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LF: Re: Re: Farnell H60/25 PSU

To: <[email protected]>
Subject: LF: Re: Re: Farnell H60/25 PSU
From: "mal hamilton" <[email protected]>
Date: Wed, 23 Nov 2011 18:08:35 -0000
References: <[email protected]> <[email protected]>
Reply-to: [email protected]
Sender: [email protected]
I have made a trolly for my PSU !! it is some weight hi, now easier to
manoeuvre into position in shack.
Not seen any acty from you on 136 yet.
de mal/g3kev

----- Original Message -----
From: "James Moritz" <[email protected]>
To: <[email protected]>
Sent: Tuesday, November 22, 2011 5:08 PM
Subject: LF: Re: Farnell H60/25 PSU

> Dear Mal, LF Group,
> >Hi Jim/M0BMU es co
> >Do you have a cct diagram for this psu Farnell H60/25. I bought one
> >recently and could do with some cct info.
> I have been working away from home for some weeks, hence the delay in
> replying... I have scanned the schematics for this PSU and they can be
> downloaded as a pdf from:
> I have used this PSU for some time to power my Decca TX. There are some
> things you should be aware of:
> It uses a thyristor pre-regulator with linear output regulator - quite a
> popular configuration in its era for high power PSUs. The thyristors are
> connected directly in series with the mains input. The switching waveforms
> result in high peak mains currents with flickering house lights etc.,
> might cause MCBs to trip with modern domestic wiring. It has a hefty mains
> RFI filter with 0.1uF capacitor from L - E, which might also trip modern
> RCDs
> The regulation is pretty good for slowly varying loads, but it does not
> on-off keyed tramsmitters as a load. Going abruptly from zero to full load
> causes a  large transient dip in output voltage. A large electrolytic
> capacitor across the PSU output is helpful.
> To make it work, the external (analogue) programming inputs on the back
> panel terminal strip have to be correctly linked. For normal operation,
> links are B-C-J, D-E-F, G-H-K.
> Over the years I have had to replace all 4 pass transistors in the output
> regulator. These usually fail s/c, which causes the PSU to shut down.
> Cheers, Jim Moritz
> 73 de M0BMU

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