[Boatanchors] Dx40 and VF1

[RAY FRIESS]

The transformer failure ... is it a case of the windings opening up?

________________________________
From: Glen Zook <gzook at yahoo.com>
Sent: Wednesday, November 7, 2018 7:57 AM
To: RAY FRIESS; boatanchors; Boatanchors QTH
Subject: Re: [Boatanchors] Dx40 and VF1

The VF-1 was actually designed to be used with the AT-1 transmitter.  Then, they came out with the DX-35 which had a transformer that failed on a regular basis without any additional load on the transformer and only a relatively small percentage of DX-35 transmitters still have an original working transmitter.



Then, Heath came out with the DX-40.  That transmitter had a slightly better transformer than the DX-35.  Unfortunately, the transformer still failed on a regular basis but not quite as many as in the DX-35.  It was not until the DX-60 series that the transmitter had a really reliable transformer.



The added load from powering the VF-1 from either the DX-35 or DX-40 is often just enough to cause a transformer that is just on the edge of failure to fail.  Running the VF-1 from a separate regulated power supply also helps prevent "chirping" because of varying voltage.



The VF-1 can be greatly improved in both stability and tendency to chirp by replacing the 6AU6 with a 6AH6 and replacing the 0A2 screen regulator with an 0B2.  Neither tube replacement requires and modification to the VF-1.  Then, use the 0A2, removed from the VF-1, to regulate an external power supply that provides 150 VDC regulated to the VF-1.  This lower plate voltage works fine.



On CW, let the VF-1 run constantly when transmitting and chirp just doesn't happen.  Of course, you have to put the VF-1 in standby when receiving.  This can be accomplished with a set of relay contacts that are connected to a phone plug plugged into the back of the VF-1.



Glen, K9STH

Website: http://k9sth.net


________________________________
From: RAY FRIESS <rayfrijr at msn.com>
To: boatanchors <boatanchors at mailman.qth.net>; Boatanchors QTH <boatanchors at qth.net>
Sent: Wednesday, November 7, 2018 12:08 AM
Subject: [Boatanchors] Dx40 and VF1

I'm a bit puzzled by something.  I keep reading things about the problems or dangers of powering a VF1 from the DX 40 instead of using a separate power supply.  What puzzles me is would Heath engineers really have built the vfo to be powered by the 40 if it was going to be a problem?  Or would they really have put a power supply into the 40 that was so underrated and overtaxed that it couldn't handle a VFO???