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CAPI 511_1-8-DB25 Back Panel
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BT50 Rev B Pictorial Build Guide HEADING_TITLE
MAKE SURE the build guide you follow matches the Revision of the PCB you are building!

Table of Contents
1. Information, Documents & Downloads
2. Parts Identification
    A. Main PCB
    B. LC~MC~HC Capacitors
    C. Other Parts

3. Main PCB Build
4. Mid-Band PCB Build
5. Switch PCB Build
6. Final Assembly
7. Copyright Notice and Disclaimer
 
1. Information, Documents & Downloads Back to Top
Preface
    The BT50 Rev B Pictorial Build Guide is written with the experienced builder in mind. Basic soldering and assembly skills are not covered here. Neither are basic resistor or capacitor sorting and identifying. Those skills are required and expected before attempting this build. I do not recommend this as a first build project. One of the simpler single stage preamps is a better place to start.

BOMs (Bill Of Materials)
  BT50-Main Rev B PCB BOM  [Last upload 11/20/2016]
  BT50-Mid Rev B BOM  [Last upload 11/20/2016]
  BT50-SW Rev A PCB BOM  [Last upload 11/20/2016]
  BT50 Hardware BOM  [Last upload 11/20/2016]

PCB Overlays
  Overlay_BT50-Main Rev B Top  [Last upload 11/20/2016]
  Overlay_BT50-Main Rev B Bottom  [Last upload 11/20/2016]
  Overlay_BT50-Mid Rev B  [Last upload 11/20/2016]
  Overlay_BT50-SW Rev A  [Last upload 11/20/2016]

Support Thread
  BT50 Rev B [Build] support thread at groupdiy.com
 
2.A Parts Identification - Main PCB Back to Top
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2.A.0 The follow parts can be found in the Main PCB bag.
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2.A.1 Fairchild 1N914 diode, label is "91 4B"
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2.A.2 Fairchild 1N4004 diode, label is "1N4004"
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2.A.3 Fairchild TIS97 transistor, label is "TIS97"
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2.A.4 Fairchild 2N5087 transistor, label is "2N 5087"
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2.A.5 Fairchild J111 transistor, label is "J111"
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2.A.6 BC 10pF ceramic capacitor, label is "BC 10J"
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2.A.7 BC 47pF ceramic capacitor, label is "BC 47J"
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2.A.8 Nichicon .0047μF film capacitor, label is "472J"
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2.A.9 Nichicon .027μF film capacitor, label is "273J"
 
2.B Parts Identification - LC~MC~HC Capacitors Back to Top
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2.B.0 The follow capacitors can be found in the LC~MC~HC Capacitors bag.
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2.B.1 Nichicon .0012μF film capacitor, label is "122J"
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2.B.2 Nichicon .0015μF film capacitor, label is "152J"
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2.B.3 Nichicon .0022μF film capacitor, label is "222J"
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2.B.4 Nichicon .0033μF film capacitor, label is "332J"
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2.B.5 Nichicon .0039μF film capacitor, label is "392J"
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2.B.6 Nichicon .0047μF film capacitor, label is "472J"
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2.B.7 Nichicon .0056μF film capacitor, label is "562J"
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2.B.8 Nichicon .0082μF film capacitor, label is "822J"
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2.B.9 Nichicon .015μF film capacitor, label is "153J"
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2.B.10 Nichicon .027μF film capacitor, label is "273J"
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2.B.11 Nichicon .039μF film capacitor, label is "393J"
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2.B.12 EPCOS / TDK .01μF film capacitor, label is "10nJ100"
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2.B.13 EPCOS / TDK .015μF film capacitor, label is "15nJ100"
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2.B.14 EPCOS / TDK .022μF film capacitor, label is "22nJ100"
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2.B.15 EPCOS / TDK .039μF film capacitor, label is "39nJ100"
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2.B.16 EPCOS / TDK .068μF film capacitor, label is "68nJ100"
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2.B.17 EPCOS / TDK .082μF film capacitor, label is "82nJ100"
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2.B.18 EPCOS / TDK .33μF film capacitor, label is "μ33J63"
 
2.C Parts Identification - Other Parts Back to Top
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2.C.0 Contains all parts for the switch PCB excluding the Toneluck pushbutton switches.
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2.C.1 Contains the hardware bag, header bag, all small format switches and CAPI® control knobs.
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2.C.2 Hardware bag.
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2.C.3 Hardware bag contents.
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2.C.4 Header bag.
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2.C.5 Header bag contents.
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2.C.6 Inserts and switch caps bag.
 
3. Main PCB Build Back to Top
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3.0 And we begin with a blank canvas.
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3.1 Identify and install the small package diodes. The silkscreen shows resistor labels but these are actually 1N914 diodes. The black-banded cathode ends MUST go in the direction shown in the pic.
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3.2 Locate and install all of the 10Ω power damping R's designated with PR.
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3.3 Identify and install all 1% .25W R's for the Main section of the PCB.
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3.4 Identify and install all LR's for the Low Freq and HR's for the Hi Freq section of the PCB.
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3.5 Install the large package diodes and the .5W resistor. Save a cutoff lead from a diode for the next step.
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3.6 Bend the saved lead from step 5 over a small screwdriver tip and solder into the GND position. This is the preferred probe hook location for testing.
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3.7 Identify and install the small package ceramic capacitors.

**Please note: OC1 and OC2 are NOT used!!
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3.8 Identify and install the main section film caps C3, C4 and C12.
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3.9 Identify and install the Low Freq film caps LC1 thru LC4.
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3.10 Identify and install the Low Freq film caps LC5 thru LC7.
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3.11 Identify and install the Low Freq film caps LC9 thru LC16.
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3.12 Identify and install the Low Freq film caps LC17 and LC18.
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3.13 Identify and install the Hi Freq film caps HC1, HC4, HC5 and HC6.
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3.14 Identify and install the Hi Freq film caps HC7, HC10, HC11 and HC12.
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3.15 Identify and install the Hi Freq film caps HC2, HC3, HC9 and HC14.
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3.16 Identify and install the Hi Freq film caps HC8, HC13, HC15, HC16 and HC17.
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3.17 Identify and install all electrolytic caps LC8, C1, C2, C6, C9 and C10.
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3.18 Install the opamp sockets for A1 and A2. These should be installed thru and only soldered at the bottom of the PCB. The solder seen at the top has leaked thru during the process.
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3.19 Identify and install the J111 FET's in OF1 and OF2. I alternate when soldering as to not overheat one of the parts.
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3.20 Identify and install the TIS97 transistors in Q1, Q3 and Q5. Alternate soldering as recommended for the FET's.
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3.21 Identify and install the 2N5087 transistors in Q2, Q4 and Q6. Again, alternate soldering is recommended.
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3.22a Solder only one pin of the 6-pin receptacle for J2.
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3.22b Make sure the body of the receptacle is perpendicular to the PCB and solder all remaining pins.
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3.23 Install the two 3-pin option headers and shunts for J4 and J5. Make sure they are perpendicular as mentioned above for J2. The grey shunts are shown in the preferred startup positions.
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3.24a Install the two C&K mini toggle switches from the bottom of the PCB by soldering only one pin first.
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3.24b Check to make sure they are seated parallel to the PCB.
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3.24c Solder the remaining pins.
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3.25a Carefully remove the black plastic protective covers from the 6-deck Grayhill switches.
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3.25b Start by slightly/partially inserting the pins at the shaft-end of the switch. Do not insert them all the way at this time.
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3.25c Due to manufacturing tolerances, the pins of the rear decks may be slightly off from the PCB holes. I have already cheated the hole pattern in the PCB beyond what the Grayhill spec sheet shows.
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3.25d Gently apply rearward pressure from the shaft end while simultaneously applying slight downward pressure. Great patience must be used. All of a sudden the switch will pop right into the holes.
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3.25e Solder two pins at the front and two pins at the rear of the switch.
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3.25f Double check the front and rear of the switch to make sure it is fully and evenly seated to the PCB. Adjust as required.
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3.25g Solder the remaining switch pins. I recommend an alternating pattern to not overheat the innards.
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3.26 Install the other 6-deck Grayhill switch.
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3.27 It is a necessity to inspect the switch pins with a magnifying glass. Be sure you have no solder bridges!!
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3.28 Install the 2503 style output transformer following the 2503 hardware guide. I used the Litz version for these builds so I had to alter the lead's color code placement. For the Litz version, you can use this pic as a reference or follow the chart on the bottom left of the datasheet. For a standard EA2503, just match the lead's colors to their respective holes.
 
4. Mid-Band PCB Build Back to Top
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4.0 And we again begin with a blank canvas.
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4.1 Identify and install the small package diode. The silkscreen shows a resistor label but its actually a 1N914 diode. The black-banded cathode end MUST go in the direction shown in the pic.
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4.2 Identify and install all resistors for the PCB.
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4.3a Identify and install all film caps. I do these all at once since the direction is the same and there's plenty of room to bend all of the leads.
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4.3b **Please note: OC1 is NOT used!!
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4.4 Identify and install the J111 FET in OF1.
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4.5a Install the 4-deck Grayhill switch using the same methods as described above. You will find this switch much easier due to there being one less deck for each section.
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4.5b Holding the switch during soldering can be tricky. Something like this makes the job easier.
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4.5c Or something like this.
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4.5d It is a necessity to inspect the switch pins with a magnifying glass. Be sure you have no solder bridges!!

4.6 DO NOT install the 6-pin gold header at this time! That will happen during the final assembly steps.
 
5. Switch PCB Build Back to Top
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5.0 And we again begin with the customary blank canvas.
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5.1 Install the lone resistor and capacitor.
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5.2a Start the install of the three 4PDT mini Toneluck pushbutton switches. Begin by soldering only 2 pins of each switch.
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5.2b Before soldering all of the pins, check that the switches are fully seated at the rear. Adjust as required.
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5.2c Also check that the fronts are fully seated. Adjust as required.
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5.2d Solder the remaining switch pins using an alternating order to not overheat the switch innards.
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5.2e Trim all of the pins for SW1. This is mandatory not optional. During final assembly these pins will interfere with caps on the main PCB if not trimmed.
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5.3 Install the pushbutton switch caps.
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5.4a Start the install of the 6-pin 90° header by soldering one of the pins. Check to make sure its seated properly.
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5.4b Solder the remaining header pins at the bottom of the PCB.
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5.5a Begin the install of the mounting hardware. Do not fully tighten at this time. Only finger tight.
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5.5b Secure the #616 Keystone brackets with 1/4" pan head screws, #4 lockwashers and 4/40 small pattern hex nuts.
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5.6a Locate the 3mm red LED and take note of the small spurs just below the body.
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5.6b Using needle nose pliers, take hold of the shorter cathode lead, lining up with the bottom edge of the spur.
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5.6c Bend the lead 90° downward.
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5.6d Take hold of the longer anode lead approximately .1" lower than where the cathode is bent.
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5.6e Bend anode lead downward so its parallel with the cathode lead.

4.6 DO NOT install the LED at this time! That will happen during the final assembly steps.
 
6. Final Assembly Back to Top
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6.1 Remove the nuts and lockwashers from the three Grayhill switches. Discard them as they are not used.
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6.2 Install the four standoffs to the L-bracket with 3/16" undercut flat head screws. I use a nut driver on the standoffs which typically works so well that a screwdriver is not needed.
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6.3 Install the 3/4" standoffs to the main PCB with 3/16" pan head screws and lockwashers. Tighten with a nut driver like above in step 6.2.
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6.4 Insert the 6-pin gold header into the J2 receptacle.
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6.5 Slip the mid-band PCB assembly over the 6-pin gold header and secure with 3/16" pan head screws and lockwashers. Lightly snug them but do not fully tighten yet.
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6.6 Insert the switch PCB assembly into position and secure with a 3/16" pan head screw and lockwasher. Lightly snug it but do not fully tighten yet.
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6.7 Insert the LED into the switch PCB and align with the center of the pushbutton switch caps. Clip the leads so they are 1/16" or a little more below the bottom of the PCB. This must be done now as there will be no access later without complete disassembly. DO NOT solder the LED at this time!
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6.8 Slip the entire assembly into position in the L-Bracket.
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6.9 Lightly snug the four pan head screws and lockwashers to the standoffs. DO NOT fully tighten at this time.
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6.10 Slip the #4 outside tooth lockwasher between the L-Bracket and Keystone bracket of the switch PCB. Install a 3/16" undercut flat head screw but DO NOT fully tighten at this time.
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6.11 Fully secure the flat head screw while tightly holding the Keystone bracket to the switch PCB with needle nose pliers. This will keep the Keystone bracket from turning and throwing the switch PCB out of alignment.
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6.12 Pinch the Low Freq Grayhill tight to the L-Bracket and fully tighten the front mounting screw.
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6.13 Pinch the Hi Freq Grayhill tight to the L-Bracket and fully tighten the front mounting screw.

6.14 Tighten both rear mounting screws.
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6.15 By design, the front mounting plate of the Grayhill switches will touch the L-Bracket while the PCB will be gapped away by .02".
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6.16 Slip faceplate into position making sure to guide LED as required.
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6.17 Finger tight snug knurled nuts onto HF and LF Grayhill switches. Make sure faceplate stays parallel to L-Bracket.
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6.18 Make sure both screws and lockwashers are slightly making contact with mid-band PCB but are still not fully tightened yet.
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6.19 Install and finger tight snug MF knurled nut.
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6.20 Fully tighten mounting screws to mid-band PCB.
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6.21 Check the three pushbutton switch caps for proper alignment in the faceplate. Make sure the switch PCB is not skewed or crooked and fully tighten the 3/16" screw from the bottom of the main PCB into the Keystone bracket.
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6.22 With a screwdriver and 3/16" wrench, tighten the hardware on the top Keystone bracket.
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6.23 Tighten the hardware on the lower Keystone bracket.
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6.24 Solder the six pins of the 90° header to the main PCB.
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6.25 Make sure the LED is fully seated to the faceplate and solder the leads to the top of the switch PCB.
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6.26 Use a screwdriver or similar to make sure the 6-pin gold header is tightly seated against the mid-band PCB.
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6.27 Solder the six pins.
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6.28 Trim the six pins.
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6.29 Using a needle nose pliers and something to protect the faceplate (I use a thin piece of cardboard), tighten all three knurled nuts.
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6.30 Using your needle nose pliers, turn each cut/boost shaft 5 clicks clockwise. The factory position is -12 so this will put them all to 0.
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6.31 Turn each frequency select shaft 2 clicks clockwise. This will put them to their respective center frequency.
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6.32 Locate and install the black knob inserts.
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6.33a Using a thin piece of cardboard or similar as a spacer, begin installing the blue frequency control knobs from the low band to hi band. The spacer is required to keep the knobs from dragging and rubbing on the faceplate.
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6.33b Something around .02" thick works perfectly.
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6.34a I recommend two layers of the .02" thick spacer under the clear cut/boost knobs.
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6.34b Install the knobs from the hi band to low band.
 
7. Copyright Notice and Disclaimer Back to Top
The contents of this assembly guide page, including but not limited to all text, photographs and diagrams, is the intellectual property of Classic Audio Products, Inc. Reproduction or re-publication by any means whatsoever, whether electronic, mechanical or electro-mechanical, is strictly prohibited under International Copyright laws. The sole purpose for this document is to aid in the assembly of the BT50 Rev B kit offered by Classic Audio Products, Inc. Commercial use is prohibited.
Classic Audio Products, Inc. is a DIY parts / kit retailer and provides no direct support for any of the products available on this site. Support for the kits can be found at the respective [Build] thread at groupdiy.com. Any support Classic Audio Products, Inc. chooses to provide, is provided "as is" without warranty of any kind. We cannot offer any guarantee as to the consequences of the support provided. Should the support cause damage or loss of any kind, Classic Audio Products, Inc. shall not be held liable to you or any other person for indirect, special, punitive, incidental, or consequential damages or losses. While the successful build rate is extremely high, there is no guaranteed favorable outcome. Always research and plan any project you undertake thoroughly. Sometimes, a project is over your head, and it just makes more sense to hire a qualified professional.
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Classic Audio Products, Inc. is not affiliated with API. Customers and fans should not refer to Classic Audio Products, Inc. as "Classic API." API is a registered trademark of Automated Processes Incorporated. Classic Audio Products, Inc. has no affiliation with Automated Processes Incorporated.
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