[SixClub] Amplifier Questions...

[Peter Chase]

If the input looks OK, then replace the final.  If not then keep checking back until you find something else wrong with the circuit up to the device, Like a voltage thats to high or  to low.  Possibly no voltage ??  something like that.  Sounds like normal stuff that goes wrong with amps. Focus on a defective component .
 
> From: kb0nly at mchsi.com
> To: sixclub at mailman.qth.net
> Date: Fri, 4 Jun 2010 12:21:48 -0500
> Subject: Re: [SixClub] Amplifier Questions...
> 
> There is no output...
> 
> Some more specifics... it's a 10w input 100w output amp. Driving with 10w 
> there is ZERO output. I think the driver, an MRF646 might also be bad.
> 
> There is no measureable output with even an RF Probe.
> 
> 73,
> 
> Scott
> 
> 
> 
> --------------------------------------------------
> From: "Peter Chase" <pdcn1j at msn.com>
> Sent: Friday, June 04, 2010 11:55 AM
> To: "6meter club" <sixclub at mailman.qth.net>
> Subject: Re: [SixClub] Amplifier Questions...
> 
> >
> > Just check the input to each final and compare it to its output. You 
> > should have a notable increase at the output of each . You should look 
> > up the RF device so you know what to expect for power output and what the 
> > normal parameters are. this can be done with basic test equipment. Hope 
> > this helps.
> >
> > Regards
> >
> > Pete N1JHF
> >
> >> From: kb0nly at mchsi.com
> >> To: sixclub at mailman.qth.net
> >> Date: Fri, 4 Jun 2010 11:45:27 -0500
> >> Subject: [SixClub] Amplifier Questions...
> >>
> >> I know this is OT, but there is a lot of smart cookies on here and the 
> >> other
> >> reflectors I have tried, like the AMPS reflector just don't get any 
> >> replies
> >> like here...
> >>
> >> Questions..
> >>
> >> 1. I have a UHF amp I'm working on, a RF Concepts 4-110. I think the
> >> finals are bad, but need someone to verify my bad memory. When testing
> >> these bipolar transistors the collector-base and base-emitter junctions
> >> should test as a diode correct? I have a dead short from base to 
> >> collector
> >> so that seems to verify they are fried. And the emitter-collector has to 
> >> be
> >> open in both directions, well of course its not because of the dead short 
> >> to
> >> the base.
> >>
> >> 2. It's been a while since I worked on a solid state amp... Whats the
> >> package type of the small capacitors used on the finals, those little 
> >> square
> >> metal jobs with a tab out of one side. For the life of me I can't 
> >> remember
> >> the package number so I can go catalog search for some new ones, as I'm 
> >> sure
> >> they need replacement after the heating they took on removal. Also, the
> >> marking on them, in this case 30 and 40, I believe that's in pF correct?
> >>
> >> 3. This amp has a bias adjust for each transistor, what is the best way 
> >> to
> >> adjust the bias after replacing the transistors, just set for minimum 
> >> idle
> >> current or is there a number I should be shooting for? No specs available
> >> from RF Concepts unfortunately but I was able to actually find a one page
> >> schematic at least.
> >>
> >> 73,
> >>
> >> Scott
> >>
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