Markoneswift
Quartz locked n ready to rock
HI all, when testing a reel to reel on a DBT, is it OK for the bulb to glow slightly or is this a sign of a problem ? Cheers.
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DBT question
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DaveVoorhis
Addicted Member
Glowing slightly is normal. Glowing full or near-full brightness is a problem. It indicates a heavy load -- like a short -- which is precisely why you use a Dim Bulb Tester.
c.coyle
Fighting the Dunning-Kruger effect.
If the bulb goes bright on power-up, then quickly dims to a low level, but doesn't go completely dark, you are OK. A higher wattage bulb for the same piece of equipment will probably go completely dark. If it starts bright and doesn't dim at all, then you have a problem.
DaveVoorhis
Addicted Member
Markoneswift
Quartz locked n ready to rock
Great answers guys and exactly what I needed to know. On start up, the bulb is out and my VU meter lights are good. When I trip the auto stop, the motor kicks in and that's when I see the bulb glow dimly so I think I'm good 
c.coyle
Fighting the Dunning-Kruger effect.
Well, it depends on what caused the smoke, I guess. Could it have been caused by a fault the DBT is not designed to look for? Or not sensitive enough to detect? Some fault less than a dead short?
Bulb size is important and should be based on the amount of current the particular unit should normally draw. "Slowly" dimmed is a little imprecise. If a properly sized bulb is used, it will get real bright then dim real fast.
Correlation is not always causation.
There used to be Youtubes showing DBT behavior in various scenarios.
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slimecity
Super Member
With amplifiers generally - a bit of a glow at first while the powersupply caps charge, is normal - then dimming after that is preferable.
Some amps I have tested on DBT glow bright while amp is in start-up protect, then bulb dims when/if amp clicks out of protect.
On a reel-to-reel I woudl personally use a 60W bulb.
Some amps I have tested on DBT glow bright while amp is in start-up protect, then bulb dims when/if amp clicks out of protect.
On a reel-to-reel I woudl personally use a 60W bulb.
Markoneswift
Quartz locked n ready to rock
I think I'm using a 60 watt @slimecity
I will do some better functional testing later today. The seller of the deck said that he connected up to the mains when he got it and the vu meters lit up. He said he tried putting it into play and nothing happened but after a few minutes there was a pop sound and some smoke.
I have inspected all components visually and see no burning. All caps look good, all fuses are intact. I did find that the earth on the power supply pcb was a tad loose so I tightened that up good. I do get the motor running if I deactivate the auto stop, so at least that isn't blown !!
I will do some better functional testing later today. The seller of the deck said that he connected up to the mains when he got it and the vu meters lit up. He said he tried putting it into play and nothing happened but after a few minutes there was a pop sound and some smoke.
I have inspected all components visually and see no burning. All caps look good, all fuses are intact. I did find that the earth on the power supply pcb was a tad loose so I tightened that up good. I do get the motor running if I deactivate the auto stop, so at least that isn't blown !!
