PRS Guitars 25th Anniversary User Manual

Tech Specs

50 Watt
25 th Anniversary Amp
Power usage
250 Watts
Pre Amp Tubes 3 each ECC83
Power Tubes** 2EA EL34
* *Power Tubes should be purchased as matched sets. Use only tubes in pairs or
quads that are factory-matched. Failure to use matched tubes can lead to tube
failure and amplifier damage or abnormal operation.
Main Fuses
120V 60Hz
2A 250V Type 3AG 4A 250V Type 3AG
Filament Fuses
2 each 10A 250V Type 3AG
2 each 500mA 250V Type 3AG
B+ Fuses
2 each 500mA
440V Type 3AG
Weight
Head
34 lbs (15.5kg)
Dimensions
Head 22.5in X 11in X
9.75in

Service Notes

Tubes
Tubes are consumables as they have a given usable lifespan. They are part of the heart of
the tone, so keeping correctly operating tubes is essential. Tubes can fail catastrophically or
gradually, and it's good to know what to look for if they start to go bad. Periodically inspect
100 Watt them and look to see if anything inside the tube is glowing cherry red other than the normal
orange glow of the filament. This would indicate a situation where the tube is conducting
more current than it is capable of handling and most likely about to fail. Two other conditions
350 Watts
to observe are 1) filaments not glowing or 2) a miniature fireworks display inside the tube. Any
of the above conditions indicate serious problems with the tube and should be taken care of
immediately. Tubes quite often are the cause of spurious noise in the amp. Microphonic tubes
4EA EL34
will squeal or rattle with the vibrations of the cabinet. If suspected, tap each tube lightly with
a pencil with the amp powered up—the suspect tube will let you know. Note that there is a
normal metallic clinking when doing this, but a microphonic tube will be quite loud.
Instructions for Qualified Service Technician: To install the tubes, check that the power cord
is not plugged in, then remove the wooden back panel with a screwdriver and notice the
tube sockets. Note that the cooling fan may need to be unplugged from the chassis. Looking
from the back, install the Power tubes (EL34, 6L6, etc.) in the left sockets. In each case, align
the center pin guide correctly with the socket, making sure that the pin guide key fits with
the corresponding slot in the socket. The ECC83 preamp tubes can then be placed in the
smaller 9-pin sockets to the right of the power tubes. Please refer to the tube chart inside
the amplifier for proper tube locations. Be aware of the pin alignment with these, as there is
only one way they can fit. We utilize tube sockets that allow relative ease of tube installation,
but never force tubes into the sockets if there becomes a problem. Also, never torque the
2 each 1A
tubes, only gently rock them from side to side during insertion or removal. After preamp tube
440V Type 3AG
installation, place the cylindrical spring tension preamp tube covers over the tubes.
Replacing preamp tubes will not require any adjustment, but the power tubes will need
rebiasing to assure proper operation. After power tube replacement, initially inspect the tubes
40 lbs (18.2kg)
often to assure there are no "cherry red" components within the tube. Tubes today can have a
wide variety of tolerances and a re-bias is highly recommended with new ones.
22.5in X 11in X
Fuses
9.75in
There are five fuses installed in the amplifier. Only one of these, the main input fuse, is
accessible and replaceable by the user. There are four fuses internally for added safety. Two
of these fuses are high voltage fuses and two fuses are for the lower filament voltages. In all
cases, labels indicate the type and rating of the fuse. Replacement fuses MUST BE THE SAME
TYPE AND RATING. If they are not you can permanently damage your amplifier. Please contact
your local PRS dealer or the PRS accessories web site for information on ordering replacement
fuses.
Instructions for Qualified Service Technician: Replacement of internal fuses requires removal
of the back panel and removal of the chassis. First, ensure the power cord is not plugged in,
then remove the back panel with a screwdriver. Turn the amplifier upside down and place on a
padded and safety-certified work surface. Loosen the 4 bolts holding the chassis to the top of
the cabinet. Check that all components are cool so that burns do not occur. Then, by holding
onto the transformers, lift the front of the amp so the front control is out of the cabinet and
carefully pull the chassis out.
NOTE! Capacitors may retain an electric charge and can be dangerous even when the unit is
off, unplugged and has not been played for an extended period of time. USE CAUTION!!!!
Locate the fuse holders, remove them, and check for continuity. Blown fuses can indicate a
failure condition and should be treated as though a problem exists. Check the label for the
proper type and rating. After all fuses have been replaced and the amp is tested as acceptable
and safe, reinstall the chassis by working in reverse. Be sure to replace the reverb pan and
hardware, then plug the reverb cords back into place. Before installing the back panel, ensure
the cooling fan cord is plugged into the proper jack (100 watt only).
25 th Anniversary Guitar Amplifier
User's Manual