Message-ID: <003a01cca943$d11a0c70$0401a8c0@xphd97xgq27nyf>
From: "mal hamilton" <g3kevmal@talktalk.net>
To: <rsgb_lf_group@blacksheep.org>
References: <003001cc964b$656408b0$0401a8c0@xphd97xgq27nyf> <0EC138C788414BE1B2B683D4D6ED2B9D@JimPC>
Date: Tue, 22 Nov 2011 18:23:21 -0000
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Subject: LF: Re: Re: Farnell H60/25 PSU
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Jim
Tnx for the cct details and operating information. I have noticed a
downwards flicker on the 60v output when I key  the driver, it seems
reasonable for qrs  work but for faster keying might be a problem.
Maybe keying the HT would be a better approach. Do you use this method on
your Decca.
Condx are good at present to the USA es Canada. If you are back home at the
TX site try QRS around 2100 utc around 136.720 to 136. 725
I have been getting into the VE2IQ grabber every night that I get on at QRS
20 es 30.
The TF3HZ grabber is a good guide to your signal strength
There has been a good bit of acty around this freq area most nights and I
usually park at 136.173
Look forward to seeing your signal on LF and agn tnx for the useful
information. If I get a PSU blow out at least I have some info.
73 gl 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
>
>