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.
Sent from AOL Mobile Mail
-----Original Message-----
From: Charles Farr <cefarr@hughes.net>
To: amps <amps@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@ludens.cl";>manfred@ludens.cl</a>>
> To: <a href="mailto:amps@contesting.com";>amps@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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