelist@www.zerobeat.net Subject: [drakelist] RE: audio waveform has warble/hum on it! Guess what; I just pick up a TR-7 last week and I heard that voice warble on it too! Ever so slight, but I heard it. I checked into the Drake technical net over the weekend and no one on the net heard of that problem. The more I listen to the TR-7, the less noticable the warble, maybe it's dirty switch contacts and just the fact that I'm exercising them helps? Tom Laird W9QI Moline, IL. _ On Behalf Of [EMAIL PROTECTED] OK, my TR-7 is getting back in line to what it left Ohio many years ago. I have been listening pretty critically on the receive and it seemed on SSB like there was a slight warble on the audio. When going to CW it was harder to hear but still there. (I listen to 35+WPM so maybe I couldn't hear it.) Went to the Calibrator and it seems like the 25kHz calibrator signal is jumping up and down (in voltage) slightly, maybe +/- 3% or so on the scope. Audio-wise it is hard to hear but.. it is there - warbling ever so slightly. There is also some sort of other signal in the background. The other signal is much lower in frequency, maybe 60Hz? but the same amplitude! The scope seemed like it had problems syncing... Any thoughts on this? Frank KG9H
[drakelist] Dial Skirt TR5
Anyone have a spare dial skirt for a TR5 they would like to sell/part with? Email me off list Tnx 73 Paul AD3G
