Amp Mods · Champ 600 and Gretsch 5222 Mod Kit
Fender 600/Gretsch 5222 Mod Kit Instructions
Optional Tools/Supplies:
- Silicone glue.
- 9/16” nut driver or socket wrench.
- 1/2” nut driver or socket wrench.
- Fine point Sharpie or similar permanent marker.
- Masking Tape
Skills required:
- Basic soldering skills .
- Basic knowledge of electronics.
- The Ability to follow instructions.
- BLACK 0 K
- BROWN 1 N
- RED 2 R
- ORANGE 3 O
- YELLOW 4 Y
- GREEN 5 G
- BLUE 6 B
- VIOLET 7 V
- GREY 8 E
- WHITE 9 W
Tips: Be careful when removing parts from the circuit board, NEVER FORCE A PART OUT. Use a solder sucker and solder braid to remove solder. I like to clip the leads of the old parts when possible before removing the lead from the PCB. The PCB is fragile and too much heat can cause the solder pad to lift off the board.
To the right is a summary of the mods that will be performed on the amp. They consist of a increasing the gain and improving the frequency response of the preamp (R2, R8 and C3).
Removing the negative feedback loop (R7) gives the amp more touch sensitivity and punch.
Finally replacing the tone stack and coupling cap (C1, C2, C8, C9)with high quality mica and orange drop caps really opens the amp up.
| Position | Stock | New |
|---|---|---|
| R2 | 1k5 | 2k7 |
| R8 | 100K | 220K .5 |
| C3 | 22uf | 1 uf |
| R19 | 15K | 27K |
| C1 | 250pf | 500pf |
| R7 | 2k2 | remove |
| C6 | 22/450 | 47/450 |
| C2 | 0.022 | 0.022 |
| C8 | 0.1 | 0.1 |
| C9 | 0.047 | 0.047 |
The Supreme kit replaces all the electrolytic caps in the amp
CAUTION: The PCB is very fragile, be careful when removing components, do not to force any component. Use a solder sucker and solder braid to remove solder. Clipping leads from the top side of the board will make removal of components easier.
Parts
- Resistor 2k7 1/4w (Code RVKNN)
- Resistor 220K 1/2w (Code RRKON)
- Resistor 27K 1/4w (Code RVKRN)
- Capacitor 1uf MLCC (Code 105 YELLOW)
- Capacitor 500p Micaf (Code 500)
- Capacitor 0.022 Wima 10mm (Code 223)
- Capacitor 0.1 Wima 15mm (Code 104)
- Capacitor 0.047 Wima 10mm (Code 473)
- Capacitor 47/450 (Code 47/450)
- Resistor 5W (To Safely Drain Filter Capacitors)
Tools
- Temperature Controlled Soldering Iron and Solder
- Solder Sucker and or de-soldering braid
- Multi-Meter Capable of reading 500V DC
- Phillips Screwdriver
- Pliers with insulated handle
- Wire Cutters
- Safety Goggles
- Alligator Leads
1
Step 1
- WARNING: Performing these modifications WILL void the warranty on your amplifier. Working on amps can be deadly if you do not take proper precautions. Follow these instructions very carefully. If you are at all unsure of your ability to perform these modifications STOP and take your amp to a professional to be modified. You can also send your amp to me for modification.
- No Warranty: This kit and the instructions included do not include any warranty of any kind. The modifications to your amplifier are at your own risk and you agree to completely hold harmless the seller of this kit against any and all claims. Tube amplifiers contain parts that operate at very high temperatures and deadly voltages. If you are not sure of your abilities to perform these modifications then do not perform them.
- CAUTION: TUBE AMPLIFIERS CAN CONTAIN DEADLY VOLTAGES EVEN WHEN THEY ARE NOT PLUGGED IN—BE SURE TO DRAIN THE FILTER CAPS BEFORE WORKING ON THE AMP—NOT DRAINING THE FILTER CAPS COULD RESULT IN SERIOUS INJURY OR DEATH.
2
Prep the Amp
- Instructions: Follow these instructions to the letter.
- It’s a good idea to have all the parts and tools you will need laid out before starting in a well lit area.
- Unplug the Amp and put on your safety goggles.
3
Step 3
- Remove the tubes, unplug the speaker, unplug the reverb from the reverb can (be sure to note which side is red and which side is black, remove the clips holding the reverb wire and power cable to the cabinet.
4
Step 4
- Remove the screws holding on the back panel and remove the panel. Then remove the chassis screws. There is a screw on each side of the cabinet as well.
5
Step 5
- The chassis should slide out easily exposing the circuit board I find it easiest to work on the amp with the chassis completely removed from the cabinet.
6
Step 6
- WARNING: SKIPPING THIS NEXT STEP COULD RESULT IN DEATH
- Drain the Filter Caps: Using your multimeter set to DC measure the voltage at D1 to ground. If the voltage is more than 15 VDC you need to drain the caps. It’s good practice to keep your left hand in your pocket and work only using your right hand. Then if you do touch something that is high voltage while grounded the current will hopefully go though your right hand to ground and miss your heart. Clip an alligator lead to the positive side of D1 and to the 470 ohm power resistor, clip another alligator lead from the other side of the resistor to ground. Measure the voltage every minute until the reading is less than 15 VDV.
7
Step 7
- Remove all the transformer leads. Be carful to note where each lead goes. I like to put a bit of masking tape on each lead and write the number it goes to in sharpie.
8
Step 8
- Remove the screws holding the large tube socket.
9
Step 9
- Remove the screws holding the main PCB. The main board should easily lift off the chassis,
10
Step 10
- Remove the following parts as indicated. The parts outlined in yellow are for the supreme kit only. Never force a component out of the holes. Use solder braid and a solder sucker to remove solder then gently remove the lead from the hole. I find that it is easier to clip the components on the top side of the board then remove the leads carefully. The PCB is fragile and if the components are not removed with care you could lift a pad or trace off the board.
11
Step 11
- Replace the components as indicated in the diagram below.
- 220K
- 500pf
- .047
- .022
- 47/450
- 1uf
- 27K
- 2.7K
- .1
12
Step 12
- When you are done put the amp back together in the reverse order that you took it apart. Remember to re-install the tubes and the speaker cable.
13
Step 13
- Dress the Transformer leads!!! Poor lead dress is a large part of the noise in an amp. Instead of using a new cable tie to put the wires back like we found them we are going to use standard wiring techniques for proper tube amp design. Twist the green heater wires and position as shown. All other lead pairs should be twisted and cross each other at 90 degree angles to avoid noise, hum, and oscillation.
14
Step 14
- CAUTION: The circuit board is very fragile and the solder pads can easily become separated from the circuit board if extreme care is not used. Carefully examine each solder pad after removing the component to make sure the solder pad is intact. If the solder pad is damaged you will need to carefully scrape away the solder mask of the trace next to the hole, bend the lead to the trace and solder directly to the trace. Remember to always check continuity with your multi-meter to insure that you have a good connection between components.