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

[howardnair]

john -thank you--forgive my bad typing and lack of punctuation-i am a terrible typist-
pin 3  0v
pin 6  438v
pin 9    0
pin1  438v

my link seems to have mind of its own-it says open to anyone with a link-why it changes of its own accord i am not certain--

 

[2wo]

That string of what looks like diodes, connected to pin 1. What is that?

 

[howardnair]

that  is the zener  diode string for the softstart-which uses a 5670 tube -the change from a 5670 to a 6cm7 may be one of my problems-paul birkeland said it would work just be cognizant of the pin out difference and the difference in the 2 sections of the tube-here is that conversation
http://www.bottlehead.com/smf/index.php/topic,3000.405.html


i sent you a personal message
howardnair@comcast.net
my email

 

[Paul Birkeland]

that  is the zener  diode string for the softstart-which uses a 5670 tube -the change from a 5670 to a 6cm7 may be one of my problems-paul birkeland said it would work

I did?  You might want to reread the post where I addressed this, I think I spelled it out pretty clearly...

Frankly, I think this project is way, way over your head.  If you'd start by just building normal Paramours, then you can at least start with a working amplifier.

http://www.bottlehead.com/smf/index.php/topic,3000.msg49671.html#msg49671

 

[howardnair]

https://picasaweb.google.com/100635555508988591604/Sr4502?authkey=Gv1sRgCLTk_5qar63CYA

https://picasaweb.google.com/100635555508988591604/Mar202013?authkey=Gv1sRgCO2NkufB29GP9QE

robert-let me ease your mind-the first link is what i am building-the second is 2 different stereomour's that i have built-i have built a reduction and a foreplay- all can be found in the gallery-i have restored several scotts, dynaco's -even a solid state kenwood 9100-no issues to speak of--this thread is a leak-over from the sr45 thread started by debk--this is my first scratch build-my first problem was instituting a proper ground plane-that was solved with help-i am not an expert and just starting to understand circuits and implementing them to a chassis is quite new to me--the softstart uses a 5670 tube-i am attempting to use a 6cm7-any help is appreciated-i have problems with my picasa links -who knows why-i apologize for the bad typing and lack of punctuation-run on sentences-just think of my post as a telegram-howie

 

[howardnair]

paul-well- yes you did-so long as i was aware that the 6cm7 was 2 different triodes-you should be ok--one for the power supply and one the driver for the 45--and get larger heatsinks-not a exact qoute but it is reply 412--am i in over myhead-yes a little-i have built several bottlehead kits-rebuilt some dynacos -scotts etc--i wanted to do a scratch build-your first has to come eventually-i would love some help--thanks howie

 

[Paul Birkeland]

The best thing you can do is to scratch build Paramours, then install the SR-45.

The SR-45 was never intended to be built from the get-go. 

 

[2wo]

OK, if the zener string was working the voltage at pin 1 would be less than 300v

Next question, when you built the boards did you use the resistor values intended for the SR-45, or the soft start, they are not interchangeable...John 

 

[2wo]

I agree with Paul, lets see if we can get this going as a stock amp or at least get the driver stage working...John

 

[howardnair]

john -thank you-i used the values for the softstart board-so you telling me that they are not interchangeable makes sense as to why the driver does not work-the amp works to a certain extent-when i did have the softstarts installed all the tubes lit up-a tiny bit of sound did come from the speakers--here are the voltages without the driver tubes-b+ to b- 456v
b+ to ground 456v--plate or pin 2 of the 45 456v  0 at the grid of the 45 of course-both sides the same-so what is in this thing-looking at the pics -far left and right 22 uf obbligatto oil cap-the parafeed cap-inboard from that the output transformer-magnequest exo 45s--the big caps below the obbligattos are 100 uf cathode bypass caps--the 4 caps in the middle -220 uf electrolytic 2 for each side-power filter caps-triad c7x 10H-- is topside-the terminal strips with the large resistors right below the filter caps is the power supply -each side is separate-plate chokes are  80h 60 ma. --grid choke is a lundahl 1670 540h 5.3kohm --cathode bypass resistor is 1.5 k--hum pots are 10 ohm with 22 ohm resistors to pins 1 and 4 -those are the  building blocks-can and will change whatever is suggested

 

[howardnair]

i am done for the evening-so running through my head as you and paul talk paramour-it seems  much more logical  to do just that-paramours -forget the sr45--i  have softstart bd, -5670-,-456 b+--the exo 45 is a 5k load-mmmhhh

 

[Paul Birkeland]

and will change whatever is suggested

Build the basic Paramour II circuit.  A 47K resistor will work as a plate load instead of the C4S, just to get you going. 

 

[howardnair]

Paul-thank you--I don't have a schematic labeled paramour II- i have the sr 45 paramour schematic-a simple enough change everything is in place -i will lift the zener string from the circuit-and the grid to ground for v2-that leaves one question -the value of the v1 cathode resistor-ie; pin3--the circuit for the sr45 shows a 5.5k resistor and a 2490 resistor in series-intercepted by a 431 sr- a+b simple enough but how much does the 431 figure into this

 

[2wo]

Disconnect pin 1 and the zener string, that should isolate the regulator.

On the C4S connected to pin 6, I would remove the 10000uf cap and 33k resistor. Now see if the LEDs light and check the voltage at pin 3. Try adjusting the pot to see if you can get ~3-8v or so at pin 3...John

 

[braubeat]

Hello

The 2490 ohm resister in series with the 5.5K resister sets the operating point of the shunt regulator. The 431 chip has a voltage reference of 2.5 volts. So the 2490 ohm resister forms a voltage divider with the 5.5K resister so the 431 chip holds the regulator at 550 volts in this case.  I would guess this is more voltage than you want for a 45 amp. And of course if your power supply won't produce at least 550 volts the shunt regulator will not work at all. 
One more thing I learned the hard way, the anode of the 431 chip must go to ground. Not the cathode as you would think if you did not read the data sheet carefully enough.

Michael

 

[Paul Birkeland]

Hello

The 2490 ohm resister in series with the 5.5K resister sets the operating point of the shunt regulator. The 431 chip has a voltage reference of 2.5 volts. So the 2490 ohm resister forms a voltage divider with the 5.5K resister so the 431 chip holds the regulator at 550 volts in this case.

2.5V across 2.5K -> 8V across 8K.

 

[howardnair]

john -rt side pin 3  0v  pin 6 381v  pin 3 at the 45 0v
  left side pin 3 4v    pin 6 85v        pin 3 at the 45 0v
left side driver tube lights up the right side does not

no leds light up--either side-moving the bias resistor  on the left side has very little effect

michael -i realized that after i walked away from my post--so i have been going through the sections of morgan jones book on voltage dividers and cathode resistors-the reading is a little more involving when you can apply it to a situation at hand

 

[2wo]

On the left side 4v is reasonable, 85v is not, sure its not 185?. But is should play. Might be time to try the 47k resistor ( at least 1W) pin 6 to B+, disconnecting the C4S.

If the right tube is not lighting up there is something wrong with the heater voltage pins 4,5 

 

[howardnair]

Do I disconnect or connect anything else

 

[howardnair]

WE HAVE MUSIC-direct from b+ via the 47k -on pin3 both sides i have 5.9v-
left side pin 6 185
right side pin 6 177
the rt side 6.3  heaters were not getting voltage--cold joint at transformer-
thank you--john
thank you -paul 
now that the amp is viable what will be the next step/s  again- thanks -your help was much appreciated
howie