[Amps] Decline of homebrewing?

Sun Jan 8 12:50:02 EST 2017

Amps like the SB220 should be brought into the 21st century.  Skip the cw/ ssb voltage change and instead run all modes at full ssb voltage.  Repurpose the cw/ssb switch to add additional operating bias in CW to lower the idle current.  The actual ssb idle current is good for SSB so the IMD holds.  For CW it can be lowered.  Adding additional operating bias in series with present level and use cw/ ssb switch to short out additional bias in ssb.  Adjust drive level for safe output levels for the various modes.  The amp should be loaded and peaked at the desired output level for constant level modes like cw,RTTY and digital modes so the efficiency is highest.  The only time the amp is loaded and peaked for full output is in multilevel modes like ssb or AM where the amplitude varies on peaks.

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-----Original Message-----
From: Charles Farr <cefarr at hughes.net>
To: amps <amps at contesting.com>
Sent: Sun, Jan 8, 2017 10:04 AM
Subject: Re: [Amps] Decline of homebrewing?

Doesn't anybody remember the "2 man rule"? I have individuals that 
belong to my lodge that work alone, even though I constantly remind them 
to get someone to be with them. Another valuable lesson from the 
military experience.

Chuck, W6AJW

On 01/07/2017 10:13 PM, Jim Thomson wrote:
> Date: Sat, 07 Jan 2017 21:30:23 +0000
> From: Manfred Mornhinweg <<a href="mailto:manfred at ludens.cl">manfred at ludens.cl</a>>
> To: <a href="mailto:amps at contesting.com">amps at contesting.com</a>
> Subject: Re: [Amps] Decline of homebrewing?
> Steve, and all,
>
>> I was nearly killed at age 15.
> ##  heres my sob story.  I was building a heath  GR-64  SW rx  between xmas + new year  1969.  Age 14
> My mum was  cooking dinner, and I was in the den, just off of the kitchen.  I had just finished building the
> kit after several days..and a had 3-4  components left over.  Thought to myself that heath was not too smart to
> be supplying parts that were not required.    Of course, when plugged in and turned on.... it was dead silent.
> I take off the lid, and flip it upside down.... and this is a tube RX.   I start probing around...with my fingers....with zero test gear,
> then got zapped with 300 vdc  off one of the filter caps..it was unplugged too.  Let out a scream, and went flying across the room.  Mother
> freaked out, and figures Im in way over my head, and has a fit. Being from the UK, she thinks nobody should touch anything unless
> they have 1st completed the 7 year apprenticeship  in the appropriate field.   My older sisters  boyfriend at the time  was a physics
> lab  instructor at the local university, and had a lot of experience with HB electronics..and also fixing every heath /  dynaco / knight kit in town.
> He fixes it in a few hrs, and all is well.  3-4 components were indeed required.
>
> ##  fast forward   to 1974. Bought a used HB  2 x  813  amp..with NO  B+ voltage meter.   Great fun driving it with  200 w po  from my used
> drake  TR-3  xcvr.   1100 w out.  Nobody even knew what IMD was back then, and could care less.   I short out the  filter choke on the fully exposed
> B+  supply, for even more B+.
>
> ## wanting more power,  around 1976,  I  buy a used  HB single  3-400Z  rf deck, no cabinet, no B+ meter, and no B+ supply.   I build a hb  5 kv no load  B+
> supply, and also cabinets for both the B+ supply + the RF deck.   Filter caps were a mess of  series and parallel 2-4-6 uf  oil caps....and no bleeder.   Drove the
> 3-400 Z with the TR-3.  No tuned input on the rf deck. 1700 w out of a single 3-400Z.  Tube ran bright orange to sorta yellowish.
> Was working out of  town those days, a week at a time.   B+ supply had been  OFF from sunday eve to the following friday night.   4 inch diam muffin was sorta loose,
> so tightened it with an xcelite   nut driver.   Tube was in the way, so tried to work around it.   Tried tightening the top pair of corner screws, and shaft of nutdriver
> was  touching the glass.    Shoulda yanked the tube but was in a rush,  contest on that weekend.  To get the driver to fit, I slide my fingers down onto the steel nutdriver shaft,
> and try to get the nuts tightened.    Wearing a T shirt with bare arms exposed.   Nut driver shaft touches the plate cap of the 3-400Z..and  also had both forearms resting on the
> aluminum  box.  Top lid was removed.   I get thrown 7 feet across the room, and wake up 5 mins later..dripping in sweat.
>
> ##  lesson learned was oil caps will stay charged for at least 5 days..... esp when  stupid enough to not include a bleeder.
> After that it was B+ meters wired in both the RF decks  and also the external B+ supplies. Bleeders  used, and ditto with shorting sticks etc.
>
> ##  Got zapped a few times while working at the telco....and each time was up 7-10 feet off the ground on a rolling ladder.   AC is bad news.
> B+  will throw you across a room..and both will easily kill you.    Had a buss bar explode in my face while trying to pry a stuck fuse out.   Blew
> a hole in the square shaft of the large screwdriver I was using at the time.   I almost had it out when the shaft touched the partially recessed mounting screw
> for the insulator block assy..in the rack.   I had shorted the input buss side of the bank of fuses.  Now you know why there is at least one guy in every
> telco office nicknamed ..... sparky.
>
> Jim   VE7RF
>
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