SEX 4 Power Transformer Voltages

[pevelg]

Hi,

I've started building my SEX 4 kit and am at the testing of the Power Supply Board Testing.

For the 6.3V DC pads, I am getting -4.29 V for both pads, which is within spec (+/- 3.5V - 4.75V)
For B++1, B+1, B++2, B+2, I am getting 493V, which is above spec (420V - 450V)

Perhaps relevant prior measurements:

Powerline AC Voltage: 123.4V (used terminals 18 & 15 for white wires going to 44U)
Power Transformer Terminals 7 & 8: 6.61V
Power Transformer Terminals 11 & 12: 178.7V

I've keep looking through the manual but can't seem to find any obvious mistakes. Including some images for reference.

p.s. Not sure if it is a misprint, but the PCB on power transformer shows 16V for the 10,000 microF capacitor, while manual and provided part states using a 10V 10,000 microF capacitor.

 

[Paul Birkeland]

That's reasonable enough, they will drop when the rest of the circuit is built out and drawing current properly.

 

[Jameson]

We’ve been discussing widening that range in the next version of the manual, too. It’s on the list to get done soon.

 

[mete]

In the Power Transformer Secondary Test (mains is 230Vac, I measured 232Vac), I am reading V_9_7=6.9Vac, whereas the range is given as 6.3Vac and 6.8Vac. Maybe that range should also be updated. V_12_11 is within range 185Vac.

 

[mete]

Even worse than pevelg, I read +-4.5Vdc on heaters, but 511Vdc and 513Vdc on B+ points. I understand this might still be OK (if 490Vdc is OK, is 515Vdc also OK?) as the circuit is completed, but the capacitors are rated 450V, can the test be dangerous for the capacitors ?

 

[Paul Birkeland]

232V on the 225-235V winding configuration should land you under 500V on the initial turn-on test.

Electrolytic capacitors are generally OK experiencing a turn-on surge voltage provided they get some run time at their intended voltage after the surge. For what it's worth, we have put the same 22uF/450V caps in that position in SEX amps for 19 years without any failures that I can remember.

 

[mete]

You said it should be under 500V for 232V, is there something I should do or shall I continue the build ?

 

[Paul Birkeland]

Can you post a photo of the wiring of your power transformer?

 

[mete]

 

[mete]

Maybe I should modify it to use 235-250Vac wiring, would it decrease B+ and 6.3V too much ?

 

[Paul Birkeland]

Yes, I think it's reasonable to go up to the 235+V configuration.

 

[mete]

I did rewired the PT-10 for 235V-250V configuration. Now I have +-4.0Vdc, 468Vdc and 469Vdc. I think it was a good decision.

 

[pevelg]

I finished assembling the SEX 4.0 a few days ago and everything worked wonderfully. Final resistance and voltage values were all within the spec margins.

The sound was incredible. I primarily listen with headphones, so I wired it for 4 ohms even though my speakers are 8 ohm. Being low sensitivity (~88db, but I listen close range in small room), the speakers sounded weak and a bit muddled, but the headphone experience was incredible.

I began building the Moreplay immediately after (its B+ values were also a bit higher than the manual spec, likely related to my higher house voltage?) and I just finished building it this evening. With the addition of the preamp and that extra bit of power, the speakers sounded perfect at my normal listening levels and still had room to be pushed to uncomfortable levels. I still need to add the Moreplay upgrade, but am already incredbiy impressed with this new system (replaces a SEX 2.0 with Submissive passive source selector). I can't wait to fully integrate this system into my normal listening.

Thank you for your continued product development and the wonderful support offered on these forums!!! I am excited to see where the experiments on this system will take it!!