[Amps] Dentron MLA2500

Thu Oct 27 01:54:57 EDT 2005

Look for a schematic for a  ML-2500 or the A model.
I had one years ago, it covered 10 m like a cheap suit.
73,
Gary...wa6fgi

rees.a at btconnect.com wrote:
> Thanks to all who replied to my original post. The plot as they say has
> thickened!
> 
> I got my other Dentron ML2500 B out tonight, and everything works FB. Loads
> up on all bands. 
> 
> Now here's the twist !
> 
> The ML2500 B is marked as 160-15M (no 10M) and I though, oh well, if 10M
> opens, I'll swap the amps around.
> 
> However, the ML2500 B has an additional setting on the switch, which when
> selected, tunes up on 10M...!
> 
> I always thought the ML2500 B I had wouldn't cover 10M. Anyone any ideas ?
> 
> The switch is definately original, and not been modded ...)
> 
> Adrian
> 
> Original Message:
> -----------------
> From: Keith Dutson kdutson at sbcglobal.net
> Date: Tue, 25 Oct 2005 09:31:38 -0500
> To: amps at contesting.com
> Subject: Re: [Amps] Dentron MLA2500
> 
> 
> During Field Day 2005 I ran into a similar situation with an Icom 775DSP and
> a 40M Yagi.  The Yagi VSWR was about 4:1 and the auto tuner in the 775 could
> not compensate.  Thus the power was dropped significantly to protect the amp
> circuit.  I inserted a separate tuner but could not match the antenna with
> this drive condition.  The front panel tuner switch was used to turn off the
> tuner, but it would automatically re-engage when it saw the high VSWR.  I
> desperately looked for a menu to disable the 775 internal tuner but could
> not find one.  Frustration!  After a bit of luck I managed to guess the
> proper manual tuner settings to get VSWR below 2:1 (tuned for max noise in
> receive), turned the auto tuner off with the switch on the front panel, then
> proceeded to fine tune down to 1:1.  We had to be careful when tuning around
> the band to re-adjust the manual tuner.
> 
> Later, back at the shack, I looked in the manual and found there is a menu
> item to deactivate the auto tune feature.  When I went menu searching again
> on the rig I discovered the menus did not match the manual.  I did a system
> reset and voila, there were the proper menus.  The auto tune feature is now
> deactivated.  The front panel tune button can still be used to temporarily
> engage the tuner.
> 
> 73, Keith NM5G
> 
> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
> Behalf Of rees.a at btconnect.com
> Sent: Tuesday, October 25, 2005 12:51 AM
> To: amps at contesting.com; rees.a at btconnect.com
> Subject: Re: [Amps] Dentron MLA2500
> 
> Hi all
> Thanks to everyone who replied.
> 
> The amp is delivering 900-1.2Kw on all bands 160-10, except for 80M.
> 
> Tuning on 80M with low drive (to avoid the auto ATU) gets me about 250W
> before the Auto ATU kicks in. Problem with the 756 is that its too clever
> for its own good, as I can't disable the Auto ATU. 
> 
> So tonight, I'll try a manual ATU between the 756 and the Amp. I have tried
> different patch leads (as someone suggested) thinking I had an intermittent
> connection, but no joy. 
> 
> A few people mentioned modifications to the input. I would be grateful to
> see these, so can you mail them off list ?
> 
> Thanks
> 
> Adrian Rees (M1LCR)
> Original Message:
> -----------------
> From: Henry  Pfizenmayer pfizenmayer at worldnet.att.net
> Date: Mon, 24 Oct 2005 17:56:52 -0700
> To: rees.a at btconnect.com
> Subject: Re: [Amps] Dentron MLA2500
> 
> 
> Adrian  - something worth trying which is pretty easy to do is to add about 
> double the length of coax you have between the amp and the 756 - it just 
> might help (or it may hurt other bands so you have to check them again ) - 
> not very scientific but it sometimes solves these sorts of issues .
> 
>  As they say , your mileage may vary !!!!
> 
> 73 - Hank K7HP
> 
> 
> ----- Original Message ----- 
> From: <rees.a at btconnect.com>
> To: <amps at contesting.com>
> Sent: Monday, October 24, 2005 1:26 PM
> Subject: [Amps] Dentron MLA2500
> 
> 
> 
>>Hi
>>I have a Dentron MLA2500 Linear. I use an Icom 756PROII as the main rig.
>>
>>I discovered a problem the Dentron MLA2500 amp. On 3.5MHz my 756proii 
>>won't
>>auto tune to the input of the amp, therefore shuts off the drive. The
>>reason being is that the 756 "sees" a high SWR.
>>
>>(All other bands work FB)
>>
>>I lifted the covers off, to discover the 100 Ohm swamping resistor had 
>>come
>>loose (dry joint..age whatever) so I soldered it back on.
>>
>>No improvement at all.
>>
>>Looking at the circuit diagram of the Dentron , there is no tuned input
>>stage to the amp.
>>I am somewhat befuddled by this. Any ideas ?
>>
>>By the way, all the tests where into a 2Kw Oil filled dummy load, with an
>>SWR of 1.1:1.
>>(Switching the amp to Standby (by passing the amplifier, and direct to the
>>dummy load, and the 756 tunes OK, as you would expect).
>>
>>Thanks
>>
>>Adrian Rees (M1LCR)
>>
>>PS I have another Dentron ML 2500 Amp, that is FB, but doesn't cover 
>>28MHz,
>>I believe it was made for the US Home market ? Any info about thhis
>>appreciated.
>>
>>
>>
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> 
> 
> 
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