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Author Topic: Heathkit SB-200  (Read 7002 times)
K4RVN
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Posts: 50




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« Reply #15 on: November 17, 2016, 02:04:28 PM »

Brian,
I am checking back every day to see if you found a fix.  Please don't leave us out of the solution. I am getting anxious here.
Howdy Lou hope all is well at your place.

Frank
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W1QJ
Member

Posts: 2638




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« Reply #16 on: November 18, 2016, 05:38:39 AM »

Hi Frank, me too.  I keep waiting for him to say he has an open grid shunt resistor like I said.  Been busy, now that Ray from QRO TECH retired I am getting those amps in for repair now.  Hope all your amps are working AOK.
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K4RVN
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Posts: 50




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« Reply #17 on: November 18, 2016, 03:19:03 PM »

Lou I never did fix my improper meter readings on my AL 80A which read low on power out. External watt meters read 900. It works fine as is and I am too lazy to take all the screws out of the cover for a look see. This winter I will get around to it while replacing a non working meter bulb. I am really having fun on 40 meters with my homebrew beam on a 25 ft. boom at 55ft. Zls were coming in last night late at 57-59. I talk to Europe on 40 almost nightly with good reports.
My AL 80 B just keeps on ticking also so I'm happy. I sold my SB 200. I sure will be glad to read what the op found on his amp.

Frank
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W1QJ
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Posts: 2638




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« Reply #18 on: November 19, 2016, 05:06:44 AM »

Frank, Old Ameritron amps with the incandescent bulbs tend to burn out all the time.  I finally figured a way to deal with that issue.  Nowadays you can buy a string of weatherproof LED's, about 16 feet long on a reel for about $10 or less.  You can cut the strip every three inches.  If you take a section of about 6 inches and cut it on the copper tab you then remove the outer coating and scrape the copper tabs.  Solder wires to the tabs and cover with epoxy to secure the connection.  The 6" strip fits nicely above the two meters on the Al-80A and AL-1200/82.  Connect to the 12v supply and you are done.  A dab of hot glue or whatever will keep the strip nicely above the meter edge.  The light that shines down from the LED's is simply beautiful.   You will probably never have to deal with blown bulbs again.  There is no need to fuss with resistors as the strip has them built in.  I suggest the weatherproof type as the heavy layer of insulation contains the heat and diffuses the light nicely.
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K4RVN
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Posts: 50




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« Reply #19 on: November 19, 2016, 01:57:53 PM »

Thanks Lou.

Frank
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KB9RGD
Member

Posts: 24




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« Reply #20 on: November 24, 2016, 03:43:49 PM »

OK, well, Sorry for not getting back.  Regarding the sockets from China, the were 0.99 and I was not aware of MFJ having them.  I have been busy with other things for awhile and have sidetracked it for a bit.  Don't think it is the Band switch. I would consider the Meter switch.  I did replace that the last time.  I am embarrassed to admit I am not sure where the shunt resistor is.  I have been going over the Manual and the schematics and can't find that jumping out at me.  Been unsoldering, testing and resoldering everything I can find in the schematic that looks like it may be a cause.  Meeting with someone in the next day or so.  Maybe he can point me in the right direction.  All the Ideas here are helpful.  Just suffering from a chronic case of air-headedness.
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KB9RGD
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Posts: 24




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« Reply #21 on: November 24, 2016, 03:47:55 PM »

Oh, K6BRN, FYI, I didn't have the cover on the unit and the lid was up.  Did this just in case something happened, as it did.  I saw the flash between the tube base and the socket on V-1 as stated in the initial post. 
« Last Edit: November 24, 2016, 03:51:56 PM by KB9RGD » Logged
KB9RGD
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Posts: 24




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« Reply #22 on: November 24, 2016, 04:14:23 PM »

Sorry if that last post sounded snarky. 
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KB9RGD
Member

Posts: 24




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« Reply #23 on: November 26, 2016, 05:26:30 PM »

Well, I had a guy that knows way more than I about it look at it.  We traced the entire meter circuit and can't find any bad parts.  That includes the SHUNT RESISTOR.  Sorry, I was hoping it would be easy. 
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W1QJ
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Posts: 2638




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« Reply #24 on: November 26, 2016, 05:46:36 PM »

Some resistors need one leg lifted to properly check it
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KB9RGD
Member

Posts: 24




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« Reply #25 on: November 26, 2016, 06:04:59 PM »

This was done that way.  The guy that looked at it is a Ham that works on Aviation electronic's for his day job.
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W1QJ
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Posts: 2638




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« Reply #26 on: November 27, 2016, 08:28:50 AM »

This was done that way.  The guy that looked at it is a Ham that works on Aviation electronic's for his day job.

FWIW...I have fixed numerous amps for all sorts for Electronic engineers with degrees in everything from computer science to rocket science and everything in between.  They were not able to fix the amps and ended up here for repair.  I am not bragging just stating facts.  At this point in time I try to talk amp owners through their own repairs from afar because I am getting tired of jackassing 50+ pound amps in and out of double boxing and down to Fed Ex for the price of a happy meal.  The most bewildering problem I encountered with a Heathkit amp took me an hour to figure out, the routine problems get discovered in minutes.  After you saw the flash of light from putting in those new tubes, what did you do next?  Did you remove them and now have a KNOWN good set of tubes in there and you are still seeing the negative going current?
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K8AXW
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Posts: 6398




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« Reply #27 on: November 27, 2016, 09:18:15 AM »

Quote
Some need one leg lifted to properly check it

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KB9RGD
Member

Posts: 24




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« Reply #28 on: November 27, 2016, 10:10:59 AM »

I am not trying to be a smartass or questioning anyone's skill.  The guy I was with, KS9Q has 30 years as an Aviation electronic tech.  He tested everything in the Bias and what was in the ALC and meter circuits.  He lifted everything.  I even tested the relay box used to trigger the amp between the FT-757GXII and the SB-200.  After the initial flash, I change back to the tubes that I pulled that were weak but good.  Still had the problem.
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KB9RGD
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Posts: 24




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« Reply #29 on: November 27, 2016, 10:14:59 AM »

Even checked everything at the tube sockets.   
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