Technics SU-V4X Dead?

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Hi, I have a Technics SUV-4X that I have had since new in 1984. It has begun intermittently shutting down to safety mode. Sometimes it runs for a few hours, other times a few seconds.

I have replaced Q501-504 but still the same. Also checked over the main board for dry joints. All psu voltages look to be correct and stable as far as I can tell.

Does anyone have any suggestions as to how I can tell if it is the dreaded SVI2004A that is dying?

I'd hate to pension the amp off - I love it and I have yet to find a modern amp that sounds anything like it. Latest audition was Arcam A70 which sounded like the bass rolled off below about 500Hz!

Any suggestions welcome.

There is a way to id the fault.

check that pins 3 and 14 are 0V

then check pins 7 and 10 should be near -rail voltage

- i have a V4X of mine doin this to me at the moment, its getting DC offset on both channels (bout 2 - 4V) - hard to trace at the moment but definately toward the front end i suspect an elusive dry joint on the front end earthing strap.
definately not the SVI
Hi, thanks for the reply.

I have a couple of these amps now and I have temporarily left the one that is cutting out to one side as I don;t have much time at the moment. Hopefully soon....

From memory, 3 and 14 are at 0v with a slight rise (80mv and noisy on the scope) to pin 3 when the fault appears. Everything else seems to stay as was when no fault, so possibly a fault further back as you suggest. If I get a chance I'll run it up and let you know what I find.

I have a second one with a slightly distorted left cd input. Only shows up on vocal harmonies, like on the first track of not too late by Norah jones - very selective and specific fault! I switched to the tape input which was fine but 6 months later that now seems to be doing the same. I think it is probably the input switch chip. Nothing to do with the switch to safety though!
I had one channel cutting out from time to time in an SUv4x - especially when cold. Spent ages finding the fault including resoldering lots of joints and replacing the relay. In the end it was a dry joint on the speaker terminal. All good now!

Old thread but may help somebody.
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.