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{{TM500 | type=AM503 | mfg=Tektronix | function=current probe amplifier | class=amplifier | image= | {{TM500 | type=AM503 | mfg=Tektronix | function=current probe amplifier | class=amplifier | image=Am503_front.jpg | introduced=1978 | discontinued=(?) | manuals= | ||
* [http://w140.com/smb/AM503_SM.pdf Tektronix AM503 Manual (OCR, PDF)] | * [http://w140.com/smb/AM503_SM.pdf Tektronix AM503 Manual (OCR, PDF)] | ||
* [http://w140.com/am503a_service.pdf Tektronix AM503A Manual (PDF)] (no schematics) | * [http://w140.com/am503a_service.pdf Tektronix AM503A Manual (PDF)] (no schematics) | ||
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The high frequency amplifier was differential to accommodate an oscilloscope’s differential input. | The high frequency amplifier was differential to accommodate an oscilloscope’s differential input. | ||
The last change was the output stage that was added to convert the differential circuit to single ended, and then output that to a front panel BNC. | The last change was the output stage that was added to convert the differential circuit to single ended, and then output that to a front panel BNC. | ||
<br | <br /> | ||
The AM503 was also intended to work with future higher frequency probes, like the [[P6022]] with an added hall device for DC measurements. | The AM503 was also intended to work with future higher frequency probes, like the [[P6022]] with an added hall device for DC measurements. | ||
The smaller P6022 had a 120 MHz bandwidth, whereas the [[P6302]] was only 50 MHz. | The smaller P6022 had a 120 MHz bandwidth, whereas the [[P6302]] was only 50 MHz. | ||
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The AM503 was one of the first plug-ins for the TM500 line of products. | The AM503 was one of the first plug-ins for the TM500 line of products. | ||
It required more power than the current plug-in designs so the transformer and supply were changed in the TM500 frames early on just for the AM503. | It required more power than the current plug-in designs so the transformer and supply were changed in the TM500 frames early on just for the AM503. | ||
<br | <br /> | ||
There were some innovations that were incorporated in this design: | There were some innovations that were incorporated in this design: | ||
The [[cam switch]] with replaceable laser trimmed attenuator resistors, a 1 GHz Gilbert cell op amp (actually developed by Howard Jones in 1963). | The [[cam switch]] with replaceable laser trimmed attenuator resistors, a 1 GHz Gilbert cell op amp (actually developed by Howard Jones in 1963). | ||
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The [[Peltola connector]], developed by Tek’s Ron Peltola, a very low cost connector that worked well, even for the highest frequencies. | The [[Peltola connector]], developed by Tek’s Ron Peltola, a very low cost connector that worked well, even for the highest frequencies. | ||
A BNC was adapted to be used with the Peltola and is used on the front panel. | A BNC was adapted to be used with the Peltola and is used on the front panel. | ||
<br | <br /> | ||
A large section of the AM503 was basically duplicating the front end of an oscilloscope since that was the original design intent, | A large section of the AM503 was basically duplicating the front end of an oscilloscope since that was the original design intent, | ||
so it was thought later that the differential amp section could be eliminated and the amplifier made much smaller and even become part of a standalone probe. | so it was thought later that the differential amp section could be eliminated and the amplifier made much smaller and even become part of a standalone probe. | ||
A prototype was created (author’s senior project at the University of Portland) but shelved, as there was no longer an engineer in Accessories for current probes. | A prototype was created (author’s senior project at the University of Portland) but shelved, as there was no longer an engineer in Accessories for current probes. | ||
Much later it gave rise to the TCP series of stand-alone current probes. | Much later it gave rise to the TCP series of stand-alone current probes. | ||
<br | <br /> | ||
The [[P6302]] and [[P6303]] probes utilized a Hall device that was manufactured in the clean room of the Accessories Manufacturing group. | The [[P6302]] and [[P6303]] probes utilized a Hall device that was manufactured in the clean room of the Accessories Manufacturing group. | ||
It was deposited onto a bar of ferrite that was later assembled into a U shape with other ferrite and potted in a mu-metal can along with the transformer bobbins. | It was deposited onto a bar of ferrite that was later assembled into a U shape with other ferrite and potted in a mu-metal can along with the transformer bobbins. | ||
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The cores were lapped and polished to a few Fresnel lines flatness to minimize the gap on the sliding ferrite. | The cores were lapped and polished to a few Fresnel lines flatness to minimize the gap on the sliding ferrite. | ||
The L/R time constant affects the point where the Hall device and coils’ bandwidths crossover. | The L/R time constant affects the point where the Hall device and coils’ bandwidths crossover. | ||
<br | <br /> | ||
An interesting aspect of the design was trying to find a way to test and calibrate the peak current pulse on the larger P6303. | An interesting aspect of the design was trying to find a way to test and calibrate the peak current pulse on the larger P6303. | ||
Luckily we had the tube lab. We developed an argon filled thyratron that could discharge a 4 kV charge line into a 4 Ω load. | Luckily we had the tube lab. We developed an argon filled thyratron that could discharge a 4 kV charge line into a 4 Ω load. | ||
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The 4 kV supply was charged into a 4 Ω transmission line so a clean high current pulse would be generated. | The 4 kV supply was charged into a 4 Ω transmission line so a clean high current pulse would be generated. | ||
This concept was taken from Tek’s [[109]] pulse generator. | This concept was taken from Tek’s [[109]] pulse generator. | ||
<br /> | |||
A trigger circuit was designed to fire the grid. It was based on the xenon flash circuit of the [[C-5|C5 camera]] flash, also in the Accessories group. | A trigger circuit was designed to fire the grid. It was based on the xenon flash circuit of the [[C-5|C5 camera]] flash, also in the Accessories group. | ||
The first prototype I made arced across the laser trim lines in the metal film resistor as they were cut perpendicular to the current flow. | The first prototype I made arced across the laser trim lines in the metal film resistor as they were cut perpendicular to the current flow. | ||
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We changed the laser trim to be parallel to the current path along the outside edges. | We changed the laser trim to be parallel to the current path along the outside edges. | ||
That’s what was used in manufacturing for calibrating the risetime of the P6303. | That’s what was used in manufacturing for calibrating the risetime of the P6303. | ||
<br | <br /> | ||
Also interesting, the P6303 required special potting epoxy developed by 3M. | Also interesting, the P6303 required special potting epoxy developed by 3M. | ||
The epoxy used in other current probes put excessive stress on the larger ferrite that caused the inductance to drop to zero. | The epoxy used in other current probes put excessive stress on the larger ferrite that caused the inductance to drop to zero. | ||
due to the magnetostriction property of ferrite. | due to the magnetostriction property of ferrite. The epoxy could even also cause shear fractures in the ferrite. | ||
The epoxy could even also cause shear fractures in the ferrite. | |||
</blockquote> | </blockquote> | ||
==Pictures== | ==Pictures== | ||
====AM503==== | |||
<gallery> | <gallery> | ||
Tek am503.jpg| | Am503_front.jpg | AM503 front | ||
Am503_left.jpg | AM503 left side | |||
Am503_right.jpg | AM503 right side | |||
Tek am503.jpg | AM503 | |||
Tek am503 t1.jpg | AM503 | Tek am503 t1.jpg | AM503 | ||
Tek am503a.jpg| | Tek am503 t2.jpg | AM503 feeding a [[TDS744|TDS744A]] | ||
Tek am503b.jpg| | </gallery> | ||
====AM503A==== | |||
<gallery> | |||
Tek am503a.jpg| AM503A | |||
</gallery> | |||
====AM503B==== | |||
<gallery> | |||
Tek am503b.jpg | AM503B | |||
Tek am503b tm502a 1.jpg| Two AM503B in a [[TM502A]] | Tek am503b tm502a 1.jpg| Two AM503B in a [[TM502A]] | ||
Tek am503b rear.jpg | Rear view of two AM503B plug-ins | |||
Tek am503b rear.jpg|Rear view of two AM503B plug-ins | |||
</gallery> | </gallery> | ||