They are meant to be current driven, see Product test conditions: "specified using a forward DC drive current of 200 mA".
Figure 4 shows that they are made of two strings of series-connected LEDs in parallel, so apparently they are not so prone to thermal runaway that you can't connect them in parallel (at least not when they are mounted on the same strip). Then again, you already knew that.
Figure 4 shows that they are made of two strings of series-connected LEDs in parallel, so apparently they are not so prone to thermal runaway that you can't connect them in parallel (at least not when they are mounted on the same strip). Then again, you already knew that.
Yes, and I usually run them at about 75% brightness level because at Full brightness they are a bit blinding... I have white countertops in the kitchen.
And I have them in aluminum channel strips with diffusers and bonded to the LED substrate with thermal adhesive.
They barely get over body temp running.
Remember, these are "mid power" type LED's that can handle 200mA.
And I have them in aluminum channel strips with diffusers and bonded to the LED substrate with thermal adhesive.
They barely get over body temp running.
Remember, these are "mid power" type LED's that can handle 200mA.
Here is my experience: Humming Amplifier in Powered Woofer
The ground point for the amplifier was at the output of the AC rectifiers/input to the power supply capacitors, power transformer secondary wires next to signal input wires, and AC rectifiers on the amplifier board next to the amplifier low level signal section.
The ground point for the amplifier was at the output of the AC rectifiers/input to the power supply capacitors, power transformer secondary wires next to signal input wires, and AC rectifiers on the amplifier board next to the amplifier low level signal section.
Most LED drivers are the constant current type.
I have seen 10 Watt mini flood lamps (sealed type), where the big single - chip on board type - LED was driven at 32V, and it ran properly after the failed driver was replaced with a 12V constant current driver unit.
Those drivers for out door use are encapsulated, repair is not possible.
I have seen 10 Watt mini flood lamps (sealed type), where the big single - chip on board type - LED was driven at 32V, and it ran properly after the failed driver was replaced with a 12V constant current driver unit.
Those drivers for out door use are encapsulated, repair is not possible.
Another "fun" trend is to use hard resin on wire ribbons and all kinds of connectors. I dare say, it is a "polite" way to tell owners, well, this is our most ingenuous planned obsolescence!
Once I had a tube powered bass guitar amplifier made in about 1969 by German manufacturer Echolette/Dynacord. The mains voltage selector still was at 220 V~, so I decided to change it to 240 V. Soon after turning the unit on, some magic smoke came out of the transformer cover and the fuse opened. It turned out that in the manufacturing process one part of the four section primary winding was wired out of phase, so I actually had switched the tranny to 200 V, which led to overloading both 20 V winding parts 😱.
Best regards!
Best regards!
Back when dinosaurs roamed the earth and God's dog was just a pup, I had a stand-alone answering machine. It was a fancy one because it stored messages in memory, not a cassette tape. It used 4 AA alkaline batteries. When the batteries got low it would light up a helpful red LED on top to let you know it was time to change them. Of course the LED would then drain the already-weak batteries so they were guaranteed to leak in just a few days, destroying the expensive answering machine. Bad design, or really clever design?
Do you remember the model no? Was it a recent product? I have just "met" a humming Soundcraft....
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One of the stupidist designs I've come across in the repair shop was those newer receivers, amps, and home theater units that utilize and rely on the Rear back panel for critical grounding purposes.
Usually Made In China hunk of crap.
If even a single jack mounting screw becomes loose or has oxidation, the unit won't work or goes crazy.
It makes servicing almost impossible too.
I don't even have to ask any of you is it's a dumb-azzed design.
Usually Made In China hunk of crap.
If even a single jack mounting screw becomes loose or has oxidation, the unit won't work or goes crazy.
It makes servicing almost impossible too.
I don't even have to ask any of you is it's a dumb-azzed design.
That was 40 years ago. Open the bottom and if it has bus wires soldered into slots on the PCB edges, one wire is ground and other(s) are the mixing bus(s), and the space between them is a loop antenna.
More:
1. I had a Panasonic answering machine and wireless phone. When the NiCad batteries died, I called Panasonic and the "tech" went on about memory effect and told me it was my fault for leaving the phone in the cradle. I replaced them with similar better batteries, and it still works 20 years later.
2. When the price of flat screen TVs came down to $2k for a 47", we bought a "Westinghouse" from Best Buy, because the picture looked good. But I left the camera cable plugged into the component input and zapped it dead. Then some internal connectors began to corrode which I fixed by reseating. Then the RF input died and then the HDMI inputs died. This was because the Chinese maker had skipped installing the ESD diodes to save a couple pennies.
3. We now have an LG TV, but the "WEBOS" software is crap. If you push the mute button twice, it brings up a factory reset which wipes out my picture set up, which is needed because the default settings are "posterized", ie too much contrast/ bad gamma and color settings.
4. Both cars have a flat list of USB album folders, which makes finding the right album in 400+ very tedious and dangerous when you are driving.
5. My Samsung phone screen keeps going black in spite of long timeout setting, and the fingerprint reader is located in the same place as the phone hang-up button.
The Sony BVW-75 and all its variants had an arithmetic error in the balanced audio
line drivers. Someone forgot the non inverting amp gain is 1+r1/r2. They built over
10,000 of those machines and nobody noticed. I found it by accident when I was
looking at both phases on a Tek DPO3034 and noticed the difference in amplitudes
and looked it up. When people get all worked up about how critical balanced line is
I'm amused just because it's not that big a deal.
G²
It beggars belief that designers are still making these mistakes with passives. The Lynx cards aren’t cheap either. Might it be that the designers were mainly digital/SW guys?
A common design mistake is to use X2 capacitors not meant for continuous pulse operation in e.g. triac controllers. These are guaranteed to fail (lose capacitance).
Another similar mistake was in Raychem underfloor heating thermostats that use transformless PSU to generate 24V DC. These use a X2 cap to lower the mains voltage prior to diode bridge. In all 4 units I have this X2 cap failed within few months after warranty expired. After replacing the cap with pulse rated X2 the thermostats have been working several years without issues.
Another similar mistake was in Raychem underfloor heating thermostats that use transformless PSU to generate 24V DC. These use a X2 cap to lower the mains voltage prior to diode bridge. In all 4 units I have this X2 cap failed within few months after warranty expired. After replacing the cap with pulse rated X2 the thermostats have been working several years without issues.
Maybe they still design like that 🙂 the one I encountered was a recent model (12... something) - it had a quite loud hum on the 2 leftmost channels but not the others.
//
In the 80's I worked for a small company in New York City that was owned by a Korean guy.
Being a proud Korean, he purchased a Hyundai Excel for a company car when they were introduced in 86.
I was asked to take care of the routine maintenance for the car.
Step 1: Get some spare parts - the oil filter wasn't available in the regular parts stores. Had to order them from the dealer with a 2-3 week lead time.
During the first oil change, I noticed the brake master cylinder was mounted on the passenger side of the firewall instead of the drivers side, which didn't make sense.
Looking under the dash revealed mechanical linkage from the brake pedal over to the passenger side where it passed through the firewall to the engine compartment.
Obviously, the car was designed for right hand drive and then crudely adapted for left hand drive for sale in America. This worked, but we found the passenger could also operate the brakes accidentally if they happened to push on the linkage with their feet, which did happen.
Later the car was stolen and by some inexplicable miracle, it was recovered by the police. Seems even the thieves didn't want it.
When I went to claim it at the storage yard I found it was missing the battery and ........ the oil filter - maybe the most valuable part at the time.
Being a proud Korean, he purchased a Hyundai Excel for a company car when they were introduced in 86.
I was asked to take care of the routine maintenance for the car.
Step 1: Get some spare parts - the oil filter wasn't available in the regular parts stores. Had to order them from the dealer with a 2-3 week lead time.
During the first oil change, I noticed the brake master cylinder was mounted on the passenger side of the firewall instead of the drivers side, which didn't make sense.
Looking under the dash revealed mechanical linkage from the brake pedal over to the passenger side where it passed through the firewall to the engine compartment.
Obviously, the car was designed for right hand drive and then crudely adapted for left hand drive for sale in America. This worked, but we found the passenger could also operate the brakes accidentally if they happened to push on the linkage with their feet, which did happen.
Later the car was stolen and by some inexplicable miracle, it was recovered by the police. Seems even the thieves didn't want it.
When I went to claim it at the storage yard I found it was missing the battery and ........ the oil filter - maybe the most valuable part at the time.