Paul,
It sounds like I should hook up a transceiver and dummy load and see
what happens. The CW/Low light definitely came on and stayed on when I
went to CW/Low.
Actually, the SSB/HI button up also flashed on briefly when I pushed it;
however, I understand that the original owner of the amp was an FCC
engineer, so he may have done something to keep it from running high
power. I may have to settle for 2KW pep, sigh. Just so no one on the
reflector gets into an uproar, I have no intention of running over 1500
watts out.
I will try to get some time tomorrow evening, Monday, to make the
definitive test with an exciter, but I have a busy day.
Jan, KX2A
On 02/20/2011 08:33 PM, Paul Christensen wrote:
> The CW/LOW light should only come on when depressed after the 3-minute
> timer activation. The light cannot activate without the 3-minute
> timer working. Also, it should not immediately come on when depressed
> if the amp is off -- only after the 3-minute wait.
>
> Check to ensure that the "READY" lamp is good and hasn't burned out.
> It sounds like the 24V supply is fine. I would next check with Glenn
> at Alpha concerning information on the CB-2A schematic. It's probably
> not too different than the prior version.
>
> Paul, W9AC
>
>
>
>
>
>
> ----- Original Message ----- From: "Jan Ditzian" <ditzian@windstream.net>
> To: "Paul Christensen" <w9ac@arrl.net>
> Cc: <Amps@contesting.com>
> Sent: Sunday, February 20, 2011 7:39 PM
> Subject: Re: [Amps] Alpha 77 start up
>
>
>> Paul,
>>
>> I note that the light on the CW/Low button came on when I pressed
>> that button. Also, one of the meters is lit. If I am reading
>> things right, all bulbs are 28 VDC, so I expect that the 24 volt
>> supply is OK.
>>
>> I looked over the original Operating and Technical Manual, and there
>> is a handwritten note on Fig 21, the CB2 board, that this unit has
>> the CB-2A board. There are other cryptic notes, but there is no
>> specific change to the schematic. I have no idea where to find a
>> CB-2A schematic.
>>
>> I will see if I can contact my friend with the test bench and a
>> 24-volt supply.
>>
>> Thank you,
>>
>> Jan, KX2A
>>
>> On 02/19/2011 02:29 PM, Paul Christensen wrote:
>>> Jan,
>>>
>>> The problem appears to be isolated to the three-minute warm-up
>>> timer. You're seeing 2600V which is correct while the three-minute
>>> timer is activating.
>>>
>>> First, measure the +24 VDC supply voltage. It should be fine since
>>> you don't seem to be blowing the step-start fuse. That would render
>>> the amp completely dead after the step-start resistors finally blew
>>> and threw shrapnel all over the inside of the amp.
>>>
>>> The timer circuit is on circuit board CB-2 and is very simple in
>>> operation. Upon sensing +24VDC, C207 (22 uF) begins charging through
>>> R222 (10 meg). This in turn activates SCR Q207, which simultaneously
>>> switches a more robust SCR Q208. Q208 fire and pulls in relay
>>> K202. Once K202's contacts close, +24VDC is supplied to the "READY"
>>> lamp (and other amp circuits) and the amp is ready to make power.
>>>
>>> CB-2 unplugs from an edge-card connector so you can safely do some
>>> troubleshooting outside of the amp -- If you have an adjustable
>>> +24VDC bench supply, use it for testing. Otherwise, be extremely
>>> careful when testing components in the amp. CB-2 is not far from
>>> the HV contact points.
>>>
>>> As W8JI once said, he's never had to troubleshoot an amp with AC
>>> power applied. He's right. It may take longer, but it's a much
>>> safer way to diagnose a root problem. If you've ever diagnosed an
>>> amp problem by yourself, now is not the time top learn on your own.
>>> Get on-site help if you cannot work on CB-2 outside the amp.
>>>
>>> Paul, W9AC.
>>>
>>>
>>>
>>> .
>>>
>>>
>>> ----- Original Message ----- From: "Jan Ditzian"
>>> <ditzian@windstream.net>
>>> To: <Amps@contesting.com>
>>> Sent: Friday, February 18, 2011 10:59 AM
>>> Subject: [Amps] Alpha 77 start up
>>>
>>>
>>>> I just received an Alpha 77 Dx, modified as a two-holer, as a gift (I
>>>> have very understanding friends). However, it came with a problem--it
>>>> does not work. The startup light does not come on. The previous owner
>>>> sent a board back to Alpha to fix this problem, and their paperwork
>>>> shows that they repaired it and then tested it in an Alpha 77Sx, which
>>>> is equivalent to the two-hole modified Dx, and it worked. However,
>>>> after putting the board into this rig, the problem remains. Since
>>>> I am
>>>> new to this amp, and did not have it integrated into my station, I
>>>> did collins amp
>>>> the following checks:
>>>>
>>>> I set up the amp with no exciter, but with power, and the fan comes on
>>>> and the voltage goes to about 2600 volts. I followed the regular
>>>> startup
>>>> procedure and, sure enough, the light does not come on after six
>>>> minutes
>>>> (it is supposed to take about 3minutes). I then put a cable into the
>>>> relay jack on the back, repeated the above process, went ahead and put
>>>> the amp into CW/low power mode after a six-minute wait, and then
>>>> shorted
>>>> the relay cable. I did not hear a relay click--nothing happened.
>>>>
>>>> Can someone help me to isolate the problem with this amp? Until this
>>>> happened, the previous owner (the donor of the amp) was using it
>>>> without
>>>> a problem. There was no cataclysmic event that preceded the
>>>> failure to
>>>> start up.
>>>>
>>>> I can imagine problems like bad contacts on the board connector, or
>>>> perhaps the failure of another relay somewhere.
>>>>
>>>> Thank you,
>>>>
>>>> Jan, KX2A
>>>>
>>>> _______________________________________________
>>>> Amps mailing list
>>>> Amps@contesting.com
>>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>>
>>
>
>
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