[Amps] Alpha 87A - strange power related issue

[k1ttt.dave at gmail.com]

Does that perhaps use solid state switches to turn on the main power?  I have seen them (in a different amp) get leaky which produced a low control voltage when they were supposed to be off, something like that on a digitally controlled amp could produce flakey displays or maybe give enough voltage to run the fan.

David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: telnet://k1ttt.net:7373


-----Original Message-----
From: Amps <amps-bounces at contesting.com> On Behalf Of gudguyham--- via Amps
Sent: Monday, October 10, 2022 09:52
To: w5cul at sbcglobal.net; 'Eric Dobrowansky' <k2cb at comcast.net>; amps at contesting.com
Subject: Re: [Amps] Alpha 87A - strange power related issue

Eric, most likely you have a problem on the primary start up board. This is where the step start is and all the primary wiring gets routed.  Often times the sticky tape gets conductive over time and it shorts out the blower traces and blows them open.  It’s possible there’s a problem with the step start relay.  It’s most likely a problem in this area.  Don’t discount a problem with those push on/off switches on the front panel of course.  But do remove that primary board and investigate it.  It removes very easily.  Here’s a step by step procedure.  1. Pull the transformer plug from the board.2. Remove all transformer wires from boards 3. Pull out transformer.4. Remove two screws near the two fuses that hold start assembly.5. Remove one nut holding one bracket on opposite side of variable cap middle divider. The board comes right out along with the AC cord, remove plug if you have to.
Once you get that board out there’s your relay on there etc.  you’ll see that sticky tape that hold down the electrolytic cap.  It’s best to remove that tape because it will create problems if it hasn’t already.   Just let the cap support itself that’s fine.  If you email me personally I can send you some photos.  Lou

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On Sunday, October 9, 2022, 8:42 PM, w5cul at sbcglobal.net <w5cul at sbcglobal.net> wrote:

Eric,

There is an 87A Email Group.  You can find them here:

Alpha87A at groups.io

You will have to sign up for an "groups.io" account and after that you should be able to query for the Alpha 87A group and request access.  

https://groups.io/

Hope this helps.

Thank you,

Mike
W5CUL

-----Original Message-----
From: Amps <amps-bounces at contesting.com> On Behalf Of Eric Dobrowansky
Sent: Sunday, October 9, 2022 7:26 PM
To: amps at contesting.com
Subject: [Amps] Alpha 87A - strange power related issue

It's been a long time, and I'm not sure if there is a dedicated Alpha 87A related mail list in existence any longer, so I will go ahead and ask here.

I have an 87A that started exhibiting a strange problem.

When the amp is plugged in, the blower automatically starts, and various band and segment LEDs illuminate, but the amp does not start up. The LEDs which illuminate vary each time the amp is plugged in. 

If I try to push the POWER OFF switch, the amp will turn off the blower and LEDs, but as soon as I release the switch, it returns to the state where the LEDs and blower are on.

If I push the POWER ON switch, the amp starts up normally. The amp works fine once it completes the warm-up period. 

If I then press the POWER OFF button to turn the amp off from when it is fully running, it shuts down properly. IE - all the LEDs turn off, and the blower stops.

However, if I leave it plugged in, out of nowhere sometime later the above symptom repeats, and I have to pull the AC plug to get it to shut down completely. 

Any recommendations as to where to start troubleshooting?  Maybe a cap going bad somewhere is pulling down a particular control circuit?


Eric
K2CB

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