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Old 25th September 2011, 11:57 AM   #1
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Default Technics SU-V7

Dear Friends,

I am trying to help fix an old Technics SU-V7 amp belonging to a cousin of mine. Everything is working fine, except the loudness circuit. On or Off makes no difference. Bass, Treble and filter switches are working fine. I notice that the Volume pot is a standard rotary 3 pin instead of a usual 4 pin pot used in loudness circuits. I checked the pot with a meter and it is fine. Can someone please some clues on what could be wrong.

Thank you in anticipation.

Rajoo
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Old 25th September 2011, 12:03 PM   #2
Mooly is offline Mooly  United Kingdom
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Check the switch operation with a meter and just trace the switch back...

This has to either physical, as in intermitent/faulty switch, or cracked print somewhere.

Without looking at a circuit I assume a 3 pin pot is correct and that it's not been swapped.

Both channels faulty ? Suspicious if so.
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Old 25th September 2011, 06:38 PM   #3
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This very recent thread discusses the solutions for bad contacts on the SUV series amps.
Dirty connections in Technics su-v7
They have silver plated contacts to the small front panel switches which many users have trouble with as they become dirty, after 25 years. It may be just that simple for you too.
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Old 25th September 2011, 09:51 PM   #4
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Volume attenuator for this amp is standard 3 pin pot 250K log. without 4th tapper. Loudness switch adds C203/C204 of 0.018uF in the path of signal, a kind of. So, either switch, or wiring defective somewhere.
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Old 25th September 2011, 10:57 PM   #5
sippy is offline sippy  United Kingdom
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Hi there,
I googled Technics SU-V7 ahd got this:

Technics SU-V7 | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine

I couldnt remember the sites name, but ive d/l'd from it before, hope this helps
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