[Elecraft] KPA-500 270V ERR

[David Gilbert]

High voltage rectifier diodes would have very low doped N-regions, which 
means fairly long carrier lifetimes so no doubt they work somewhat like 
a PIN diode if properly biased.  But they aren't really the same thing, 
and I still say that a PIN diode has performance advantages in many 
situations.  They are more difficult and costly to build, though.

I used to manage a large semiconductor entity that manufactured these 
things.

73,
Dave   AB7E




On 8/26/2021 2:05 PM, jerry wrote:
> Using 1N4007's and 1N5208's ( I could have the last # wrong ) as "Poor 
> Man PIN
> diodes" is pretty established practice in the amateur community. Look up
> W6JL on QRZ.com.  He has an extensive article about it on his page there.
>
> Also Hans Summers of qrp-labs uses them in his 50W QSK amplifier.
>
>   Apparently, these kilovolt rectifiers behave very much like PIN diodes,
> at speed.
>
>                - Jerry KF6VB
>
>
>
> On 2021-08-26 11:46, David Gilbert wrote:
>> That sounds odd to me.  True PIN diodes are current actuated devices.
>> The carrier lifetimes are long enough that the devices are "on" even
>> if the signal peaks exceed the voltage of the control current ... as
>> long, of course, as the control current exceeds the signal current.
>>
>> On the other hand, I've heard that Elecraft has sometimes used regular
>> switching diodes instead of PINs, and for those you need a voltage
>> that exceeds the peak voltage of whatever you're switching.
>>
>> Both types of diodes have their place ... using one where the other
>> works better is not good practice.
>>
>> 73,
>> Dave   AB7E
>>
>>
>>
>> On 8/26/2021 11:33 AM, Fred Jensen wrote:
>>> I think the 270 V circuit is DC bias for the PIN diodes in the 
>>> TR-switch.
>>>
>>> 73,
>>>
>>> Fred ["Skip"] K6DGW
>>> Sparks NV DM09dn
>>> Washoe County
>>>
>>> On 8/26/2021 10:32 AM, Chuck Chandler wrote:
>>>> My KPA-500 has been running great for several years.  Recently I 
>>>> noticed it
>>>> was making the occasional extra "click" or "thunk" upon powering up or
>>>> down.  Usually it would "click" when powered up and again when powered
>>>> down, but recently a few seconds after the first click there would be
>>>> another one, maybe more of a thunk sound.
>>>>
>>>> This afternoon I turned it on and when I pushed the Operate/Standby 
>>>> button
>>>> I got a fault light and the 270V ERR message on the display. The 
>>>> menu HV
>>>> option shows 68.4V, varying a bit, on my 240V line.  I put it on 
>>>> the bench
>>>> and opened up the top cover.  There is a smell of overheated 
>>>> components,
>>>> maybe burnt but more like too hot.
>>>>
>>>> I've submitted the contact form on the Elecraft support page. Any
>>>> suggestions?  For now, I'm running barefoot...
>>>>
>>>> 73 de Chuck, WS1L
>>>>
>>>>
>>>
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