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Re: [Amps] Alpha 77 start up

To: Paul Christensen <>
Subject: Re: [Amps] Alpha 77 start up
From: Jan Ditzian <>
Date: Sun, 20 Feb 2011 23:04:42 -0500
List-post: <">>

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" <>
> To: "Paul Christensen" <>
> Cc: <>
> 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" 
>>> <>
>>> To: <>
>>> 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
>>>> _______________________________________________
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