Re: [Drakelist] R-4A Recap
Neil - You'll get two sides (maybe more!) on this. The FACTS are ... Electrolytic capacitors have a finite lifetime. Various sources give widely different _estimates_ of what this time 'is', and typically settle around 10 years in _typical_ environmental conditions, whatever those are. The cap has a paste that forms the dielectric, which contains water. Over time, this water evaporates resulting in a loss of insulating capabilities and/or capacity. Heat of course speeds up this evaporation, and depending upon how much stuff is piled on top of the radio, it can get pretty hot. There are four main 'failure' conditions for an electrolytic. One is that the capacitance decreases considerably, another is that a 'series resistance' (presents as a resistor in series with the capacitor), another is it becomes 'open', usually as a result of a corroded internal lead, or, it just shorts out completely. All but the last one causes the power supply ripple to increase, (HUM,) and if the last one does happen, hopefully the power supply fuse will blow before the power transformer is destroyed! This last one is why the FIRST thing I do with a 'new' piece of vintage gear is check the fuse. I have found everything from the correct fuse, to a piece of #8 copper wire So obviously all of our Drake gear is on borrowed time if it has the original power supply caps. They may work for another ten years, or they may short out today. The choice is yours, 'do you feel lucky?', or are you a belt and suspenders kind of guy? If you feel lucky, just make sure the fuse is the RIGHT one. If B S, check with Tom at hayseedhamfest.com. He has Twist-Lok caps that are a drop-in replacement and offers a complete kit that replaces ALL electrolytics in the various Drake radios. 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 www.k4oah.com Neil M Califano wrote: Should I recap my R-4A no matter what just because it is 30 years old? ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] R-4A Recap
Gary covered it all quite nicely (no surprise there!) and I am of the same mind as he, i.e., replace the main power supply caps (the big can) *FIRST* before you put much on time on the radio. You do *NOT* want to risk the power transformer! You will need a heavy-duty soldering gun or iron (200 watts or so) to desolder the lugs that are soldered to the chassis. You will also need to move the small audio transformer over to gain access to all of the lugs without burning anything with the iron. *CAREFULLY* observe and *WRITE DOWN* which color wires and how many go to each lug of the can (triangle, square, semicircle or unmarked). Also note that some variants have a resistor across two of the lugs, so note which two and the resistor value (it can VARY!) and have a replacement resistor on hand in case you cannot successfully remove the old one (there is almost ZERO spare lead length to work with). I've done close to ten (10) R-4, R-4A and R-4B models and after a while you start to get pretty good at it. ;-) Hayseed Hamfest has all you need in the way of replacement caps for any flavor of R-4 or for a 2B. There is also a separate source for rebuild kits for the AC-3 AC-4 power supplies and I highly recommend that you rebuild these supplies if you have one and it is still all-original (I forget what the link is but you can Google it and find it easily enough). 73/Paul, K4MSG In a message dated 2/4/2011 10:36:39 A.M. Eastern Standard Time, k4...@mindspring.com writes: Neil - You'll get two sides (maybe more!) on this. The FACTS are ... Electrolytic capacitors have a finite lifetime. Various sources give widely different _estimates_ of what this time 'is', and typically settle around 10 years in _typical_ environmental conditions, whatever those are. The cap has a paste that forms the dielectric, which contains water. Over time, this water evaporates resulting in a loss of insulating capabilities and/or capacity. Heat of course speeds up this evaporation, and depending upon how much stuff is piled on top of the radio, it can get pretty hot. There are four main 'failure' conditions for an electrolytic. One is that the capacitance decreases considerably, another is that a 'series resistance' (presents as a resistor in series with the capacitor), another is it becomes 'open', usually as a result of a corroded internal lead, or, it just shorts out completely. All but the last one causes the power supply ripple to increase, (HUM,) and if the last one does happen, hopefully the power supply fuse will blow before the power transformer is destroyed! This last one is why the FIRST thing I do with a 'new' piece of vintage gear is check the fuse. I have found everything from the correct fuse, to a piece of #8 copper wire So obviously all of our Drake gear is on borrowed time if it has the original power supply caps. They may work for another ten years, or they may short out today. The choice is yours, 'do you feel lucky?', or are you a belt and suspenders kind of guy? If you feel lucky, just make sure the fuse is the RIGHT one. If B S, check with Tom at hayseedhamfest.com. He has Twist-Lok caps that are a drop-in replacement and offers a complete kit that replaces ALL electrolytics in the various Drake radios. 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 www.k4oah.com Neil M Califano wrote: Should I recap my R-4A no matter what just because it is 30 years old? ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] R-4A Recap
Neil, I too agonized about recaps, especially after one op opined that he'd never buy a recapped radio. Finally decided that risk of ruining a transformer from a shorted cap was higher than cared for and now routinely replace the paper and electrolytic caps before bringing them up with the variac. In the case of my AC-4, first thing I did was install the AC-4r kit. Others swear by reforming, I personally have no faith in the procedure. I routinely contact Hayseed for replacements, if he doesn't stock what you need, he will have it fabricated. My most recent was a multi-section cap for a Globe Chief modulator. I'm certainly no expert at this, but for me replacing the old caps takes the worry out of using these old rigs. GL 73, Curt ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] L-75 question
Hello Evan, I just open my L75 and that switch has two capacitors on the switched side that go to a common terminal on the other side of the switch. That terminal is not used by the switch. It appears to be a common junction point. From that point I have a braided ground strip from that common terminal going to the ground terminal attached to the chassis about ½ inch away. On the switch output side I have a connection from the switch to the high side of the loading capacitor. The switch is just switching in one of two fixed value capacitors across the loading capacitor to get the antenna loading in range for best match. Ron / WB4HFN From: drakelist-boun...@zerobeat.net [mailto:drakelist-boun...@zerobeat.net] On Behalf Of K9sqg Sent: Friday, February 04, 2011 12:38 PM To: drakelist@zerobeat.net Subject: [Drakelist] L-75 question Fellow enthusiasts, Have a question about S2C in the L-75 linear, it is the wafer switch controlled by the lever on the front panel for use on 160 and 80 meters. The two switchable load capacitors are located from some terminals with one end of each cap going to a common terminal on the switch, and then a lead from there to ground. However, that common terminal is not connected electrically to any part of the circuit. Was just curious as to why the ground side of each cap is connected to an unused terminal when in fact there is a ground lug very close to that switch that could be used for the ground termination. I'm going to be replacing those caps and plan on using the ground lug rather than that electrically isolated switch terminal. But then, am I missing something here? I'm sure Drake had a reason for doing what they did, but I can't figure out what it is. At one time I thought that maybe it would be a simplified manufacturing process to mount the caps to the switch before installation but then that didn't make sense since a wire/braid had to be run from that terminal to the ground lug anyway. Your thoughts? 73, Evan, K9SQG ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] L-75 question
Evan - OK, I see them. I can't figure out what they were thinking. There doesn't appear to be any reason for that, unless the new capacitor leads weren't long enough to reach the ground lug. Anyway, that's my guess and I'm sticking to it! :-) 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 www.k4oah.com K9sqg wrote: Garey, These are C34 and C36. They are 700 pf disc ceramic. 73, Evan -Original Message- From: Garey Barrell k4...@mindspring.com To: K9sqg k9...@aol.com Sent: Fri, Feb 4, 2011 12:47 pm Subject: Re: [Drakelist] L-75 question Evan - What are the two caps you are referring to? 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 www.k4oah.com http://www.k4oah.com K9sqg wrote: Fellow enthusiasts, Have a question about S2C in the L-75 linear, it is the wafer switch controlled by the lever on the front panel for use on 160 and 80 meters. The two switchable load capacitors are located from some terminals with one end of each cap going to a common terminal on the switch, and then a lead from there to ground. However, that common terminal is not connected electrically to any part of the circuit. Was just curious as to why the ground side of each cap is connected to an unused terminal when in fact there is a ground lug very close to that switch that could be used for the ground termination. I'm going to be replacing those caps and plan on using the ground lug rather than that electrically isolated switch terminal. But then, am I missing something here? I'm sure Drake had a reason for doing what they did, but I can't figure out what it is. At one time I thought that maybe it would be a simplified manufacturing process to mount the caps to the switch before installation but then that didn't make sense since a wire/braid had to be run from that terminal to the ground lug anyway. Your thoughts? 73, Evan, K9SQG ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] L-75 question
The only thing I can see is it may be an RF current issue, Both capacitors together may create a current carrying issue which is why Drake used a wire braid jumper from the common point and the chassis ground lug.I know today they would be taken directly to the ground lug, but who knows what they were thinking 30 years ago. Ron / WB4HFN -Original Message- From: drakelist-boun...@zerobeat.net [mailto:drakelist-boun...@zerobeat.net] On Behalf Of Garey Barrell Sent: Friday, February 04, 2011 3:36 PM To: drakelist Subject: Re: [Drakelist] L-75 question Evan - OK, I see them. I can't figure out what they were thinking. There doesn't appear to be any reason for that, unless the new capacitor leads weren't long enough to reach the ground lug. Anyway, that's my guess and I'm sticking to it! :-) 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 www.k4oah.com K9sqg wrote: Garey, These are C34 and C36. They are 700 pf disc ceramic. 73, Evan -Original Message- From: Garey Barrell k4...@mindspring.com To: K9sqg k9...@aol.com Sent: Fri, Feb 4, 2011 12:47 pm Subject: Re: [Drakelist] L-75 question Evan - What are the two caps you are referring to? 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 www.k4oah.com http://www.k4oah.com K9sqg wrote: Fellow enthusiasts, Have a question about S2C in the L-75 linear, it is the wafer switch controlled by the lever on the front panel for use on 160 and 80 meters. The two switchable load capacitors are located from some terminals with one end of each cap going to a common terminal on the switch, and then a lead from there to ground. However, that common terminal is not connected electrically to any part of the circuit. Was just curious as to why the ground side of each cap is connected to an unused terminal when in fact there is a ground lug very close to that switch that could be used for the ground termination. I'm going to be replacing those caps and plan on using the ground lug rather than that electrically isolated switch terminal. But then, am I missing something here? I'm sure Drake had a reason for doing what they did, but I can't figure out what it is. At one time I thought that maybe it would be a simplified manufacturing process to mount the caps to the switch before installation but then that didn't make sense since a wire/braid had to be run from that terminal to the ground lug anyway. Your thoughts? 73, Evan, K9SQG ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] L-75 question
- Original Message - From: Garey Barrell k4...@mindspring.com To: drakelist Drakelist@zerobeat.net Sent: Friday, February 04, 2011 1:13 PM Subject: Re: [Drakelist] L-75 question I'm still betting on supplied lead length of the original caps!! :-) Yes, RF current is likely the reason for the braid, but if the cap's leads reached there wouldn't be any more of a current problem. Yet another wild thought, perhaps the longer cap leads would have caused an inconvenient series resonance. Bottom line, it WAS DESIGNED intentionally by some pretty good engineers, and I would be reluctant to change it without proving I understood why it was done. It wouldn't have cost much to add that blank terminal to the switch wafer, probably less than special ordered caps with longer leads, but neither would have been done without a good reason. (Spoken by an RF engineer who has had to defend more than one 'crazy design decision'.) 73, Garey - K4OAH Glen Allen, VA I'm not at all familiar with this equipment. I wonder about the lead length to the common point vs: to wherever the ground ribbon goes. That might be a clue as to whether the arrangement was done because of limited lead length on the caps or to reduce inductance. Or, perhaps for some other reason that isn't obvious but turned up in the prototyping stage. Drake engineers seem in general to have known what they were doing. -- Richard Knoppow Los Angeles WB6KBL dickb...@ix.netcom.com ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] L-75 question
Well I took another look at my L75 which I have on the bench anyway. I think I figured out why the braid jumper and that wiring arrangement is the way it is. If you look down each side in the front, there are three screws on each side that hold the front chassis sub-panel, which the aluminum front is attached. If you remove the three screws down each side, that whole front assembly will fold out to gain easy access to the front area of the chassis along the bottom. That rotor switch is attached to the front subpanel along with the power switch.When that panel is folded out that long braided ground strap allows the panel to come out easily an inch or so. If the two capacitor were soldered directly to the chassis ground lug, pull out that front panel assemble would probably pull loose the wire lead from those two capacitors and damage them. I remembered that but it took a while. When you reach my age the thinking processor runs slow.I repaired an L75 a few years ago and was perturbed because it was almost impossible to get down inside the amp in the front. I found loosing and folding down the front assembly make it a whole lot easier to work on the amp in the front. Ron / WB4HFN -Original Message- From: drakelist-boun...@zerobeat.net [mailto:drakelist-boun...@zerobeat.net] On Behalf Of Garey Barrell Sent: Friday, February 04, 2011 4:14 PM To: drakelist Subject: Re: [Drakelist] L-75 question I'm still betting on supplied lead length of the original caps!! :-) Yes, RF current is likely the reason for the braid, but if the cap's leads reached there wouldn't be any more of a current problem. Yet another wild thought, perhaps the longer cap leads would have caused an inconvenient series resonance. Bottom line, it WAS DESIGNED intentionally by some pretty good engineers, and I would be reluctant to change it without proving I understood why it was done. It wouldn't have cost much to add that blank terminal to the switch wafer, probably less than special ordered caps with longer leads, but neither would have been done without a good reason. (Spoken by an RF engineer who has had to defend more than one 'crazy design decision'.) 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 www.k4oah.com Ron wrote: The only thing I can see is it may be an RF current issue, Both capacitors together may create a current carrying issue which is why Drake used a wire braid jumper from the common point and the chassis ground lug.I know today they would be taken directly to the ground lug, but who knows what they were thinking 30 years ago. Ron / WB4HFN -Original Message- From:drakelist-boun...@zerobeat.net [mailto:drakelist-boun...@zerobeat.net] On Behalf Of Garey Barrell Sent: Friday, February 04, 2011 3:36 PM To: drakelist Subject: Re: [Drakelist] L-75 question Evan - OK, I see them. I can't figure out what they were thinking. There doesn't appear to be any reason for that, unless the new capacitor leads weren't long enough to reach the ground lug. Anyway, that's my guess and I'm sticking to it! :-) 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 www.k4oah.com K9sqg wrote: Garey, These are C34 and C36. They are 700 pf disc ceramic. 73, Evan -Original Message- From: Garey Barrellk4...@mindspring.com To: K9sqgk9...@aol.com Sent: Fri, Feb 4, 2011 12:47 pm Subject: Re: [Drakelist] L-75 question Evan - What are the two caps you are referring to? 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 www.k4oah.com http://www.k4oah.com K9sqg wrote: Fellow enthusiasts, Have a question about S2C in the L-75 linear, it is the wafer switch controlled by the lever on the front panel for use on 160 and 80 meters. The two switchable load capacitors are located from some terminals with one end of each cap going to a common terminal on the switch, and then a lead from there to ground. However, that common terminal is not connected electrically to any part of the circuit. Was just curious as to why the ground side of each cap is connected to an unused terminal when in fact there is a ground lug very close to that switch that could be used for the ground termination. I'm going to be replacing those caps and plan on using the ground lug rather than that electrically isolated switch terminal. But then, am I missing something here? I'm sure Drake had a reason for doing what they did, but I can't figure out what it is. At one time I thought that maybe it would be a simplified manufacturing process to mount the caps to the switch before
Re: [Drakelist] L-75 question
Ron - OK, I can accept that. I've never seen an L-75, so stuck with just the schematic. Joe Ham would probably yanked those cap leads out by the root if they were to try and drop the panel. The capacitor leads went to the switch tag, and then a lower inductance lead (and flexible) to ground the common. 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 www.k4oah.com Ron wrote: Well I took another look at my L75 which I have on the bench anyway. I think I figured out why the braid jumper and that wiring arrangement is the way it is. If you look down each side in the front, there are three screws on each side that hold the front chassis sub-panel, which the aluminum front is attached. If you remove the three screws down each side, that whole front assembly will fold out to gain easy access to the front area of the chassis along the bottom. That rotor switch is attached to the front subpanel along with the power switch.When that panel is folded out that long braided ground strap allows the panel to come out easily an inch or so. If the two capacitor were soldered directly to the chassis ground lug, pull out that front panel assemble would probably pull loose the wire lead from those two capacitors and damage them. I remembered that but it took a while. When you reach my age the thinking processor runs slow.I repaired an L75 a few years ago and was perturbed because it was almost impossible to get down inside the amp in the front. I found loosing and folding down the front assembly make it a whole lot easier to work on the amp in the front. Ron / WB4HFN -Original Message- From: drakelist-boun...@zerobeat.net [mailto:drakelist-boun...@zerobeat.net] On Behalf Of Garey Barrell Sent: Friday, February 04, 2011 4:14 PM To: drakelist Subject: Re: [Drakelist] L-75 question I'm still betting on supplied lead length of the original caps!! :-) Yes, RF current is likely the reason for the braid, but if the cap's leads reached there wouldn't be any more of a current problem. Yet another wild thought, perhaps the longer cap leads would have caused an inconvenient series resonance. Bottom line, it WAS DESIGNED intentionally by some pretty good engineers, and I would be reluctant to change it without proving I understood why it was done. It wouldn't have cost much to add that blank terminal to the switch wafer, probably less than special ordered caps with longer leads, but neither would have been done without a good reason. (Spoken by an RF engineer who has had to defend more than one 'crazy design decision'.) 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 www.k4oah.com Ron wrote: The only thing I can see is it may be an RF current issue, Both capacitors together may create a current carrying issue which is why Drake used a wire braid jumper from the common point and the chassis ground lug.I know today they would be taken directly to the ground lug, but who knows what they were thinking 30 years ago. Ron / WB4HFN -Original Message- From:drakelist-boun...@zerobeat.net [mailto:drakelist-boun...@zerobeat.net] On Behalf Of Garey Barrell Sent: Friday, February 04, 2011 3:36 PM To: drakelist Subject: Re: [Drakelist] L-75 question Evan - OK, I see them. I can't figure out what they were thinking. There doesn't appear to be any reason for that, unless the new capacitor leads weren't long enough to reach the ground lug. Anyway, that's my guess and I'm sticking to it! :-) 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 www.k4oah.com K9sqg wrote: Garey, These are C34 and C36. They are 700 pf disc ceramic. 73, Evan -Original Message- From: Garey Barrellk4...@mindspring.com To: K9sqgk9...@aol.com Sent: Fri, Feb 4, 2011 12:47 pm Subject: Re: [Drakelist] L-75 question Evan - What are the two caps you are referring to? 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 CDswww.k4oah.comhttp://www.k4oah.com K9sqg wrote: Fellow enthusiasts, Have a question about S2C in the L-75 linear, it is the wafer switch controlled by the lever on the front panel for use on 160 and 80 meters. The two switchable load capacitors are located from some terminals with one end of each cap going to a common terminal on the switch, and then a lead from there to ground. However, that common terminal is not connected electrically to any part of the circuit. Was just curious as to why the ground side of each cap is connected to an unused terminal when in fact there is a ground lug
[Drakelist] Repair R-4A
Who would anyone suggest to repair/restore the R-4A if I don't have the time or expertise? ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
