Original THD Hot Plate Light Bulbs for 4, 8, and 16 ohm Models, Set of 2 Bulbs

These are replacement light bulbs for the 4 ohm, 8 ohm, and 16 ohm models of our Hot Plate power attenuators. (The 2 ohm and 2.7 ohm versions use a different bulb, which should also be listed in our store.) 

The listed price is for two bulbs, but you can buy as many as you need. 

These are custom-made to our specifications, including being very robust and shock-resistant, and last much longer in use than other replacements. Most customers get 10 to 20 years out of them. 

When turned on, they bulbs create a passive expander circuit, which reduces the noise between notes, and also slightly reduces the treble response of the signal passed to the speakers. 

They are also ideal for the Gibson-branded attenuators that we made, which were sold as the Gibson Power Stealth. 

This is NOT for the noise-reduction circuits that are built into our UniValve and BiValve-30 amplifiers, only for the stand-alone Hot Plates. 

To replace the light bulbs, complete the following steps: 

1. Remove the metal wrap-around on the Hot Plate chassis. This is best accomplished by unscrewing the four Philips-head screws on the side of the attenuator (two on each side).  

2. Slide the inner chassis part-way out of the wrap-around, far enough to access the bulbs from the bottom of the chassis. This is usually easiest done by putting it on the edge of a table with the front two feet hanging over the front edge of the table, thus keeping the wrap-around from moving. You then hold the outside of the wrap-around, and press the inner chassis away from you using your thumbs. Once you get it started moving, it gets easier. Some move very easily, others take some effort. 

3. Use a small blade screwdriver to pry the metal end of the bulb from its holder. Please use a resistance meter or continuity tester to make sure that the bulb is blown. In the 8 ohm and 16 ohm Hot Plates, the bulbs are in series, so if one blows, neither will light. There’s no need to replace a good bulb! 

4. Push the wrap-around back on the chassis, and fasten it with the 4 screws you removed earlier, taking care not to cross-thread the chassis in the process. They should go in easily. Sometimes a tiny bit of oil or grease on the threads helps reduce the friction, but they should go in easily. 

You are done. Enjoy your new bulbs!