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
>>> 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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