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Author Topic: SB 200 meter problem  (Read 3656 times)
KA9VAA
Member

Posts: 55




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« on: December 20, 2004, 04:51:48 AM »

I have a heathkit sb 200, it works fine but for some reason the rel power / swr meter setting stoped working, the meter also does not show a grid current at idle, anyone have any ideas where to start looking.

Thanks
Happy Holidays.
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K7KBN
Member

Posts: 3693




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« Reply #1 on: December 20, 2004, 07:39:06 AM »

Does the meter ever indicate ANYTHING?

I'd check continuity through the meter switch up to the meter terminals.  If that's good, I'd very briefly "tickle" the meter terminals with a 1.5V cell through a one megohm or so resistor, just enough to see if there is any pointer movement.
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73
Pat K7KBN
CWO4 USNR Ret.
KA9VAA
Member

Posts: 55




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« Reply #2 on: December 21, 2004, 02:11:11 AM »

> Does the meter ever indicate ANYTHING?<

I guess I stated the question wrong, sorry, the meter in the hv setting shows 2400 v, in the plate setting after tune up and key down shows about 450 ma, grid setting shows about 100 ma, it is the swr and rel out put settings that show nothing ever.

Thank you.
ka9vaa de tom
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K7KBN
Member

Posts: 3693




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« Reply #3 on: December 21, 2004, 11:23:33 AM »

Okay - SOME of the contacts on the meter selector switch are working.  I'd check those that aren't working to see if there's a loose or broken contact.  I don't have a schematic of the SB200, and it's been quite a while since I played with one.  Just be careful of the HV.
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73
Pat K7KBN
CWO4 USNR Ret.
AE6RV
Member

Posts: 146




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« Reply #4 on: December 21, 2004, 12:50:55 PM »

A quick look at the schematic would make me think it's the relative power pot.  Be very very careful of the HV.  Be Sure it's safe in there!
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K7KBN
Member

Posts: 3693




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« Reply #5 on: December 21, 2004, 09:27:44 PM »

Ah!  Somebody with a schematic...welcome!!
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73
Pat K7KBN
CWO4 USNR Ret.
N0TONE
Member

Posts: 173




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« Reply #6 on: December 21, 2004, 10:18:20 PM »

Well, you should never see grid current when it's in idle, so that's a good thing.

Basically, you've narrowed it down.  There's something amiss in the rel power/SWR circuitry.  That could be the rel power pot, or you could have blown the detector diode (more common).  Remember, that SWR circuit is designed for exciter power, not the amp power.

AM
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AE6RV
Member

Posts: 146




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« Reply #7 on: December 21, 2004, 10:27:45 PM »

I got the schematic from bama.sbc.edu.  It's an ftp site, but enter the address just bama.sbc.edu.  It's a very very busy site, and you probably won't have any luck using IE or any other browser to connect.  It's best if you use a dedicated ftp program such as leechftp.  They only allow one connection, so if your ftp program is multi-threaded like leechftp is, cut the threads back to 1.  That site is a godsend to hams.  They have schematics or uploaded manuals for all sorts of stuff.

Bob
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W7DJM
Member

Posts: 1




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« Reply #8 on: December 22, 2004, 08:19:42 AM »

When you go to bama, if you go down the page to the "mirror" site, it works much better.  I've had NO problem downloading "from the browser", i.e, "IE"!!!!!


Use this:

http://bama.edebris.com  

I see that part of the SB-200 "stuff" is "djvu" files.


http://bama.edebris.com/manuals/heath/sb220/

Go here:

http://www.lizardtech.com/

and get the djvu "plug in."  
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W6SZG
Member

Posts: 35




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« Reply #9 on: December 30, 2004, 09:50:21 AM »

I have an SB-200 and the pot for the relative power is very intermittent.  I have yet to get around to replacing it.  I'd bet that is the where your problem is coming from.  I would check the switch too but that seems less likely.  I do have a manual and schematic and will check the valve of the pot and post here.  Maybe that will get me started on replacing mine too.  You could get by for now with external power/swr meter.  As others have said, there is lethal high voltage in there, watch out.
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N0TONE
Member

Posts: 173




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« Reply #10 on: February 08, 2005, 06:12:21 PM »

On anything this old, dirty contacts are a major problem.  When I buy something this old, I always clean the contacts.  Go to www.caig.com and look for the "starter kit" or "sample" kit or whatever of four (or is it six?) squeeze tubes of contact cleaner and lube.  Deox-IT is the stuff you want to very gently (use a Q-tip, don't spray it) use.

AM
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