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Author Topic: Do you own a Heath SB-200 or 201?  (Read 1687 times)
W1QJ
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« on: November 23, 2017, 03:54:43 AM »

Happy Thanksgiving all!    Do you own an SB-200 or SB-201 and did you install new filter caps and bleeder resistors on the old board?  I don’t mean using a total rebuild kit.  I mean using the old PS board.  If so, what value filters caps did you use for replacement and what value bleeder resistors did you use?
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KM1H
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« Reply #1 on: November 23, 2017, 12:49:07 PM »

I havent reused the old board for ages since cheap new ones became available.
BUT back in the day I used 220uF CDE 450V LX series caps and modified the board as needed......probably a few hundred over the years.

Equalizing resistors were the usual 100K 3W MOX Ive used with all modern caps and havent had or heard of any problems even almost 30 years later.

I wouldnt go over that value and a step start is a waste of money/time.

Carl
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K6BRN
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« Reply #2 on: November 24, 2017, 08:56:46 AM »

I have an old SB-200 I rebuilt a year ago.  When I examined the voltage doubler board of the power supply, it had become a crumbly, phenolic mess.  This was NOT obvious until I began replacing the resistors and caps and the board began to disintigrate with the top metal flaking off.  At that point I realized any "patch fix" I could do would be unreliable and ordered a Harbach replacement kit.

This kit uses 220 uF, 450V caps, which is significantly higher value (but smaller physical size) than the originals.  But going too high in cap value will cause the breakers to trip on power up and require addition of a soft-start kit.

If you have a PWB problem like I did, the doubler board alone is about $25 from Harbach...

https://harbachelectronics.com/shop/heathkit-sb-200-sb-201/pm-200-replacement-power-supply-module/
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K3LI
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« Reply #3 on: November 24, 2017, 11:03:08 AM »

To simplify all the SB this or that talk.  If you want inexpensive (as far as amps go) There is the obvious choice of an AL811H Ameritron.  These work very well and are 850 to 900 bucks.  If tubes are not your thing, ALS 600 solid state.

Unless your somewhat experienced with electronics and High voltage, I suggest new rather than used ones that may have problems.
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KM1H
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« Reply #4 on: November 24, 2017, 03:32:34 PM »

Quote
To simplify all the SB this or that talk.  If you want inexpensive (as far as amps go) There is the obvious choice of an AL811H Ameritron
.

As discussed for several years on here the AL-811 series are one step above pure junk.

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K6BRN
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« Reply #5 on: November 24, 2017, 08:13:23 PM »

Quote
As discussed for several years on here the AL-811 series are one step above pure junk.

Yes... well... if it's cheap enough, somebody will buy and try to use it.
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W1QJ
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« Reply #6 on: November 25, 2017, 04:01:19 AM »

Thread moving in wrong direction.  The reason I asked this question was to see what value bleeder resistors were being used when hams take it upon themselves to make modifications on their own accord.  If you buy a Harbach replacement PS board for these amps all the thinking has been done for you.  If you make changes to the original supply board by changing the caps and bleeder resistors on your own without further consideration of the circuit used, you will find potential  problems down the road.  In the case of the SB-200.  On the PS board there is a 700 ohm 5 watt resistor.  This resistor is in series with the last 30K ohm bleeder resistor on the last filter cap.  The combination of the 30K ohm resistor and the 700 ohm resistor creates a voltage divider which sets the ALC voltage.  If you change the bleeder resistors to anything but the original 30K ohms, you have to change the 700 ohm resistor accordingly to satisfy the proper divider network to set the ALC voltage.  The original ALC divider sets the voltage at about 9vdc.  Take this into consideration if you use ALC in that amp.
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K8AXW
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« Reply #7 on: November 25, 2017, 08:05:19 AM »

When I rebuilt my SB-200 power supply I used components as close to the original as possible....both caps and bleeder resistors.  My philosophy is why mess with success?

As for the caps, I couldn't locate the original type so had to re-engineer how to mount them.  Otherwise, go with the flow.
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WA0SSV
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« Reply #8 on: November 30, 2017, 08:27:04 AM »

Lou,
A few years back I reworked the HV section of a SB200, using their board. If I remember, I changed the bleeder resistors to about 56k ceramic film power resistors, and sized the capacitor bank so the functional capacitance was around 30 to 35 ufd and good for a 3200 volt setup. Hope this helps.
The snap in mount type caps will work.
73's
Larry
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W1QJ
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Posts: 2638




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« Reply #9 on: November 30, 2017, 10:03:20 AM »

Lou,
A few years back I reworked the HV section of a SB200, using their board. If I remember, I changed the bleeder resistors to about 56k ceramic film power resistors, and sized the capacitor bank so the functional capacitance was around 30 to 35 ufd and good for a 3200 volt setup. Hope this helps.
The snap in mount type caps will work.
73's
Larry

That's fine Larry, the question is what did you do to address the ALC voltage that was screwed up when you changed the value of the bleeder resistors?  Does not make any difference if you don't use ALC but it would if you or someone else would eventually use it.
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WA0SSV
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« Reply #10 on: November 30, 2017, 11:30:08 AM »

Lou,
At the time, I wanted to reduce the waisted bleeder heat, and since my TenTec Omni had fairly good power limiting, I did not worry much about the ALC circuit. I admit you do raise a valid point that may be important to some folks.
Larry
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KM1H
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« Reply #11 on: November 30, 2017, 12:34:00 PM »

Quote
Thread moving in wrong direction.  The reason I asked this question was to see what value bleeder resistors were being used when hams take it upon themselves to make modifications on their own accord.

You should have asked that in the beginning Roll Eyes

I used 100K 3W MOX from the first conversion to Snap In caps on the original board which was long before kits and new boards were available.

The SB-200 ALC isnt used with modern rigs which provide their own loops. If you insist then use a 9V battery.

Carl
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W0XX
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« Reply #12 on: December 05, 2017, 06:05:51 PM »

Happy Thanksgiving all!    Do you own an SB-200 or SB-201 and did you install new filter caps and bleeder resistors on the old board?  I don’t mean using a total rebuild kit.  I mean using the old PS board.  If so, what value filters caps did you use for replacement and what value bleeder resistors did you use?

Sorry, can't speak to the 200, but I replaced my 220's caps via sprague or mallory 450VDC caps, was costly but worth the piece of mind, along with the resistors, relay, and the HV metering resistors, but that was a while back.  All installed on the boards or panels that were in the amp.
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KM1H
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« Reply #13 on: December 06, 2017, 03:28:45 PM »

Quote
Lou,
At the time, I wanted to reduce the waisted bleeder heat, and since my TenTec Omni had fairly good power limiting, I did not worry much about the ALC circuit. I admit you do raise a valid point that may be important to some folks.
Larry

When that amp was designed in the early 60's cap tolerance was poor  so the 30K resistors forced equal voltage splits.

With modern Snap In caps Ive measured unsorted batches to be well within 5% from several well known brands and not hamfest garbage; 100K is now a common value for replacement PS boards.

Carl
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