PHANTOM RETUBED

[2RT307]

I enjoy all of Sonar's old school stuff. I had a friend back in '79 that had a Tram D201A and one of those big 13 tube (I think) D+A Phantom amplifiers. It was gray though, not tan/brown. IIRC, it would do about 1200 watts. We had a lot of fun shooting skip with his Shooting Star.

Glad to see you're getting it all working, Sonar!

73,
Brett

 

[Sonar]

This restoration of Sonar's amp is a fine example of solid workmanship and re-engineering.
Nice.

I don't know why the diode bridges/rectifiers are still set up that way, other than to keep it original.
Think I would have used a couple of large pre-fabbed rectifier blocks, so as allow some heat sinking to the chassis. Should do well enough - as is.

I don't know why myself but I wouldn't be surprised if you hit the nail on the head and it was left that way to keep it as original as possible.
Mike's done that in the past.
When he recapped two of my fs 2340's he left this large multi can type caps in and put the new modern ones underneath.
I cant recall now but there was another item he restored for me and did something similar.

 

[wavrider]

ROBB, cosmetics, I try to install the new caps on bottom of chassis of the Trams and Brownings . I leave the old style original can caps intact, for the vintage look,.

 

[Tallman]

The person that refurbished the amp used 600V capacitors, that's why there's only 6 capacitors instead 8. The idea of using 8 originally is because the original caps were rated at 350V apiece. Since it generates about 900V on on the high setting, it needs 3 x 350V caps to prevent the caps from blowing up from over-voltage, since 3 x 350V = 1050V. He uses 2 x 600V caps in this case, so 2 x 600V = 1200V. Substantially more headroom.

The original setup of 3/3/2 allows for a max of 1050V@33uf/1050V@33uf/700V@50uf.

What's required is 900V/450V per the schematic.

The current setup allows a max of 1200V@50uf/1200V@50uf/1200V@50uf, so with that being said, the current setup is a nice upgrade and will provide many years of service with no problems.

~Cheers~

I studied the photos for about 20 minutes with high magnification and of course Exit Thirteen is spot on. The terminal lug is isolated from ground as I had hoped.
It has been a very long time since I saw a hand wired chassis. I have had to rebuild radios that were "Re-Capped" and miswired and the results are catastrophic.
The interiors of the caps explode with significant force and causes secondary failures of surrounding components by causing short circuits.