[Central-Electronics] SS rectifiers? 100V/200V?

[ehertz]

Jon, this is VERY interesting indeed! Do you have any idea what the make up is of the replacement rectifiers? Are all three rectifiers replaced? I would love to know what Wes used to replace them.
Eugene

>-----Original Message-----
>From: K6JEK [mailto:k6jek at comcast.net]
>Sent: Sunday, March 11, 2007 05:32 PM
>To: 'Eugene Hertz'
>Cc: central-electronics at mailman.qth.net
>Subject: Re: [Central-Electronics] SS rectifiers? 100V/200V?
>
>My 100V had the tube rectifiers replaced with solid state plug-ins by 
>none other than Wes Schaum, President of Central Electronics. 
>After he left Zenith he did a little business refurbishing CE gear 
>and my 100V went through his shop way way back when someone else 
>owned it. This made me think SS rectifiers are not anathema to 
>100V's, that plus they put them in 200V's. 
> 
>However, I suspect that the LV is so high it's driving the voltage 
>regulator out of regulation. I was getting frequency hopping and 
>I'm not getting it now that I run it at 110V. I'm not sure about 
>this, it's just a theory. 
> 
>Like Eugene, I wonder if the 200V had a different transformer to go 
>with the silicon rectifiers to take the HV down a peg. 
> 
>Jon, K6JEK 
> 
> 
>On Mar 10, 2007, at 2:18 PM, Eugene Hertz wrote: 
> 
>> Hi All (long email-apologies up front), 
>> 
>> While trying to set the FSK shift on my 100V last night, it coughed 
>> up some smoke. I am pretty sure the smoke was from one of the 6AU4 
>> rectifier tubes used in a 600V supply (for 6550 finals). 
>> 
>> Reason I think the tube gave up the smoke was because after I saw 
>> flashing in the tube, there was soot at where pin number 1 would 
>> be . I also observed actual smoke lingering in the pin hole of the 
>> socket in which pin #1 would be. Pin number 1 actually has a 
>> structural support to hold up the guts of the tube. This support 
>> does not protrude beneath the glass envelope, but is held in place 
>> by the glass. Observing this with a magnifier, I can see 
>> discoloration at the point at which the support is affixed in the 
>> glass. And last but not least, the base of the tube stinks! Just 
>> like the smell when the smoke was emitted. Of course, a very valid 
>> question is, could something have failed and caused too much 
>> current through the tube to destroy it? I will put it on the bench 
>> to make sure nothing else has suffered. 
>> 
>> So, I am thinking about replacing the rectifiers with solid state. 
>> You may ask why? Simple answer is there are 3 rectifiers in the 
>> transmitter consuming a total of 37W of filament power and heat. 
>> For those concerned, I always run the transmitter through a variac 
>> and can adjust it down to lower the B+ if necessary. Also, as far 
>> as inrush through the power transformer, I think I'm ok because the 
>> power transformer does not directly feed filter caps, it first goes 
>> through some mighty chokes. So I think the choke will moderate the 
>> current filling up those capacitors. 
>> 
>> On the subject of reducing the mains voltage to compensate for the 
>> higher HV—Seems the 200V had solid state rectifiers for all 
>> rectification. I will also note that the HV supply in the 100V 
>> model is 600VDC and on the 200V model its 680VDC! Given that the HV 
>> in both models is used for the 6550s and the CRT tube, this leads 
>> me to think that even if my HV B+ went to 680 as a result of 
>> replacing the tubes with ss rectifiers, there should be no reason 
>> to worry. I also checked the resistors and caps in the HV sections 
>> for both models and they all remain the same values and ratings. Of 
>> course, this may be an oversimplification. 
>> 
>> I looked through the manual of the 200V and looked at the schematic 
>> as posted on bama and could not find this. Can any 200V owner tell 
>> me what the B+ voltage is? 100V is 340VDC. Looking at the 200V 
>> diagram, it looks like it should be ½ HV can anyone confirm? 
>> 
>> In any case, the real question is, does anyone have any experience 
>> with SS replacements for the 6AU4? My google research has only 
>> located one which can be found here: http://tinyurl.com/2crs5e 
>> 
>> This is the only one I've located. Anyone ever use this brand? 
>> Anyone know of any other product? Transmitter also has a 5U4 which 
>> I will probably replace with the weber copper cap. 
>> 
>> 
>> If I replace the rectifiers with solid state and if HV ends up at 
>> 680V as a result, can anyone think of a reason why this would be a 
>> bad idea? 
>> 
>> I am particularly interested in what other folks have used to 
>> replace the 6AU6. 
>> 
>> Has anyone tried to completely replace the power supply section of 
>> the 100V with the same circuit as the 200V? Remove all rectifier 
>> tubes, put in a standard solid state full-wave-bridge tap the 
>> center and be done? 
>> Thanks! 
>> 
>> 
>> 
>> 
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