Technics SUV5 Amplifier Cold Start Issues

Thread Starter

ssid

Joined Jul 7, 2020
35
Hi

I have a Technics SU-V5 Amplifier which sounds fantastic with incredibly low DC of about 1.5mv per channel.

The only issue is it has a cold start problem if left for more than a day or two. This improves the more you use it.

The relay struggles to come on until after about a minute or so and click on on off rapidly until it settles.

So far I have changed the relay and C502 which is connected to IC501 Pin 1 after some advice that this drying out will prevent relay from coming on. This seemed to solve the problem until I left the amp for a month and the problem returned.

Once running it is fine and can be switched off for a few hours and will come back on normally.

I have been advised that it could be an issues with the differential pairs when cold but want to look at a simpler fix first such as a cold solder or damaged trace. I cannot see any obvious cold solder joits, etc.

Any help would be appreciated

Best Wishes

Mr Siri
 

MrChips

Joined Oct 2, 2009
31,001
Technics SU-V5 Test Points

The amplifier checks that the DC output is close to 0V before connecting the loudspeakers via the output relay.
Open the unit and measure the voltages at test points TP1, TP2, TP3, and TP4 with respect to GROUND. If the output is not 0VDC then there is a problem in the DC balance of the amplifier circuit.

Technics SU-V5 test points.jpg
 
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