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 Post subject: Heathkit HP-1144 rebuilding
PostPosted: Dec Sat 09, 2017 2:26 pm 
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Location: Beaver Falls, PA. USA
The unobtainable MFC6030 regulator chip in my HP-1144 power supply has blown. I'm thinking of redesigning the circuit to use the commonly available 723 chip. Has anyone here done this mod?

I need to provide some transient suppression to the circuit. I added the Far Circuits crowbar kit to the thing, and it worked too well! After calibrating the crowbar to trip at 15 volts, I hooked it up and turned up the voltage. When the crowbar circuit triggered, the spike took out the regulator chip and the 2N3055 driver transistor! I did have the power supply rewired so the fuse was at the input of the regulator, instead of at the output as originally designed.

I'm looking forward to getting the SB-104A checked out and on the air, once the power supply is rebuilt.

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 Post subject: Re: Heathkit HP-1144 rebuilding
PostPosted: Dec Sat 09, 2017 6:30 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 17066
Location: Albuquerque, NM 87123
https://www.ebay.com/itm/RARE-VINTAGE-M ... SwCmNZwTf0

Unobtainable? 3 sources on eBay now.


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 Post subject: Re: Heathkit HP-1144 rebuilding
PostPosted: Dec Sat 09, 2017 6:43 pm 
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Joined: Jul Sun 15, 2007 9:34 pm
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Location: PA
Tim;

Ages ago, I bought an HP-1144 at a hamfest that had no output. Transformer and filter capacitors tested good. There is room inside to be creative with a different design.

I started off with a 50A 100V four terminal bridge rectifier. Back then I has a stash of 3 terminal 7815 regulators, and decided to use one as the heart of the regulation circuit. I added 250 ohm or so pot from an isolated tab / pin 2 connector to circuit common, to adjust output to 13.8 volts. Device data sheets show sample circuits.

Someone else had already designed a decent crowbar circuit, so I modeled one after the Astron RS series of linear supplies. Changed pass transistors to 2N5686. which carry at least 2X current of 2N3055. Added binding posts, toggle on-off switch.

Very simple to do, with a low parts count.

Voltage regulation was very acceptable from no load to full load. That supply was used for at least 15 years, without issue. For a while, I ran a Yaesu FT-990 off it. Gave the supply away and bought the Yaesu FP 1030A to match the transceiver. Other than aesthetics and metering, it doesn't perform better than the modified Heathkit.

Just an idea to share on a snowy Saturday....


-O.B.


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 Post subject: Re: Heathkit HP-1144 rebuilding
PostPosted: Dec Tue 19, 2017 11:32 pm 
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Location: Beaver Falls, PA. USA
Poking around on the web, I found this site:

http://www.bwcelectronics.com/main/page_projects.html Scroll down to see the regulator board kit.

This guy is a ham, and a design engineer. He has come up with an improved regulator circuit which will retrofit into any old linear supply with a little rewiring. The regulator circuit features current limiting, transient overvoltage protection, and improved regulation over the older IC-based designs. The pass transistors have been moved to the negative leg, which allows the collectors to be connected directly to ground; this provides improved heat dissapation for the transistors, since no mica insulators are required. His price for the regulator board kit is about the same as what the original regulator chip is selling for!

Although originally intended for the Astron power supplies, the board will easily adapt to the HP-1144, as much of the circuit is the same.

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Tim KA3JRT


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 Post subject: Re: Heathkit HP-1144 rebuilding
PostPosted: Dec Wed 20, 2017 1:16 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 17066
Location: Albuquerque, NM 87123
[quote="Tim Tress"]

The pass transistors have been moved to the negative leg, which allows the collectors to be connected directly to ground;

Wouldn't that require new regulator transistors, as they would have to be PNP instead of NPN?


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 Post subject: Re: Heathkit HP-1144 rebuilding
PostPosted: Dec Wed 20, 2017 2:31 am 
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No, it's a very clever circuit, using a power FET as a driver; the design specifies 2N3771 or 2N5886 NPN pass transistors. Full details are at PS15D090.pdf on his website.

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Tim KA3JRT


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 Post subject: Re: Heathkit HP-1144 rebuilding
PostPosted: Jan Sun 28, 2018 2:45 pm 
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Location: Beaver Falls, PA. USA
I have received all of the parts, and the rebuilding has begun! I'll post some pictures when it is finished.

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Tim KA3JRT


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