S.E.X. Power Light

mcandmar · 2442

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Offline mcandmar

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on: November 06, 2013, 05:05:31 AM
I bought one of these 6.3v guitar amp pilot lights http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=121198277720 , with a plan of connecting it to the 6v ac tap of the transformer.  Can anybody confirm if it is ok to do so, or will the current draw have any effect on the tube heater circuit?   I believe the bulbs are .15a

Thanks,

Mark

M.McCandless

Offline porcupunctis

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Reply #1 on: November 06, 2013, 03:57:47 PM
Mark, that is exactly what I did when I built my S.E.X. 2.1.  That was several months ago and with many hours of use, I have had no problems.  Since I didn't need the headphone jack with this build, I reamed that hole out a bit to accommodate the pilot light.  It takes a pretty good sized hole.

I used a green bulb that matches the green anodizing I had done on the plate.  Looks great.

I will be honest and admit that I didn't do the math before installing.  I'm hoping that someone more familiar with the transformer specs will chime in and confirm/deny whether that was a good idea or not in terms of load on the transformer.

Randall Massey
Teacher of Mathematics
Lifetime audio-electronics junkie

Offline mcandmar

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Reply #2 on: November 06, 2013, 04:09:42 PM
"Teacher of Mathematics" who didn't do the math, tut tut :P

I have a vague memory of reading somewhere that heater circuits run around 1mp so i suspect the bulbs load is insignificant, but figured it better to ask incase it does push the load on the transformer near its limit.

Thanks for confirming that anyway, at least i know its not going to release the magic smoke.

M.McCandless

Offline porcupunctis

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Reply #3 on: November 06, 2013, 04:14:56 PM
Well, that was how I reasoned it.  I didn't have the exact specs on the tranny so I couldn't really do the math anyway.  I was trusting that Doc and PJ put in just enough cushion in the specs.  One thing I have really liked about the BH kits is that they are never "barely adequate" in the spec department.  Always solid and well engineered.

Randall Massey
Teacher of Mathematics
Lifetime audio-electronics junkie

Offline mcandmar

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Reply #4 on: November 08, 2013, 02:43:25 AM
Just noticed the blurb for the S.E.X. states the transformer heater secondary is 6.3V @3.5A rms, guess the bulb load really is insignificant.

M.McCandless

Offline Grainger49

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Reply #5 on: November 08, 2013, 04:25:26 AM
I'll tell you a secret.  Even if you were at the rated current, it would still be insignificant.  Tube differences would run you over by 0.15A so Paul Joppa has current headroom that he doesn't talk about.


Offline Paul Joppa

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Reply #6 on: November 09, 2013, 10:07:06 AM
I also have cautions. One of them is that the SEX has DC heaters, and the DC power supply draws nearly twice as much RMS current as DC. But SEX is OK with 6EM7s which draw 1.05 amps, so if you use 6DN7s at 0.9 amps, you have 0.3A left over for sure.

The Rev 2.1 with the PT-7 has a little more headroom, 4.0A rms.

Paul Joppa

Offline mcandmar

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Reply #7 on: November 09, 2013, 02:27:29 PM
Good to know, Thanks Paul.

M.McCandless

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