Change Guitar Amp Tubes Peavey 5150 212 Combo
Edited by Alexander Avdeev, Eng, VC
Method 1: Peavey 5150 212 Combo
If your amplifier or combo started to produce extra noise or lost its original clarity or distortion, then I would suggest that you replace the whole tube set inside the amplifier or combo. You also have to do it approximately every five years of use.
Please note that there are dangerous currents inside the unit, so if you have not dealt with electricity before, then I suggest that you relegate the duty to an experienced electrician who will do it for you as shown in the video.
Disconnect your Peavey 5150 2x12 combo from any sources and let it stay for an hour to cool down and discharge.
Discharge yourself by touching any metal part on it.
To gain access to the tube section, turn the whole amplifier around.
Remove five screws on the backplate of the combo by using a cross-point screwdriver. I did not know that there was the fifth screw. I pulled the backplate, saw where it would not move, and found the last screw to remove.
Take a can of compressed air and clean the inside thoroughly from dust. Hold the can vertically at all times.
Start by replacing the five gain-stage tubes (or valves). Those are located on the right side of the amplifier and are hidden under caps.
For the gain stage, pick any unmatched tubes that you like. This amplifier allows you to experiment with 12AX7, ECC83, 7025, ECC803, E83CC, 6681 (gain factor: 100); 12AU7, ECC82, 5963, 5814, 6189 (gain factor: 19); 12AV7, 5965 (gain factor: 41); 12AT7, ECC81, 6201, 6679 (gain factor: 60); 5751 (gain factor: 70); and 12AY7, 6072 (gain factor: 45) tubes. One of those tubes goes for the reverb section, one for the effects loop, and three for the gain stage itself. I picked five similar Electro-Harmonix 12AX7 tubes.
Remove all of the caps first. To unlock the cap, push it slightly up and turn it counterclockwise a bit (if you look at it from below). Then, just pull it down.
Remove the first tube. I suggest using a piece of cloth to avoid leaving oil or fat from your fingers on it. Pull the tube down to remove it.
If you do not remember how the lugs were oriented, use a mirror to find the socket layout.
Unpack a new tube and push it up into the socket, but be wary of the lugs for they have to be oriented correctly.
Repeat the same for the next tubes.
Wipe the tubes or valves with a dry cloth if you touched them during the installation.
To lock the caps back, push them up, turn them clockwise a bit, and release them. As you can see, they have holes and grooves for the lock.
Replace the two tubes in the power stage. We have two big tubes here that we have to take out. Just pull them down. You may do it without a piece of cloth.
For the power stage, order a matched couple of any 6L6-series tubes (GC, WXT+, etc). Do not attempt to put any other tubes such as EL34 or 6550. I ordered a pair of matched Electro-Harmonix 6L6WXT+ tubes.
The 6L6 tube has a specific lug layout and a small plastic pin in the middle to prevent any wrong positioning.
Use a mirror If you do not know how you have to position the tube to match the pin and lugs of the socket and the tube itself.
Position the tube correctly and push it up. The black pin has to be placed away from you.
This is how the power tube slot looks. Notice the small hole for the pin.
This is the gain stage tube slot.
Please ascertain the absence of a gap between the power-tube plate and the socket. Push a tube up if you see a gap with lugs. As you can see, there are no gap here.
Place the backplate and screws back.
Tighten the five screws holding it.
Test if the combo works. First, both "Power" and "Standby" on the top of the amplifier must be turned off. Connect the power plug to the socket.
Push the "Power" button and let the amplifier heat up for five minutes. Also, plug the guitar into one of the inputs (high or low gain).
All potentiometers must be set to 0.
Push the "Standby" button now.
Test the sound. The amplifier should work.
Enjoy your new set of tubes (or valves)! Thank you for watching VisiHow!
Video: Change Guitar Amp Tubes Peavey 5150 212 Combo
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Recent edits by: Eng, Alexander Avdeev