[Central-Electronics] Fwd: 100V Problem/Questions

[Grant Youngman]

Sent from my iPhone

Begin forwarded message:

> From: Grant Youngman <nq5t at tx.rr.com>
> Date: April 21, 2014 at 4:38:16 PM CDT
> To: Bob Sullivan <robert at isquare.com>
> Subject: Re: [Central-Electronics] 100V Problem/Questions
> 
> I suppose it's possible that the slight movement from wiggling the driver tube is affecting a pin(s) on the coil socket.  Generally, carefully wiggling the coil box doesn't seem to have an effect -- I suspect that when I thought it did I was also fat-fingering the tube. 
> 
> I also tried a new tube, but it tested about the same as the one I have in there, and behaves the same way. 
> 
> I plan to reheat all of the socket connections (although a couple of them are not so easy to get to), do the same to the coil socket, and gently recrimp them all.  I may poke at each pin first with a chopstick while it's powered up to see if anything becomes obvious ..
> 
> Grant NQ5T
> 
> 
> 
> Sent from my iPhone
> 
>> On Apr 21, 2014, at 4:15 PM, Bob Sullivan <robert at isquare.com> wrote:
>> 
>> Grant,
>> 
>> It's always hard to guess but one thing I have learned after restoring a number of 100V and 200V's is that the pins on the plug-ins can be an issue. Sometimes cleaning is not enough. I have had to carefully crimp the contacts to ensure continued good contact. There is nothing "special" about the driver circuitry as relates to 15m. Check the pins carefully on the driver plug-in module.
>> 
>> The 6BQ5 bias is not so critical that your .04v difference would make an appreciable difference.
>> 
>> 73, Bob
>> WØYVA
>> http://www.isquare.com/personal_pages/ras-hardware.htm
>> 
>> 
>> 
>>> On Apr 21, 2014, at 4:40 PM, GRANT YOUNGMAN <nq5t at tx.rr.com> wrote:
>>> 
>>> I have a very nice 100V that I restored several years ago, complete with a Tusa-rebuilt PTO, that was working fine last time I had it on line.  No good deed going unpunished, I decided to bring it back into the mix paired with an SX-115 as well as rework the mic cable routing to eliminate the little bit of hummmm that won’t go away, and of course, it wasn’t working.
>>> 
>>> Specifically it worked fine on 15M, but would produce no output on any other band.  In working stage by stage through the RF chain, I’ve settled in on the V14 6BQ5 driver stage.  “Sometimes” — after wiggling the tube and/or the coil plugin it will begin producing output on all bands for a while.  I can wiggle the tube and usually force it to work on a band that produces no output.  But then it eventually goes back to working on 15M only.  Clearly, there’s some kind of mechanical issue, bad solder joint, etc. with the socket or something around the socket, but whatever it is it doesn’t effect 15M operation, ever.  In the process I’ve checked pins on all of the plugins, including the RF deck, cleaned them up, applied some D100L, etc.
>>> 
>>> Also, when checking the bias on pin 3 of the 6BQ5 it is around 0.27-0.29v (depends on band) rather then the 0.32v spec.  So I’m going blind tracing through the schematic and also visually inspecting the hard-to-see mess around V14 (6BQ5) to attempt to figure out what might be amiss.
>>> 
>>> Two questions:
>>> 
>>> 1.  Anyone have a clue what is different if anything about 15M that would leave it unaffected by whatever might affect 10,20,40,80 intermittently?  10M input (by the meter) on CW will only run up to around 100W, but when it works at least there’s something.  
>>> 
>>> 2.  Is the bias on pin 3 of the 6BQ5 (spec’d at .32v) critical enough that I should rework the voltage divider to get it up from the (around) 0.28v current value?
>>> 
>>> Thanks … Grant NQ5T
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>>