Last-PAS Reg B+ Board GB Inquiry

[jackinnj]

In 1982 Vorhis and Jung collaborated on a Dynaco PAS Modification "The Last PAS" (although you could have fooled me, as there have been umpteen since.) The Regulated supply was designed by Walt Jung and is the same as the one used in a Marantz 7 mod.

I was going to burn a few boards, but if there is sufficient interest I can get the unit cost down to around $6 or $7.

Here's the schematic:



This is a drawing



email me jack@tech-diy.com if interested.

[GaryB]

Jack,
I'm sure the 1982 circuit will work fine but its a bit complicated due to the fact the the regulator chip wasn't really designed to handle high voltages. ICs have made a lot of progress and there are some high voltage regulators that allow this circuit to be a bit simpler. Here are links to an article and datasheet using the Supertex LR8 high voltage regulator to good effect.
---Gary

http://www.antiquewireless.org/otb/resto0504.htm

http://www.supertex.com/pdf/datasheets/LR8.pdf

[jackinnj]

Originally posted by GaryB
Jack,
I'm sure the 1982 circuit will work fine but its a bit complicated due to the fact the the regulator chip wasn't really designed to handle high voltages. ICs have made a lot of progress and there are some high voltage regulators that allow this circuit to be a bit simpler. Here are links to an article and datasheet using the Supertex LR8 high voltage regulator to good effect.
---Gary

http://www.antiquewireless.org/otb/resto0504.htm

http://www.supertex.com/pdf/datasheets/LR8.pdf

When you use an IC like the LR8 you multiply the noise of its voltage reference by the gain, although I will have to determine empirically whether the zener string with the filter is better or inferior to the setup shown. This circuit has the distinct advantage that the zener reference is driven from the regulated output -- similar to the way that Jung derived the reference for the Super Regulator.

I have received a few notes for some modifications -- the big polypropylenes should probably have L of 27.5, 31.5 and 37.5 mm, some have requested big pads for a choke , full wave bridge, etc. One thing I might consider is an option for a different transistor, but the MJE3439 is a nice TO-225 -- mbe TO-220 as well (which will require some gymnastics.) I haven't sent the boards out, won't do so for a few days until I hear back.

[jackinnj]

some changes -- I worked the board around so that it would fit without major gymnastics into the PAS cabinet -- (note -- the silk isn't dropped in yet). The blue vertical line is a 1/8" saw mark so that the boards can be split. The size of the eyelets were increased pretty substantially. I also allowed for the possibility of employing a full wave bridge.



here's how I propose the two boards will fit into the PAS:

[SY]

Jack, I'd like to get in on this for 5 or 6 boards.

If possible, I'd like to see an option for a small resistor in series with the big electrolytics.

[jackinnj]

Originally posted by SY
Jack, I'd like to get in on this for 5 or 6 boards.

If possible, I'd like to see an option for a small resistor in series with the big electrolytics.

How about a Vishay (maybe now it's GE) Inrush Current Limiter -- one -- is this the problem you are seeking to address?

[SY]

Partially, but I've also found putting a couple of ohms in series with output caps can be useful for stabilty.

For my own applications, I'll probably end up using a bypassed resistor in place of the zener string (i.e., use this as a Maida-type reg), but that's my worry, not the board designer's.

[jackinnj]

the question becomes size -- R0207 or R0417 ? Hmmmm, mbe they don't have to lie on their bellies but can be standing upright.

[SY]

To quote the father in Eraserhead, "Li'l tiny things, no bigger'n yer fist!"

Standing up 1/4 watters is good enough.

[SvErD]

Maybe it's the print, but I still think some of the pads look too small.
What is the size of the board?