Re: {Collins} 32V-3 5V4 Transformer Killer?

You might want to make note of Glen's info. Good stuff. Over the years I have bought three HT-32's and an HT-37 at hamfests really cheap (like $20 cheap) because they supposedly had "bad power transformers". On all of them I totally disconnected the filament windings from the rectifier sockets, solid-stated them, and -voila- the transformers worked. I had high voltage and no blown fuses. 

73, Ernie, k0occ 

--- Original Message ----- 
From: "Glen Zook" <gzook@xxxxxxxxx> 
To: "John Painter" <johnpainter@xxxxxxxxxxx>, "Colin Lamb" <k7fm@xxxxxxxxxxxx>, "Mack McCormick" <w4ax.mack@xxxxxxxxx>, "Collins" <collins@xxxxxxxxxxxxx>, "Greg Mijal" <bluebirdtele@xxxxxxxxxxxxxx> 
Sent: Sunday, March 20, 2011 11:27:51 AM 
Subject: Re: {Collins} 32V-3 5V4 Transformer Killer? 

The problem that I have run into with the Collins 32V- series transmitter transformers is actually a short between the 5.0 volt windings and other windings. This seems to be caused by an insulation failure caused by the fact that the rectified B+ is on these windings. To prevent this failure, and, in a few cases to effectively "save" the transformer after an insulation failure, is to completely disconnect this winding and use solid-state rectifiers. 

There is the same problem with certain other manufacturers' equipment including the Hallicrafters HT-32 series and the HT-37. 

Now I don't normally recommend replacing the tube rectifiers with solid-state. However, in the case of the 32V- series and the Hallicrafters transmitters, the fact that the transformer can be "saved" by going to solid-state definitely overrides the desire to keep the unit "original". 

Also, I have not run into any problems with "inrush" current caused by the fact that there is no "warm up" time with the solid-state rectifiers. There are numerous situations with tube type equipment that originally came with solid-state rectifiers and those units do not have any problems including units that originally had tube type rectifiers and were changed in mid production to solid-state rectifiers. Of course, there are those who are going to disagree with this. But, again in my several decades experience of working on "boat anchor" equipment, I have not had any problems with going solid-state when the situation is a choice between losing a transformer and keeping the transformer. 

Again, I don't recommend changing to solid-state rectifiers just to change them. But, I do recommend changing to solid-state rectifiers when making the change helps prolong the life of the equipment. 

Glen, K9STH 


--- On Sat, 3/19/11, Greg Mijal <bluebirdtele@xxxxxxxxxxxxxx> wrote: 

Something just pooped into my mind concerning the 5V4 in the Collins transmitter. The 5V4 may be one of the slow start up rectifiers. Slow starters were made to delay the filament emission until the other tubes warmed up and began pulling current from the supply. As the transformer ramped up the current to the rig, the voltage went down to the manufacture's spec for the particular set. Substituting the orignal rectifier with a standard start rectifier may cause the supply to overshoot. Perhaps beyond the ratings of the circuit components. My home made KWM-1 supply has this situation and I go around it with a B plus switch. I turn on the B plus after about 1 minute of power on to the rig's tube filaments. 


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