Message-ID: <D5406E34951346E9B5C8CCF68B297844@DELL4>
From: <jrusgrove@comcast.net>
To: <rsgb_lf_group@blacksheep.org>
References: <1019495001.20190502130019@gmail.com>
Date: Thu, 2 May 2019 10:01:09 -0400
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Subject: LF: Re: Toroids
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Chris

None in stock but would be happy to get them for you. Only possible problem is the customs forms ... 
I'm required to list the values of items accurately. I had a run in with US Customs years ago and 
don't wish to take a chance getting tangled up with them again. Let me know and I'll check pricing 
for the cores and shipping.

A pi-type filter is what's required for current mode. The amplifier as shown in the schematic 
'appears' to be current mode since there's no bypass at the centertap of the transformer. Not sure 
why you're seeing hot components. In the schematic it appears the ground was left off the bottom of 
LPF capacitors ... I'm sure
you picked up on this. Don't think I'd use a -26 core at 500 kHz ... this may or may not be the 
problem.

Jay W1VD

----- Original Message ----- 
From: "Chris Wilson" <dead.fets@gmail.com>
To: <jrusgrove@comcast.net>
Sent: Thursday, May 02, 2019 8:00 AM
Subject: Toroids


>
>
> Hello  Jay,
>
> I  am going to build the MF version of your 1kW amp deck to compliment
> the  LF  versions that have proven superb! I am struggling getting the
> T-225A-2  toroids  and  the T-157-3 ones here in the UK without Amidon
> trying  to  charge  far  more  than  the cost in postage, plus a hefty
> import  duty  /  tax.  Would  you  consider supplying these direct and
> marking  the package note as a low value (at my risk)? I could do with
> three  of T-225A-2 and 4 of the T-157-3 toroids. Here in the UK no one
> has  any  stock of either. If it's a PITA and you are unable to oblige
> or you don't have them, no worries :) Thanks. Chris Wilson 2E0ILY.
>
> BTW, off list, I built the G0MRF MF 300W amp and at full power it runs
> the  toroids  and  C19  C20  mad  hot,  plus  the drain waveforms look
> horrible.  Am  I  right in thinking he's using a current mode LPF on a
> voltage  mode  amp?  And  are  the  components  like  caps and toroids
> marginal  at  this  power  level?  I  am sure your MF amp is much more
> robust :)
>
> -- 
> Best regards,
> Chris                          mailto:dead.fets@gmail.com