LaChapell Audio 992 Tube Mic Pre - Manual (Page 3)

2
• SERVICE/REPAIR- WARNING:
With the exception of tube replacement (see below) the
user should NOT attempt to service this unit. Due to the risk of electrical shock and the presents of
lethal voltages inside the chassis. Only LaChapell Audio or other highly qualified personnel are to
perform maintenance and service activities.
Tube replacement: Turn the unit off, disconnect the power cord and let the unit stand for
at least 20 minutes. Vacuum tubes run very hot, replacing them when they’ve had enough
time to cool to room temperature is recommended. It is also VERY important that enough
time is given to allow power supply voltages to drain. After 20 minutes has past remove the
top panel using a standard Phillips type driver.
To remove the tubes apply a slight circular/rotating motion as you pull it away from the
socket. DO NOT pull strait up as it will stress the PC board and the tube. It is important to
replace tubes with the same type of tube! When new tubes are installed double, triple
check that you’ve inserted the correct tubes into the V1~V4 sockets BEFORE you power-
up.
NOTE: Each tube socket has a designation (V1 to V4) silk-screened onto the P.C. board of
each channel. V1 & 2 are the input tubes (12AX7/ECC83 or 6072), V3 & 4 are the output
tubes 12AU7/ECC82/6189 (The 5814 is also an acceptable 12AU7 replacement.) We
recommend that you send the unit back for tube replacement as there will likely be the need for grid balancing.
WARNING: Warrantee may be voided if tubes other than those listed above
have been used at any time.
Rear Main Fuse replacement (1amp slow-blow) : Located within the rear power entry module (PEM)
are the two main AC fuses. To replace these fuses make sure the rocker power switch is turned off then,
disconnect the AC cord. Locate the two small slots along the top edge of the PEM; place your screw driver
in one of these slots and pull back on the housing door. Do not attempt to pry back the PEM from the rear panel
itself! The housing door will rotate back and expose the red sub-module. Note the fuse orientation inside this
module before you remove the fuses. Re-insert the housing back into the PEM making sure the 115v/230v
text is correctly oriented. Always replace fuses with same type from factory. See International Power
Settings below.
Contact LaChapell Audio for any other servicing questions at 209-383-3486.
CAUTION
RISK OF ELECTRICAL
SHOCK DO NOT OPEN