[VHFcontesting] A Weird Dressler D 200 S Linear Amp Problem

[Will M0GYZ]

Right.

The Microswitch was loose so I tightened it up a bit and thats now sorted
The RF out N-type Socket was a bit worn and had a cold joint on so 
redone that
and my plug on the end of the URM112 was a bit rubbish so redone that

Been using it for 24 hours not 1 problem.

Fixed.
Thanks
Will M0GYZ





On 18/03/2010 18:52, Will M0GYZ wrote:
> Okie Dokie
>
> I've fitted the mains plug with a 13 amp fuse this time and put the lid
> on the amp so the micro switch is down which should allow me to transmit.
> I have the lid down before I switch it on and wait for the HV to get to
> 480 and the green light comes on, I go to operate and key up and nothing.
>
> 2nd time around I switch it on with the case open and the micro switch
> up and wait again go to operate and I press the micro switch down and it
> works
> The amp transmits this way but not the 1st way so i've defiantly found
> problem.
>
> Its as if the amp thinks the switch is up when its off and must pressed
> down whilst it's on for it to transmit.
>
> Thanks
> Will M0GYZ
>
>
>
>
>
> On 18/03/2010 10:59, John Lemay wrote:
>    
>> Willa
>>
>> That little safety mechanism is designed to ensure that operation of the
>> amplifier is not possible with the cover removed. It will ensure that at
>> least some of the dangerous voltages are not present with the top off.
>> Exactly which voltages are removed would only be evident with scrutiny and
>> understanding of the circuit diagram.
>>
>> I think it's quite possible that moving the amplifier around will cause the
>> case to flex a little bit, thus affecting the safety mechanism. Maybe the
>> table top was a little bit warped ?
>>
>> As others have said, be very careful indeed inside this amplifier. 2kV will
>> kill. In addition, if memory serves correct, mains voltages are present on
>> the circuit board between the rear power connector and the front panel main
>> switch. These voltages are present as soon as the amp is plugged in to the
>> mains.
>>
>> Good luck
>>
>> John G4ZTR
>>
>> -----Original Message-----
>> From: uk-contest-bounces at contesting.com
>> [mailto:uk-contest-bounces at contesting.com] On Behalf Of Will M0GYZ
>> Sent: 17 March 2010 23:23
>> To: vhfcontesting at contesting.com; uk-contest at contesting.com
>> Subject: [UK-CONTEST] A Weird Dressler D 200 S Linear Amp Problem
>>
>> Hi All
>>
>> Thanks for all the help
>>
>> I opened the case today to find to a little safety mechanism (which is
>> connected by 2 red leads going to somewhere underneath to the right of
>> the fan) which pushes down when the case is on otherwise the linear does
>> not transmit so after pushing it down a couple of times seemed to fix it
>> I must have been using it for at least 3 hours this evening without a
>> hitch untill i moved to a more perminant location and then it stopped
>> working again and when i pushed down the mechanism again with the linear
>> in standby it all turned off and it turned out I blew a fuse in the
>> mains plug which was only 5 amps.
>>
>> At least I think ive found the problem though which is step 1
>> now for the solution
>>
>> Here is the Manuel for it
>> http://www.qth.at/oe1cwj/Dressler%20Manual%20D70_eng.pdf
>>
>> and here is a better pic of the inside so you can see what i'm talking
>> about
>>
>> http://img225.imageshack.us/img225/4453/dressler.jpg
>>
>> As you can see there is a yellow wheel like thing to the right of the
>> fan with 2 red leads coming off it
>> thats the safety mechanism
>>
>> Thanks
>> Will M0GYZ
>>
>>
>>
>>
>>
>>
>> On 17/03/2010 18:05, Paul Kiesel wrote:
>>
>>      
>>> Hi Will,
>>>
>>> Check that the solder on the output coax connector  is not open. Some
>>> brick amplifiers will "bend" when being moved around. Very often the
>>> solder will fracture where the output lead is soldered to the
>>> connector. Look closely as it is hard to see. Good luck!
>>>
>>> 73,
>>> Paul, K7CW
>>>
>>>
>>> ------------------------------------------------------------------------
>>> *From:* Will M0GYZ<m0gyz at gb3hp.com>
>>> *To:* vhfcontesting at contesting.com
>>> *Cc:* uk-contest at contesting.com
>>> *Sent:* Tue, March 16, 2010 12:54:46 PM
>>> *Subject:* [VHFcontesting] A Weird Dressler D 200 S Linear Amp Problem
>>>
>>> Hi All
>>>
>>> Got a weird one for you.
>>>
>>> I have Dressler D200S VHF Linear Amp which was given to me for contesting.
>>> There has always been a strange problem which i originally thought was a
>>> sticky relay
>>> However after a while of looking at it. Its as if the amp wont Transmit
>>> without it being on a really flat surface which caused problems for me
>>> at the recent 144/432mhz contest
>>> I can't figure out why it would require such a dead flat surface before
>>> the needle moves and im putting power out.
>>>
>>> It was working ok apart from this at home as i was putting out 120w with
>>> 5w drive provided I found the right spot for it but when i took it out
>>> to the contest it just didn't want to Transmit at all and when it did
>>> the power just decreased over 3-10 seconds and I couldn't get 120w out
>>> of it max.
>>>
>>> My thoughts are thats it might be a dry joint but the guy who had it
>>> before me didn't ever report it had a problem but unforuntly he died a
>>> couple of years ago.
>>> So it only Transmits when its in a spot it likes after moving around my
>>> windowsill
>>>
>>> So any thoughts  ?
>>>
>>> Thanks
>>> Will M0GYZ
>>> _______________________________________________
>>> VHFcontesting mailing list
>>> VHFcontesting at contesting.com<mailto:VHFcontesting at contesting.com>
>>> http://lists.contesting.com/mailman/listinfo/vhfcontesting
>>>
>>>
>>>        
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