SR-1 SPRING REVERB BUILD GUIDE
STEP 1: RESISTORS
Populate and solder resistors R19, R20, R21, R23, R24, R25.
STEP 2: TEST POINTSSave 3 of the cut resistor leads [or use bus wire] to form hoops for test points: GND2, +18vdc, -18VDC. Solder them in place.
STEP 3: DUAL OPAMPPopulate and solder the dual opamp U3. Be sure that the opamp is inserted in the right direction. The “dot” on the top should align the direction of the notch printed on the circuit board. [Note that the opamps in the photo are socketed, this is not included/required.]
STEP 4: CAPACITORSPopulate and solder capacitors C10, C11, C12, C15, C8, C9, C17, C18. Be sure to follow the correct polarity for electrolytic capacitors.
STEP 5: POTENTIOMETERPopulate and solder potentiometer R22. We recommend breaking off the tabs on the side of the pot with pliers before populating them. This allows the pots to be flush to a front panel.
STEP 6: PREAMP TEST
- Measure between test points +18vdc and -18vdc. Turn on power [Bring up slowly if possible]. Meter should read +36VDC. Or you can measure each individually [+18 to ground] [-18 to ground].
- With function generator, input 0.1v 1khz signal to “instrument in.”
- On the “high” side of the preamp pot [R22], you should see 1.01v.
- Turn preamp pot [R22] all the way up.
- Measure output at “line in” on the pad titled TS, signal should be 10.2v.
STEP 7: RESISTORSPopulate and solder resistors R4, R7,R8, R9, R12, R13, R14, R15, R16, R27, R28.
STEP 8: DUAL OPAMPPopulate and solder dual opamp U2. Be sure to insert it in the proper direction, with the “dot” on top of the part facing the direction of the notch printed on the circuit board.
STEP 9: CAPACITORSPopulate capacitors C6, C7, C16. C20 is an optional filter cap for the makeup gain section. This capacitor can be used to high pass the signal after the tank return. Jumper these pads to bypass the filter. To experiment with this value, reference the table in the C20 Table.
STEP 10: POTENTIOMETERSPopulate potentiometers R10 and R11.
STEP 11: MAKEUP GAIN TEST
- Input 0.1v 1khz signal into “tank return.”
- Turn reverb pot [R10] all the way up.
- “Line Out” pad should see a 9.16v signal.
- “Instrument Out” pad should see a 0.428v signal.
STEP 12: RESISTORSPopulate and solder resistors R2, R3, R26.
STEP 13: CAPACITORSPopulate and solder capacitors C1, C2, C3, C5, C13, C14.
STEP 14: SWITCHSolder the switch [SWT1] to the board. Be sure that the switch is straight, and fully pressed down to the board.
STEP 15: INDUCTORSPopulate and solder inductors L1 and L2. Be very careful to not bend or overheat, inductors are especially fragile.
STEP 16: HEATSINKPopulate and solder the heatsink to the board. Be sure that the heatsink is straight and pulled flush to the board.
STEP 17: DRIVER ICAssemble the isolation hardware as shown in the picture to the left. Be sure that the black shoulder washer fits into the hole on the top of the driver IC for proper isolation. Install the hardware in proper order and screw the driver IC tight to the heatsink. To test whether your IC chip is properly isolated, use a meter to test connection between the silver top of the IC and the heatsink. They should NOT make connection. Solder the IC chip into place from the bottom of the board. Be sure to never short the output of the IC driver to ground during operation or testing.
STEP 18: POWER RESISTORSBend power resistors R5, R6, R17, R18. Populate them suspended up off the board as high as possible. These parts must be up off the board for proper heat dissipation.
STEP 19: NON-POLARIZED CAPACITORPopulate and solder the non-polarized capacitor C4. Pay no attention to the + sign on the board, the cap can go in either direction.
STEP 20: POTENTIOMETERPopulate and solder in potentiometer R1.
STEP 21: DRIVER TEST
- Input 0.1v 1khz signal to “line in” on the pad labeled “T.”
- Turn tank drive pot [R1] all the way up.
- Measure the output at the “tank drive” pad for each varying frequency given in the table on the downloadable test document. This measures the drive slope.