Mac MR-71 Tuning Mystery

Tubes Asylum

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A while ago, a fellow inmate was kind enough to answer my question here in the Tubes Asylum about my MR-71 "squealing" when I tuned below 104 MHz. I took his advice and got a new 6BN4A oscillator tube. I also got a new 6DS4 and 12AT7 to complete the front-end renewal.
The squealing has almost completely gone away now, but I've noticed that when I tune below 96 MHz, I pick up almost no stations and there is a lot of noise, even with muting "in.". I have our local TV cable-service line (via 300-ohm input) connected to the Mac and the one station I'm really interested in--at 94.5 MHz--doesn't come in. The tuner seems to detect the stereo carrier (red light comes on), but there is no audio.
My questions:
- Does the MR-71 need more than these new tubes?
- Why will it bring in stations on the higher end of the dial rather than the lower end?
- Is some idiot-owner fix possible?
When I connect the cable line to a cheap SS receiver, I get the full array of stations. I purchased the Mac in 1969 and it has seen very limited use. I'm going to connect it to my old Finco FM-5 outside antenna (via the 75-ohm input) to see if I can get anything below 96 MHz.
I'm posting this on the General Asylum also. Thanks, fellow inmates.

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Topic - Mac MR-71 Tuning Mystery - Dave 06:57:02 02/23/00 (1)

Re: Mac MR-71 Tuning Mystery - John 16:30:55 02/23/00 (0)

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