[Top] [All Lists]

[AMPS] Step Start for Ameritron AL-80A

To: <>
Subject: [AMPS] Step Start for Ameritron AL-80A
From: (Steve Thompson)
Date: Mon, 16 Mar 1998 21:02:25 +0000
Mike Willis wrote:

>The relay is across the transformer primary, an AC one which activates
>after about
>a second. So far so good.

>For the EHT short problem, I have a resistor in series with the EHT. 

The problem I was thinking of was when you get a trouble in the
transformer or bridge or HV caps; then the mains limiting resistors
don't get switched out.

In message <19980316102421.AAC10088@[]>, Rich Measures
<> writes

>> If there is a fault which draws high primary current and
>>stops the HV output rising to the value that shorts out the resistors,
>>they sit there with most of your line voltage across them until they go
>That is the idea.  The resistors act as fuses in the event of a major 
>circuit fault. If all's well, the 7w resistors barely get warm during the 
>c. 1 second step-start.  

I guess you can't mistake the fault indication, but I find it easier to
replace a fuse :-)

>>I guess it's more difficult with a single transformer as you need
>>to let the auxilliary supplies build up to operate the relay.
>-  Two or more transformers act like a single transformer when the 
>primaries are in parallel. 

Indeed - I was thinking of the difference between a commercial amp with
one transformer for all supplies and home brew system where the
auxilliary supplies are often separate.

>>Having suffered once, I now use a fixed timer which gives a few seconds
>>delay - if there's a fault then the line fuse blows.
>A fixed timer changes only the capital investment. 

True, but it's only pennies.

73, Steve

FAQ on WWW:     
Administrative requests:

<Prev in Thread] Current Thread [Next in Thread>