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

H

howardnair

New member
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
 
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-
 
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
 
howardnair said:
...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--...
Click to expand...
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.
 
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   
 
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
 
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
 
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--
 
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
 
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
 
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
 
john--yes i keep looking at that to make sure i have it right -and the other connections into/out of the softstart--paul joppa suggested someone to look over my shoulder--how i wish -it seems odd but there does not seem to be  anyone here on the island with that knowledge -so this being a schematic and not a kit i am a little bit out on a limb-oh well i am going to feed myself and puzzle on this some more==sometimes you can't see for looking--howie
 
I can't help much with the soft start board as I don't own one.

What I would do next is see if I could get one of the drivers to work. That might mean disconnecting or bypassing the Shunt reg and just running off B+.

This may well run your 45 beyond spec but for a short proving session, probably be OK...John 
 
i have been to busy to fool with this --so now i have some time-lets see if this drawing will come out
good!! it does--sooo!!! does anyone see anything wrong --i have removed the softstart boards and cked them out- all seems fine --i did not ck the transistors out of circuit-i will just replace them if i do that --at the moment they seem to ck out-i have all 3 types on the way just in case--i will post a link to some pics-also
https://picasaweb.google.com/100635555508988591604/January182014?authkey=Gv1sRgCLKAtazdoePJCw
 

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I think PJ was absolutely correct on this one. I have read and re-read your posts and can't understand what you are doing here. Nor is it clear from your photos since I get a dead link. If you were to try posting in English, that is with capital letters and proper punctuation we might have a better chance of comprehending your problem :) BTW hyphens are not really a form of punctuation ;D Your schematic makes no sense to me. You seem to be dealing with voltages of ~ 500 and I am seriously concerned that you will end up hurting yourself since you seem to have only the vaguest idea what you are doing :(

With great sincerity and concern

Robert Lees
 
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