Topband: DX-100 adventure contiunued

[Bill Cromwell]

On 01/08/2014 05:19 PM, Charlie Cunningham wrote:
> Well, here in Raleigh, I've seen it go a good bit more than 5% high at
> night. Still, I wonder if Bill could just put some higher voltage
> electrolytics in there, tune for "maximum smoke" and "let 'er rip" - and
> count on the key-down sag to keep the 6146s safe? ( Maybe I spent too many
> years around electric  utilities) I  think that +/- 5% guideline is honored
> more in the breach  than in the observance.  In the  meter business "480
> high-line" was 530 VAC!
>
> 73,
> Charlie.K4OTV
>
>
Hi,

So far I haven't found the line voltage lower than 125 Volts and in 
early afternoon it was at 130 volts. The transmitter was working and no 
problem with the finals at all before I did the recap. I did the power 
supply recap in all three power supplies because the low voltage supply 
was getting really hot. I'm not sure what the high voltage was before 
the recap so it may not be all that much higher now. The DX-100 worked 
before. Somebody suggested using a Fluke DMM. Maybe that was inspired by 
my comment about the front panel plate voltage meter. I don't have a 
Fluke and I am not worried a bout a few millivolts. I did use a VTVM 
when I wanted to know. The panel meter turns out to be close enough.

Two or three hams have mentioned the neutralizing circuit for the 
finals. I would have suspected that too. But - the DX-100 doesn't have a 
neutralizing circuit! I reread the entire assembly and operating manual 
(I have the original). Nope. Not a word about neutralizing. No 
neutralizing cap. No funny little wire to bend. Nothing. When I was 
working on the wiring and removing/replacing caps I moved wire harnesses 
out of the way. I thought that I put them back where they were. Probably 
some of what I am seeing is because a wire or two is "sticking out" too 
far. I did see a warning to dress the leads as shown *everywhere*. I 
told you I reread the entire manual <evil grin>. I will configure the 
high voltage filter cap(s) for the higher voltage and make sure the 
wiring in the chassis looks exactly like the wiring in the pictures. 
Nice to have all those big diagrams and pictures.

A few hams have suggested that the DX-100 is just a piece of junk 
anyway. If it doesn't yield pretty soon I will probably make some 
changes that update it to more modern circuitry (NOT SOLID STATE - 
MRF454s, ETC). This one had the modulation iron and even the modulator 
tube sockets removed by a previous owner. Some more modification won't 
hurt much. Meanwhile I do have other radios to get me on the air. Just 
not on Top Band.

Thanks for the comments and hints.

73,

Bill  KU8H