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Compact Dim Bulb Tester Wiring

This is just another case where policy changes of F-bucket have let us down.

There are many posts here about the DBT and its construction. The AK search function often has problems with number or short search strings, like "DBT". Try using Google to search for this string: "site:audiokarma.org DBT wiring". That will restrict the search to AK and get you to a lot of threads/posts.
 
Thanks everyone for the fast responses. I'm able to see everyone's images - with the only exception being those posted by OverLoad on the first post of this thread.
The only reason I'm fixated on those is because I'm really looking for exact instructions. Meaning I really am looking for images and instructions that will guide me all the way through. This way, when i go buy the line cord, the light switch, the light switch box, the outlet, the outlet box - I really want guidance on each and every step - as in (connect black wire from line in to XX, connect green wire to XX, remove jumper on XX, etc.). I have found a lot of great stuff on the web - but nothing that give a me exact, clear steps.
I'm getting ready to recap a Pioneer SX-1250 - so want to make sure I'm preparing as much as possible.
Thanks again for your patience and knowledge.
 
I'll try and get the pics restored. Unfortunately the plug-in extension "fix" for firefox is not working for me. PB pics are still not showing up after the firefox extension install.
 
I had similar experience with the Chrome extension -- loaded the extension but still couldn't see the PhotoBucket images. Then I realized I needed to pull a new copy of the page from the server: Ctrl-F5 (refresh page, ignoring cached elements) and things were lovely.
 
I've tried reloading, clearing cache, reboot, the works and no love.

Now for the latest wrench, those older posts are without editing privileges.
 
Thanks everyone for jumping in and trying to help. I think I will be able to manage by using the great details OverLoad posted on the first thread. Great to know I have such a supportive and smart audience!
 
gort69 said:
There are a couple of "fixes" that allow you to see Photobucket images on a PC, at least until p/b decides to disable them. I see the pictures from the OP just fine, using Firefox and the fix.
Click to expand...

Excellent tip, and works brilliantly here with Firefox, as you say.... until p/b disable it.... At least in the mean time, I can download and save copies of some of the 'reference' photos I've previously used.

Many thanks for the tip :thumbsup:
 
Make sure the bulb is an INCANDESCENT STANDARD FILAMENT LAMP BULB. No HALOGEN, No CFL's, No Mercury or Halide. INCANDESCENT! I've seen too many guys use the wrong type and size bulb and either get no indication and toss the gear out the door, or the bulb goes bright and stays there with no dimming, causing the same reaction.

If the unit is now working, get a variety of bulb wattages from 60w to 150W. You want a dimming of approx 80%-90% down from full brightness to get a decent voltage going to the unit, and still not starve it too bad so you can test it. Change bulbs until you get that dimming with the controls set as follows:
Volume....0(ZERO)
Bass & Treble.....Centered
Balance.........Centered
Loudness......out
Tape monitor OFF
Spkrs..............A or 1
SELECTOR SWITCH ........AUX (NO SOURCE CONNECTED).

You want the unit idling with no source input which is what the above will do. Use this setup on your unit at all times when testing with a DBT. DO NOT ever Set BIAS AND / OR OFFSET While on DBT without reducing the bias back to full resistance(this is called tickling the Dragon and can be dangerous to your unit if left as is and then plugging in to the wall.) before plugging your unit into the wall. Then with full voltage you can set the dragon to full spec.
 
This is DBT I've built with a bit of dremmel and soldering work.

From this (similar model taken from internet)

A64E66C1-FF59-402A-A777-7CC9C07E5282_4_5005_c.jpeg

To this

A58E45A9-85C1-4FAD-80B3-6A9E1585C98B.jpeg

it's very compact and the biggest complexity is the internal cabling in order to close the case. If someone is interested I can post some intermediate steps I've taken in photo
 
I need to label mine "Dim Bulb Tester" so people will quit asking what it is.

5BCO005.jpg
 
On my DBT I have an additional switch that shorts out the lamp, much more convenient since you can leave the unit under test connected all the time.
 
photo_2025-10-01_10-08-07.jpg
I need a DBT for a project and wanted to keep it really simple. All I did was cutting the cable of an extension cord, and put a lamp socket in series with the brown cable (which carries the voltage). The blue and yellow-green cable I just connected together. (I'm in Germany, so it's 230V, brown is hot, blue is cold, yellow/green is protective earth/PE. The white device at the power plug is a voltage/wattage sensor, so I have a display that shows how much power is drawn from the wall.

The connection was made with wago-clamps (equivalent to screw-terminals). In the other DBT designs I checked online, people would often add a 10A fuse. Is that necessary, or not really?

photo_2025-10-01_10-08-05.jpg

Another question to the wattage of the bulb. Often people use 100W bulbs, but I only have a 40W here at the moment. I haven't fully understood what happens when the lamp lights up. I get that it's a very low ohmic resistor at low power/current when it's not glowing, and as soon as power/current rise, it starts glowing and the resistance builds up, eventually reaching it's designed resistance/current/power at the given voltage. Can I use this mode with the glowing bulb to diagnose an issue at the amplifier with limited current, or should I immediately switch off the setup as soon as the lamp starts glowing?

The amp I'm working on has (probably?) some burnt resistor so I want to limit the power while measuring the voltages at the test points. When powered off I couldn't find the issue, all transistors are ok with the diode check function, and all the large resistors measure ok. So could I continue diagnosing with a glowing bulb, and would 40W be better for this, or is the current then too small?
photo_2025-10-01_10-08-08.jpg
 
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