marantz 7t schematic

sportsroom · 2nd October 2007, 07:35 AM

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.

jblmar · 2nd October 2007, 04:16 PM

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

dangus · 2nd October 2007, 08:29 PM

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.

dangus · 3rd October 2007, 02:18 AM

Here it is:

Marantz 7T Aug 1966 Schematic

Bigred · 3rd October 2007, 05:27 AM

Check your serial number. The previous schematic is the 1966 for serials starting 12501. I have the 1967 starting 15001 if needed.

dangus · 3rd October 2007, 09:27 AM

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.

WENGER · 24th February 2010, 07:45 AM

caracteristique du transfo alimentation please
primaire 220v secondaire ? puissance ?
merci de me repondre

sakis · 24th February 2010, 10:49 AM

Quote:

Originally Posted by WENGER

caracteristique du transfo alimentation please
primaire 220v secondaire ? puissance ?
merci de me repondre

english speaking forum .....

WENGER · 24th February 2010, 04:28 PM

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

thanks to all

WENGER · 24th February 2010, 05:59 PM

voltage power supply please

2nd October 2007, 07:35 AM	#1
sportsroom diyAudio Member Join Date: Oct 2007	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.

24th February 2010, 07:45 AM	#7
WENGER diyAudio Member Join Date: Oct 2008	Marantz t7 caracteristique du transfo alimentation please primaire 220v secondaire ? puissance ? merci de me repondre

24th February 2010, 04:28 PM	#9
WENGER diyAudio Member Join Date: Oct 2008	Marantz 7t Which are lack characteristics motivation for realization its tensions in not watch not potency thanks to all

24th February 2010, 05:59 PM	#10
WENGER diyAudio Member Join Date: Oct 2008	Marantz 7t voltage power supply please

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2nd October 2007, 04:16 PM	#2
jblmar diyAudio Member Join Date: Dec 2005 Location: Brooklyn, New York	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

2nd October 2007, 08:29 PM	#3
dangus diyAudio Member Join Date: May 2004 Location: Vancouver Island	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.

3rd October 2007, 02:18 AM	#4
dangus diyAudio Member Join Date: May 2004 Location: Vancouver Island	Here it is: Marantz 7T Aug 1966 Schematic

3rd October 2007, 05:27 AM	#5
Bigred diyAudio Member Join Date: Jul 2007	Check your serial number. The previous schematic is the 1966 for serials starting 12501. I have the 1967 starting 15001 if needed.

3rd October 2007, 09:27 AM	#6
dangus diyAudio Member Join Date: May 2004 Location: Vancouver Island	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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