[Heathkit] [Boatanchors] DX-35 Power Transformer

[RAY FRIESS]

I recently picked up a very good condition DX 20 at a swap meet for $20 and also a Hallicrafters HT 40 for $25.
Would your advice be the same for the DX 20 as for the 35 and 40?

Date: Tue, 10 May 2016 23:38:33 +0000
From: gzook at yahoo.com
To: rayfrijr at msn.com; gharmon at idworld.net; heathkit at yahoogroups.com; heathkit at mailman.qth.net
Subject: Re: [Heathkit] [Boatanchors] DX-35 Power Transformer

The power transformer in the DX-40 is a little bit heavier.  However, it is also pushed over its real limits.  There are a lot of DX-40s "out there" with blown power transformers.  However, percentage wise, not as many as DX-35 blown transformers.  To protect an original DX-40 transformer, the input power needs to be kept to no more than 60% to 75% of the ratings, the lower the better!


It was not until the DX-60 that Heath used a transformer that was not overloaded.  Like the DX-35, in the DX-40 the VFO definitely should not be powered by the transmitter's power supply.


Also, the VF-1 and HG-10 really need to be powered by a separate, regulated, power supply.  In the HG-10/HG-10B manual, there is like a couple of sentences that do recommend using a separate power supply.


For the VF-1, there are 2-thing,s that require no modification to the VFO, that need to be done to really stabilize the VFO.  The first thing is to replace the 6AU6 oscillator tube with a 6AH6.  Then, replace the 0A2 screen voltage regulator with an 0B2.  This reduces the screen voltage to 108 VDC instead of 150 VDC.  Then, the 0A2 removed from the VF-1 can be used to regulate the voltage from an external power supply to 150 VDC.  The VF-1 works fine with 150 VDC and the stability is increased even more.


The HG-10 also is much more stable with a regulated 108 VDC applied from an external power supply.

 Glen, K9STH 
Website:  http://k9sth.net

       From: RAY FRIESS <rayfrijr at msn.com>
 To: Glen Zook <gzook at yahoo.com>; "Gary H. Harmon, Jr." <gharmon at idworld.net>; Heathkit3 LIST <heathkit at yahoogroups.com>; Heathkit2 <heathkit at mailman.qth.net> 
 Sent: Tuesday, May 10, 2016 6:02 PM
 Subject: Re: [Heathkit] [Boatanchors] DX-35 Power Transformer
   
Have you found the same problem with the DX 40?   I have a 40 and a VF1.  Also have an HG 10 that I can use with it.