This Dim Bulb (Dimbulb) Guitar Amp Current Limiting Test Fixture is now available in 3 models and each model comes with an 11 watt incandescent starter bulb (a low power 11 watt bulb is helpful for reforming capacitors in amps that haven’t been powered up for 6 months or longer), a 60 watt medium power incandescent bulb, and a 150 watt high power incandescent bulb. The video included with the pictures shows the 3 amp box – the 5 amp box works identical to the 3 amp box (except it can handle more current) and the dual range box is a new item (newly released May 8, 2023) and I will be making a video for it soon. A Dimbulb Current Limiting Test Fixture is a helpful tool during testing of guitar amplifiers and other electronic equipment by safely powering up the equipment by limiting the current through an incandescent light bulb (the bulb must be an incandescent, LED and other bulb types will not work properly) This box is available in a 3 amp version, a 5 amp version, and a dual range 1&5 amp version; the 3 amp version has a 3 amp meter and a 3 amp circuit breaker, the 5 amp version has a 5 amp meter and a 5 amp circuit breaker, and the dual range has a 5 amp circuit breaker and both a 1 amp and a 5 amp ammeters; when the dual range box is switched to the 1 amp meter the current is limited to slightly under 1 amp by the 100 watt bulb. This box takes away all the guesswork by showing you the exact voltage and current that the amplifier is receiving. The problem with most Dim Bulb Current Limiting Test Boxes is that they apply power to the amp while the bulb is cold while the bulb has a very low resistance which allows a huge current flow, which pretty much completely eliminates the entire point of the Dim Bulb box; the bulb must be hot for the device to work properly. I also sell an economy Dim Bulb Current Limiting Test Cable that is just two bulbs, which is better than nothing, but to get full protection and have the Dim Bulb circuit function as intended there just be a bulb preheat feature. Once it has been determined that there is no dead short in the amp (a bright light indicates a short and the amp needs to be repaired, a dim light indicates all systems normal) the bulb limiting feature can be switched out (to DIRECT/BYPASS) so that the amp gets full direct voltage while the current can be monitored on the meter The current meter is on at all times and even measures the current of the bulb while in PREHEAT mode. The boxes have a cover on the back and come with a standard power cord and 3 bulbs: a low power 11 watt incandescent bulb to use as a low current starter bulb to reform filter capacitors that haven’t been powered on for 6 months or longer, a medium power 60 watt incandescent bulb, and a 150 watt high power incandescent bulb. The box is 9.5″ wide x 5″ tall without bulb (or bulbs) x 3 deep. All wiring and soldered by hand. The new dual range test box allows more precise current measurements to be made by having a high resolution 1 amp meter – once tests are completed with 1 amp meter (100 watt bulb max) the test box can be switched over to the 5 amp meter which is connected to the high power bulb. I will be making a video highlighting the additional features of the dual range box soon. Reforming Filter Capacitors with the Dimbulb Tester: NOTE: A Dimbulb Tester ONLY works with an INCANDESCENT bulb. With the Dimbulb Tester OFF, insert an 11 watt bulb and set the middle toggle switch: BULB LIMITING / DIRECT/BYPASS to the up position to BULB LIMITING and set the TEST AMP / PREHEAT BULB on the right toggle switch to the down position to PREHEAT BULB. Plug the amp being tested into the output of the Dimbulb Tester box and turn the amp on; if the amp has a standby switch don’t use it – leave the amp turned on. Verify that the amp is turned on, the box is in BULB LIMITING (middle toggle switch up), and PREHEAT BULB mode (right toggle switch down). Turn on the Dimbulb box – the bulb will glow full brightness (an 11 watt incandescent bulb isn’t very bright). The middle toggle switch stays up in the BULB LIMITING position until the end of the test. Switch the right toggle switch up from PREHEAT BULB to TEST AMP. The right meter AMPLIFIER VOLTAGE should bump up a hair – continue either way, but always pay attention to both meters. The 11 watt bulb will limit the current to the amp so the voltage going to the amp will be low, the AMPLIFIER VOLTAGE meter will typically read around 10 volts. Starting with a bulb with a wattage as low as 11 watts is extremely helpful if an amp has been unpowered for a long period of time; it allows the filter caps to reform gently without a huge current spike. Turn off the DB box, change the bulb from 11 watts to 60 watts, and repeat: Verify that the amp is turned on, the box is in BULB LIMITING (middle toggle switch up), and PREHEAT BULB mode (right toggle switch down). As you increase the wattage of the bulb the voltage going to the amp should continue going up – if the AMPLIFIER VOLTAGE stays near zero and the AMPLIFIER CURRENT is moving above zero then the amp has a problem that would ordinarily blow the fuse. If desired an amp can be tested with as many incandescent bulbs as you want to: 11 watt, 25, watt, 40 watt, 60 watt, 100 watt, 200 watt, just start with the lowest wattage and work your way up. If you are using the new dual range box then the 1 amp meter should not be used with higher than a 100 watt bulb but the 5 amp box can accommodate any bulb up to 600 watts. The dual range test fixture also has a spare bulb socket to safely store whichever bulb is currently being unused. This item is in the category “Business & Industrial\Test, Measurement & Inspection\Test Meters & Detectors\Other Test Meters & Detectors”. The seller is “saugusmark” and is located in this country: US. 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- MPN: Dual Range Version
- Brand: Dim Bulb
- Type: Dim Bulb Tester
- Country/Region of Manufacture: United States