[Boatanchors] DX-100 adventure - progress

[WQ9E at btsnetworks.net]

The stock plate supply value is two 125uf in series to yield a bit over 60uf, 50uf would be sufficient and going significantly higher than stock does increase power supply stress with no real benefit.

I am not sure about converting the low voltage supply to choke input.  The VFO and low level audio stages must have very low ripple and a pi section filter is far more effective than choke input.  Typically choke input is used for the high power stages and is necessary with MV rectifiers but the regular high vacuum rectifier works fine with reasonable values of input C (like the original DX-100 circuit).  In summary you are thinking about adding more filtering than needed to the plate supply but you probably don't have sufficient filtering in the critical B+ supply.

While you are in the power supply carefully check the 5R4 sockets and tube bases for carbon tracks and clean away any dust/dirt before tracks appear.  This is a common issue with 5R4 tubes in many transmitters and I have had to replace sockets in Johnson Viking 1 and 2 rigs because of damage from this issue.

Rodger WQ9E


-------- Original Message --------
> From: Rob Atkinson <ranchorobbo at gmail.com>
> Sent: Saturday, December 21, 2013 5:06 AM
> To: Bill Cromwell <wrcromwell at gmail.com>
> Subject: Re: [Boatanchors] DX-100 adventure - progress
> 
> I don't know much about the DX100 but with a choke input filter, 50
> mfd filter cap seems like way more than enough and 100 seems dangerous
> frankly.