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Someone brought in a little PV PR10. Nice enough little plastic speaker cab with a 10 and a little compression horn. Uses it for a monitor for a synth. Has a burnt out bulb in the tweeter crossover. One of those fat fuse-looking things, the "SK-3 with end caps." Warranty.
Tweeter OK, just a failed bulb. Customer also complained something was loose and rattling around. Took forever to get the darn bulb. backordered.
Unit seemed solid to me, woofer not buzzing and nothing seemed loose. Worked without the tweeter without buzz. Due to lengthy back order delay, I didn't want to go through addirional parts order cycles, so I replaced the woofer just to be safe.
Eventually the bulb came in, I stuck it in the big clips, played music through it to verify everything worked. Sounded good, returned to customer.
"Still buzzes."
Had customer drop back by with it, and I tackled it while he watched. First off I hit it with a rubber mallet, and sure enough something inside was loose. Music playing didn;t trigger the loose thing, but I could see that a low synth note might shake it. I pulled the crossover to see what was what and quickly found the loose something was on the crossover. (Like many PV and other speakers, the large rectangle jack plate is also the crossover) Cab was tight.
pretty quick I discover it is the damned light bulb buzzing. The way the bulb is made, the metal end caps are press fit, not glued. On this one, they made electrical contact just fine, but the glass could wiggle a bit, and made a noise. I could have tightened it up, but since I had ordered a half dozen, I selected another bulb that was tight. The noisy bulb will be fine in some other application.
Customer watching, I determined this bulb sat snug in the clips. The two fuse-type clips are of course larger than those for fuses, and the tops of them stick outwards as little wings. I tugged a small tie wrap around the wings at each end to hold them together tightly. Customer thought that was nice attention to detail, thank you.
My mistake was assuming the music test was sufficient. I should have also run a sweep through the box to look for resonant frequencies in the cab. And even that would not have revealed this before the bulb was installed. Experience tells us that the low freq notes will be what resonates in a speaker cab and causes buzzes. That is largely true, but that doesn;t mean a component in the tweeter crossover can't be the buzzing part. I had made the working assumption that my tests without the tweeter running would reveal buzzes. And even if I had disconnected the tweeter wires and ran a sweep, I would have discovered this noisy bulb. But there was no bulb at the time. I had assumed that didn't matter.
Always run a FULL diagnostic after the repair is complete. My customer had to make two trips. he was OK that I hopped right on it and resolved it for him promptly while he waited, but he shouldn't have had to.
All the high tech stuff I know, all the things I work on, and I get tripped up by a loose light bulb in a speaker. You can never stop paying attention.
Tweeter OK, just a failed bulb. Customer also complained something was loose and rattling around. Took forever to get the darn bulb. backordered.
Unit seemed solid to me, woofer not buzzing and nothing seemed loose. Worked without the tweeter without buzz. Due to lengthy back order delay, I didn't want to go through addirional parts order cycles, so I replaced the woofer just to be safe.
Eventually the bulb came in, I stuck it in the big clips, played music through it to verify everything worked. Sounded good, returned to customer.
"Still buzzes."
Had customer drop back by with it, and I tackled it while he watched. First off I hit it with a rubber mallet, and sure enough something inside was loose. Music playing didn;t trigger the loose thing, but I could see that a low synth note might shake it. I pulled the crossover to see what was what and quickly found the loose something was on the crossover. (Like many PV and other speakers, the large rectangle jack plate is also the crossover) Cab was tight.
pretty quick I discover it is the damned light bulb buzzing. The way the bulb is made, the metal end caps are press fit, not glued. On this one, they made electrical contact just fine, but the glass could wiggle a bit, and made a noise. I could have tightened it up, but since I had ordered a half dozen, I selected another bulb that was tight. The noisy bulb will be fine in some other application.
Customer watching, I determined this bulb sat snug in the clips. The two fuse-type clips are of course larger than those for fuses, and the tops of them stick outwards as little wings. I tugged a small tie wrap around the wings at each end to hold them together tightly. Customer thought that was nice attention to detail, thank you.
My mistake was assuming the music test was sufficient. I should have also run a sweep through the box to look for resonant frequencies in the cab. And even that would not have revealed this before the bulb was installed. Experience tells us that the low freq notes will be what resonates in a speaker cab and causes buzzes. That is largely true, but that doesn;t mean a component in the tweeter crossover can't be the buzzing part. I had made the working assumption that my tests without the tweeter running would reveal buzzes. And even if I had disconnected the tweeter wires and ran a sweep, I would have discovered this noisy bulb. But there was no bulb at the time. I had assumed that didn't matter.
Always run a FULL diagnostic after the repair is complete. My customer had to make two trips. he was OK that I hopped right on it and resolved it for him promptly while he waited, but he shouldn't have had to.
All the high tech stuff I know, all the things I work on, and I get tripped up by a loose light bulb in a speaker. You can never stop paying attention.
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