[Heath] Heath Digest, Vol 86, Issue 7

Mon Feb 12 10:52:41 EST 2018

A better way is to leave the supply untouched and use an autotransformer at the input.
Al 
WB9UVJ

Sent from my HTC

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From: heath-request at puck.nether.net
To: <heath at puck.nether.net>
Subject: Heath Digest, Vol 86, Issue 7
Date: Sun, Feb 4, 2018 18:07

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Today's Topics:

1. HP-23 power supplies - an idea and some questions.
(Kenneth G. Gordon)
2. HP-23 (Mike Fitzgerald)
3. Re: HP-23 power supplies - an idea and some questions.
(Kenneth G. Gordon)
4. Re: HP-23 power supplies - an idea and some questions.
(Kenneth G. Gordon)
5. HP-23 (Mike Fitzgerald)
6. Re: HP-23 power supplies - an idea and some questions. (Glen Zook)

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Message: 1
Date: Sun, 04 Feb 2018 13:20:01 -0800
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: Heath at puck.nether.net
Subject: [Heath] HP-23 power supplies - an idea and some questions.
Message-ID: <5A777901.15147.1147466 at kgordon2006.frontier.com>
Content-Type: text/plain; charset=US-ASCII

If one looks closely at the schematic diagrams for the HP-23 series of power supplies, one 
notices an interesting thing:

In the first-model HP-23 supply, the AC winding which feeds the voltage doubler which 
provides the HV is 268 volts, whereas that winding in all subsequent supplies is 282 volts, 
an increase of 14 VAC.

268 * 2.828 = 741 VDC whereas 282 * 2.828 = 798 VDC, an increase of 57 volts. 

ALL HP-23 power supplies are "rated" by Heathkit at 820 VDC output, but as is clear from 
the info above, this cannot possible be so as far as the HP-23 is concerned. 750 VDC 
output is far more likely, and in fact, I have measured it at that voltage when attached to an 
HW-101 and in the transmit condition in CW.

In my experience, it has been almost impossible to realize the full output power of a pair of 
6146s when using the first-model HP-23 power supply, whereas using the later models, full 
power output is easily realizable.

So, I have considered installing a small 110 VAC to 12.6 VAC transformer in the HP-23 with 
the 12.6 Volt winding added in series between the bottom end of the original power 
transformer's HV winding and ground to boost the HV output closer to the "correct" voltage.

What is holding me back is that, as far as I can see, there would be at least 410 VDC 
between that point and the frame of the added transformer.

Now, most modern insulation is rated, according to the National Electric Code, at 600 VDC, 
so, if this is so, then that would, it seems, give me an almost 200 volt safety margin.

Even so, I am still suspicious.

Has anyone here attempted what I am proposing, and if so, what was your result?

If not, I'll go ahead and try this out. I have at least two HP-23s so I can afford to use one as 
a test bench.

Comments?

Ken W7EKB

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Message: 2
Date: Sun, 4 Feb 2018 15:58:10 -0800
From: "Mike Fitzgerald" <MLF42 at Q.com>
To: Heath at puck.nether.net
Subject: [Heath] HP-23
Message-ID: <1UQNoGvir0.ZI9FPe4yLN9 at mike-pc>
Content-Type: text/plain; charset="utf-8"

Ken...

Ken....A lot of trouble for a few more watts out of the 6146's that no one can hear anyway....I have made numerous tests asking receiving stations if they can hear any differende when I QRO from 100  to 150 watts. Not one said they heard any appreciable differe

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nce...Just sayin"....

Mike AA7WU

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Message: 3
Date: Sun, 04 Feb 2018 17:11:45 -0800
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: Chuck Moore <wcmoore at verizon.net>
Cc: Heath at puck.nether.net
Subject: Re: [Heath] HP-23 power supplies - an idea and some
questions.
Message-ID: <5A77AF51.6775.1E89C59 at kgordon2006.frontier.com>
Content-Type: text/plain; charset=US-ASCII

On 4 Feb 2018 at 18:35, Chuck Moore wrote:

> Why?  The difference in output will likely be less than 1dB. 

Efficiency suffers at the lower voltage.

Ken W7EKB

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Message: 4
Date: Sun, 04 Feb 2018 17:33:16 -0800
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: Heath at puck.nether.net
Subject: Re: [Heath] HP-23 power supplies - an idea and some
questions.
Message-ID: <5A77B45C.3629.1FC4C92 at kgordon2006.frontier.com>
Content-Type: text/plain; charset=US-ASCII

On 4 Feb 2018 at 15:54, Mike Fitzgerald wrote:

> Ken....A lot of trouble for a few more watts out of the 6146's that no
> one can hear anyway....I have made numerous tests asking receiving
> stations if they can hear any differende when I QRO from 100  to 150
> watts. Not one said they heard any appreciable difference...Just sayin"....
> 
> Mike AA7WU

You are absolutely correct, of course. 

In fact, in order to increase the signal level at the receiver enough to hear a difference, one 
must double the output power of the transmitter. 100 watts to 200 watts for 1 db difference 
at the receiver.

1 entire S unit (or 6 db, i.e. a power ratio of 4) increase at the receiver requires increasing 
transmitter output power from 100 watts to 400 watts. Then another S unit above that 
requires 1600 watts. No thanks.

I am not concerned about power output here: to my way of thinking, the lower voltage simply 
"isn't right.".

If it was not important, why did Heathkit change the AC voltage from 268 to 282?

Are there deleterious effects due to the lower voltage OTHER THAN power output? I 
suspect so. 

Screen-grid issues come to mind.

But none of the above concerns me.

So, I still have not gotten an opinion or an answer to my question: is it likely that the 410 
VDC across the 12.6 V winding of the added transformer is too much, or is it acceptable?

If no one knows, I believe I'll try it to see. Empirical evidence is always good.

Ken W7EKB

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Message: 5
Date: Sun, 4 Feb 2018 18:00:11 -0800
From: "Mike Fitzgerald" <MLF42 at Q.com>
To: "Heath at puck.nether.net" <Heath at puck.nether.net>
Subject: [Heath] HP-23
Message-ID: <1UQNoIZGhF.a6VWWgIovs8 at mike-pc>
Content-Type: text/plain; charset="utf-8"

The "reason" that transformer was used might have been that's what was available...A productiuon error perhap,  corrected in the later models

Mike AA7WU

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Message: 6
Date: Mon, 5 Feb 2018 02:02:26 +0000 (UTC)
From: Glen Zook <gzook at yahoo.com>
To: "Kenneth G. Gordon" <kgordon2006 at frontier.com>,
"Heath at puck.nether.net" <Heath at puck.nether.net>
Subject: Re: [Heath] HP-23 power supplies - an idea and some
questions.
Message-ID: <1073031498.3387663.1517796146269 at mail.yahoo.com>
Content-Type: text/plain; charset="utf-8"

Methinks you mean 3 dB instead of 1 dB with an increase from 100-watts to 200-watts.? However, even that increase will not be noted in most situations.

As far as why Heath increased the voltage:? A new power transformer was used in the HP-23A that had dual primary windings for 120 VAC and 240 VAC.? Since a new transformer was being used, Heath went ahead and increased the secondary voltage as well to increase the power on the HW-10X and SB-1XX slightly.? Of course, Heath was never conservative on the power ratings of their transmitters.? Having the slightly higher voltage did allow the equipment to come closer to the power ratings.? However, it has been my experience working on a lot of Heath equipment that to make the power claimed by Heath involved pushing the 6146 final amplifier tubes often to beyond their ratings.

Remember, the original 6146 and 6146A / 8298 were rated at 90-watts for Class "C" operation, 85-watts for AB-1 / AB-2 for SSB, and 67.5-watts for AM (all input ratings).? Heath pushed the tubes very hard for both SSB and AM operation.? Of course, back then, the 6146 was in production and very common.? Therefore, who worried if the tubes did not last as long as possible!

?Glen, K9STH?
Website: http://k9sth.net

From: Kenneth G. Gordon <kgordon2006 at frontier.com>
To: Heath at puck.nether.net 
Sent: Sunday, February 4, 2018 7:35 PM
Subject: Re: [Heath] HP-23 power supplies - an idea and some questions.