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#1
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EICO HF12 amplifier component
Hi, Vacuumlanders,
This is a long shot... I'm refurbishing an EICO HF12 integrated amplifier (it is working.) Part of the pre-amp contains a wax- covered, so-called "printed circuit" component with 7 pins, about one inch square. EICO Stock No. 29751. Name: PC1 It has the treble and bass controls connected to it. It's looks a bit like those multi-pinned wax components in some AA5 radios at the detector/AVC/audio stage (I invariably replace these with the generic circuit at the back of the RCA tube manual.) Does anyone have the internal schematic of this thing in the EICO? I've replaced all the wax caps. As a wax item, I'd replace it, too, with new discrete parts if I knew what they were. Thanks and cheers, Roger |
#2
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EICO HF12 amplifier component
On Saturday, March 10, 2012 4:00:05 PM UTC-5, Roger Jones wrote:
Hi, Vacuumlanders, This is a long shot... I'm refurbishing an EICO HF12 integrated amplifier (it is working.) Part of the pre-amp contains a wax- covered, so-called "printed circuit" component with 7 pins, about one inch square. EICO Stock No. 29751. Name: PC1 It has the treble and bass controls connected to it. It's looks a bit like those multi-pinned wax components in some AA5 radios at the detector/AVC/audio stage (I invariably replace these with the generic circuit at the back of the RCA tube manual.) Does anyone have the internal schematic of this thing in the EICO? I've replaced all the wax caps. As a wax item, I'd replace it, too, with new discrete parts if I knew what they were. Thanks and cheers, Roger That is what it is : the actual OEM is Centralab PC-191. Pins : 1-2=100K . 2-3=4700pF . 3-4=120k + 330pF . 4-5=1k + 330pF . 3-6=4700pF . 6-7=100K . It is a small project . |
#3
Posted to rec.audio.tubes
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EICO HF12 amplifier component
On Mar 11, 3:03*am, wrote:
On Saturday, March 10, 2012 4:00:05 PM UTC-5, Roger Jones wrote: Hi, Vacuumlanders, This is a long shot... I'm refurbishing an EICO HF12 integrated amplifier (it is working.) *Part of the pre-amp contains a wax- covered, so-called "printed circuit" component with 7 pins, about one inch square. EICO Stock No. 29751. *Name: PC1 It has the treble and bass controls connected to it. It's looks a bit like those multi-pinned wax components in some AA5 radios at the detector/AVC/audio stage (I invariably replace these with the generic circuit at the back of the RCA tube manual.) Does anyone have the internal schematic of this thing in the EICO? I've replaced all the wax caps. As a wax item, I'd replace it, too, with new discrete parts if I knew what they were. Thanks and cheers, Roger * *That is what it is : the actual OEM is Centralab PC-191. Pins : *1-2=100K . 2-3=4700pF . 3-4=120k + 330pF . 4-5=1k + 330pF . 3-6=4700pF . 6-7=100K . It is a small project . Many thanks. I'll sketch it out to see what the overall TC schematic is before doing any replacement with discrete components. At this time the TC's work correctly, so I have to presume this thing is OK. Thanks again for the sleuthing. I googled a few things could not find anything! Cheers, Roger PS. For general interest, here's what I've done so far on the EICO HF12: Tested all tubes: 12AX7's all at least "good", but not "good+"... left them all in. Replaced both EL84's, aka 6BQ5's, now semi-matched for current (before, one was dead... it had +1.2 VDC on g1 from leaky coupling cap. Other had about +10 mVDC on g1, OK.) Did not add a current balancing pot as close enough for now. Replaced coupling caps to all tube g1's (they were wax and paper types.) Both 6BQ5 g1's now at about +5 mVDC, OK. Replaced 6BQ5 single 165 ohm cathode bias resistor with two matched 330 ohm WW's, each bypassed by 100 uF. I left the hum pot slider on one of them (gives about +11 VDC on all heaters to reduce hum.) Moved both 6BQ5 screen supplies from EZ81 cathode (highest B+, was more than the plates after OPT secondary DC voltage loss) to one filter section down on the B+ filter after the original 10K resistor. Replaced this 10K with 4.7K WW to get most of the voltage back. Added extra 20 uF (to hand) after this 4.7K to get better B+ filtering with the now lower series R value. Other B+ filter caps left "as is" - they seem OK now reformed. Replaced all wax and paper capacitors with modern caps (on subsequent test all paper caps were above stated capacity, some by a large amount.) Replaced first B+ filter cap with new 20 uF, 450 volts (precautionary only, but ESR of original not known and I can't test it!) Added 100 ohm WW to cathode of EZ81 before new first filter cap to cut ripple current and slightly improve filtering. B+ now about 10 VDC low from original value and final pre-amp B+ about 2 VDC low (with 117 VAC in.) Cleaned all pots and switches with Deoxit D5 (VC was very noisy, now OK.) Hope this helps... |
#4
Posted to rec.audio.tubes
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EICO HF12 amplifier component
In article ,
Roger Jones wrote: On Mar 11, 3:03*am, wrote: On Saturday, March 10, 2012 4:00:05 PM UTC-5, Roger Jones wrote: Hi, Vacuumlanders, This is a long shot... I'm refurbishing an EICO HF12 integrated amplifier (it is working.) *Part of the pre-amp contains a wax- covered, so-called "printed circuit" component with 7 pins, about one inch square. EICO Stock No. 29751. *Name: PC1 It has the treble and bass controls connected to it. It's looks a bit like those multi-pinned wax components in some AA5 radios at the detector/AVC/audio stage (I invariably replace these with the generic circuit at the back of the RCA tube manual.) Does anyone have the internal schematic of this thing in the EICO? I've replaced all the wax caps. As a wax item, I'd replace it, too, with new discrete parts if I knew what they were. Thanks and cheers, Roger * *That is what it is : the actual OEM is Centralab PC-191. Pins : *1-2=100K . 2-3=4700pF . 3-4=120k + 330pF . 4-5=1k + 330pF . 3-6=4700pF . 6-7=100K . It is a small project . Many thanks. I'll sketch it out to see what the overall TC schematic is before doing any replacement with discrete components. At this time the TC's work correctly, so I have to presume this thing is OK. Thanks again for the sleuthing. I googled a few things could not find anything! Cheers, Roger PS. For general interest, here's what I've done so far on the EICO HF12: Tested all tubes: 12AX7's all at least "good", but not "good+"... left them all in. Replaced both EL84's, aka 6BQ5's, now semi-matched for current (before, one was dead... it had +1.2 VDC on g1 from leaky coupling cap. Other had about +10 mVDC on g1, OK.) Did not add a current balancing pot as close enough for now. Replaced coupling caps to all tube g1's (they were wax and paper types.) Both 6BQ5 g1's now at about +5 mVDC, OK. Replaced 6BQ5 single 165 ohm cathode bias resistor with two matched 330 ohm WW's, each bypassed by 100 uF. I left the hum pot slider on one of them (gives about +11 VDC on all heaters to reduce hum.) Moved both 6BQ5 screen supplies from EZ81 cathode (highest B+, was more than the plates after OPT secondary DC voltage loss) to one filter section down on the B+ filter after the original 10K resistor. Replaced this 10K with 4.7K WW to get most of the voltage back. Added extra 20 uF (to hand) after this 4.7K to get better B+ filtering with the now lower series R value. Other B+ filter caps left "as is" - they seem OK now reformed. Replaced all wax and paper capacitors with modern caps (on subsequent test all paper caps were above stated capacity, some by a large amount.) Replaced first B+ filter cap with new 20 uF, 450 volts (precautionary only, but ESR of original not known and I can't test it!) Added 100 ohm WW to cathode of EZ81 before new first filter cap to cut ripple current and slightly improve filtering. B+ now about 10 VDC low from original value and final pre-amp B+ about 2 VDC low (with 117 VAC in.) Cleaned all pots and switches with Deoxit D5 (VC was very noisy, now OK.) Hope this helps... Here is another take on what is inside the PC-191 that I eviscerated from the schematic of another EICO amp. http://fmamradios.com/stuff/PC-191.gif Note that the connection to pin 5 is different than the one described in the previous response. I suspect that wiring it as in the previous description will cause the tone controls to function in an aberrant way! -- Regards, John Byrns Surf my web pages at, http://fmamradios.com/ |
#5
Posted to rec.audio.tubes
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EICO HF12 amplifier component
On Mar 11, 2:03*pm, John Byrns wrote:
In article , *Roger Jones wrote: On Mar 11, 3:03*am, wrote: On Saturday, March 10, 2012 4:00:05 PM UTC-5, Roger Jones wrote: Hi, Vacuumlanders, This is a long shot... I'm refurbishing an EICO HF12 integrated amplifier (it is working.) *Part of the pre-amp contains a wax- covered, so-called "printed circuit" component with 7 pins, about one inch square. EICO Stock No. 29751. *Name: PC1 It has the treble and bass controls connected to it. It's looks a bit like those multi-pinned wax components in some AA5 radios at the detector/AVC/audio stage (I invariably replace these with the generic circuit at the back of the RCA tube manual.) Does anyone have the internal schematic of this thing in the EICO? I've replaced all the wax caps. As a wax item, I'd replace it, too, with new discrete parts if I knew what they were. Thanks and cheers, Roger * *That is what it is : the actual OEM is Centralab PC-191. Pins : *1-2=100K . 2-3=4700pF . 3-4=120k + 330pF . 4-5=1k + 330pF .. 3-6=4700pF . 6-7=100K . It is a small project . Many thanks. *I'll sketch it out to see what the overall TC schematic is before doing any replacement with discrete components. *At this time the TC's work correctly, so I have to presume this thing is OK. Thanks again for the sleuthing. *I googled a few things could not find anything! Cheers, Roger PS. *For general interest, here's what I've done so far on the EICO HF12: Tested all tubes: 12AX7's all at least "good", but not "good+"... left them all in. Replaced both EL84's, aka 6BQ5's, now semi-matched for current (before, one was dead... it had +1.2 VDC on g1 from leaky coupling cap. *Other had about +10 mVDC on g1, OK.) Did not add a current balancing pot as close enough for now. Replaced coupling caps to all tube g1's (they were wax and paper types.) *Both 6BQ5 g1's now at about +5 mVDC, OK. Replaced 6BQ5 single 165 ohm cathode bias resistor with two matched 330 ohm WW's, each bypassed by 100 uF. I left the hum pot slider on one of them (gives about +11 VDC on all heaters to reduce hum.) Moved both 6BQ5 screen supplies from EZ81 cathode (highest B+, was more than the plates after OPT secondary DC voltage loss) to one filter section down on the B+ filter after the original 10K resistor. Replaced this 10K with 4.7K WW to get most of the voltage back. Added extra 20 uF (to hand) after this 4.7K to get better B+ filtering with the now lower series R value. *Other B+ filter caps left "as is" - they seem OK now reformed. Replaced all wax and paper capacitors with modern caps (on subsequent test all paper caps were above stated capacity, some by a large amount.) Replaced first B+ filter cap with new 20 uF, 450 volts (precautionary only, but ESR of original not known and I can't test it!) Added 100 ohm WW to cathode of EZ81 before new first filter cap to cut ripple current and slightly improve filtering. *B+ now about 10 VDC low from original value and final pre-amp B+ about 2 VDC low (with 117 VAC in.) Cleaned all pots and switches with Deoxit D5 (VC was very noisy, now OK.) Hope this helps... Here is another take on what is inside the PC-191 that I eviscerated from the schematic of another EICO amp. http://fmamradios.com/stuff/PC-191.gif Note that the connection to pin 5 is different than the one described in the previous response. *I suspect that wiring it as in the previous description will cause the tone controls to function in an aberrant way! -- Regards, John Byrns Surf my web pages at, *http://fmamradios.com/ Hi, John, The linked schematic is different from the EICO HF12 "printed circuit" as mine has NO TAP on the treble pot and NO 1200 mmF cap across the bass pot. Thus, the first one may make more sense (but not reverse engineered yet.) Cheers, Roger |
#6
Posted to rec.audio.tubes
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EICO HF12 amplifier component
"Roger Jones" wrote in message ... On Mar 11, 2:03 pm, John Byrns wrote: In article , Roger Jones wrote: On Mar 11, 3:03 am, wrote: On Saturday, March 10, 2012 4:00:05 PM UTC-5, Roger Jones wrote: Hi, Vacuumlanders, This is a long shot... I'm refurbishing an EICO HF12 integrated amplifier (it is working.) Part of the pre-amp contains a wax- covered, so-called "printed circuit" component with 7 pins, about one inch square. EICO Stock No. 29751. Name: PC1 It has the treble and bass controls connected to it. It's looks a bit like those multi-pinned wax components in some AA5 radios at the detector/AVC/audio stage (I invariably replace these with the generic circuit at the back of the RCA tube manual.) Does anyone have the internal schematic of this thing in the EICO? I've replaced all the wax caps. As a wax item, I'd replace it, too, with new discrete parts if I knew what they were. Thanks and cheers, Roger That is what it is : the actual OEM is Centralab PC-191. Pins : 1-2=100K . 2-3=4700pF . 3-4=120k + 330pF . 4-5=1k + 330pF . 3-6=4700pF . 6-7=100K . It is a small project . Many thanks. I'll sketch it out to see what the overall TC schematic is before doing any replacement with discrete components. At this time the TC's work correctly, so I have to presume this thing is OK. Thanks again for the sleuthing. I googled a few things could not find anything! Cheers, Roger PS. For general interest, here's what I've done so far on the EICO HF12: Tested all tubes: 12AX7's all at least "good", but not "good+"... left them all in. Replaced both EL84's, aka 6BQ5's, now semi-matched for current (before, one was dead... it had +1.2 VDC on g1 from leaky coupling cap. Other had about +10 mVDC on g1, OK.) Did not add a current balancing pot as close enough for now. Replaced coupling caps to all tube g1's (they were wax and paper types.) Both 6BQ5 g1's now at about +5 mVDC, OK. Replaced 6BQ5 single 165 ohm cathode bias resistor with two matched 330 ohm WW's, each bypassed by 100 uF. I left the hum pot slider on one of them (gives about +11 VDC on all heaters to reduce hum.) Moved both 6BQ5 screen supplies from EZ81 cathode (highest B+, was more than the plates after OPT secondary DC voltage loss) to one filter section down on the B+ filter after the original 10K resistor. Replaced this 10K with 4.7K WW to get most of the voltage back. Added extra 20 uF (to hand) after this 4.7K to get better B+ filtering with the now lower series R value. Other B+ filter caps left "as is" - they seem OK now reformed. Replaced all wax and paper capacitors with modern caps (on subsequent test all paper caps were above stated capacity, some by a large amount.) Replaced first B+ filter cap with new 20 uF, 450 volts (precautionary only, but ESR of original not known and I can't test it!) Added 100 ohm WW to cathode of EZ81 before new first filter cap to cut ripple current and slightly improve filtering. B+ now about 10 VDC low from original value and final pre-amp B+ about 2 VDC low (with 117 VAC in.) Cleaned all pots and switches with Deoxit D5 (VC was very noisy, now OK.) Hope this helps... Here is another take on what is inside the PC-191 that I eviscerated from the schematic of another EICO amp. http://fmamradios.com/stuff/PC-191.gif Note that the connection to pin 5 is different than the one described in the previous response. I suspect that wiring it as in the previous description will cause the tone controls to function in an aberrant way! -- Regards, John Byrns Surf my web pages at, http://fmamradios.com/ Hi, John, The linked schematic is different from the EICO HF12 "printed circuit" as mine has NO TAP on the treble pot and NO 1200 mmF cap across the bass pot. Thus, the first one may make more sense (but not reverse engineered yet.) Cheers, Roger --------------------------------------------------------------------------------------------------------- Interesting thread. Here are a few more links. The Triode Electronics ST40 schematic is similar to the ST12- no tap on the treble control. At first glance, the difference between this one and John's link is the 1K resistor in the leg of pin 5; otherwise the PC-191 circuit looks the same but he surrounding circuit different. The other link is to a forum that discusses a PC-191 (29751) in an ST40. http://www.triodeel.com/images/eicost40.pdf http://www.audiokarma.org/forums/arc.../t-314550.html BR's, Mark |
#7
Posted to rec.audio.tubes
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EICO HF12 amplifier component
On Sunday, March 11, 2012 2:03:01 PM UTC-4, John Byrns wrote:
In article , Roger Jones wrote: On Mar 11, 3:03*am, wrote: On Saturday, March 10, 2012 4:00:05 PM UTC-5, Roger Jones wrote: Hi, Vacuumlanders, This is a long shot... I'm refurbishing an EICO HF12 integrated amplifier (it is working.) *Part of the pre-amp contains a wax- covered, so-called "printed circuit" component with 7 pins, about one inch square. EICO Stock No. 29751. *Name: PC1 It has the treble and bass controls connected to it. It's looks a bit like those multi-pinned wax components in some AA5 radios at the detector/AVC/audio stage (I invariably replace these with the generic circuit at the back of the RCA tube manual.) Does anyone have the internal schematic of this thing in the EICO? I've replaced all the wax caps. As a wax item, I'd replace it, too, with new discrete parts if I knew what they were. Thanks and cheers, Roger * *That is what it is : the actual OEM is Centralab PC-191. Pins : *1-2=100K . 2-3=4700pF . 3-4=120k + 330pF . 4-5=1k + 330pF .. 3-6=4700pF . 6-7=100K . It is a small project . Many thanks. I'll sketch it out to see what the overall TC schematic is before doing any replacement with discrete components. At this time the TC's work correctly, so I have to presume this thing is OK. Thanks again for the sleuthing. I googled a few things could not find anything! Cheers, Roger PS. For general interest, here's what I've done so far on the EICO HF12: Tested all tubes: 12AX7's all at least "good", but not "good+"... left them all in. Replaced both EL84's, aka 6BQ5's, now semi-matched for current (before, one was dead... it had +1.2 VDC on g1 from leaky coupling cap. Other had about +10 mVDC on g1, OK.) Did not add a current balancing pot as close enough for now. Replaced coupling caps to all tube g1's (they were wax and paper types.) Both 6BQ5 g1's now at about +5 mVDC, OK. Replaced 6BQ5 single 165 ohm cathode bias resistor with two matched 330 ohm WW's, each bypassed by 100 uF. I left the hum pot slider on one of them (gives about +11 VDC on all heaters to reduce hum.) Moved both 6BQ5 screen supplies from EZ81 cathode (highest B+, was more than the plates after OPT secondary DC voltage loss) to one filter section down on the B+ filter after the original 10K resistor. Replaced this 10K with 4.7K WW to get most of the voltage back. Added extra 20 uF (to hand) after this 4.7K to get better B+ filtering with the now lower series R value. Other B+ filter caps left "as is" - they seem OK now reformed. Replaced all wax and paper capacitors with modern caps (on subsequent test all paper caps were above stated capacity, some by a large amount.) Replaced first B+ filter cap with new 20 uF, 450 volts (precautionary only, but ESR of original not known and I can't test it!) Added 100 ohm WW to cathode of EZ81 before new first filter cap to cut ripple current and slightly improve filtering. B+ now about 10 VDC low from original value and final pre-amp B+ about 2 VDC low (with 117 VAC in.) Cleaned all pots and switches with Deoxit D5 (VC was very noisy, now OK.) Hope this helps... Here is another take on what is inside the PC-191 that I eviscerated from the schematic of another EICO amp. http://fmamradios.com/stuff/PC-191.gif Note that the connection to pin 5 is different than the one described in the previous response. I suspect that wiring it as in the previous description will cause the tone controls to function in an aberrant way! -- Regards, John Byrns Surf my web pages at, http://fmamradios.com/ Absolutely. A picture is worth a 1000 words ! In general,that is... |
#8
Posted to rec.audio.tubes
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EICO HF12 amplifier component
On Mar 11, 6:24*pm, "MarkS" wrote:
"Roger Jones" *wrote in message ... On Mar 11, 2:03 pm, John Byrns wrote: In article , *Roger Jones wrote: On Mar 11, 3:03 am, wrote: On Saturday, March 10, 2012 4:00:05 PM UTC-5, Roger Jones wrote: Hi, Vacuumlanders, This is a long shot... I'm refurbishing an EICO HF12 integrated amplifier (it is working.) Part of the pre-amp contains a wax- covered, so-called "printed circuit" component with 7 pins, about one inch square. EICO Stock No. 29751. *Name: PC1 It has the treble and bass controls connected to it. It's looks a bit like those multi-pinned wax components in some AA5 radios at the detector/AVC/audio stage (I invariably replace these with the generic circuit at the back of the RCA tube manual.) Does anyone have the internal schematic of this thing in the EICO? I've replaced all the wax caps. As a wax item, I'd replace it, too, with new discrete parts if I knew what they were. Thanks and cheers, Roger * *That is what it is : the actual OEM is Centralab PC-191. Pins : *1-2=100K . 2-3=4700pF . 3-4=120k + 330pF . 4-5=1k + 330pF . 3-6=4700pF . 6-7=100K . It is a small project . Many thanks. *I'll sketch it out to see what the overall TC schematic is before doing any replacement with discrete components. *At this time the TC's work correctly, so I have to presume this thing is OK. Thanks again for the sleuthing. *I googled a few things could not find anything! Cheers, Roger PS. *For general interest, here's what I've done so far on the EICO HF12: Tested all tubes: 12AX7's all at least "good", but not "good+"... left them all in. Replaced both EL84's, aka 6BQ5's, now semi-matched for current (before, one was dead... it had +1.2 VDC on g1 from leaky coupling cap. *Other had about +10 mVDC on g1, OK.) Did not add a current balancing pot as close enough for now. Replaced coupling caps to all tube g1's (they were wax and paper types.) *Both 6BQ5 g1's now at about +5 mVDC, OK. Replaced 6BQ5 single 165 ohm cathode bias resistor with two matched 330 ohm WW's, each bypassed by 100 uF. I left the hum pot slider on one of them (gives about +11 VDC on all heaters to reduce hum.) Moved both 6BQ5 screen supplies from EZ81 cathode (highest B+, was more than the plates after OPT secondary DC voltage loss) to one filter section down on the B+ filter after the original 10K resistor. Replaced this 10K with 4.7K WW to get most of the voltage back. Added extra 20 uF (to hand) after this 4.7K to get better B+ filtering with the now lower series R value. *Other B+ filter caps left "as is" - they seem OK now reformed. Replaced all wax and paper capacitors with modern caps (on subsequent test all paper caps were above stated capacity, some by a large amount.) Replaced first B+ filter cap with new 20 uF, 450 volts (precautionary only, but ESR of original not known and I can't test it!) Added 100 ohm WW to cathode of EZ81 before new first filter cap to cut ripple current and slightly improve filtering. *B+ now about 10 VDC low from original value and final pre-amp B+ about 2 VDC low (with 117 VAC in.) Cleaned all pots and switches with Deoxit D5 (VC was very noisy, now OK.) Hope this helps... Here is another take on what is inside the PC-191 that I eviscerated from the schematic of another EICO amp. http://fmamradios.com/stuff/PC-191.gif Note that the connection to pin 5 is different than the one described in the previous response. *I suspect that wiring it as in the previous description will cause the tone controls to function in an aberrant way! -- Regards, John Byrns Surf my web pages at, *http://fmamradios.com/ Hi, John, The linked schematic is different from the EICO HF12 "printed circuit" as mine has NO TAP on the treble pot and NO 1200 mmF cap across the bass pot. Thus, the first one may make more sense (but not reverse engineered yet.) Cheers, Roger --------------------------------------------------------------------------------------------------------- Interesting thread. Here are a few more links. The Triode Electronics ST40 schematic is similar to the ST12- no tap on the treble control. At first glance, the difference between this one and John's link is the 1K resistor in the leg of pin 5; otherwise the PC-191 circuit looks the same but he surrounding circuit different. The other link is to a forum that discusses a PC-191 (29751) in an ST40. http://www.triodeel.com/images/eicost40.pdf http://www.audiokarma.org/forums/arc.../t-314550.html BR's, Mark Thanks, interesting stuff here... but which are the correct values? I'll do some more forensics! Cheers, Roger |
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