Message-ID: <002301ccaa0d$30c4c380$0401a8c0@xphd97xgq27nyf>
From: "mal hamilton" <g3kevmal@talktalk.net>
To: <rsgb_lf_group@blacksheep.org>
References: <003001cc964b$656408b0$0401a8c0@xphd97xgq27nyf> <0EC138C788414BE1B2B683D4D6ED2B9D@JimPC>
Date: Wed, 23 Nov 2011 18:08:35 -0000
MIME-Version: 1.0
Subject: LF: Re: Re: Farnell H60/25 PSU
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Jim
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" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
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:
> http://dl.dropbox.com/u/50525290/FarnellH6025.pdf
>
> 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.,
which
> 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
like
> 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,
the
> 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
>
>