[Central-Electronics] VFO for 10B and 20A

[Jim Candela]

David said;

You mention the 6BH6 again.  I see that it is rated at .15A vs the .3A
filament for the 6CB6.
Is this still a significant improvement to do even if I don't go with the
Huff Puff Cumbria board as you did?


Reply by Jim, WD5JKO;

I made the change to lower filament power, and heat. Part of the issue is I 
ran the filament off DC regulated with a LM7806 3 terminal regulator. The 
regulator ran pretty hot with just a small heatsink, so instead of getting a 
larger heatsink I reduced the load current by half with just a tube change. 
This makes the regulator cooler. Otherwise, the 6CB6 is an excellent tube 
for the application.

Whether or not you add a stabilizer, I still recommend regulating the 
filament of the VFO tube. With the BC-458 and the 1626 triode, varying the 
filament voltage 10-15% (say 115 to 100v) might shift the oscillator a KC or 
more. Some tubes are far better than others, so having a pile of tubes to 
choose from is a good thing. Regulating is better though.

If you use a stabilizer, regulating is a must since the VFO will pull with a 
line voltage change as if you turned the knob.

On the BH, I also removed the 6X4 FW-rectifier and replaced with 2 of those 
thick legged diodes (1N5408) that fit perfect into a tube socket as a pin. 
The voltage was high now, so I changed the pi C-L-C filter to a choke input 
L-C filter. This cut the voltage back around normal, and way less heat.

Jim
WD5JKO
----- Original Message ----- 
From: "David" <texasroadrunner at comcast.net>
To: "Jim Candela" <jcandela at prodigy.net>; 
<central-electronics at mailman.qth.net>
Sent: Saturday, May 30, 2009 2:08 PM
Subject: Re: [Central-Electronics] VFO for 10B and 20A


> Jim-
> Great info- I never would have figured this out.
> Learning from others that have traveled this road is the way to go.
> You mention the 6BH6 again.  I see that it is rated at .15A vs the .3A 
> filament for the 6CB6.
> Is this still a significant improvement to do even if I don't go with the 
> Huff Puff Cumbria board as you did?
> The Cumbria really sounds like a neat way to go, but I'd like to play with 
> the native performance before going Hollywood on it (or it might be more 
> accurate to say, "British").
>
> Nope.  Didn't see any Lakeshore SSB (Phasemaster, right?) nor any other 
> potentially valuable BA's there.
> I'll ask my buddy to scout the future shows for George.  I can't say that 
> I've ever seen one myself.  Would be interesting to hear of any stories 
> about Lakeshore; they didn't appear to last very long.  Maybe bought out 
> by another company?
> In the interest of sharing great info, I added this response back to the 
> listserve in hopes it can help someone along the way.
> 73
> -dave
> W5OC
>
>
> ----- Original Message ----- 
> From: "Jim Candela" <jcandela at prodigy.net>
> To: "David" <texasroadrunner at comcast.net>
> Sent: Saturday, May 30, 2009 1:46 PM
> Subject: Re: [Central-Electronics] VFO for 10B and 20A (Tisha)
>
>
>>
>> Dave,
>>
>>   The center dial shaft 'floats' in a slight vertically elongated hole. 
>> When everything is right, you can just lift that screw with a Phillips 
>> screwdriver in it, then turn a little until the frequency is spot on, and 
>> then lower until the gear teeth re-engage. Mine was all messed up, and I 
>> didn't figure it all out until I reconditioned the 2nd BH for Doc Kalsa 
>> (also on our CE group). Then I went back and made mine correct. It is 
>> definitely kinda funky...the screw if allowed to tighten will jam the 
>> dial from turning.
>>
>> BTW, with my BH now with the 6BH6, it doesn't move after the initial lock 
>> which is about 60 seconds after turn on. The VFO is like a rock. What 
>> moves is the 9.0000 Mhz crystal in the 20A. I went through 4 crystals, 
>> and the warmup drift from them alone was about 60, 140, 200, and 600 Hz. 
>> These crystals all look the same, but are not. I have ideas about them 
>> too (PTC varistor as a heater). So far the ideas are just ideas. For now 
>> I'm using the best of 4 crystals..
>>
>> Any chance that the companion Lakeshore SSB transmitter is still at that 
>> sale? George, w1lsb, who recently posted on the CE reflector has one, and 
>> he is looking for parts (maybe the case?)
>>
>> Jim
>>
>>
>>
>> ----- Original Message ----
>> From: David <texasroadrunner at comcast.net>
>> To: Jim Candela <jcandela at prodigy.net>
>> Sent: Saturday, May 30, 2009 11:57:46 AM
>> Subject: Re: [Central-Electronics] VFO for 10B and 20A (Tisha)
>>
>> Hi Jim-
>> I think you're right about the BH on it's way to the dump.  It was pretty 
>> lonely item sitting on the rusted shelves alongside other vintage 
>> carcasses which didn't get much of glance from others.
>> Of course, when I spotted it, I did a double take and immediately cradled 
>> it.  Still can't belive my good fortune.
>> Thanks for the offer of your help.  It's sitting on the ground alongside 
>> the computer right now.  I've got a pesky Navigator which has hogged all 
>> of my bench space for the last month, but the BH is next.
>> The window (plastic?) is missing, but the dial is good shape.  Though it 
>> tracks with the tuning knob, I just noticed that it seems loose on it's 
>> shaft.  I hand tightened the front screw, but something else isn't 
>> tightening.  once I get it on the bench I'm sure I'll discover other 
>> items that need band aids. The good news is that it's all intact and 
>> unmodified.
>> I enjoyed your database of BH and CE (and other stuff).  The H&P Cumbria 
>> is a very interesting addition.  But like you mentioned in another post 
>> (googled), it's most effective for units that remain on all the time- 
>> which won't be my case.  I won't hesitate to ask for help if needed. 
>> Again, thanks for the kind offer of assistance.
>> -dave
>>
>>
>>
>>
>> ----- Original Message ----- From: "Jim Candela" <jcandela at prodigy.net>
>> To: "David" <texasroadrunner at comcast.net>
>> Sent: Saturday, May 30, 2009 10:42 AM
>> Subject: Re: [Central-Electronics] VFO for 10B and 20A (Tisha)
>>
>>
>>>
>>>
>>> Dave,
>>>
>>>   If you had not attended that sale, that BH might have been tossed into 
>>> the dump. Very few hams know anything about it.
>>>
>>> So what does the dial and window look like? Many dials are really messed 
>>> up, and the windows are yellow and no longer flat.
>>>
>>> I have a high resolution image of that dial that can be printed out with 
>>> a good laser printer and glued on to the metal dial.
>>>
>>> I also stabilized my BH so it stays within +/- 10 Hz very well.
>>>
>>> http://pages.prodigy.net/jcandela/Band%20Hopper/
>>>
>>> I have since replaced the 6CB6 VFO tube with a 6BH6 to cut the filament 
>>> power in half (less heat for 7806 6 volt regulator to deal with).
>>>
>>> Feel free to ask questions about that BH since I have now restored two 
>>> of them.
>>>
>>> Regards,
>>> Jim
>>> WD5JKO
>>>
>>>
>>>
>>> ----- Original Message ----
>>> From: David <texasroadrunner at comcast.net>
>>> To: central-electronics at mailman.qth.net
>>> Sent: Saturday, May 30, 2009 9:50:47 AM
>>> Subject: Re: [Central-Electronics] VFO for 10B and 20A (Tisha)
>>>
>>> Belated thank you for all the informative and thoughtful responses to my
>>> original post.
>>> It sounds like the BC 458 conversion is the most popular and the best
>>> practical match for the CE 10/20 Xmtrs.
>>> I acutally bought the Dan's Small Parts kit Universal VFO Kit (5.0-5.5 
>>> MHz)
>>> for $29.95 + $6.75 shipping (Note: it's a Kit closeout so, not sure how 
>>> long
>>> these will be stocked).  It comes complete with all parts, including PCB 
>>> and
>>> main tuning cap (mfr Hammarlund).   It looks like a terrific sandstate
>>> solution, including an extra amplifier stage to accommodate extra drive
>>> needs. Designed by W1CER Doug DeMaw (SK). Well, as fate sometimes works,
>>> last weekend I attended the local Houston Vintage Radio Assn's sale at 
>>> one
>>> of the member's yard.  Because a co-worker kinda encouraged me to come, 
>>> I
>>> drove over there within unexpected hopes of finding an ARC5 carcass.  To
>>> make long story short, in a storgage shed with misc radios, I found a
>>> Lakeshore Bandhopper for $25!
>>> The guts are perfect and the case only needs a sandblast and paint! 
>>> This
>>> clearly was one of the astounding moments of divine radio invervention.
>>> Someone upstairs wants to hear the BA combo that I will shortly get on 
>>> the
>>> air (Bandhopper+CE20A+600L).  Life is sweet.  Thanks again to all.
>>>
>>> 73
>>> -dave
>>> W5OC
>