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SPECS. ON PT3 POWER TRANSFORMER

207.35.119.205

I would like to know what are the voltage/miliamp specs. re the secondary of the high voltage windings(per winding) for the PT3 power transformer.

Thanks in advance.

Bernie.

Follow Ups:

RE: SPECS. ON PT3 POWER TRANSFORMER - Doc B. 10:06:16 04/17/09 (5)
My agreement with PJ, who owns that design, prohibits me from supporting any other use of the transformer besides its installation in a FPIII or S.E.X. kit exactly as described in the manuals. Because of that I can't discuss the spec without PJ's OK. PJ's concern is that someone will attempt to wire it up in some other design without considering the proper phasing of the two high voltage secondaries and fry it. In that situation we would not be able to offer any replacement guarantee.
- RE: SPECS. ON PT3 POWER TRANSFORMER - Coca 14:19:12 04/17/09 (4)
  Doc. I understand your concern. My reason for wanting that spec. only, is because I did not use my chassis plates that came with my FP3 or my S.E.X. amp, and would like to build something else having the same B+ voltage as the FP3, and utilize those chassis plates. I plan to buy an off the shelf trans. I, knowing the situation with the dual secondaries of the PT3 trans, and the possiblity of someone hooking something up incorectly, also knew I could not purchase it seperately. It was only that one spec. that I needed in order to secure a different trans. Nevertheless, No harm done, and as I said before, I do understand.
  
  Kindest regards.
  
  Bernie.
  - RE: SPECS. ON PT3 POWER TRANSFORMER - Caucasian Blackplate 15:50:29 04/17/09 (3)
    For what you seem to be interested in, the Magnequest PGP-8.1 is something to look into. It should fit into the hole and give you good project flexibility. You will have a tough time finding another drop in replacement.
    - RE: SPECS. ON PT3 POWER TRANSFORMER - Paul Joppa 17:03:46 04/17/09 (2)
      Unfortunately there are not many off the shelf transformers designed for horizontal mounting, and none that I know of with dual high-voltage windings.
      
      The difficult rating to interpret is the heater current, since transformers are rated for RMS current, while in our applications we rectify it and draw DC current. The required AC RMS rating will usually be less than twice the actual DC current, and if you can make suitable measurements the PSUD program will give you a good estimate of the RMS current.
      
      In addition to the Magnequest mentioned above, there are three Hammond units that mount horizontally but only one of them is the right size - that's the 273AZ. It has a center-tapped winding and a 5v/2A heater winding for a rectifier tube, and in that configuration would generate a similar B+ voltage to the SEX amp or the stock (not extended) Foreplay III. Its rated high-voltage DC current is only 40mA, and the RMS AC current on the heater winding is only 2 amps, indicating 1 amp of DC if rectified the way we have done it. I prefer the Hammond 300 series because they have a bit more magnetic headroom, but there are no horizontal-mount units in that line that I know of.
      
      For what it's worth, I hope to re-design the PT-3 eventually, as it's been a good workhorse for us. I want to give up the problematical bifilar high voltage winding at that time, but I can't do that without new output transformers for the SEX and a revised circuit that abandons the WE-style split-rail bias scheme and the autoformer wiring of the output.
      
      Also for what it's worth, the Eros power transformer would fit, and it may eventually become available along with its power supply PC board for experimenters. It's a very quiet transformer magnetically but of course has limited current capability.
      - RE: SPECS. ON PT3 POWER TRANSFORMER - Coca 18:20:41 04/17/09 (1)
        
        In Reply to: RE: SPECS. ON PT3 POWER TRANSFORMER posted by Paul Joppa on April 17, 2009 at 17:03:46
        
        Thanks both to Caucasian Blackplate and Paul Joppa. You have just given me a pile of good information for what I had in mind. I am not that concern as to whether the power transformer is horizontal or vertical, and a single secondary is fine too. Thanks again, you have provided me with all that I need.
        
        Kindest regards.
        
        Bernie.
        
        RE: SPECS. ON PT3 POWER TRANSFORMER - Paul Joppa 22:19:07 04/17/09 (0)
        
        In Reply to: RE: SPECS. ON PT3 POWER TRANSFORMER posted by Coca on April 17, 2009 at 18:20:41
        
        Excellent! Please keep us informed of your progress - I'm sure a lot of forum members will be interested.

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