[Elecraft] KPA500 question

Jack Brindle jackbrindle at earthlink.net
Wed Jun 15 19:08:15 EDT 2011 

Let me restate this. The diode needs to "point" at the K3 in order for  
the K3 to pull the BCD signal low.
So the bar (cathode) is towards the K3, while the triangle (anode) is  
connected to the bandswitch.

Looks like I got the two terms backwards in my earlier email.

Jack Brindle, W6FB

On Jun 15, 2011, at 3:39 PM, Joe Subich, W4TV wrote:

>
>> Anodes towards K3/KPA500 signal junction. Just one diode needed per
>> BCD signal.
>
> No, that will not work since anode to K3/KPA500 will not allow the K3
> to pull the RCS-12 inputs low.  Since I don't have a schematic for the
> RCS-12 (none published as far as I can fine), my assumption is that
> the RC-12 has pull-ups on its BCD input.
>
> I suppose Dave could measure the voltage on pins 1,2,8 & 9 of the
> RCS-12 "Radio Input" jack.  That would give some hint as to the
> circuit design.  (I don't know why I'm trying to debug MFJ stuff -
> just get a real band decoder <G>).
>
> 73,
>
>    ... Joe, W4TV
>
>
> On 6/15/2011 6:18 PM, Jack Brindle wrote:
>> Nope. That won't work. The BCD outputs are open drain/collector, so
>> connecting them in this way will actually do nothing.
>> Anodes towards K3/KPA500 signal junction. Just one diode needed per  
>> BCD
>> signal.
>>
>> Jack Brindle, W6FB
>>
>> On Jun 15, 2011, at 3:06 PM, Joe Subich, W4TV wrote:
>>
>>>
>>>> What kind of isolation diodes would you suggest?
>>>
>>> Any switching diode (1N4148, etc.) would be fine.
>>>
>>>> Any how should they be connected?
>>>
>>> As any set to isolation diodes ... two diodes per data line  
>>> (A,B,C,D)
>>> cathodes to the K3, anodes to the RCS-12 and KPA-500.
>>>
>>> 73,
>>>
>>> ... Joe, W4TV
>>>
>>>
>>> On 6/15/2011 12:11 AM, Dave Perry wrote:
>>>> Joe,
>>>>
>>>> Yes, I am using the four pins corresponding to Band 0 through  
>>>> Band 3
>>>> plus the pin for ground. The RCS-12 works fine connected directly  
>>>> to the
>>>> ACC port on the K3. It also works fine when the KPA500 is  
>>>> connected via
>>>> the Y cable. It is just that the KPA500 is not switching bands when
>>>> connected with the RCS-12. So your suspicion may be correct. What  
>>>> kind
>>>> of isolation diodes would you suggest? Any how should they be  
>>>> connected?
>>>>
>>>> Thank you.
>>>>
>>>> Dave, N4QS
>>>>
>>>> ----- Original Message ----- From: "Joe Subich, W4TV" <lists at subich.com 
>>>> >
>>>> To: <elecraft at mailman.qth.net>
>>>> Sent: Tuesday, June 14, 2011 10:43 PM
>>>> Subject: Re: [Elecraft] KPA500 question
>>>>
>>>>
>>>>>
>>>>> You might try isolation diodes between the antenna switch and/or
>>>>> KPA and the K3. If the KPA is not band switching with the RCS-12
>>>>> connected, I would suspect the RCS-12 is loading the band data
>>>>> lines.
>>>>>
>>>>> How are you connecting the RCS-12? Are you using the "Yaesu BCD"
>>>>> connections?
>>>>>
>>>>> 73,
>>>>>
>>>>> ... Joe, W4TV
>>>>>
>>>>>
>>>>>
>>>>> On 6/14/2011 11:24 PM, Dave Perry wrote:
>>>>>> Gary,
>>>>>>
>>>>>> Good suggestion. I removed the cable going to the antenna  
>>>>>> switch and
>>>>>> now the K3 and KPA500 appear to talk to one another when changing
>>>>>> bands. Pushing a band button on the amp changes the amp and the  
>>>>>> K3 to
>>>>>> the new band. I still cannot get the two power levels to work.  
>>>>>> I also
>>>>>> need to figure out how to get the band switch working with the Y
>>>>>> cable.
>>>>>>
>>>>>> Dave, N4QS
>>>>>> ----- Original Message -----
>>>>>> From: Gary Gregory
>>>>>> To: Dave Perry
>>>>>> Sent: Tuesday, June 14, 2011 10:12 PM
>>>>>> Subject: Re: [Elecraft] KPA500 question
>>>>>>
>>>>>>
>>>>>> What bothers me is the amp was not switching bands you  
>>>>>> said?...If the
>>>>>> OPER switch is set then the aux cable should allow you to switch
>>>>>> bands either way and the amp should indeed switch bands and  
>>>>>> indicate
>>>>>> that on the LCD.
>>>>>>
>>>>>>
>>>>>> Unfortunately, my FT unit has the original I/O board so I can't
>>>>>> verify this for you...sorry
>>>>>>
>>>>>>
>>>>>> remove the antenna switch and try see if that makes any  
>>>>>> difference.
>>>>>>
>>>>>>
>>>>>> Gary
>>>>>>
>>>>>>
>>>>>> On 15 June 2011 13:02, Dave Perry<n4qs at comcast.net> wrote:
>>>>>>
>>>>>> Gary,
>>>>>>
>>>>>> No, I did not remove any pins on the cable. This is the one  
>>>>>> supplied
>>>>>> by Elecraft and I figured that it would be good to go. I just  
>>>>>> checked
>>>>>> the cable and five pins have been removed. I just removed the Aux
>>>>>> Cable from the back of the KPA500 and now the band buttons work  
>>>>>> on
>>>>>> the amp. So it does appear that the Aux Cable is the culprit.
>>>>>>
>>>>>> Dave
>>>>>> ----- Original Message -----
>>>>>> From: Gary Gregory
>>>>>> To: Dave Perry
>>>>>> Sent: Tuesday, June 14, 2011 9:49 PM
>>>>>> Subject: Re: [Elecraft] KPA500 question
>>>>>>
>>>>>>
>>>>>> Do you have PIN 10 removed on the KPA-500 end of the Y cable?
>>>>>>
>>>>>>
>>>>>> Gary
>>>>>>
>>>>>>
>>>>>> On 15 June 2011 12:33, Dave Perry<n4qs at comcast.net> wrote:
>>>>>>
>>>>>> My KPA500 sn 70 arrived tonight (factory assembled). It took  
>>>>>> just a
>>>>>> few minutes to hook up and get it on the air. I am using the Y  
>>>>>> cable
>>>>>> on the ACC port to split off two cables from the K3 ACC port --  
>>>>>> one
>>>>>> goes to a new RCS-12 Automatic Antenna Switch and the other  
>>>>>> goes to
>>>>>> the KPA500.
>>>>>>
>>>>>> I have AUX BUS on the KPA500 menu turned on and Band Change set  
>>>>>> to
>>>>>> normal. If I press a band button on the amp, the K3 changes  
>>>>>> bands and
>>>>>> so does the new antenna switch -- pretty neat. But the band  
>>>>>> display
>>>>>> on the KPA does not change. I have to hit the key and transmit  
>>>>>> to get
>>>>>> the band to change on the KPA500. This does not seem correct. It
>>>>>> would seem that pressing any on the band buttons on the amp  
>>>>>> should
>>>>>> change the band on the amp and the frequency display as well.
>>>>>>
>>>>>> Likewise if I change bands on the K3 or via my logging  
>>>>>> software, the
>>>>>> K3 and antenna switch change bands, but the KPA500 does not. I  
>>>>>> have
>>>>>> to tap the paddle and transmit to get the KPA500 to change to the
>>>>>> correct band. I am wondering if there is a problem with the Aux
>>>>>> Cable. Any other suggestions?
>>>>>>
>>>>>> I am up to date on firmware for both the K3 and KPA500.
>>>>>>
>>>>>> The amp runs very quiet and is silky smooth in full QSK mode. I  
>>>>>> just
>>>>>> need to get the band changing issue resolved. Any help would be
>>>>>> appreciated.
>>>>>>
>>>>>> Thank you.
>>>>>>
>>>>>> Dave, N4QS
>>>>>> ______________________________________________________________
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>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>>
>>>>>> VK4FD - Motorhome Mobile
>>>>>> Elecraft Equipment
>>>>>> K3 #679, KPA-500 #018
>>>>>> Living the dream!!!
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>>
>>>>>> VK4FD - Motorhome Mobile
>>>>>> Elecraft Equipment
>>>>>> K3 #679, KPA-500 #018
>>>>>> Living the dream!!!
>>>>>>
>>>>>> ______________________________________________________________
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>>>>
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