220V current from where?

[jeffrowland]

Just out of curiosity, since I'm not a technician and Mooly's experience is at least ten billions times greater than mine, I took a look at the photos you linked describing it as "the conditions of the amplifier as it arrived to me 30 years ago etc. etc." and the following is a detail of one photo

View attachment 1460628

where you can clearly see the cut ground wire inside the thermal glue that seals the power cable that originally has no switch at all.
For this reason I guess that the amplifier has double insulation and does not need a ground connection.
However, if I understood correctly you put a switch on the power cable for your convenience, right?
Is the switch bipolar?
In the sense that both the neutral and the phase are disconnected?
Does the switch have a built-in fuse?
Is the switch for 230VAC?
Rated for how many amps?
What quality?
Is it new or used?
How did you attach it to the amplifier chassis?

Just out of curiosity. 🙂

snap/push button, PC power supply type. the wires you see are from the new cable I used, PC power type with cables of the same section as the original ones and as also said at Mooly the ground has never been used/connected. as to whether it is bipolar, I don't know, but I'll open it and take a detailed photo of the button area.

 

[Mooly]

I found a manual but it is a poor copy and pretty much unreadable (the circuit). It does indeed use a triac controlled supply though.
One interesting thing was a service bulletin for buzzing.

The PSU circuits (lots of different variants in the manual) is to poor to follow 🙁

This shows the triac controlled primary at the top and the secondary is at the bottom.

 

[jeffrowland]

@Mooly
I have the complete manual too, but I don't know much about these things. I showed it to a craftsman who reconditions power supplies, but he told me that to replicate it he would have had reservations and he didn't feel like it.

 

[Mooly]

It is a an unusual PSU, one of a kind really. I have reservations on triac control of the primary because the triac does not reduce the voltage applied to the primary in a linear way but rather reduces the average voltage by firing (turning on and off) the triac and that to me a recipe for things to make noise (buzz). That said it was obviously a successful design so maybe those things were manageable.

I've no quick or easy answers I'm afraid.

 

[jeffrowland]

hey Mooly, thanks anyway for all your interest, thanks. it's been buzzing for many years, a little, but it buzzes...

on the button...
maybe there's a mistake in this connection that I made, now that I see it again - what do you think?
the phase and neutral enter the ampli - the blue cable passes from the original glass fuse and goes to the triac, the brown goes directly to the connection that you see. in practice, the button intercepts the passage of current on the board and performs the on-off