Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: Prev 1 2 3 4 5 [6] 7 Next   Go Down
  Print  
Author Topic: Heathkit HB-200 renovation  (Read 51370 times)
N2EY
Member

Posts: 5096




Ignore
« Reply #75 on: October 06, 2011, 02:19:24 PM »

<I have found that MOST hams that I know don't even own an ARRL Handbook!>

Oh dear. It wasn't quite the first thing I learned to read, but almost.....I only have 14 now, dating between 1927 and 2008.

Let's see....ten ARRL handbooks and one RSGB handbook in paper. Two ARRL handbooks, one Orr handbook and one Jones handbook on PDF.

The old 1949 is quite frazzled but it got me started back when. You don't let an old friend like that go away.

73 de Jim, N2EY
Logged
AG6K
Member

Posts: 1




Ignore
« Reply #76 on: October 06, 2011, 04:39:18 PM »

<I have found that MOST hams that I know don't even own an ARRL Handbook!>

Oh dear. It wasn't quite the first thing I learned to read, but almost.....I only have 14 now, dating between 1927 and 2008.

Let's see....ten ARRL handbooks and one RSGB handbook in paper. Two ARRL handbooks, one Orr handbook and one Jones handbook on PDF.

The old 1949 is quite frazzled but it got me started back when. You don't let an old friend like that go away.

73 de Jim, N2EY

  As I understand it there are several coffin manufacturers who install internal custom compartments.  Maybe it would be a good idea to order one with a book rack for Amateur Radio Handbooks and a bulletin board for displaying rare QSL cards ?  cheers Jim
Logged
K8AXW
Member

Posts: 7042




Ignore
« Reply #77 on: October 07, 2011, 09:55:24 AM »

Quote
As I understand it there are several coffin manufacturers who install internal custom compartments.  Maybe it would be a good idea to order one with a book rack for Amateur Radio Handbooks and a bulletin board for displaying rare QSL cards ?  cheers Jim

I saw one of these for the first time about a week ago!  I'm thinking of mentioning this to my wife to get me one (just in case) for my gun.  Just in case..... ya never know.....
Logged

A Pessimist is Never Disappointed!
AG6K
Member

Posts: 1




Ignore
« Reply #78 on: October 09, 2011, 11:21:28 AM »

Quote
As I understand it there are several coffin manufacturers who install internal custom compartments.  Maybe it would be a good idea to order one with a book rack for Amateur Radio Handbooks and a bulletin board for displaying rare QSL cards ?  cheers Jim

I saw one of these for the first time about a week ago!  I'm thinking of mentioning this to my wife to get me one (just in case) for my gun.  Just in case..... ya never know.....

  chortle.  Good idea.  Maybe some moneypockets to hold greenbacks too just in case you can take it with you.?
Logged
K8AXW
Member

Posts: 7042




Ignore
« Reply #79 on: October 10, 2011, 08:42:41 AM »

Quote
chortle.  Good idea.  Maybe some moneypockets to hold greenbacks too just in case you can take it with you.?
   

Knowing my wife as I do she would put a check in the drawer instead of cash!
Logged

A Pessimist is Never Disappointed!
AG6K
Member

Posts: 1




Ignore
« Reply #80 on: October 12, 2011, 06:26:24 AM »

Panicos,

There is one USA source constantly pushing the idea that the resistors across the capacitors cause a heat problem.

  When the plastic sleeve partially melts on the HV filter caps, , what does that tell us about the heat from the equalizer resistors?

 
Quote
If we look at that claim carefully and other claims from that same source, we find most of it is just an opinion or guess with no facts.

Based on the service life history of SB200's, there are very few design problems. There can be some bandswitch issues, the grid bypassing system is not good, and the relay runs very high voltage. If I used one with modern 572 tubes I would add a good fault current limiting resistance

  Good idea Mr. Rauch.  It's called a glitch R and it has to be capable of discharging the HV filter caps without being damaged.  The glitch R is important with 811As and 572Bs because it limits peak cathode-I during unexpected events like an intermittent VHF parasitic oscillation where the filament wires could be broken off by the EMF due to high grid current flow during VHF osc.  Ohmite currently mfgs a 120J, 15Ω surge R that will do this job in most Ham amplifiers.

Quote
and some negative rail power supply clamping. I would also swap from carbons in the suppressor to metal composition resistors

  Another good idea -- Provided one does not wind the suppressor's wire coil around the  metal oxide film resistors, but instead winds the coil next to it so that the two are spaced c. 2mm apart.   Also, the Q of the SB-200's original Cu-wire VHF suppressors is c. 5 at 100MHz.  The Q can be reduced to less than half that by winding the coils from #22 resistance-wire and adding one more turn.  This reduces  VHF-amplification and reduces the possibility of VHF oscillation.  The tradeoff is slightly less P-out at 28MHz. 

Quote
like the Ohmmite OX/OY series with no other change in the suppression  system.

  "no other change" is not a very good idea unless you like  surprises while you are operating.

Quote
Other than that you will find very few repeating complaints or problems that can be documented.

Most of the modifications are more to make people feel like they have done something, because they fix things that historically are never problems even though the amp is around 30-40 years old or older.

My opinion is the designers are almost always much more insightful into what they did than most people trying to re-engineer. In a 40 year life of something normally considered to have a service life of 10-15 years (consumer electronics), any problems show.

Most of things I pointed out are problems for obvious reasons.

For example the relay voltage of around 130 volts was never a problem with tube radios, when the 200 was designed. The band switch issues were an oversight and could have been planned better, so that was a miss.

  The SB-200's bandswitch has an open-contact measured breakdown potential of c. 4900v at sea level.  The peak HF potential during operation is less than half of that.  The bandswitch should not arc unless there is an anomaly. 

Quote
The grid problem with bypass values was created by strong industry influence to use a bad circuit. One person really pushed that mistake.

  namely William Orr. W6SAI. .   RF bypassing the grid with C sounds like it might be a way of improving stability since XC does cancel some of the XL in the 572B's long grid lead to the grid pin - thereby raising the grid's resonant freq. - but Orr's improvement is small.  Since there is no way to cancel the 572B's 0.6pF of feedback C,  to improve VHF stability one needs to reduce VHF gain by decreasing the Q of the anode's VHF suppressor.

end.  Rich, ag6k

Quote
The lack of a negative rail clamp and HV fault limiting was not an issue because back then tubes almost never arced. The carbon parasitic resistors were the only thing available, but now there are much longer life and more rugged metal compositions.

Everything is explainable and measurable. If it cannot be measured as a problem, or explained in a logical way with proof, it is a guess or opinion.

Much of that is driven by people making money, or being misled into thinking things that are not problems are issues.

73 Tom
Logged
K8AXW
Member

Posts: 7042




Ignore
« Reply #81 on: October 12, 2011, 09:28:54 AM »

Quote
  The SB-200's bandswitch has an open-contact measured breakdown potential of c. 4900v at sea level.  The peak HF potential during operation is less than half of that.  The bandswitch should not arc unless there is an anomaly. 




Rich: What is the "breakdown voltage" between the 80M padder capacitor terminal and the grounded bandswitch mounting screw in the early models of the SB-200? 

(Later models put the padder cap ground side lead to the terminal next to the bandswitch mounting screw)
Logged

A Pessimist is Never Disappointed!
G3RZP
Member

Posts: 1321




Ignore
« Reply #82 on: October 13, 2011, 02:00:38 AM »

Is the 4900 volts DC or peak LF AC? For reasons I do not understand - maybe Tom knows - it appears that RF can jump a bit more than DC. I have been told that in perfectly dry air, it doesn't, which suggests that humidity has something to do with it.
Logged
W8JI
Member

Posts: 9748


WWW

Ignore
« Reply #83 on: October 13, 2011, 02:49:34 AM »

Is the 4900 volts DC or peak LF AC? For reasons I do not understand - maybe Tom knows - it appears that RF can jump a bit more than DC. I have been told that in perfectly dry air, it doesn't, which suggests that humidity has something to do with it.

The SB200 wafers and such are the same basic style and manufacturer as the smaller Ameritron and Dentron switches.

The voltage cannot be given as "4900 volts" or some firm number like that. Voltage varies with the arc point, contact style, location on the wafer, the mounting hardware, and even how leads are soldered. Claiming some voltage like 4900 volts is as bad as saying all 3-500 filaments should be set to 4.8 volts, or suppressor inductors should be nichrome.

Between the same points Ameritron's wafers have significantly higher voltage than the same size Dentron wafer. This is because Dentron used "shorting" or make before break rotor contacts that extend further toward the adjacent contact. Ameritron used break before make or non-shorting, which increased spacing.

If you examine similar looking switches, you'll find a significant difference in breakdown between the same points for subtle changes.

The only thing RF causes is a tendency to jump to small isolated areas, or have a bit more corona, because of capacitance. It's bit like the effect of drawing an arc with a screwdriver blade with a well-insulated handle. It happens at RF, but not at DC.

73 Tom
Logged
AG6K
Member

Posts: 1




Ignore
« Reply #84 on: October 13, 2011, 03:12:18 AM »

Quote
  The SB-200's bandswitch has an open-contact measured breakdown potential of c. 4900v at sea level.  The peak HF potential during operation is less than half of that.  The bandswitch should not arc unless there is an anomaly. 




Quote
Rich: What is the "breakdown voltage" between the 80M padder capacitor terminal and the grounded bandswitch mounting screw in the early models of the SB-200? 

  Since the bandswitch ordinarily arcs across the open 80m Tune-C padder contacts when the amp is being operated on other bands, I never measured that BD potential Allen.  cheers, Rich, ag6k.

Quote
(Later models put the padder cap ground side lead to the terminal next to the bandswitch mounting screw)
Logged
AG6K
Member

Posts: 1




Ignore
« Reply #85 on: October 13, 2011, 03:20:16 AM »

Is the 4900 volts DC or peak LF AC?

  DC.  IME, VHF and especially UHF are better able to arc across an air gap than DC or 60Hz.   At 30MHz Jennings uses a derating factor of 60%.  Rich, ag6k



Quote
For reasons I do not understand - maybe Tom knows - it appears that RF can jump a bit more than DC. I have been told that in perfectly dry air, it doesn't, which suggests that humidity has something to do with it.
Logged
AG6K
Member

Posts: 1




Ignore
« Reply #86 on: October 13, 2011, 03:59:28 AM »

Is the 4900 volts DC or peak LF AC? For reasons I do not understand - maybe Tom knows - it appears that RF can jump a bit more than DC. I have been told that in perfectly dry air, it doesn't, which suggests that humidity has something to do with it.

The SB200 wafers and such are the same basic style and manufacturer as the smaller Ameritron and Dentron switches.

The voltage cannot be given as "4900 volts" or some firm number like that.

  Tom R, -- "c. 4900V" means 'around 4900V'.  The c. stands for circa, which in Latin means around.

Quote
Voltage varies with the arc point, contact style, location on the wafer, the mounting hardware,

  Bandswithes typically fail by arcing across open contacts.  Due to the arc temp of over 30kºC, this can cause the fixed contact, or the moving contact, or both to evaporate.
••  Example of evaporated contacts due to intermittent VHF osc.:
http://www.somis.org/bandsw3.html

 
Quote
and even how leads are soldered.

  I have yet to see a bandswitch arc where the wires are soldered to the switch. All of the damaged bandswitches I have seen arced across open contacts. 

Quote
Claiming some voltage like 4900 volts is as bad as saying all 3-500 filaments should be set to 4.8 volts,

  The Amperex or Eimac min. fil-V rating is 4.75v.  One of the Amperex tubes in my SB-220 was mfg in 1967 and it's still doing its job at c. 4.8v. 

Quote
or suppressor inductors should be nichrome.

  A suppressor's job assignment is to dampen the flow of electrons.  Does it make sense to construct a suppressor out of either of the two best conductors of electrons in the Universe -- I.E., Ag or Cu - or to make it out of a lousy conductor of electrons -- I.E., resistance-wire? 
cheers, Rich, ag6k

Quote
Between the same points Ameritron's wafers have significantly higher voltage than the same size Dentron wafer. This is because Dentron used "shorting" or make before break rotor contacts that extend further toward the adjacent contact. Ameritron used break before make or non-shorting, which increased spacing.

If you examine similar looking switches, you'll find a significant difference in breakdown between the same points for subtle changes.

The only thing RF causes is a tendency to jump to small isolated areas, or have a bit more corona, because of capacitance. It's bit like the effect of drawing an arc with a screwdriver blade with a well-insulated handle. It happens at RF, but not at DC.

73 Tom
Logged
5B4AET
Member

Posts: 41




Ignore
« Reply #87 on: October 23, 2011, 03:10:13 PM »

So....
After cheking and rechecking all conections and parts of my SB-200, found few connection mistakes on the "updates" but nothing wrong on the original kit. The only problem was the old damaged resistors on the suppressors and my ignorance to use ordinary resistors instead.

Few days ago I received a nice suppressor kit with lots of info and parts from Mr Measures (THANK YOU SO MUCH).
And the result........
600W on 40 meters, 550 on 20 meters and down to 400 and 350 for 15 and 10 with the old tubes (probably the stock ones)!! Made few contacts just few minutes ago and received good reports on the audio as well.

The bottom line......I learn alot about grounded grid amps. Shocked
Next step, make few more mods (one at a time)  Wink  make few more mistakes and get to learn even more about amps !!

Many many thanks to all of you people who helped and gave me so much info.

Panicos







 



Logged
W1QJ
Member

Posts: 2984




Ignore
« Reply #88 on: October 23, 2011, 05:34:27 PM »

So....
After cheking and rechecking all conections and parts of my SB-200, found few connection mistakes on the "updates" but nothing wrong on the original kit. The only problem was the old damaged resistors on the suppressors and my ignorance to use ordinary resistors instead.

Few days ago I received a nice suppressor kit with lots of info and parts from Mr Measures (THANK YOU SO MUCH).
And the result........
600W on 40 meters, 550 on 20 meters and down to 400 and 350 for 15 and 10 with the old tubes (probably the stock ones)!! Made few contacts just few minutes ago and received good reports on the audio as well.

The bottom line......I learn alot about grounded grid amps. Shocked
Next step, make few more mods (one at a time)  Wink  make few more mistakes and get to learn even more about amps !!

Many many thanks to all of you people who helped and gave me so much info.

Panicos

Drank the cool aid.   Huh
Logged
AG6K
Member

Posts: 1




Ignore
« Reply #89 on: October 24, 2011, 04:40:57 AM »

Quote
So....
After cheking and rechecking all conections and parts of my SB-200, found few connection mistakes on the "updates" but nothing wrong on the original kit. The only problem was the old damaged resistors on the suppressors and my ignorance to use ordinary resistors instead.

Few days ago I received a nice suppressor kit with lots of info and parts from Mr Measures (THANK YOU SO MUCH).
And the result........
600W on 40 meters, 550 on 20 meters and down to 400 and 350 for 15 and 10 with the old tubes (probably the stock ones)!! Made few contacts just few minutes ago and received good reports on the audio as well.

The bottom line......I learn alot about grounded grid amps. Shocked
Next step, make few more mods (one at a time)  Wink  make few more mistakes and get to learn even more about amps !!

Many many thanks to all of you people who helped and gave me so much info.

Panicos

  Tnx for the good news Panicos.  cheers
Rich, ag6k
Logged
Pages: Prev 1 2 3 4 5 [6] 7 Next   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!