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#1
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problem with old mac mono block
hi, i have a pair of old mac 50-w2 mono blocks and one got sick tonight. the first symptom was a rushing noise a few seconds after the amp was turned on, much like being between channels with a old tube AM radio. i powered it off and suspecting a tube swapped tubes with the working amp. problem satyed with the same amp - so not likely a tube. i then swapped outputs to the speakers - problem stayed with the amp - so not the speaker. when i put it all back together and tried again, one of the output tubes flashed blue and the fuse blew. when i've had similar problems in the past, it's been a bad tube, but it doesn't look like that this time. thoughts? -- Lance |
#2
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#3
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If it has a rectifier tube check that or the power supply caps..that's where
I'd start. Dan wrote in message ... hi, i have a pair of old mac 50-w2 mono blocks and one got sick tonight. the first symptom was a rushing noise a few seconds after the amp was turned on, much like being between channels with a old tube AM radio. i powered it off and suspecting a tube swapped tubes with the working amp. problem satyed with the same amp - so not likely a tube. i then swapped outputs to the speakers - problem stayed with the amp - so not the speaker. when i put it all back together and tried again, one of the output tubes flashed blue and the fuse blew. when i've had similar problems in the past, it's been a bad tube, but it doesn't look like that this time. thoughts? -- Lance |
#4
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Lance:
Typically a PSU cap (Especially vintage FP types) will have a ticking or spitting sound prior to failing when the capacitor plates short-out and the electrolyte starts to ooze out of the bottom seal (Whitish_Brown Powder like stuff). If you had a whooshing sound and actually had a Tube Fail you must suspect something like a shorting signal capacitor, a bias problem or a crispy resistor that shorted out vs.opening-up. Also a shorting wire could also have caused this. Open her up and with a good 100 Watt lamp spend about 1/2 hour looking at the underside of the chassis for telltale signs of carbon deposits, visually burned components or anything like a shorted wire or funny smells. Most often a failure that takes out the fuse has it's roots in a DC short which caused the Power Transformer to exceed its ratings and take out the fuse. Thanks heavens for thiose 0.25cent fuses, they have saved many a precious Mac Transformer. Buena suerte amigo, Rich Sherman wrote in message ... hi, i have a pair of old mac 50-w2 mono blocks and one got sick tonight. the first symptom was a rushing noise a few seconds after the amp was turned on, much like being between channels with a old tube AM radio. i powered it off and suspecting a tube swapped tubes with the working amp. problem satyed with the same amp - so not likely a tube. i then swapped outputs to the speakers - problem stayed with the amp - so not the speaker. when i put it all back together and tried again, one of the output tubes flashed blue and the fuse blew. when i've had similar problems in the past, it's been a bad tube, but it doesn't look like that this time. thoughts? -- Lance |
#5
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Lance:
Definetly open the amplifier up and with a good 100 Watt spot-lamp give her a good look. If you have never upgraded the Power Supply or Power Tube Bias components now is a great moment to consider this. Look for signs of anything that is discolored, charred or smells like it has 'cooked' Whatever you do to your Mac's consider that the other Monoblock will be next in line for an inspection as well. A whooshing sound can be any number of things. In my experience a failing power supply cap emits a spitting or ticking sound. Whoosh from the speakers has to be from a DC short of a Signal Cap or some other component that has failed after so many years of faithful service. Thanks, Ricky wrote in message ... hi, i have a pair of old mac 50-w2 mono blocks and one got sick tonight. the first symptom was a rushing noise a few seconds after the amp was turned on, much like being between channels with a old tube AM radio. i powered it off and suspecting a tube swapped tubes with the working amp. problem satyed with the same amp - so not likely a tube. i then swapped outputs to the speakers - problem stayed with the amp - so not the speaker. when i put it all back together and tried again, one of the output tubes flashed blue and the fuse blew. when i've had similar problems in the past, it's been a bad tube, but it doesn't look like that this time. thoughts? -- Lance |
#6
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