Technics SU-V7

Carlosraj · 25th September 2011, 11:57 AM

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

Mooly · 25th September 2011, 12:03 PM

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.

Ian Finch · 25th September 2011, 06:38 PM

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.

tornislv · 25th September 2011, 09:51 PM

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.

sippy · 25th September 2011, 10:57 PM

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

25th September 2011, 11:57 AM	#1
Carlosraj diyAudio Member Join Date: Jan 2010	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

25th September 2011, 12:03 PM	#2
Mooly diyAudio Moderator Join Date: Sep 2007	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. __________________ ------------------------------------------------------- *A simulation free zone.* *Design it, build it, test it.*

25th September 2011, 06:38 PM	#3
Ian Finch diyAudio Member Join Date: Apr 2010 Location: Coffs Harbour, on the east coast	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. __________________ regards

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25th September 2011, 09:51 PM	#4
tornislv diyAudio Member Join Date: Sep 2010 Location: Riga	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.

25th September 2011, 10:57 PM	#5
sippy diyAudio Member Join Date: Jun 2008	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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