Sony TA-5650 recap and mod

[Brzzl]

I have a fully working Sony TA-5650, with the varactor diodes already replaced, here. I ran the amp for some time and must say that I'm quite surprised by the sound of this vintage V-Fet amp, especially bypassing the preamp section and using it as a power amp.
However, I also have the fear that the amp might fail sooner or later due to a bad cap and therefore only had the amp playing music for a day in total.
I haven't worked on any V-Fet amp before and since some little mistake could kill the unobtanioum V-Fets, I thought it would be better to get someone else to do the job this time.


Does anyone know someone who worked on a couple of V-Fet amps before, is located in Europe and would be willing to fully recap my amp, change out the bias pots and maybe do some recommended mods like the double-diode mod for the voltage doubler described in this thread?


Thanks for any input

[MarsBravo]

After analysing this circuits, I'm quite sure the Vfet's are destroyed by the power supply.
The higher driver voltage is made with voltage multipliers, which capacitors fail in time causing the driver voltage to drop, causing the Vfet's to conduct at max current, ultimately frying them.
Replace these caps indicated in the purple squares or build a proper supply.

[Brzzl]

Thank you very much for the quick and helpful reply. Have a nice weekend.

[spind]

Search. There are lots of tips here on diyAudio and over at AudioKarma to help you. (I don't have the info right at my fingertips, but it's out there).

[Brzzl]

Originally Posted by spind

Search. There are lots of tips here on diyAudio and over at AudioKarma to help you. (I don't have the info right at my fingertips, but it's out there).

Thank you, but I already checked the threads on diya and ak for tips and mods.


Right now I'm looking for someone in Europe who has experience with V-Fet amps and would be willing to recap/mod the amp since I don't want to take any risks with this amp...