{Collins} Re: 75A2



Does anyone know with which serial # (approx?) Cedar Rapids would have
changed versions?  Just Curious!

73,
Brian    wj0p

.net>
To: <rrkrr@xxxxxxxxxxxxxx>; <K7OX@xxxxxxx>
Cc: <collins@xxxxxxxxxxxxx>
Sent: Thursday, July 22, 2004 3:59 PM
Subject: {Collins} Re: 75A2


> The 75A-2 has 2 models.....the early models with the metal escutcheon
> has a different tube lineup than the later models with the bakelite
> escutcheon similar to the A-4.
> The older model has V1 6AK5, V2 6BE6. there may be other differences as
> well.
>
>
> Regards
>
> Dave Harmon
> NSRCA 586
> K6XYZ[at]comcast[dot]net
> Torrance, Ca.
>
> -----Original Message-----
> From: collins-bounce@xxxxxxxxxxxxxxxxxxxxx
> [mailto:collins-bounce@xxxxxxxxxxxxxxxxxxxxx] On Behalf Of rrkrr
> Sent: Thursday, July 22, 2004 12:33 PM
> To: K7OX@xxxxxxx
> Cc: collins@xxxxxxxxxxxxx
> Subject: {Collins} Re: 75A2
>
> Gary,
> The 6BE6 and 6BA7 are both pentagrid converter tubes (heptodes).  The
> 6BE6 has a 7-pin base and the 6BA7 has a 9-pin base.  I believe the 6BA7
>
> is a newer design.  I don't have any first hand information about the
> 75A-2, but my guess is that the 6BA7 was a later model change in the
> 75A-2.  The 75A-4 receiver used 6BA7 mixer tubes from the outset.
>
> If you think you want to modify your receiver to a newer design, I would
>
> have a look at some of the mods published for the 75A-4, rather than
> changing to the 6BA7.  Pentagrid converters are rather noisy mixer tubes
>
> and there are better alternatives out there that provide lower noise
> figure and better dynamic range.  I would recommend the mixer designs
> described by N0DMS in the Electric Radio Modification Compendium for the
>
> 75A-4.
>
> Bob
> WB4TGG
>
> GARY ELLIOT wrote:
>
> >As I continue with my restoration of a 75A2 I have run into some
> discrepancies, namely the reproduction manual that came with the
> receiver has the 1St & 2ND mixers listed as 6BA7's.  Yet the chassis is
> stamped V2 & V4 as 6BE6's.  The schematic shows the output of the 70E12
> PTO to pin 2 of the 6BA7.  Yet my radio has the output of the PTO
> connected to Pin 1.  Also there are some different resistor values
> associated with this scoket then is shown on the schematic.
> >Was there a service bulletin or any mods that may have appeared in Ham
> Magazines changing the mixers in the 75A2 ?  The schematic I am working
> off is dated April 1954.
> >
> >Couple other questions regarding the 75A2, does any one make the
> Kilocycles (round dial) reproductions ?
> >
> >I also need the PTO coupling which is apparently .25 inch on one end
> and 3/16 or some other close dia on the PTO shaft, not having a
> micrometer I can't measure the actual shaft size on the 70E-12 PTO.
> >
> >The difference in the mixers has me rather confused and appreciate any
> comments from anyone familiar with this receiver, Thanks
> >
> >73 Gary
> >
> >
> >Sponsored by the Collins Collectors Association
> http://www.collinsradio.org
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> >Sun AM Net: 29.050 Mc-1200 Central
> >
> >
> >
> >
>
> Sponsored by the Collins Collectors Association
> http://www.collinsradio.org
> Nets: Tues: 3.805 Mc-2000 Central / Thur: 3.875 Mc-2000 Central
> Fri: 3.895 Mc-2000 Pacific / Sun: 14.263 Mc-2000 UTC
> 1st Wed (of the month) AM Net 3.880 Mc-2000 local (ET, CT, MT, PT)
> Sun AM Net: 29.050 Mc-1200 Central
>
>
> Sponsored by the Collins Collectors Association
http://www.collinsradio.org
> Nets: Tues: 3.805 Mc-2000 Central / Thur: 3.875 Mc-2000 Central
> Fri: 3.895 Mc-2000 Pacific / Sun: 14.263 Mc-2000 UTC
> 1st Wed (of the month) AM Net 3.880 Mc-2000 local (ET, CT, MT, PT)
> Sun AM Net: 29.050 Mc-1200 Central
Sponsored by the Collins Collectors Association http://www.collinsradio.org
Nets: Tues: 3.805 Mc-2000 Central / Thur: 3.875 Mc-2000 Central
Fri: 3.895 Mc-2000 Pacific / Sun: 14.263 Mc-2000 UTC
1st Wed (of the month) AM Net 3.880 Mc-2000 local (ET, CT, MT, PT)
Sun AM Net: 29.050 Mc-1200 Central






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