Dim Bulb Tester
SCompRacer
Posts: 8,504
A dim bulb tester is typically used in series with a variac to slowly increase voltage when powering up questionable gear. Think of it as a soft-start test for identifying shorts without damaging the set. Dim bulb tester uses a series circuit. Line voltage goes through the bulb(s) to outlet short slot hot, flows to gear being tested and returns through outlet long slot neutral.
As you increase voltage, if light gets really bright you can stop before smoking something. You can use various wattage of now hard-to-find incandescent bulbs to match the anticipated load. My usual setup was a Kill A Watt meter after the variac and plug the dim bulb tester into it. I could monitor amperage on the Kill A Watt.
My old dim bulb tester only had one bulb. I had to jury rig a second bulb when testing the Scott 399 due to it being a higher amperage. So, I built a fancy two-bulb model. It is fused with on/off switch. Not my design, I found it on the internet searching for ideas.
It sports a meter that shows voltage and amperage. The meter will actually display more info than I really need but it was said to be accurate. It reads voltage, current, wattage, watt hour, Hz and power factor.
It has an ON/ON DPDT switch to feed the meter line voltage or after bulb load voltage. (An SPDT switch would be fine there, just used what I had). I was pleasantly surprised the voltage and amperage on the meter matched the Kill A Watt meter.
One or both bulbs can be easily bypassed by flipping a switch. Both bulbs bypassed would result in no load. I used 16 gauge wire so while it could do 13 amps, I rated it safely for 10. Most old tube receiver amperage I’ve been servicing has been around three amps. The fuse would have to be changed to adjust for anticipated loads.
I had a solder iron plugged into the dim bulb tester while testing it. This one is actually for Ed the SRT King so I’ll have to build another for myself. The last pic, the meter is switched to load voltage (after bulb). Meter shows 39 volts, surprised it still worked.
I carefully cut out the case to fit around the duplex outlet. A dab of epoxy holds the current transformer in place.
Amps match the Kill A Watt.
Volts match the Kill A Watt
Meter switched to after bulb voltage.
As you increase voltage, if light gets really bright you can stop before smoking something. You can use various wattage of now hard-to-find incandescent bulbs to match the anticipated load. My usual setup was a Kill A Watt meter after the variac and plug the dim bulb tester into it. I could monitor amperage on the Kill A Watt.
My old dim bulb tester only had one bulb. I had to jury rig a second bulb when testing the Scott 399 due to it being a higher amperage. So, I built a fancy two-bulb model. It is fused with on/off switch. Not my design, I found it on the internet searching for ideas.
It sports a meter that shows voltage and amperage. The meter will actually display more info than I really need but it was said to be accurate. It reads voltage, current, wattage, watt hour, Hz and power factor.
It has an ON/ON DPDT switch to feed the meter line voltage or after bulb load voltage. (An SPDT switch would be fine there, just used what I had). I was pleasantly surprised the voltage and amperage on the meter matched the Kill A Watt meter.
One or both bulbs can be easily bypassed by flipping a switch. Both bulbs bypassed would result in no load. I used 16 gauge wire so while it could do 13 amps, I rated it safely for 10. Most old tube receiver amperage I’ve been servicing has been around three amps. The fuse would have to be changed to adjust for anticipated loads.
I had a solder iron plugged into the dim bulb tester while testing it. This one is actually for Ed the SRT King so I’ll have to build another for myself. The last pic, the meter is switched to load voltage (after bulb). Meter shows 39 volts, surprised it still worked.
I carefully cut out the case to fit around the duplex outlet. A dab of epoxy holds the current transformer in place.
Amps match the Kill A Watt.
Volts match the Kill A Watt
Meter switched to after bulb voltage.
Salk SoundScape 8's * Audio Research Reference 3 * Bottlehead Eros Phono * Park's Audio Budgie SUT * Krell KSA-250 * Harmonic Technology Pro 9+ * Signature Series Sonore Music Server w/Deux PS * Roon * Gustard R26 DAC / Singxer SU-6 DDC * Heavy Plinth Lenco L75 Idler Drive * AA MG-1 Linear Air Bearing Arm * AT33PTG/II & Denon 103R * Richard Gray 600S * NHT B-12d subs * GIK Acoustic Treatments * Sennheiser HD650 *
Comments
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Holy crap Rich, that thing with digital screen and functionality is wild! I want one!
BTW, is that my Variac?
Carl -
Holy crap Rich, that thing with digital screen and functionality is wild! I want one!
BTW, is that my Variac?
Why, yes it is! I can slap another one together for ya.Salk SoundScape 8's * Audio Research Reference 3 * Bottlehead Eros Phono * Park's Audio Budgie SUT * Krell KSA-250 * Harmonic Technology Pro 9+ * Signature Series Sonore Music Server w/Deux PS * Roon * Gustard R26 DAC / Singxer SU-6 DDC * Heavy Plinth Lenco L75 Idler Drive * AA MG-1 Linear Air Bearing Arm * AT33PTG/II & Denon 103R * Richard Gray 600S * NHT B-12d subs * GIK Acoustic Treatments * Sennheiser HD650 * -
I concur that looks rad! I’m jealous lol…"....not everything that can be counted counts, and not everything that counts can be counted." William Bruce Cameron, Informal Sociology: A Casual Introduction to Sociological Thinking (1963)
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It'll never make it through airport security!!
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SCompRacer wrote: »
How many units do you need confirmed in order to do a group buy? -
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How many units do you need confirmed in order to do a group buy?
I wouldn't want to deny anyone the fun of diy.
Salk SoundScape 8's * Audio Research Reference 3 * Bottlehead Eros Phono * Park's Audio Budgie SUT * Krell KSA-250 * Harmonic Technology Pro 9+ * Signature Series Sonore Music Server w/Deux PS * Roon * Gustard R26 DAC / Singxer SU-6 DDC * Heavy Plinth Lenco L75 Idler Drive * AA MG-1 Linear Air Bearing Arm * AT33PTG/II & Denon 103R * Richard Gray 600S * NHT B-12d subs * GIK Acoustic Treatments * Sennheiser HD650 * -
my problem is that I am too danged lazy to gather the parts!
Heck, I have the bits and bobs to build a simple/basic DBT downstairs in a paper bag. I bought the stuff probably 20 years ago to whip one up... and it's still waitin' for me to do so.
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mhardy6647 wrote: »my problem is that I am too danged lazy to gather the parts!
Well, you better hurry up. Halloween is just a little more than 3 months away.
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My problem is now I'm too danged lazy to do anything complicated! (Made some exceptions for Ed and Carl).
I have this Lenco PTP5 project that I started years ago. I got the plates in 2013. Later years I acquired the Walnut that will match my Bottlehead Eros phono base, also from Aaron's dads tree farm. I've tried the Tom Sawyer whitewash the fence trick with @ALL212 to finish it but he didn't fall for it.
I have 1:1 plans to trace out the cutouts and drill the holes. Would love to get the several Baltic Birch layers CNC machined.
PTP plates originated from the mind of Peter Reinders in the Netherlands. There are multiple styles of PTP plates. What they do is separate the motor from main bearing where the original Lenco plate is one piece. Some have sliders for speed control that move the idler along the tapered motor shaft. My PTP plates are designed that the idler be fixed as I have an electronic speed control. I just push a button to switch between 33/45 speeds.
My Lenco sounds really good so not much motivation to finish it.
I cut my top plate down removing the non-essential portions and for a nicer look.
Salk SoundScape 8's * Audio Research Reference 3 * Bottlehead Eros Phono * Park's Audio Budgie SUT * Krell KSA-250 * Harmonic Technology Pro 9+ * Signature Series Sonore Music Server w/Deux PS * Roon * Gustard R26 DAC / Singxer SU-6 DDC * Heavy Plinth Lenco L75 Idler Drive * AA MG-1 Linear Air Bearing Arm * AT33PTG/II & Denon 103R * Richard Gray 600S * NHT B-12d subs * GIK Acoustic Treatments * Sennheiser HD650 * -
"....not everything that can be counted counts, and not everything that counts can be counted." William Bruce Cameron, Informal Sociology: A Casual Introduction to Sociological Thinking (1963)
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EndersShadow wrote: »
Such a diplomatic was of saying No F***ing way…
Now that's funny! I'm just too lazy.....Salk SoundScape 8's * Audio Research Reference 3 * Bottlehead Eros Phono * Park's Audio Budgie SUT * Krell KSA-250 * Harmonic Technology Pro 9+ * Signature Series Sonore Music Server w/Deux PS * Roon * Gustard R26 DAC / Singxer SU-6 DDC * Heavy Plinth Lenco L75 Idler Drive * AA MG-1 Linear Air Bearing Arm * AT33PTG/II & Denon 103R * Richard Gray 600S * NHT B-12d subs * GIK Acoustic Treatments * Sennheiser HD650 *
