As far as the Power Supply goes, there are still a lot of server supplies
out
there that deliver ~ 50 vdc @ ~ 50 Amps. Put a pair in series and you have
some serious power.
73, Dick, W1KSZ
On Wed, Jun 5, 2013 at 10:05 PM, Alex Eban <alexeban@gmail.com> wrote:
> No, the problem really lies with the devices.
> I used a pair of these devices from AR and they took a lot of abuse without
> complaints!
> I heard from local sources that microsemi have problems with voids in the
> bond -when attaching the dies to the header- they still can't handle the
> peculiar package.
> If you get off the high voltage verion you might as well switch back to
> classics like the MRF 157 et al, but then you won't get anything new done!
> Alex 4Z5KS
>
> -----Original Message-----
> From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of MU 4CX250B
> Sent: Thursday, June 06, 2013 4:43 AM
> To: Paul Decker
> Cc: amps@contesting.com
> Subject: Re: [Amps] Advice needed for SS amp
>
> Seems to me the 50V limit would be a deal breaker. I love the idea of a
> transformerless design. I wonder if the THP problems were really the
> devices, as opposed to a design glitch they never figured out.
> 73,
> Jim W8ZR
>
> Sent from my iPhone
>
> On Jun 5, 2013, at 6:45 PM, Paul Decker <kg7hf@comcast.net> wrote:
>
> > Hi Bill,
> > I had an amp using the MRF1500 parts, based on the commercial Tokyo high
> power design.
> >
> > I also talked to the THP guys for a while at Dayton and they are phasing
> out their ARF1500 design using the Microsemi. The reason I was told is
> because of quality issues with the parts themselves.
> >
> > IMHO, it may be better to go with the NXP BLF578XR since it is a 1500W
> part although it is only 50V.
> >
> > Paul,
> > kg7hf
> >
> >
> >
> > Message: 1 Date: Wed, 05 Jun 2013 09:07:14 -0700 From: Bill Turner
> To:
> Amps Subject: [Amps] Advice needed for SS amp Message-ID:
> Content-Type:
> text/plain; charset=us-ascii I'm thinking of building a solid state 1500
> watt amp using some of MicroSemi's high voltage MOSFETs. This is a new
> kind
> of project for me and I would appreciate any comments you might have which
> would help me avoid any blunders. The MicroSemi ARF1500 looks
> attractive
> because of its high power capabilities and relatively low price. Digi-Key
> carries these for $205 each. A single one is rated at 750 watts output so
> I
> would use two of them. I'm thinking of water cooling. MicroSemi data
> sheet is at http://www.microsemi.com/existing-parts/parts/81770 and there
> are other versions with similar ratings. Notice the unusually high
> power supply voltage. I'm thinking of running a full wave bridge rectifier
> directly off the 240 VAC line, thus eliminating the power transformer and
> giving
> about 340 VDC
> > no-load. The amp would have to be isolated from ground of course, with
> input and output coupling via toroid transformers and PTT switching done
> by
> a well-insulated relay. A set of four 10 amp 600 PIV diodes is
> available
> on eBay for less than $30 and a 6800 uF 450 VDC capacitor is available for
> about $50 including shipping. There's most of your power supply. Pretty
> cheap, huh? :-) Of course with that size cap a step-start circuit
> would
> be mandatory lest you blow your main house breaker when you power up.
> My
> main use would be RTTY and CW so linearity is not an issue, but do you
> have
> any thoughts on what the IMD might be for SSB? I can't find any data on
> MicroSemi's website for that. Maybe it's no good for SSB. Since the
> output impedance is about 50 ohms, I'm wondering if a 1:1 broadband
> antenna
> balun might serve for the output toroid? Just a thought. Might not be a
> good idea. Like I said, I'm a complete newbie at solid state amps so
> all
> comments
> are welcome. Th
> > is almost seems to be too easy to be true. Go ahead, burst my bubble.
> :-) 73, Bill W6WRT
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