[Amps] QSK5-PC in a AL1200

[Ed Swiderski, KU4BP]

Thanks Bill. I'll check that out.

On 1/13/2024 5:43 PM, hzp_electronics at juno.com wrote:
> Hi Ed,
> I don't know if this will help.  I repaired an external QSK-5 for a SK's widow.  I think it uses the same PCB as the internal unit.  The problem was that Q4 2N6740 was shorted to ground.  The device Collector-to-Emitter is rated for 400 volts.  However, the voltage on its collector can exceed 400 volts at times.  I installed a 800 volt device (2SC3460) which solved the problem for that unit.  The point is that your PIN diodes might be OK.  It is worth a check.  Getting PIN replacements is very difficult.
>        73
> .... Bill K3HZP
>
>
> ---------- Original Message ----------
> From: "Ed Swiderski, KU4BP"<ku4bp at triad.rr.com>
> To:Amps at contesting.com
> Subject: [Amps] QSK5-PC in a AL1200
> Date: Sat, 13 Jan 2024 13:01:51 -0500
>
> Hello all,
>
> As the subject line says, I have an issue with the QSK5-PC board in my
> AL1200. The QSK5 board has been blowing it's fuse lamps. I think I've
> replaced them 3 times in the past 12 months.
>
> I haven't been doing anything abnormal with the board in the years I've
> had the amp. It was already installed when I purchased it in 2009. Never
> had any issues with it and I have only used it with SSB. The only time I
> use CW with it has been to tune it up in a dummy load with a straight
> key. A couple times during normal use in SSB, the fuse lamps on the
> board would blow. The latest use had the lamps blow while tweaking my
> settings on the amp.
>
> I contacted Ameritron for advice. They told me to "try operating in semi
> break mode and increase the delay speed and see if that clears it up". I
> did that but since I'm not operating CW in the first place, it didn't
> help. Ameritron also said the board may have a bad PIN diode. I haven't
> removed any of them to check. I think it's possible because the board
> was installed in 1994(30 years).
>
> So, I'm asking first if anyone has had a similar issue that can give any
> advice. Second, I'm toying with either getting a new board or, just
> undoing the modification altogether. Doing either is not a problem. I
> would like to keep the mod in place though which is why I'm indecisive
> right now. Hope to get the amp back in use by the end of this year for
> when 3Y0/B is planned to come on.
>
> I hope I have given enough information. When I first had this problem
> last year, I didn't provide enough information and I think I upset a
> couple people by not doing so and I apologize for that.
>
> Will try to respond to replies promptly.
>
> Thank you,
> Ed KU4BP
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