2 PT-2 power transformers on 1 chassis--SR45 amp

[howardnair]

i have 2 pt-2 power trannies on one chassis-on one side/channel i have 450v at b+ on the other side/channel  i don't really get a reading-i get fluctuated readings=---this  is at b+ and at the plate on the 45 tube-there are no tubes in yet-the odd  readings are  from ground-yet from b- to b+ i get 450v on both sides -the power trannies are each grounded at a separate point for each - i am beginning to suspect that i need to isolate both trannies from the chassis and find one ground pt for both--a little insight would be greatly appreciated--thanks --howie

[2wo]

Can you sketch out how you have them hooked up?...John

[howardnair]

this will be a interesting lesson--i had not soldered all the circuits-so completing the ground plane etc-i isolated one transformer completely and then connected its ground to star ground with the other power transformer ground -i have on one channel at b+ 445v--on the other channel a  low fluctuating negative reading at b+ but on the b- i have negative 445---this means of course that i am out of phase--so do i connect my transformers in series??

i have no led's lighting up on my softstart bds--but that is the next problem-

[howardnair]

john i will post a pic in about 2 mins or so--howie

[howardnair]

https://picasaweb.google.com/100635555508988591604/January182014?authkey=Gv1sRgCLKAtazdoePJCw
here is a link to my picasa

i will also attempt to attach a photo in the next reply

[Paul Joppa]

...i have on one channel at b+ 445v--on the other channel a  low fluctuating negative reading at b+ but on the b- i have negative 445---this means of course that i am out of phase--...

No, that's not what it means. You need the help of someone who can see what you have in person, and understands more about circuits - there is a limit to how much can be done in forum posts.

[2wo]

What I can see in your pic.  on the input side of the PT-2 you have the hot AC (red) leed connected to '0' unlike the left. This shouldn't  really matter, but its the little things...

Next, grounds. Start with safety ground. Each PT-2 shell should make good contact to the chassis through one of the mounting bolts (star washers) then in turn should be connected to the ground pin of the AC input connector.     

Power supply ground (common). It looks like this is the top row of pins on the large turret board. The right and left side should not be connected together, at least at this point.

Now disconnect any other grounds that connect the 2 sides together and disconnect the B+ just past the last cap/470k resistor(looks like the red wire?) and check your DC voltage across those resistors.

BTW which side seems to work correctly?...John     

[howardnair]

the red lead was a experiment which did not change things--they are both as they should be-the b- or nuetral is not connected from one side to the other-the transformer grounds share the same star ground-i will take the time and isolate them from each other-that may be my issue is that i have the ground terminal on the amp is connected to the chassis-i will change that-looking at the picture the left side is waht works or at least the voltages make sense-thanks howie

[howardnair]

very strange!!!-as of now--power trannies are grounded only at 1 throughbolt-then to power ground--the ground terminal on the transformers now has its own separate set of terminals not connected to the chassis-i still get+ 445v at left side b+-and the fluctuating negative reading on the rt side b+ and at the b- on the right side i get negative 445--i most likely mis-wired something but i cannot seem to find it-at the moment a beer with a scotch chaser is in order-will worry about this later --like tomorow

[Grainger49]

You need to get a good night's sleep and look at it fresh tomorrow. 

[howardnair]

i received a little help from tre on the audioasylum--it seems i did not understand nor implement the grounding scheme--so  i have proper voltages and the amp turns on-the tubes light up --but almost no volume --no leds light on the boards---my pinout for the 6cm7 to the board  4+5 are the heaters---ob on the bd goes to pin 6 -kreg A to pin 3-rca input to pin 7 via a 220 resistor--OA to pin 1-kreg B to pin 9 and pin 8 to ground via a 220 resistor---
-reg goes to ground--

[braubeat]

I am in San Diego if you are anywhere near. I have several amps with similar topology and would be happy to take a look. A schematic would be good. I always make a layout drawing also.
Michael

[howardnair]

ok --have  some voltages on the soft start bds--both sides are the same

             schematic      actual
kregA     4v                      0
kregB     0                        0  ?
OB       175                       354
OA        300                    357
IA        441                     441

at pin 2 the plate of the 45 tube  i have 438--should have 300
at pin 3 iof the 45 tube  the grid -i have 0-should be  175v
so i either have the  6cm7 pinout wrong for the softstart or something wrong on the board


there is some confusion as the sr paramour 45 i think used a different transformer-so i am not sure exactly what voltages are correct but doing some backreading things appear to be somewhat inline except of course kregA and OB--the sun is out and it is 45%  i am going for a bike ride and get the stink blown off--thanks so much for the help---howie

[howardnair]

michael--i am about as far away as one can get --nantucket island is just about as east  in the continental us as one can get--next stop going east is portugal--thanks for your kind offer
howie

[2wo]

The pin out of the 6CM7 is very different from the 5670. I would start there...John