Sorry, just now found a need and interest for VVR. have Question

[madnis]

I would like to use this VVR but noticed It refers to a TIP147 and shows a
part pic of a NPN device. Am I missing something? shouldn't it be a TIP142?
The pic looks like it's straight out of Valve Wizard. ( I don't have Merlins book )


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my last reply moved to here with corrected parts on diagram

Re: Sorry, just now found a need and interest for VVR. have Question
« Reply #26 on: June 12, 2017, 03:05:42 pm »

Without changing the 100 ohm resistor in the circuit I tried the pot adjust again and to my surprise found it varied ~65 VDC! I can now go from 415 B+ to 350.So I'd say the circuit worked just fine for me.
Lowers all the B+ rail.
I'd encourage anyone to give it a try.let me know if YOU have different results.I'm HAPPY and only out the cost of correct part.$1.23

[tubenit]

There is a considerable amount of information on VVR's and cathode biased amps in ARCHIVES:

http://el34world.com/Forum/index.php?topic=6899.0

Maybe something in there will be useful in answering your question.

With respect, Tubenit

[sluckey]

shouldn't it be a TIP142?

yes

[kagliostro]

That circuit is planned to be used between the CT (of a PT) and Ground

So .... where is the error, is wrong the label (TIP147) or is wrong the NPN simbol ??

(Solid State is very difficult for me ....)

Thanks

Franco

[shooter]

wrong the label

The "arrow point" typically points in the more negative direction

a tip 147 is PNP 

[2deaf]

.... where is the error, is wrong the label (TIP147) or is wrong the NPN simbol ??

The part number (label) is incorrect and the NPN symbol is correct.  Disregard the ground symbol and look at the direction of the current.  The conventional current goes into the Collector and comes out of the Emitter, which makes the Collector end positive and the Emitter end negative.  This is the way that an NPN transistor is connected.  A PNP transistor would have the Emitter connected to positive and the Collector connected to negative.

[Tony Bones]

The thing that's confusing about dropping volts at the CT of the power transformer is that the CT ends up being more negative than ground. So, as far as this little circuit is concerned, ground is the 'positive rail' and the CT is the 'negative rail.'

Should the transistor be NPN or PNP? To answer that question, look at where the base referenced to. In this case it's the negative rail (a.k.a. CT.) That means you need a NPN transistor; TIP142. Connect the emitter to the CT and the collector to ground.

The drawing shows the wrong part number, but is correct otherwise.

(When I first wrote this post I came to 'the other' conclusion based on a different arrangement of this basic circuit. On closer examination I realized I was wrong and edited the post.)

[DummyLoad]

NPN - Not Pointing iN. and how i was taught to remember it in trade school - for bipolar devices. FET's are reverse.


--pete

[madnis]

Thanks, all who replied.
I appreciate prompt reply
and the help.

Thanks Tony B., that helped a lot.

Well I ordered the wrong part
and... did it before I looked closer
and saw the discrepancy. So off
to Mouser I go again
______________________________________________

Has anyone used this design I
like it but...?
Again, Thanks all.
______________________________________________
My apologies to senior members who responded.
I didn't provide much more than the question.
Yes, I did extensive research in the archives here
and looked at other sites on the subject info before
asking my question. yes new to using this forum. I
go by ?mark else where.

It's cathode biased. I've got a higher B+ over all so want to lower all across the board. My choices lower PT sec. with different PT, don't have or drop in Zener(s) at tap. I wanted variable so...

Thanks Franco didn't see the Akins in my search, thank you.

[kagliostro]

Long time ago a friend tried that circuit without success

Now I can think that the problem was the wrong transistor

Franco

[PRR]

Re-draw it as Plus Up.

As connected, the transistor must be an NPN (and by the values, probably a Darlington).

I still have doubts about this plan. But it is late, I need sleep.

[kagliostro]

On my archive I've find also this





Download for full resolution


From Aiken Amplification

Franco

[madnis]

Ok TIP142 used and circuit installed.

I now have 354 VDC at 1st cap,(instead of 425 VDC.)
and overall rail voltages in range. 351 VDC at anode, 300 VDC
at screens and 325 VDC anode to cathode on a pair of tung sol 6v6gt.

But...not much variable. I can only change B+ ~5 VDC
down from 354 VDC. I was hoping for a variable from 425 VDC down to
350 VDC or so. My ignorance is showing. 

[DummyLoad]

Ok TIP142 used and circuit installed.

I now have 354 VDC at 1st cap,(instead of 425 VDC.)
and overall rail voltages in range. 351 VDC at anode, 300 VDC
at screens and 325 VDC anode to cathode on a pair of tung sol 6v6gt.

But...not much variable. I can only change B+ ~5 VDC
down from 354 VDC. I was hoping for a variable from 425 VDC down to
350 VDC or so. My ignorance is showing. 

that circuit does not work. consider using the dana hall VVR.


--pete

[kagliostro]

http://el34world.com/Forum/index.php?topic=6899.0

---

A possible variant on the use of a VVR is to feed with it G2 of the power tubes instead of the plates (less stress on the mosfet due to the lower current)

https://www.tube-town.net/cms/?DIY/Amp-Tools/VoCo_Variable_Voltage_Control

https://www.tube-town.net/ttstore/Kits/Power-Supply/Kit-TT-VoCoM-Variable-Voltage-Regulator::5651.html

Franco

[PRR]

> not much variable.

That was my suspicion. The author is usually spot-on, but this seems to have got by him. (Or it is a trap for people who don't buy/read the book?)

Merlin is a member here.

[DummyLoad]

> not much variable.

That was my suspicion. The author is usually spot-on, but this seems to have got by him. (Or it is a trap for people who don't buy/read the book?)

Merlin is a member here.

if you make the 100R a 470R or thereabouts it's like a switch - full on ~40V drop or full output with about 5% sweep of the pot.


--pete

[2deaf]

Merlin is a member here.

Member Merlin is THE Merlin?  I thought it was just some guy who took that name before Merlin could.  Had I known that it was Merlin himself, I might have asked for a clarification instead of proclaiming he was wrong in some past thread.

[madnis]

Since I'm the one who brought Mr. Blencowe's name into this discussion,
I feel the need to clarify. I had no knowledge of whose circuit diagram I was using. To me it looked like every diagram I had seen in Mr. Blencowe's book and I made the mistake of saying so. My apologies to all.
... Every circuit design I have "lifted" from Mr. Blencowe’s has been correct in theory and in application. I've been VERY happy with what I've used from his knowledge.
 
To the circuit at hand. Upon closer inspection, I realized it was dubious in its depiction of a part number and its orientation in the diagram. I thought I'd ask all of you if you might concur and offer suggestions on using it based on experience with it.
 
Thanks to all who replied.
I've gotten my answer and
greatly appreciate the help.
 
Sorry about any confusion.

[pompeiisneaks]

It is possible that came from his power supply design book that he refuses to reprint until he can do a major rewrite.  He said something on his site about it having quite a few serious problems he needed to rectify before he releases a second edition.  Hopefully he's on that now, as he released a HIFI preamp book recently, and now maybe he will go back to that old topic ;).  I have the tube preamp book and love it, but don't recall if it contained that, but seems unlikely.  I too think that it looks like his format.  He sent me some of his files he uses in the tube books so I can create some images for planned videos on my youtube channel, he's super helpful and very nice.  I don't know if he'll respond here, I've only seen him chat up once or twice in the year or so I've been on.

~Phil

[madnis]

Thanks Phil,


I posted my own re-draw.
with part # used and pin-out.
As suggested, (but not tried yet)
I'll try the 470R instead of 100R.
for more voltage variance.

[sluckey]

It is possible that came from his power supply design book that he refuses to reprint until he can do a major rewrite.

That's where it came from. Page 214

[pompeiisneaks]

It is possible that came from his power supply design book that he refuses to reprint until he can do a major rewrite.

That's where it came from. Page 214

Oh sure rub it in, I'm guessing that means you have one :(  I WANT ONE :P  I need merlin to get busy on that revision 2 stat

lol

~Phil

[madnis]

what he said,
dido.

[sluckey]

Don't hold your breath on that one. He said on his site "Fortunately, all the best material from the power supply book can now be found in the final chapter of my hi-fi preamps book!"

[pompeiisneaks]

Oh I didn't realize that part, maybe I do need to just buy that one.  I'm not as interested in the HIFI side of things personally, but I guess I may learn more about tubes in general by reading that too. 

~Phil

[madnis]

Without changing the 100 ohm resistor in the circuit
I tried the pot adjust again and to my surprise found
it varied ~65 VDC!
I can now go from 415 B+ to 350.


So I'd say the circuit worked just fine for me.
Lowers all the B+ on rail.


    I'd  encourage anyone to give it a try.
let me know if YOU have different results.
I'm HAPPY and only out the cost of correct part.
$1.23