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

howardnair · 9920

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Offline howardnair

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Reply #45 on: January 25, 2014, 08:54:03 AM
john ----i had to replace 1 led--prior to removing the softstarts and with b+ hooked -OB to 6 and the 47k in circuit also-i get 200v at pin 6--i then removed the bds replaced the one led that did not light- same one both bds-pulled the 2907's and cked them -they are fine so it seems are the 5371 transistors-using a fluke 115-i would replace  them just to be sure  but have been let down by the mail-you asked to me  remove the 300k Rld and install a 160k to ground at bD-i have no bD-i have bB-i have a Rdb which was the 33k across the 10,000uf cap-could you clarify this plz-
Grainger-the bourbon that was forced on me is from a local distillery called Triple 8
the bourbon goes by the name of Nor'Easter--it is a little too easy to drink-I suffer badly when i drink to much
thanks howie
« Last Edit: January 25, 2014, 09:31:17 AM by howardnair »



Offline 2wo

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Reply #46 on: January 25, 2014, 12:06:58 PM
Sorry I meant bB, the lower end of the 149K R2(b). Looking to break the connection to Kreg.

Adding the 160k from there to ground gives you ~309K, look at the SR Schematic   .

Once you think it is working you can replace the 47K with a 1K. If the C4S is working you should see something like 3-5 volts across it and about 200V at pin 6...John 

John Scanlon


Offline howardnair

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Reply #47 on: January 25, 2014, 12:14:20 PM
john - I know this might be a stupid question-do i want to go to ground  or -reg on the board



Offline howardnair

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Reply #48 on: January 25, 2014, 12:44:58 PM
 OK-i took the 160k to ground actually 150k for the moment--with 6.9v at pin 3 --i get 202v at pin6
no led's light up-the music plays-rt now it is just a ipod and some crappy speakers---just so we are on same page-the 47k is still installed-the 10000uf is not reinstalled and neither is the 33k -b+{IA]  is not connected nor is zener string



Offline 2wo

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Reply #49 on: January 25, 2014, 07:25:51 PM
150k may not be enough, I have not calculated the diode current. Add 15-20k

Then measure the voltage across each led, be careful. Looking for 1-2v. Specify  1.5-1.7v...John

John Scanlon


Offline howardnair

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Reply #50 on: January 26, 2014, 12:21:58 AM
upped to 168k -pin 3 6.9v and pin 6 204v----0v across the led's--cked them again with battery- still good--



Offline 2wo

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Reply #51 on: January 26, 2014, 08:14:57 AM
If you have B+ at LED 1, then something is not connected right. Its only 2 LEDs and 2 resistors. You should be able to figure it out...John 

John Scanlon


Offline howardnair

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Reply #52 on: February 23, 2014, 08:54:49 AM
where did i go?--i didn't --the slowstart bds did go--they do not like to be fooled with -i bought a ccs from k&k audio hooked it to the plate of v1 of the 6cm7 put a 2.k cathode resistor and 33uf cathode bypass cap in and i am using the  amp without the second half of the  6cm7 tube -it sounds very good and the voltages are in line-i am considering using a 76 tube -the modifications would be simple- except for  my wood top plate even though easily drilled would have to be completely refinished--i know the 76 has been used with a 2A3 but has it been done with a 45-any comments would be appreciated

i would like to thank john and paul for their help even tho it was to no avail--howie



Offline Paul Birkeland

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Reply #53 on: February 23, 2014, 09:13:19 AM
Yeah, essentially, you're rolling the amp back to being a Paramour-II, which is a good choice.

The 37/76 are nice old driver tubes, nothing wrong there!

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline 2wo

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Reply #54 on: February 23, 2014, 01:38:32 PM
OK, glad you got it going. Just check that you are not running the 45 too hard. we need the value of the cathode resistor, the voltage across it and the the voltage from the plate to ground...John 

John Scanlon