Re: Topband: DX-100 adventure - progress

[Charlie Cunningham]

After reflecting on your point, that is obviously true, Tom, I would go
ahead and spend a few cents on some rectifiers to put across those
electrolytics!

Operating electrolytics in series is just something I don't do -except in a
voltage-doubler or a Cockroft-Walton multiplier.

Have a Merry Christmas!

Charlie,  K4OTV

-Original Message-
From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Charlie
Cunningham
Sent: Saturday, December 21, 2013 1:32 PM
To: 'Tom W8JI'; 'Bill Cromwell'; 'top Band'
Subject: Re: Topband: DX-100 adventure - progress

Diodes across the electrolytics ro prevent reverse chargin would probably be
a good idea. 1N4007 1000 PIV, 1 A rectifiers should do nicely.

-Original Message-
From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Tom W8JI
Sent: Saturday, December 21, 2013 1:02 PM
To: Charlie Cunningham; 'Bill Cromwell'; 'top Band'
Subject: Re: Topband: DX-100 adventure - progress

> BTW, Biii - tip/suggestion  - for those series-connected electrolytics 
> you probably should put a pair of equal value resistors - one across 
> each series capacitor, as the leakage currents will not be equal in 
> each capacitor in each series string and the DC voltage won't divide 
> equally across each capacitor unless you put individual "bleeder" or 
> "swamping" resistors across each cap in the series pair to equalize 
> the DC across each capacitor in the series!

It is worse than that.

With a single bleeder for two series capacitors, the capacitor with the
least capacitance will always be reversed charged upon every power down. So
even you have equal voltages by equal leakages, you have to add a parallel
diode or the discharge will reverse charge the cap with the lowest
capacitance value. 

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Re: Topband: DX-100 adventure - progress

[Charlie Cunningham]

Diodes across the electrolytics ro prevent reverse chargin would probably be
a good idea. 1N4007 1000 PIV, 1 A rectifiers should do nicely.

-Original Message-
From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Tom W8JI
Sent: Saturday, December 21, 2013 1:02 PM
To: Charlie Cunningham; 'Bill Cromwell'; 'top Band'
Subject: Re: Topband: DX-100 adventure - progress

> BTW, Biii - tip/suggestion  - for those series-connected electrolytics you
> probably should put a pair of equal value resistors - one across each 
> series
> capacitor, as the leakage currents will not be equal in each capacitor in
> each series string and the DC voltage won't divide equally across each
> capacitor unless you put individual "bleeder" or "swamping" resistors 
> across
> each cap in the series pair to equalize the DC across each capacitor in 
> the
> series!

It is worse than that.

With a single bleeder for two series capacitors, the capacitor with the 
least capacitance will always be reversed charged upon every power down. So 
even you have equal voltages by equal leakages, you have to add a parallel 
diode or the discharge will reverse charge the cap with the lowest 
capacitance value. 

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Re: Topband: DX-100 adventure - progress

[Charlie Cunningham]

I REALLY don't care for connecting electrolytics in series. However, Bill
does say that the DX-100  already is configured with individual bleeders
across each capacitor in those series pairs - so he may be OK.



-Original Message-
From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Tom W8JI
Sent: Saturday, December 21, 2013 1:02 PM
To: Charlie Cunningham; 'Bill Cromwell'; 'top Band'
Subject: Re: Topband: DX-100 adventure - progress

> BTW, Biii - tip/suggestion  - for those series-connected electrolytics you
> probably should put a pair of equal value resistors - one across each 
> series
> capacitor, as the leakage currents will not be equal in each capacitor in
> each series string and the DC voltage won't divide equally across each
> capacitor unless you put individual "bleeder" or "swamping" resistors 
> across
> each cap in the series pair to equalize the DC across each capacitor in 
> the
> series!

It is worse than that.

With a single bleeder for two series capacitors, the capacitor with the 
least capacitance will always be reversed charged upon every power down. So 
even you have equal voltages by equal leakages, you have to add a parallel 
diode or the discharge will reverse charge the cap with the lowest 
capacitance value. 

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Re: Topband: DX-100 adventure - progress

[Tom W8JI]

BTW, Biii - tip/suggestion  - for those series-connected electrolytics you
probably should put a pair of equal value resistors - one across each 
series

capacitor, as the leakage currents will not be equal in each capacitor in
each series string and the DC voltage won't divide equally across each
capacitor unless you put individual "bleeder" or "swamping" resistors 
across
each cap in the series pair to equalize the DC across each capacitor in 
the

series!


It is worse than that.

With a single bleeder for two series capacitors, the capacitor with the 
least capacitance will always be reversed charged upon every power down. So 
even you have equal voltages by equal leakages, you have to add a parallel 
diode or the discharge will reverse charge the cap with the lowest 
capacitance value. 


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Re: Topband: DX-100 adventure - progress

[ZR]

Ive been using a 6AH6 in the VFO and regulating the screen and plate with a 
120V 5W zener and suitable dropping resistor and a 47uF 'lytic with a 
.01disc. Grid drive is still sufficient for 100W+ on 10M with full audio 
after those mods are also done.
A 6AH6 is also the better tube in the VF-1, Johnson 122, Globe Champs and 
others using a 6AU6.


The change to choke input on the LV goes back decades since the original way 
was too much LV for some circuits for long reliability.


I use a scope to get ripple down in all circuits to where I like it since 
most of my customers use them on AM but it shouls also help on CW.


I did make a few contacts in the Stew using a 1939 Meissner Signal Shifter 
at 7W and a 1934 National FB-XA receiver.


Carl
KM1H


- Original Message - 
From: "Charlie Cunningham" 

To: "'Bill Cromwell'" 
Cc: "'top Band'" 
Sent: Saturday, December 21, 2013 12:21 AM
Subject: Re: Topband: DX-100 adventure - progress



Hi, Bill!

That's great! You're good to go with the elecrolytics, then!

BTW - as for the chirp on the signal - the DX-100 VFO  and voltage 
regulator
was pretty much  what they sold separately as the VF-1 vfo. The DX-40 had 
a
socket to power it, but I never could get rid of the chirp, until I built 
a

separate PS for the VFO. The OA2 gas tube just wasn't stiff enough to
eliminate the chirp. You might be able to eliminate most of the chirp by
replacing the gas tube with a Zener Diode. By the time you get up ro a 100
volts with the Zener, it's really avalanche breakdown and has a pretty 
stiff

knee. Might improve your chirp!

Have Fun!

73,
Charlie, K4OTV

-Original Message-
From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Bill
Cromwell
Sent: Friday, December 20, 2013 11:12 PM
To: Charlie Cunningham
Cc: 'top Band'
Subject: Re: Topband: DX-100 adventure - progress

On 12/20/2013 11:00 PM, Charlie Cunningham wrote:
BTW, Biii - tip/suggestion  - for those series-connected electrolytics 
you

probably should put a pair of equal value resistors - one across each

series

capacitor, as the leakage currents will not be equal in each capacitor in
each series string and the DC voltage won't divide equally across each
capacitor unless you put individual "bleeder" or "swamping" resistors

across

each cap in the series pair to equalize the DC across each capacitor in

the

series!  I'll be interested to see how it turns out! I never had a DX-100
"Benton Harbor Kilowatt"!  I did  have a DX-40 for a while, but no 160 on
that one, though! I do have an EF Johnson Navigator in pretty good

condition

that needs to  have all of its electrolytics replaced because of their

age.

I does have 160 (and 11 meters also!).

Good luck and Merry Christmas!

73,
Charlie, K4OTV



Hi Charlie,

In the DX-100 there is already a big honking pair of bleeder resistors
so that the bleeder is divided with one half across each half of the
series pair. I think that's what you meant. The DX-100 originally had
two caps rated at 450 volts in series and the bleeder set up that way.

73,

Bill  KU8H
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Re: Topband: DX-100 adventure - progress

[Rich Hallman - N7TR]

For the 0A2 replacement...might want to check this out..

http://www.solidstatetubes.com/0a2-and-0b2.html

Thanks..Rich N7TR

Rich N7TR
ex KI3V, N3AMK, WB3JOV
www.n7tr.com
http://www.qrz.com/db/N7TR
Telnet: dxc.n7tr.com N7TR DXCluster

-Original Message-
From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Charlie 
Cunningham
Sent: Friday, December 20, 2013 9:21 PM
To: 'Bill Cromwell'
Cc: 'top Band'
Subject: Re: Topband: DX-100 adventure - progress

Hi, Bill!

That's great! You're good to go with the elecrolytics, then!

BTW - as for the chirp on the signal - the DX-100 VFO  and voltage regulator 
was pretty much  what they sold separately as the VF-1 vfo. The DX-40 had a 
socket to power it, but I never could get rid of the chirp, until I built a 
separate PS for the VFO. The OA2 gas tube just wasn't stiff enough to eliminate 
the chirp. You might be able to eliminate most of the chirp by replacing the 
gas tube with a Zener Diode. By the time you get up ro a 100 volts with the 
Zener, it's really avalanche breakdown and has a pretty stiff knee. Might 
improve your chirp!

Have Fun!

73,
Charlie, K4OTV

-Original Message-
From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Bill Cromwell
Sent: Friday, December 20, 2013 11:12 PM
To: Charlie Cunningham
Cc: 'top Band'
Subject: Re: Topband: DX-100 adventure - progress

On 12/20/2013 11:00 PM, Charlie Cunningham wrote:
> BTW, Biii - tip/suggestion  - for those series-connected electrolytics
> you probably should put a pair of equal value resistors - one across
> each
series
> capacitor, as the leakage currents will not be equal in each capacitor
> in each series string and the DC voltage won't divide equally across
> each capacitor unless you put individual "bleeder" or "swamping"
> resistors
across
> each cap in the series pair to equalize the DC across each capacitor
> in
the
> series!  I'll be interested to see how it turns out! I never had a
> DX-100 "Benton Harbor Kilowatt"!  I did  have a DX-40 for a while, but
> no 160 on that one, though! I do have an EF Johnson Navigator in
> pretty good
condition
> that needs to  have all of its electrolytics replaced because of their
age.
> I does have 160 (and 11 meters also!).
>
> Good luck and Merry Christmas!
>
> 73,
> Charlie, K4OTV
>
>
Hi Charlie,

In the DX-100 there is already a big honking pair of bleeder resistors so that 
the bleeder is divided with one half across each half of the series pair. I 
think that's what you meant. The DX-100 originally had two caps rated at 450 
volts in series and the bleeder set up that way.

73,

Bill  KU8H
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