[Boatanchors] Mod transformer for Multi-Elmac AF67

[Roger Basford]

Hi Bob,

Thanks for the fast response! It looks as though the TX has been converted 
for CW-only operation at some point; the mod transformer, driver transformer 
and bias battery have gone and one of the 6L6s has been replaced by a VR105, 
which is stabilising the screen of the 6146 PA with a large wire-wound 
resistor above the chassis. Nothing there that can't be put right again but 
it does look as though I will need both transformers, if you have them. If 
you do, then a photo of where the driver transformer goes would be great, if 
I can impose on you some more :-)). I have had similar trouble with Heathkit 
DX-100U (UK Model) driver transformers failing and Hammond were able to 
supply a replacement for those.

73,

Roger - G3VKM



----- Original Message ----- 
From: "rrkrr" <rrkrr at comcast.net>
To: "Roger Basford" <roger at new-gate.co.uk>
Cc: "boatanchor" <boatanchors at mailman.qth.net>
Sent: Monday, July 09, 2007 5:05 PM
Subject: Re: [Boatanchors] Mod transformer for Multi-Elmac AF67


> Roger,
> It happens that I do have an AF-67 modulation transformer, which I'll be 
> happy to send for the cost of shipping.
> Have you checked the transformer that couples the audio driver stage to 
> the grids of the push-pull modulator stage?  These are notorious for going 
> bad, due to defective enamel wire insulation.  I'm not sure if my junker 
> has one of those, but I'll check.  Also, the AF-67 used a 22 Volt battery 
> for grid bias on the modulator tubes.  I've seen several schemes for 
> eliminating this, one of which was to put a high wattage 22 volt avalanche 
> diode between the cathodes and ground.
>
> Bob K4ERR
>



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