The #1 Mistake You're Making with Dim Bulb Testers - Don't Make It Again!
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- čas přidán 28. 04. 2023
- Safely Repairing And Restoring Vintage Electronics With A Dim Bulb Tester.
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I m compelled to thank you for taking the time and making the effort to create videos like this. You don’t need to, but because you do many of us have opportunity to learn. Thank you!
Your welcome, I really appreciate your kind words.
I appreciate the information videos such as your share with many new to electronics. In truth a huge mistake for many is not reading the service information and making sure the input line voltage to the device is what it should be when making any post repair adjustments, alignments, final measurements, etc. The DBT is absolutely an excellent aid for repair but should never be left in circuit once you get to the adjustment and alignment stage. It lowers the input voltage and current and can make adjustments way off even in equipment with modern design power supplies. With any DBT you should have more than various wattage bulbs to use. You should use one sized to the input power rating of the equipment you are working on. Smaller ones are ok but they may drop the input line voltage to the point the device may not come on even for initial testing.
Hello, I hope you are well, once again thank you very much for all the learning you give us.
You are very welcome.
For me, I usually don't figure it out until after I blow the new transistor. That's why I order spares. Thanks from the dim bulb in Colorado.
I've done it plenty. Thanks for watching.
Hey Craig! Cheers from the dim bulb in Utah! 😎🤟🤓
@@fullwaverecked howdy
You are not the only one. When I hear the little click when it shorts it is usually followed immediately by a four letter word.
@@PoppinWheeliezSnap!
Love the insight and experience here! You have helped me understand things quicker and taken some of the learning curve time out . Thank you Sir ! :- )
Your welcome and thanks for watching. I'm glad that the video's help.
Subbed. This is the exact sort of video I like, someone that's had the problem, figured out the solution and doesn't mind sharing. I'll be building a dim bulb soon (I fried a vintage heathkit function generator) and this drawback is definitely something I'm happy to be aware of beforehand. Thank you, sir!
Ive added a rocker switch that glows red (STOP) to my DBT for convenience, to bypass the DBT, and i also added a red and a green indicator lamp so I'm more certain i don't damage the DUT. One can never be too safe, but just like getting out of bed in the morning, there are no guarantees... Cheers!
Good idea! Thanks for sharing.
Great info here. Wish this video was around years ago, would have saved me a steep learning curve. Ive been caught out with biasing amps while plugged in to a limiter. That can be damaging on old amps, they can overheat if the bias is too high.
Yes, it's an easy mistake to make. Thanks for watching.
Thank you for your detailed explanation. Much appreciated. I look forward to each of your videos.
Your welcome and thank you so much for watching.
Great explanation on dim bulb tester and troubleshooting!
Chris, can u cover isolation transformer? So confusing about the ground and it being truly isolated. Thx.!
Do you know the scene from Fear and Loathing in Las Vegas when the guy shouts "Finish... The effin story man... What happened? What about the gland?". That's how I felt trying to watch this.
THANK-YOU SO MUCH FOR SHARING YOUR KNOWLEDGE SIR !! YOU DA MAN , STAY AWESOME !!
Thank you for this video. I’m new to vintage electronics, and it seemed gospel to always use a dim bulb tester, so it’s great to see when using one is *not* appropriate.
This jig should only be used during troubleshooting. After confirming that the repair is done successfully the equipment shoulld be powered directly from mains.
wonderful video, I learned a lot! does a 100W bulb work on vintage monster receivers too, something with a 560W power supply for example?
Many many thanks for the video.
Your welcome and thank you for watching.
great info thanks
Thanks so much for this. I learned from lots of folks on AK to remove the DUT from the dim bulb before making any adjustments so I completely understand your point. One thing I could never wrap my head around was what wattage of bulb to use. It seemed like most were using 60 to 100 watts but I never understood why. Greetings from up the coast in St. Pete!
Your welcome and thank you for watching. I thought it was worth mentioning. It's an easy mistake to make when you are first using a DBT.
it's going to vary a bit depending on the type of equipment you're working on, but you want a good amount of current, but not enough to blow things up. if you're working with a device that takes 100w peak you might want to use a 40w bulb, while the 40w bulb isn't going to be enough if what you're working on takes 1000w, or if it powers up the device, the bulb might stay fairly lit fooling you into thinking there's a problem when there isn't one
Very useful information
Thanks a lot
Great information. Annoying music is not needed.
Fully agree with all your procedures. I only use a dim bulb to find a catastrophic failure and fix it. I also will use my dim bulb when powering up my vintage amps if they have been sitting unused for many month's or years. I will run them through a 300 watt bulb. My theory is doing that the amp will not be "shocked" back to life. It allows a more gradual charging of filter caps. What about using a dim bulb for equipment with switching power supplies? Instead of an old linear PS that just says "here is all the power/voltage you will even need, so just take what you need". A switching PS will consume more or less current from the mains to maintain a regulated output "on the fly". Unlike a conventional old school power supply, the SMP only stores a small reserve of power, but relies on a good power source to grab the power it needs. If the mains voltage drops, the SMS will draw more current to compensate for drop to maintain output voltage. I feel a dim bulb inserted into the supply line could cause a failure because the poor SMS will try everything to get the output where it is supposed to be! That means a huge current flow when it is undervoltaged. I feel something will pop?
Thanks so much for sharing. Using a DBT takes some experience because of the differences between the equipment and the bulb wattage used.
Another electronics channel I follow does a lot of ATX power supply repairs and uses a DBT all the time on them.. Really good channel as well www.youtube.com/@LearnElectronicsRepair
The wattage of the lamp should be less than or equal to the wattage of the device under repair. Higher than that offers no protection.
I was working on an NAD receiver and was getting 3 or 4 V DC offset when using my dim bulb tester. The bulb would stay bright from what I remember. Without a dim bulb I was getting millivolts and no issues. I think I was using a 40W bulb. I went to a larger bulb and everything was fine. For some reason the smaller bulb wasn't allowing the receiver to power up correctly and wreaking havoc with the DC offset.
Thanks for sharing. I have had a few issues but generally the 100 watt works for me with most equipment. The only issue I remember having with the 100 watt bulb was my Sansui BA-5000 power amp. It would not even power up on the dim bulb tester until I installed a 200 watt bulb. Not sure why that would happen? But it did.
@bmboldt " I went to a larger bulb and everything was fine. For some reason the smaller bulb wasn't allowing the receiver to power up correctly"
This is the reason: watts = volts ^ 2 / ohms. So a higher watt bulb means it has a lower resistance. volts = amps * ohms. So a lower resistance bulb means less volts lost across it, meaning more of the 120V from the wall outlet makes it to your receiver. If your receiver doesn't have enough volts, it's not going to power up correctly. The more current your item draws under normal operation, the more volts you'll lose across the bulb. So higher current items that need an accurate power supply will need a higher watt bulb.
I am just figuring out a wiring diagram for my first DBT. I know where to get some 200 watt incandescent bulbs. I'll go get them for something that needs extra power. I should have bought them when I was there, but I had a mountain of things I was buying
The test lamp wattage should be less than or equal to the device power, but not higher than that because in this case it offers no protection.
I had the EXACT experience yesterday with my dim bulb tester. I was working on a Hafler DH220 and was plugged I to my dim bulb tester. The bias current was a little low since the AC power was a little low due to the voltage drop through the bulb. I had to redo the adjustments.
I noticed that you were using tamper-resistant outlets. I was watching some electrician videos and I realized that I could easily have wire bits and components fall into the receptacles, so I bought that type.
TIP: Plug the dim bulb into a kill-a-watt type meter and keep an eye on that, too. Whenever I adjust bias, as well as the DC voltage, I also watch the input watts vs the rated watts of the amplifier.
Hi. Can i use a 130v 100watts bulb for dimbulb tester? Thanks
Was wondering what size bulb.. had paused the video near the end to get some food.. I see you gave the details thank you !!
Your welcome and thanks for watching. 100 watt usually works well for most equipment.
@@vintageaudioaddict glad i have one..they are becoming hard to find !
What is the advantage of using bulbs instead of testing devices with ammeters? As far as i know you combine isolation transformer with a variac and while you raise the voltage slowly, you keep an eye on the amps. Dim bulb testers are better?
You can see the changes really fast without thinking. If you want to use an ammeter, be sure to get an analog one. You could definitely use a high wattage resistor plus an ammeter. But bulbs are cheap. Throw in a digital ammeter if you just want the data. It's possible that a wirewound resistor could have an inductive effect. I have two 8 ohm non-inductive resistors. That lets me get 8 ohms, 4 ohms if parallel and 16 ohms if in series. These would be good for speaker dummy loads. They are not cheap. I have a goofy lamp that has colored night light incandescent bulbs that I may add to show if it is connected to the mains directly or if not. I haven't decided yet.
The variac, if used alone, will blow up your device if it reaches the critical voltage. The lamp prevents this effect. It acts as a PTC thermistor.
I have question. What wattage bulbs You reccomend for amplifier testing?
Kindle regards.
The answer to your question is in my comment above in the pile.
A 100w bulb is a little low for powerful amplifiers. I use a 300w clear glass bulb so, of course it lights it up bright when there's a dead short but, I still can see the dimmest of illumination if there's an issue without turning the shop lights off.
I have 2 150w clear bulbs in parallel.
Directly related to your text, is my comment above in the pile, regarding the proper wattage of the test lamp.
Hi,
I got a powered mixer 110V 700W power consumption,
I powered it up with a dim bulb tester with 100W bulb. When press power, the dim bulb flashes on and off. You think the dim bulb is limiting the current stopping the mixer to start up.
Yes. (If you want to know why, you can see my comment above in the pile).
Oh man I got lucky then... I was doing exactly what was described in this video NOT to do, and I did not blow up my Marantz 2325. New to doing this, and definitely won't do that again. Thanks!
Your welcome and thanks for watching. You should probably check your idle current again off the dim bulb tester.
@@vintageaudioaddict Did check it off of house power, but then I went to put a new relay in and lifted some traces... since I'm fairly new, I dropped it off at a tech to repair the lifted pads and get it working again, then will slowly recap the boards with a desolder and solder iron.
👍👍
Thanks for watching.
if the old Q620 was shorted why no light ?
Hi, I was thinking that too. The only thing I can think of is if Q620 was open cct, and the continuity beep from the meter was when he tested between the tab and the center pin. Cheers.
There must be a good reason, but im not ambitious enough to Google it, so while I'm here, why do we still use tantilums? Thanks!
The wattage of the bulb should always be less or equal (but not greater than) the wattage of the equipment under repair. Otherwise it doesn't offer any protection. This means that a 100W lamp cannot be used for any repair. Therefore many lamps of different wattage should be available for this test jig...
Can u turn the music down a tad:)
ONE OF A MILLION QUESTIONS , ISN,T THAT THE PURPOSE OF A VARIAC ??
Yes, but it will still blow up your (still defective) device when reaching the critical voltage. The lamp prevents that by lighting up.
Common sense tells you, if you have a dim bulb tester hooked up to a piece of equipment that you're testing for shorts, you are limiting current!
Why in the world would anyone adjust current flow with a dim bulb tester connected? lol
If you can't figure that one out, I guess you need not be repairing electronics right!? There is no room for mistakes like that!
Thanks for commenting and for watching.
I tend to agree. I use it in combination with a Variac. Then when the unit starts, I bypass the dim bulb immediately. I put an abnormally small fuse on the Variac for protection.
The dim bulb needs removed immediately because it can glow without you tend to notice.
Starting off in this hobby, I blew up some output transistors and the lightning strike took out random things on the left amp board on a McIntosh by shorting with my multimeter, and it ended up costing me a pretty penny to get right again... After that, I was so nervous to do anything, that I kept my components on a dim bulb for everything, so for me, the fear was outweighing the logic for a bit, but now that I have good grabbers, I can think clearly again. Apprenticeship helps greatly, to flatten the curve a bit.
What if you forget? Anything can happen if you are fatigued or distracted. No one is infallible.
Haha, yes! On the one hand you have audiophiles who are worried about what power cord to use for best sound reproduction, and on the other you have techs (hobbyists?) adjusting audio equipment with a light bulb in series with the power line! 😆
Newbie question: must the bulb be incandescent?
Yes!
Why are you asuming people are making this mistake? I have never heard that happend.
I am not assuming anything. I am trying to prevent inexperienced people from making a mistake.
@@vintageaudioaddict "Mistake You're Making" ...Aren't you assuming here?
@@geirendre I was one of the people who made that mistake. Why are you assuming that it has "never" happened, just because you haven't heard of it happening?
"The #1 Mistake "You're" Making...?????" "You're" ??? Come'on man!!! That's why you have a bypass switch on the DBT. Only someone who is a dim bulb would do that. You lost me on that one.
There's no downside to using the dim bulb tester, you just don't understand how it works if you think you should make adjustments when plugged into a dbt?? It depends what wattage bulb you're using etc that decides what voltage is fed to the unit. See my explainations of how a dbt works @stevee4444