DBT is a current limiter. The current is limited by the bulb you put in.
Circuit breaker interrupts after a current overload and the device might not be able to survive.
Dim Bulb Tester Build and How-To
- Thread starter EngineerNate
- Start date
Circuit breaker interrupts after a current overload and the device might not be able to survive.
quanghuy147
Member
I see, thank you for your explanation! If I am going to test an amp (400-watt consumption), how many watts should the bulb have?
JB6789
New Member
Just wondering if it would be more convenient to buy a power strip (2 or 3 (3-pronged) sockets) and open it up; cut the + and - brass strips (with a 3 socket strip voiding socket #2 for a little space) and simply wire and solder the circuit, accordingly; with the dim bulb closest to the switch and the test load at the far end. I suppose a 4 or 5 socket strip could be used for a 3 bulb tester...but I am not bothering with that.
I used a three way switch light, and a 3 way bulb of 50,100 and 150 watt . I marked the knob switch with a white dot and then three white dots on the socket so I could know where each wattage filament was being used.
EDIT 12/18/2023: the final product with labels .
Athanasios
Last edited:
VintageDutch
Active Member
Try to grasp this one......
I live in the Netherlands.....yes yes wooden shoes, windmils and tulips
.... but guess what...
We can not buy normal filament lightbulbs anymore.....It's all LED!...
So it will be a task to go to thrift shops and so on... to find them...
I think I need a very fancy one.... 2x 30 watt. 2x 60 watt and 2x 100 watt ...(I service musician tube amps aswell)
I live in the Netherlands.....yes yes wooden shoes, windmils and tulips
.... but guess what...We can not buy normal filament lightbulbs anymore.....It's all LED!...
So it will be a task to go to thrift shops and so on... to find them...
I think I need a very fancy one.... 2x 30 watt. 2x 60 watt and 2x 100 watt ...(I service musician tube amps aswell)
Anyone know why a DBT won't light up at all on a non working Kenwood KA-4002 that was given to me. The DBT has been tested and working fine. NO light whatsoever.I put this together based on the pics that @Jailtime posted a while back, and figured I'd take some in process shots. There were a number of threads on these with dead links to imageshack or photobucket (the scourges of the internet) so this should be a good post on the issue that won't have dead links for a few more years at least.
Firstly we need the following:
-1 grounded socket
-1 socket -> standard light bulb converter
-1 light switch
-1 plastic in wall enclosure, I used an "old work" one meant to mount to sheet rock
-1-2' of 14-2 romex or equivalent. I only ever used single strands out of this, but it's nice to have the color coding without having to buy multiple things and they strip easily.
-1 switchplate
-1 sacrificial grounded extension cord.
-Suggested: bulb protector of some sort
We'll be following this schematic courtesy of @inkboy1 with the addition of a ground not shown in the schematic. The ground is pretty self explanatory: connect all the green stuff together.
Step 1: Prepare the socket. Break off the tabs linking the two outlets on both sides. I purposefully bought a cheaper outlet for this because the tabs were less substantial. Since this will see intermittent use we don't really need the hospital grade outlet.
Step-2: Next, cut the end off of your extension cord and insert it into the box through one of the built-in slots. These are nice because they provide some level of strain relief. Strip back the outer sheathing and trim the inner wires so that you have about 4" for the hot wire and 6-7" for the other two. Black is hot, white is neutral, green is ground. You'll want about an inch of exposed wire on each to wrap around the post.
Step 3: Attach the hot wire to the bottom post of the switch:
Step 4: Next, prep the outlet side. We have already electrically isolated the two sockets, we now need to connect them. Run a black wire from the "neutral" side of the bulb socket (in my case, the upper one) to the hot side of the plug you'll use for whatever equipment gets hooked up.
Step 5: Connect the switch output to the hot side of the bulb socket:
and connect the neutral to the neutral side of the test socket:
Lastly, connect the ground to the socket and if desired, ground your switch as well as shown. This isn't strictly necessary but is good insurance against any unwanted zappage.
Step 8:
Mount everything in your box. I may swap mine around so that the plug comes out the back.
Step 9: Install switchplate and bulb socket + bulb and you're done!
To make sure that you've gotten all the connections properly, stick a probe from your multimeter into the hot side test socket. With the bulb unplugged, even with the switch turned on the circuit should be open when connected to the hot side of the plug:
And with the bulb installed, it should be closed:
That's it! I chose this style for it's compactness-I live in an apartment with no garage and storage space is limited. This will store away a lost smaller than the switchplate + ceramic socket versions. If you bought a few different bulb sockets you could have different wattage bulbs ready to go, no screwing required!
Cheers
Nathan
Maybe the Kenwood has an open fuse?
lumoStoria
Member
Just wanted to share some photos of the somehow over-engineered and oversized dim bulb tester I built a couple of weeks ago. It is a bit different from the ones that have already been shown here since in Germany we use so-called Schuko sockets and I could not find any socket -> light bulb converters for it. Probably, they are not allowed for some reasons. Therefore, I had to use some cheap wall/ceiling lamp holders for E27 bulbs instead.
The tester is about 26x18cm with the output socket at the front and two lamp holders, a multimeter (voltage/current/power/energy) and an emergency stop switch (for paranoid users like me
) on top. The lamp holders are connected in parallel and can be switched on/off individually. This way, two bulbs are sufficient to cover three wattages without the need to swap a bulb. Currently, I'm using a 40W and a 60W bulb so that I can switch between 40W, 60W, and 100W. There is also a switch to bypass the bulbs in case no protection is needed.
The tester is about 26x18cm with the output socket at the front and two lamp holders, a multimeter (voltage/current/power/energy) and an emergency stop switch (for paranoid users like me
) on top. The lamp holders are connected in parallel and can be switched on/off individually. This way, two bulbs are sufficient to cover three wattages without the need to swap a bulb. Currently, I'm using a 40W and a 60W bulb so that I can switch between 40W, 60W, and 100W. There is also a switch to bypass the bulbs in case no protection is needed.Fred_Stone
New Member
sorry for bring this back to life but here in the US you cant get incandescent light bulbs anymore - will LED lights work
No. Nor will fluorescent. You can still find them online and sometimes at the dollar stores.
Fred_Stone
New Member
thanks I will go check at the dollar store tomorrow - may have to stock up - forgot to ask what wattage?
Fred_Stone
New Member
got a schematic? I see a lot of switchesJust wanted to share some photos of the somehow over-engineered and oversized dim bulb tester I built a couple of weeks ago. It is a bit different from the ones that have already been shown here since in Germany we use so-called Schuko sockets and I could not find any socket -> light bulb converters for it. Probably, they are not allowed for some reasons. Therefore, I had to use some cheap wall/ceiling lamp holders for E27 bulbs instead.
View attachment 3075020
View attachment 3075021
View attachment 3075022
The tester is about 26x18cm with the output socket at the front and two lamp holders, a multimeter (voltage/current/power/energy) and an emergency stop switch (for paranoid users like me
seely
Well-Known Member
Wattage, as I understand it, is somewhat relative to the power draw of the equipment you're working on. If wattage is too low, you can blow the bulb, if wattage is too high, it will be difficult to tell if the bulb is bright/dim (someone please correct me if I am wrong on this).
As far as incandescent bulbs in the US, most hardware stores (like Ace) still carry them around me, though price has definitely gone up. I've got some I've picked up at estate sales and garage sales... lots of people are either replacing bulbs with LED or selling off their old incandescents after replacing with LED.
lumoStoria
Member
I had one but I could not find it anymore. However, it's rather simple:
- The two light bulb sockets are connected in parallel.
- Additionally, each socket can be switched on/off with the switch in front of the respective socket. This is only a convenience feature, you could just unscrew the bulb you did not need.
- The switch between the sockets can be used to bypass the bulbs. In this case, the connected device gets the full voltage without any protection. I use this setting when adjusting bias and DC offset of amplifiers.
- The big 'Emergency Stop' switch disconnect both leads of the output socket.
- When restoring my Pioneer SX-737 I usually started with the left bulb (40W). When everything looked OK, I added the right bulb (40W + 60W = 100W). For devices that draw more current you might need higher wattages.
No you can't. Even if the unit being tested is dead shorted, it will just light at full brightness.
Fred_Stone
New Member
I thought the bulb was being use more like a fuse in the circuit