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Old 2nd October 2007, 08:35 AM   #1
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Default marantz 7t schematic

I've got a marantz 7t with very low level audio even with the pot cranked. In addition, the audio is heavily distorted, kind of like listening to a big piece of gunk on the phono needle. I'm trying to find a schematic, or if anybody out there knows what type of transistors were used, any drop-in replacements, etc., that would be very helpful.
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Old 2nd October 2007, 05:16 PM   #2
jblmar is offline jblmar  United States
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The 7T uses Germanium transistors. They may be difficult to get.
If the 7T has a relay, I would clean its contacts first. If that doesn't help, you'll need an oscioolscope to signal trace the signal.

Ron
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Old 2nd October 2007, 09:29 PM   #3
dangus is offline dangus  Canada
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I've got the schematic (came with the owner's manual for my swap-meet 7T). I'll scan it later today if someone doesn't beat me to it. (version is Aug 1966 - Units Starting With Serial No. 12501)

There's a penciled note on it saying that the transistor with Marantz part no. DTM4 is equivalent to F2N3638A, or 2N3626 or SK3025

The 7T is beautifully made, and ready for a 1960's home theater with a TV input and center channel output. I was disappointed that it wasn't a 7C, but bought it anyway since it came with a Dynaco ST-70 and FM-3. The last time I used it I though it sounded "grittier" than the Hafler DH101; when I get around to it, I want to test it with RightMark Audio Analyzer and see if it meets specs.

According to the owner's manual:
IM distortion was rated at 0.15% at 10 volts rms equivalent peak output; the Performance Documentation card for this unit says it did 0.05% to 0.08% on the bench.
THD was "non-measurable" at 1 volt @ 2kHz, 0.03% at 10 volts @ 2kHz.
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Old 3rd October 2007, 03:18 AM   #4
dangus is offline dangus  Canada
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Here it is:

Marantz 7T Aug 1966 Schematic
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Old 3rd October 2007, 06:27 AM   #5
Bigred is offline Bigred  Canada
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Check your serial number. The previous schematic is the 1966 for serials starting 12501. I have the 1967 starting 15001 if needed.
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Old 3rd October 2007, 10:27 AM   #6
dangus is offline dangus  Canada
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If both channels are misbehaving in the same way, that suggests a single cause. Check the power supply first. A wild guess would be that Q601 or the DC fuse is open.
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Old 24th February 2010, 08:45 AM   #7
WENGER is offline WENGER  France
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Default Marantz t7

caracteristique du transfo alimentation please
primaire 220v secondaire ? puissance ?
merci de me repondre
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Old 24th February 2010, 11:49 AM   #8
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Quote:
Originally Posted by WENGER View Post
caracteristique du transfo alimentation please
primaire 220v secondaire ? puissance ?
merci de me repondre
english speaking forum .....
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Old 24th February 2010, 05:28 PM   #9
WENGER is offline WENGER  France
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Default Marantz 7t

Which are lack characteristics motivation for realization
its tensions in not watch not potency

thanks to all
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Old 24th February 2010, 06:59 PM   #10
WENGER is offline WENGER  France
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Default Marantz 7t

voltage power supply please
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