Fw: Re: Fw: RE: [HBR] Restoration info

[windy10605 at juno.com]

Thanks for the first input.
  
I have noticed that there are very few mods available for the 2B which
may be an indication of how well it was designed. 

So far we've come up with the following:

1) get the 2BQ "Q" multiplier feature to go with the radio
2) replace the four .01mfd paper caps on general principle. Replace the 
    electrolytics too. Check "the usual suspects".
3) replace the 1mfd AVC paper cap with a 1.5mfd Mylar
4) replace the .005 mfd audio coupling cap with a .01mfd Mylar
5) replace the 6U8 with a 6EA8
6) replace the 6BF6 with a 6AV6 (make sure the leakage is EXTREMELY low)
7) since the AVC is Hi-Z you must use a 10Meg+ impedance meter and you 
    will still be 10-15% off on your bias voltage measurements. A 1000Meg
    input Fluke is OK. 
8) there is something not right about the audio feedback circuit design
9) would like to see more ceramic switches and higher "Q" coils in the
frontend
10) noise limiter can stand more improvement
11) BNC antenna connector 
12) carefull look at dual use tubes for interference
13) separate BFO function from Product Detector function in 6BE6 ?
14) find better RF amp tube than a 6BZ6
15) look into use of pullen mixers
16) add a second .005mfd cap across the BFO divider into the 6BF6 cathode
      to increase the BFO signal level.

73 Kees K5BCQ


--------- Forwarded message ----------
From: "DW Holtman" <future212 at comcast.net>
To: "HBR Receiver List" <hbr at mailman.qth.net>
Date: Wed, 27 Jul 2005 19:53:50 -0600
Subject: Re: Fw: RE: [HBR] Restoration info
Message-ID: <001f01c59317$33954a80$61c3b643 at dw2q2am1a08eq5>
References: <20050727.203458.1864.4.windy10605 at juno.com>

Kees,

I have had several 2-B over the years. I really don't think you are going
to 
make much improvment in such things as Receiver sensivity, noise floor, 
selectivity ( without adding crystal filters). If I was going to try to 
improve on a 2-b, I might build a digital VFO using DDS technology. You 
would have a very nice 1.5 to 30 MHZ  shortwave receiver. For what it is 
worth.

Best,
DW Holtman



----- Original Message ----- 
From: <windy10605 at juno.com>
To: <hbr at mailman.qth.net>
Sent: Wednesday, July 27, 2005 7:34 PM
Subject: Fw: Fw: RE: [HBR] Restoration info


> It's a 100 page Word document which I will distribute via email once I
> get a list of names together. You can print it or file it as you wish.
I
> also have the 80 or so page RSGB Receiver document by G2DAF as a Word
> document for those interested. They are both on my CD but occupy too
much
> space on the web site. They are both great pieces of info to have if
you
> are working on quality tube receivers.
>
> Right now, a friend of mine and I are working to improve the Drake 2B
> receiver. Triple conversion without the typical string of IF stages. If
> you can find one cheap, buy it. I've always thought the 2B was a great
> example of a commercial tube type HF receiver of the early 60s
timeframe
> which is physically compact, sensitive (0.5uV or better), selective
(good
> permeability tuned passband), simple slide switches, multiple Hi-Z AVC
> points, copper plate chassis (there are no "bad grounds" to tube
> sockets), screws vs rivets, low power (less than 40W), "low" voltage
> (less than 180VDC) and uniquely efficient design (have you seen the
> outstanding use of vertical terminal strips ? super simple graticule
> adjustment, etc). It also offers the distinct "ease of use" advantage
of
> bandswitching and crystal converters. Still an excellent design in this
> day and age. Maybe some of you have some input on improving that design
?
>
>
> 73 Kees K5BCQ
> ************************************
> Visit the HBR Receiver Web Site with over 100 pictures of receivers and
> construction notes...... via http://www.qsl.net/k5bcq/
> there is also a mirror (faster response)at http://k5bcq.edebris.com/
>
>
> Retrieve reflector archived data via 
> http://mailman.qth.net/mailman/listinfo/hbr
>
> 


************************************
Visit the HBR Receiver Web Site with over 100 pictures of receivers and 
construction notes...... via http://www.qsl.net/k5bcq/ 
there is also a mirror (faster response)at http://k5bcq.edebris.com/


Retrieve reflector archived data via
http://mailman.qth.net/mailman/listinfo/hbr