Page 1
Technical Information Bulletin
SLM Electronics, Inc. Saint Louis, Missouri, USA
TIB0003 SVT2PRO/SVTCL/SVTAV Power Tube Board Modification page 1 of 5
June 4, 2001 #TIB0003
Units Affected:
Model
Serial Numbers Model Serial Numbers
SVT-2PRO T2PDxxxxxxxxx SVTAV AXVDxxxxxxxxx
ATLDxxxxxxxxx
BJIDMAxxxxxxx
SVT-2PROJ T2PJxxxxxxxxx SVTAVJ BAHJxxxxxxxxx
ATLJxxxxxxxxx
BJJJMAxxxxxxx
SVT-2PROU ATLUxxxxxxxxx SVTAVU BAIUxxxxxxxxx
BJKUMAxxxxxxx
SVT-2PROW T2PWxxxxxxxxx SVTAVW AXVWxxxxxxxxx
ATLWxxxxxxxxx
BJMWMAxxxxxxx
SVT-CL TCLDxxxxxxxxx SVT-CLJ TCLJxxxxxxxxx
BCYDxxxxxxxxx BCYJxxxxxxxxx
BJNDMAxxxxxxx BJOJMAxxxxxxx
SVT-CLW TCLWxxxxxxxxx
BCZWxxxxxxxxx
Purpose:
(1) To extend the life of the amplifier’s power tubes.
Recommended Actions:
(1) Remove six 1N4007 diodes from power amp tube circuit.
(2) Replace six 22 ohm resistors in power amp tube circuit with 220 ohm, 1/2W 5% flame-proof
resistors (SLME p/n 77-221-03).
Tools Needed:
• #2 phillips screwdriver • 5/64” allen wrench • wire cutters
• soldering iron • solder
CAUTION!
DISCONNECT THE AMPLIFIER FROM ANY
SOURCE OF AC POWER BEFORE PROCEEDING!
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Technical Information Bulletin
SLM Electronics, Inc. Saint Louis, Missouri, USA
Corrective Action:
SVT-2PRO:
(1) Place the amplifier on the work surface, right side up, front panel facing you.
(2) Remove the 12 screws from the top cover. Remove the top cover and set it aside.
Proceed to step 7.
SVT-CL/SVT-AV:
(1) Place the amplifier on the work surface, on one
end, cabinet bottom facing you.
(2) Remove four of the five large bolts from the
bottom of the cabinet, leaving the upper bolt in
place. (Refer to the adjacent picture.)
(3) Lower the amplifier onto its feet on the work sur-
face. Position the amplifier so the end with the
remaining bolt hangs over the edge of the work sur-
face. (Refer to the adjacent picture.) Remove the
remaining bolt from the bottom of the cabinet.
(4) Reposition amp on work surface, right side up, front panel facing away from you.
(5) Remove the seven screws from the rear grille screen. Remove the screen and set it aside.
(6) Slowly and carefully work the amplifier assembly about 2/3 of the way out of the cabinet – far
enough to allow access to the tubes and the tube board. Avoid putting excessive strain on the con-
necting cables!
(7) Grasp one of the power tube retainers by its
top ring. Lift the retainer up and away from the
power tube, then slowly lower it to the plate at the
base of the tubes as shown in the adjacent pictures.
Repeat for the remaining tube retainers.
TIB0003 SVT2PRO/SVTCL/SVTAV Power Tube Board Modification page 2 of 5
Page 3
Technical Information Bulletin
SLM Electronics, Inc. Saint Louis, Missouri, USA
CAUTION: The tension on the retainers’ springs
may cause them to snap back towards the base of
the tubes, possibly cracking their glass casings -
slowly lower each retainer down to the base of the
tubes to avoid such damage.
(8) Carefully remove each of the power tubes by gently rocking it side to side while lifting it straight
up. Set the tubes aside.
(9) Each tube retainer is secured to the tube socket with two 5/64” allen head screws. Remove the
screws, then remove the tube retainers and set them aside.
(10) Remove the eight screws from the tube plate. Remove the tube plate and set it aside.
(11) Lift the power tube circuit board assembly
up slightly and disconnect the white two-wire
connector from the two-pin header on the edge
of the board as shown in the adjacent picture.
(12) Lift the tube board assembly further up
until the ribbon connector beneath it is accessi-
ble. Disconnect the ribbon connector from the
multi-pin header on the circuit board beneath as
shown in the adjacent picture.
(13) Disconnect the remaining five wires from the underside of the tube board assembly. Place the
tube board assembly on the work surface so the printing reads right side up.
(14) Locate, cut and remove the six 1N4007
diodes (D1, D2, D3, D7, D8, D9) from the
tube board. (These are located in the high-
lighted areas of the adjacent picture.)
(15) Locate, desolder and remove the six 22
ohm resistors (R2, R4, R6, R7, R9, R11) from
the tube board. (These are also located in the
highlighted areas of the adjacent picture.)
TIB0003 SVT2PRO/SVTCL/SVTAV Power Tube Board Modification page 3 of 5
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Technical Information Bulletin
SLM Electronics, Inc. Saint Louis, Missouri, USA
TIB0003 SVT2PRO/SVTCL/SVTAV Power Tube Board Modification page 4 of 5
(16) Install a 220 ohm 1/2 watt 5% flame proof resistor (SLME p/n 77-221-03) in place of each resis-
tor removed in step 15.
(17) Return the tube board assembly to its place
in the amplifier. Connect the five wires to the tabs
on the underside of the circuit board as shown in
the adjacent picture.
(18) Carefully reconnect the ribbon cable to the
multi-pin header on the circuit board beneath the
tube amp board. Make certain that the connector is
properly aligned and oriented with the header as
shown in the adjacent picture so that all of the pins
mate into the connector.
(19) Reconnect the white two-wire connector to the two-pin header on the edge of the tube board.
(20) Rest the tube board assembly in place and set the tube plate over the board assembly so the tube
sockets line up with the large holes in the plate.
(21) Install each of the tube retainers. Orient the tabs
of the retainers so their elevated tabs (where the
springs are attached) are furthest from the socket as
shown in the adjacent picture.
(22) Install the eight screws which secure the tube plate and tighten them firmly.
(23) Replace each of the power tubes into the tube sockets and secure each one with its tube retainer.
SVT-2PRO:
(24) Replace the top cover and install the 12 screws which secure it to the amplifier chassis. Tighten
the screws firmly.
Proceed to step 28.
SVT-CL/SVT-AV:
(24) Carefully return the amp assembly into its original position within the cabinet. Push the chassis
all the way into the cabinet.
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Technical Information Bulletin
SLM Electronics, Inc. Saint Louis, Missouri, USA
A Division of St. Louis Music, Inc. • 11880 Borman Drive • St. Louis, MO 63146
Phone (314) 569-0141 • Fax (314) 567-7278 • Service Department (800) 738-7563
TIB0003 SVT2PRO/SVTCL/SVTAV Power Tube Board Modification page 5 of 5
(25) Turn the cabinet so one end hangs over the edge of the
work surface. (Refer to the adjacent picture.) Insert one of
the large bolts into the mounting hole in the cabinet. Work
the bolt and the amplifier around as needed until the bolt
threads into the amp chassis. Avoid cross-threading the bolt!
Tighten the bolt securely into the amplifier.
(26) Stand the amplifier on one end, with the bolt installed in step 25 towards the top. Insert the
remaining four bolts into their mounting holes and thread them into the chassis. Avoid cross-thread-
ing the bolts! Tighten each bolt securely.
(27) Replace the rear grille screen and install the seven screws which secure it to the cabinet. Tighten
each screw firmly.
(28) Connect the AC line cord and turn the amplifier on. Verify illumination of the front panel LED.
Look through the rear grille and verify each power tube glows slightly near its top. (If the LED does
not illuminate, or if the power tubes do not have a slight glow, disconnect the AC line cord, open the
unit up and double check all wiring. If the problem persists contact your Ampeg Service Center.)
(29) Repack the amplifier into its original shipping carton.
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