Original Sewell Amp
50 Watt
100 Watt
Power usage
250 Watts
300 Watts
Pre Amp Tubes
3 each ECC83
Power Tubes*
2EA EL34
4EA EL34
Power Tube Option
2EA 6L6
4EA 6L6
* 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
100V 50Hz/60Hz
2A 250V Type 3AG
4A 250V Type 3AG
120V 60Hz
2A 250V Type 3AG
4A 250V Type 3AG
230V 50Hz
1.5A 250V Type 3AG 2.5A 250V Type 3AG
Filament Fuses
2 each 10A 250V Type 3AG
B+ Fuses
2 each 500mA 440V Type 3AG
Weight
Head
34 lbs (15.5kg)
40 lbs (18.2kg)
1x12 Combo
54 lbs (24.5kg)
N/A
2x12 Combo
62 lbs (28.2kg)
68 lbs (31kg)
Dimensions
Head
22.5in X 11in X 9.75in
22.5in X 11in X
9.75in
1x12 Combo
22.5in X 20in X
9.75in
N/A
2x12 Combo
26.5in X 21in X
9.75in
26.5in X 21in 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
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
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
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
tubes, only gently rock them from side to side during insertion or removal. After preamp tube
installation, place the cylindrical spring tension preamp tube covers over the tubes. Ensure
the cooling fan is plugged back into the jack on the chassis. Failing to do so can create a safety
hazard.
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 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
Fuses
There are 5 fuses installed in the amplifier. Only 1 of these, the main input fuse, is accessible
and replaceable by the user. There are 4 fuses internally for added safety. 2 of these fuses are
high voltage fuses, and 2 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
padded and safety-certified work surface. Loosen the 4 bolts holding the chassis to the top
of the cabinet. The reverb pan may need to be removed before removing the chassis. Ensure
the reverb cords are unplugged, and remove the hardware holding the reverb pan in place.
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 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 and 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, and plug the reverb cords back into place. Before installing the back panel, ensure
the cooling fan cord is plugged into the proper jack.
Original Sewell Guitar Amplifier
User’s Manual
Tech Specs
