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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: Mac MR-71 Tuning Mystery posted by Dave on February 23, 2000 at 06:57:02:
Hi Dave,Let me ask you, do you hear any hum at all through your speakers, and is there a scratchy sound when you turn the tuning knob to adjust to stations? If there is, I would check the quad filter capacitor first. If I remember right, it is a quad section, each section rated at 50mfd @ 300vdc. If this is leaky, it will cause the voltages in the power supply to be low, which can cause many weird problems to happen. Also check the selenium rectifier in this stage, as they get resistive with age, and can also cause lower voltage in the power supply.
Also, not that this is the problem, but the 12AU7, and the 6U8/6EA8 in the multiplex stage of these tuners, generally are two of the tubes that go bad first. I would also check the 6BL8 output tubes also, as by now they may be weak.
If you are not familiar with working around high voltages that ARE present in this tuner, I would suggest you take it to a reputable service facility for repairs, or McIntosh does continue to do repairs on their older tuners as well. It is not cheap to have them repair these, probably would cost over 300.00.......but IMO the MR71 is a first class tuner and well worth it.......hope this helps.
John
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- Re: Mac MR-71 Tuning Mystery - John 16:30:55 02/23/00 (0)
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