Paramour I to Paramour II.5 rebuild buildup

[ssssly]

I recently decided to rebuild my Paramour I with upgraded everything. This thread will be to chronical the rebuild as parts come in and to bounce any further ideas about the rebuild off the respective big brains that lurk the board.

First up the top plates have come in as well as a few of the caps for the power supply. For the power end planning on a PT-2 to a full wave Schottky, into a CLCRC filter. 40uf, 50h, 40uf, 1.1k, 47uf. The 40uf motor runs and 47uf Solen can be seen in the pic bellow. And the rebuild will be for 45s not 2a3s hence the large resistor value.

In need of much more room for capacitors and a desire to bring the signal pathway further into the 3rd dimension to maintain short path but maximize keeping power away from signal and improved ground paths I went with a couple of huge aluminum C channels. 13x8x3.75. Planning on tapping all bolts directly into the aluminum to reduce vibration and so that no bolts are externally visible. 

I still have not figured out how I am going to cut through the aluminum for the top mounted iron. I know have drill bits that will go through aluminum that thick but I am fairly certain that I don't have anything that will cut it.

Any suggestions?

I am off to sanding and polishing.

Be well
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[Grainger49]

Since you are drilling and tapping you probably have a center punch to start your holes.  You probably know that regular tapping oil will gall on aluminum too.  And obviously you will need to have a drill stop to keep you from going through the aluminum channel.

But I'm uncertain what you are asking about drilling through aluminum that thick.  I guess I don't understand the question.

[2wo]

You can use a combination of closely spaced,  drilled holes and a saw. If you have a saber saw, and some fine metal blades, your good to go. Or if you drill enough holes you can even get by with a copeing saw and a fine wood blade. For soft aluminum, this is not as hard as it sounds. Finish up with a file, get one of those that look like a rasp with a single set of large curved teeth. They cut aluminum quickly and smoothly

[Paul Birkeland]

I would get a scroll saw and some appropriate blades and give that a shot, drilling your starting holes in the corners of the holes that you need.  You will get a good enough hole for the power transformers, but probably not anything good enough for a square IEC receptacle. 

[ssssly]

Its T6 aluminum so it is fairly workable. Had been debating the drill a ton of small holes method. Think I will end up doing that but drilling them 1/8" shallow. Then cut it out with a coping saw and file/sand it to the desired square shape for the tranny.

Grainger: Yeah I can ramble a bit, especially early in the morning. Was debating how to cut a square out for the power tranny. I have all the stuff to drill and tap the holes for the bolts. And to drill the holes for the tube sockets, power switch, bias knob and, RCAs. Planning on putting the IEC in the wood end cap. Power switch might end up there as well.   

[Grainger49]

I think I wasn't putting it together.  I didn't see that your transformer needs a big square hole below it.

I'm all for power tools.  In your case starting with small holes at the corners and cutting the hole with a Dremel tool using an adapter that will allow it to get close to the top is my suggestion.  Dremel has a thin circular saw blade that will cut metal.  I have never cut anything near that thick but I was surprised that it cut the aluminum that I cut.  And keep your eyes covered I have had metal stuck in my eye and it isn't fun.

Good luck!

[RPMac]

Do you have access to a drill press? That will make things much easier. Be sure to get the cutting fluid for AL like Granger suggested. Helps with the drilling as well as being a requirement for thread cutting.
Step drill...1/8"...1/4"...3/8"...so on. Clamp channels securely..AL is soft and bigger bits will grab...go slow and hold on tight if you are hand drilling.

For the square hole, drill the corners(just large enough to get blade thru) and cut with a hand jigsaw with metal blade(use a medium-course metal blade...less teeth...but not wood blade). Stay inside your line,but close...then finish with a file.

[ssssly]

Thank for the advice. Have several more updates but I am still waiting for tsome of the major parts, such as the Magnequest iron and the soft start shunt boards. I did get the power trannies in and most everything else save a couple of the power supply caps. Hopefully will be able to start the actual layout and markup for cutting the channels in 2-3 weeks.

[ssssly]

Some more parts have come in. Have all the power supply caps (Diversitech motor runs and Obbligato PS) for the CLCRC. Also have the Obbligato parafeed cap in the pic. The power trannies are nice new Bottlehead PT-2s (a special thanks to Eileen for special ordering them for me). Also got the NOS RCA 45s and Sylvania 5670s. Hopefully Mike will have the rest of the iron wound and shipped soon, prob still a week or two, and I can start the markup for final parts placement.

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[ssssly]

Just got notification from Mike Lefever that my iron is on its way. TFA-2004 Nickel Stripe, BCP-15, EXO-003. Now to decide whether I want to add a rectifier tube to go with a 5670 shunt regulated 45 variant or non shunted 5670 45. Have to do some calcs to see if I have enough headroom for the extra tube for the shunt reg.

Also have an Eros and SEX with upgraded iron on the way. The soldering iron will be busy for a while.  

[Paul Birkeland]

Just got notification from Mike Lefever that my iron is on its way. TFA-2004 Nickel Stripe, BCP-15, EXO-003. Now to decide whether I want to add a rectifier tube to go with a 5670 shunt regulated 45 variant or non shunted 5670 45. Have to do some calcs to see if I have enough headroom for the extra tube for the shunt reg.   

You will need a triode for the regulator, not a rectifier.  The PT-2 doesn't have a whole lot of heater current on the 6.3v winding.  You will need to ditch the 5670 as the driver tube, or go with something besides the SR-45. 

[Paul Joppa]

The PT-2 can carry 1.2Arms in the 6.3v winding.

You could do a 5670 driver/regulator for the driver stage, and a 45/6AQ5 output/regulator for the output stage, or you could do what we did - a 6CM7 or 6DN7 with the small triode as driver and the large one as a single shunt regulator for the whole amp. Here's the current breakdown I used:

Output 36mA
driver 3.6mA
driver C4S bias 1mA
Shunt reg 12.9mA
Shunt reg C4S bias 4.9mA
PSU bleeders 1.6mA

Total is 60mA, the rated maximum PT-2 DC current.

To run the second half of the 5670 as a separate shunt regulator would take another 4 or 5 mA, which you'd have to make up somewhere else. The output shunt reg current is already pretty marginal at 12.9mA, so most of that reduction would have to come from the 45 tube. It will run fine at 30mA but distortion into a 3K load will be increased a bit.

Just some food for thought. Engineering is all about compromises and balancing them!

[Paul Birkeland]

Is the 6AQ5 cathode voltage getting a little high for the TL-431 in that circuit?  I seem to remember getting ancy about that, and thinking that 25-35ma of current would be a good idea to keep the cathode voltage at least in the mid 20's. 

All that sure makes me think highly of the good old 6CM7!

[Paul Joppa]

Is the 6AQ5 cathode voltage getting a little high for the TL-431 in that circuit?...

Ouch! You are right; I thought the tube had more gain than that. Better to use a 6BQ5 or a 6S4 or something like that.

[ssssly]

So let me see if i understand everything from this and the shunt reg post correctly:

With the PT-2 I have enough available current to either

A) Shunt regulate the driver stage with a 5670 (Paramount shunt reg scheme)
or
B) Shunt reg both the driver and output stage with a 6cm7 (SR-45 shunt reg scheme)
or
C) Find 5ma to run output and driver with a 5670

If I understand that correctly couple of questions

Does anyone who has heard an SR-45 and a 5670 regulated paramour have anything to say about pros and cons to sonic character?

(Now for the obvious I am not an engineer question) As I sit here staring at the half complete Quickee on my floor I'm wondering why I can't just use some batteries to make up 5ma of heater voltage? I'm sure there is fairly simple reason.

I do however have a set of irons from my Paramour 1s. I was going to use the P1s as a experiment testbed once I had the SEX up and running while I was building this project. But if they could be used to assist in a 5670 fully regulated 45 amp so be it.

Or would it be possible to get custom PT-2s wound able to handle the 65mA needed?