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Dueling transformers

Started by Govmnt_Lacky, October 13, 2012, 05:57:01 PM

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Jdansti

#20
October 15, 2012, 05:13:53 PM
Would using a TL783 be a viable option?  It's variable from 1.25V to 125V and rated at 700mA.  I don't mean to steer the thread in a different direction, but thought I'd just mention it to at least learn more about the pros and cons.

http://www.ti.com/lit/ds/symlink/tl783.pdf
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R.G. Keene: EXPECT there to be errors, and defeat them...

Govmnt_Lacky

#21
October 15, 2012, 07:19:52 PM
Quote from: R.G. on October 15, 2012, 04:56:30 PM
It's really, really close. I make it 37.096Vdc before the regulator (Q6) to make 35Vdc. That's certainly not impossible. I'd say go for it with one on a test basis. You may be OK. If not, you can add the other trannie or make a voltage doubler.

Thanks RG and John.... I really appreciate all the help.

So, if I decide to try this with just one transformer.... Should I still use FWB1 and run the AC through it? I am assuming so.

Also, RG... you elude to Q6 as a regulator. I thought that Q6 was an NPN transistor in the Ludwig  ???

Finally, when I do try the single transformer... where would I check for the defining voltage to ensure I am getting what I need?
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

R.G.

#22
October 15, 2012, 10:21:30 PM
Quote from: Govmnt_Lacky on October 15, 2012, 07:19:52 PM
So, if I decide to try this with just one transformer.... Should I still use FWB1 and run the AC through it? I am assuming so.
Yes. Put in the link to use the bridge rectifier as a full wave bridge rectifier, and connect the transformer secondary leads to the two "AC" pads on the PCB.


QuoteAlso, RG... you elude to Q6 as a regulator. I thought that Q6 was an NPN transistor in the Ludwig  ???
Q6 is an NPN transistors that is used as a voltage regulator, albeit a crude one.

QuoteFinally, when I do try the single transformer... where would I check for the defining voltage to ensure I am getting what I need?
Check the voltages to ground on all three leads of Q6. The collector should be 36V or more, the base 35.7 or more, and the emitter 35+/- half a volt.
R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.

Govmnt_Lacky

#23
October 15, 2012, 10:25:53 PM
Thanks again RG  ;)

I must admit that I am quite a ways away from actually testing my Ludwig as I am still awaiting parts to show up  :-\

Once I get the build up finished and try out these transformers, I will post back with results.

BTW..... PM coming your way RG  ;)
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Govmnt_Lacky

#24
October 23, 2012, 01:59:04 PM Last Edit: October 23, 2012, 02:03:46 PM by Govmnt_Lacky
OK....

I mocked up the PS section of the Ludwig on breadboard using all of the called-for components (TIP112 for Q6) and my transformer.

I ended up getting 34.25VDC at Q6 Emitter  :'(  A bit low.

Is there anything I can do to bump it up a bit? Perhaps some adjustments with R26 or R23. Will 34.25V with no load suffice in the circuit?

Thanks for the assistance  ;)
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Jdansti

#25
October 23, 2012, 07:30:13 PM
Quote from: Govmnt_Lacky on October 23, 2012, 01:59:04 PM
OK....

I mocked up the PS section of the Ludwig on breadboard using all of the called-for components (TIP112 for Q6) and my transformer.

I ended up getting 34.25VDC at Q6 Emitter  :'(  A bit low.

Is there anything I can do to bump it up a bit? Perhaps some adjustments with R26 or R23. Will 34.25V with no load suffice in the circuit?

Thanks for the assistance  ;)

As for whether 34V will work or making some changes to get a little more voltage, I'll leave that to R.G.

If you need a DC/DC booster, the UC2577-ADJ might work, but it's not cheap at around $18.

http://www.ti.com/lit/ds/slus216a/slus216a.pdf

From the data sheet: "The UC2577-ADJ device provides all the active functions necessary to implement step-up (boost), flyback, and forward converter switching regulators. Requiring only a few components, these simple regulators efficiently provide up to 60V as a step-up regulator, and even higher voltages as a flyback or forward converter regulator."

"The UC2577-ADJ features a wide input voltage range of 3.0V to 40V and an adjustable output voltage. An on-chip 3.0A NPN switch is included with undervoltage lockout, thermal protection circuitry, and current limiting, as well as soft start mode operation to reduce current during startup. Other features include a 52kHz fixed fre- quency on-chip oscillator with no external components and current mode control for better line and load regulation."

http://www.mouser.com/Search/m_ProductDetail.aspx?Texas-Instruments/UC2577T-ADJ/&qs=/ha2pyFaduggwaU7%252bB8sFQLVDZIYB1n2MLatPrsmyLw=
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R.G. Keene: EXPECT there to be errors, and defeat them...

Govmnt_Lacky

#26
October 24, 2012, 12:19:38 PM
Fixed some not-so-obvious wiring issues on the breadboard  :icon_redface: And re-measured (this time without the transformer getting toasty  :icon_eek:)

Q6-

Base: 35.75V
Collector: 37.25V
Emitter: 35.70V

It was explained to me that in an "ideal" situation, you want the Collector at 3-6V higher than Emitter. This is obviously lacking (only 1.5V higher)

So the question now is... Can I run with this setup (with or without possible PS resistor value adjustments) -OR- do I need to look at running 2 transformers in series to bump up the voltages to get a larger seperation between Q6 Collector and Emitter voltages  ???

Hmmmmm.... help for the clueless please  ::)
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

R.G.

#27
October 24, 2012, 01:14:28 PM
Any chance you have a wall wart around that puts out 16vac to 18vac?
That would be about right to try a doubler on.
R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.

Govmnt_Lacky

#28
October 24, 2012, 01:58:28 PM
Quote from: R.G. on October 24, 2012, 01:14:28 PM
Any chance you have a wall wart around that puts out 16vac to 18vac?
That would be about right to try a doubler on.

Dont have any of those  :icon_cry:

I would really like to get these transformers into the Ludwig. I have 2 just begging to be used. If it is a matter of voltage being insufficient, I could always try running the 2 in series.

In the end, if I cannot get this to work within reason I will probably just go ahead and purchase the recommended wall wart but I would like to try Plan A first.  ;D

Thanks for all your help with this!!
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

R.G.

#29
October 24, 2012, 04:23:42 PM
The only thing I have against two 24Vac transformers in series is that they're likely to cause about 5W of heating in Q6. If you go that way, you'll need something similar to this:

http://www.mouser.com/ProductDetail/Aavid-Thermalloy/507302B00000G/?qs=%2fha2pyFaduguOHMd%2fQeWiVI5mWG%252bm0yKQkNwV4yhhPywG40xOa5m3g%3d%3d
R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.
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