IanB Posted August 27, 2019 Share Posted August 27, 2019 I purchased the Sony Vfet amp from the US about 8 weeks ago. To make it more reliable, as precribed by many, changed the killer diodes and bias resistors. Have been playing amp for last month without a hicup. Turned the amp on yesterday no sound. Turned it off and on again and noticed that the relays are'nt switching on either. Felt the heat sinks, which I image dissipate the heat from the VFets, they felt hot. Not sure how hot they should be? Then read the power supply and bias voltages. Power voltage reads correctly at 20 volts. The bias reading on right reads correctly at 45 volts but the bias reading on the left channel is down reading at 15 volts. No sign of burnt componets. Not sure if the above scenario helps with general diagnose. Hopefully have not blown Vfets? Anyway because of my lack of techical knowledge will need someone who can help. So I tryed connacting Dallas Clark in Melbourne and Liquid Audio in Perth. Neither at this stage are interested in looking at it. So need recommendations of an experanced repair person preferable in Melbourne who would look at it. Would also consider paying knowable DIYer. Link to comment Share on other sites More sharing options...
Guest Posted August 27, 2019 Share Posted August 27, 2019 @Tubularbells Link to comment Share on other sites More sharing options...
tubularbells Posted August 27, 2019 Share Posted August 27, 2019 I would but have 4 repairs on the go will all them being either extremely difficult and lengthy and/or intermittent making it hard to diagnose so the last thing I need right now is a finicky VFET . Don't even have the time to work on my own stuff (JBL active crossover) that needs some TLC. Link to comment Share on other sites More sharing options...
vintagejapan Posted July 16, 2020 Share Posted July 16, 2020 On 27/08/2019 at 1:45 PM, IanB said: I purchased the Sony Vfet amp from the US about 8 weeks ago. To make it more reliable, as precribed by many, changed the killer diodes and bias resistors. Have been playing amp for last month without a hicup. Turned the amp on yesterday no sound. Turned it off and on again and noticed that the relays are'nt switching on either. Felt the heat sinks, which I image dissipate the heat from the VFets, they felt hot. Not sure how hot they should be? Then read the power supply and bias voltages. Power voltage reads correctly at 20 volts. The bias reading on right reads correctly at 45 volts but the bias reading on the left channel is down reading at 15 volts. No sign of burnt componets. Not sure if the above scenario helps with general diagnose. Hopefully have not blown Vfets? Anyway because of my lack of techical knowledge will need someone who can help. So I tryed connacting Dallas Clark in Melbourne and Liquid Audio in Perth. Neither at this stage are interested in looking at it. So need recommendations of an experanced repair person preferable in Melbourne who would look at it. Would also consider paying knowable DIYer. Did you get this sorted? Link to comment Share on other sites More sharing options...
IanB Posted July 19, 2020 Author Share Posted July 19, 2020 Had it looked at. 1 vfet not working. But managed to swap the 3 remaining vfets for a matching set of 4 good vfets. Still sitting on the shelf. Might sell to someone who knows how to fix it. I believe because I have 4 good vfets it is worth fixing. In the meantime I brought a refurbished Sony TA N7 vfet 100 watt power amp which I am very happy with Link to comment Share on other sites More sharing options...
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