[MRCA] AN/PRC-70 continued

[Scott Pastor]

James,

Can you share the details of that 10 AH NIMH D-Cell power pack? I'm curious
if I could fit it into the large battery box for my PRC-104b.

Thanks, 73
Scott, kc8kbk

On Mon, Nov 21, 2022 at 12:41 PM <jkarlow at comcast.net> wrote:

> Ray –
>
>
>
> There were actually 2 versions of the PRC-70 radio from Cincinnati
> Electronics that have been on the surplus market. The earlier one (a design
> prove-out unit) was made between about 1970 and 1976. It included
> components like the “Flyback/Trigger.” There were probably 15 to 20 of
> these units produced. Once the design was approved, Cincinnati Electronics
> in 1977 went into production with a design with many improvements over the
> original. They made about 2500 of these for the US Army Special Forces. The
> newer design units look very close in external appearance but they are
> quite different in internal content from the original. These are the more
> common units on the surplus market. Make sure that you check the unit you
> have to see which version it is. Many of the parts are not interchangeable
> between the two versions.
>
>
>
> The later PRC-70 is an outstanding performer when properly used and
> maintained. Years ago I put together a series of modifications to improve
> the radio for Ham Radio use. These include one to add the LSB mode, one to
> allow FM transmit below 30 MHz and one to provide internal switching power
> supply shutdown when the battery voltage drops below 19.5 volts, to keep
> the switching power supply in the A4 module from overheating and burning
> out under low voltage conditions. The low voltage shutdown also allowed me
> to throw away the “frezzolini board” on the top of the BB-542/U battery and
> to be able to mount 10AH NIMH D – Cell batteries in the battery case to
> extend battery life with Hi Power transmitting.
>
>
>
> Good luck with your project and let me know if you have any questions
> about this radio!
>
>
>
> 73’s
>
>
>
> Jim
>
>
>
> Jim Karlow
>
> KA8TUR
>
>
>
> 4907 Oakwood Court
>
> Commerce Township,  Mi 48382
>
> E-Mail: jkarlow at comcast.net
>
> Tel/Cell: 248-961-2034
>
>
>
>
>
>
>
>
>
> *From:* mrca-bounces at mailman.qth.net <mrca-bounces at mailman.qth.net> *On
> Behalf Of *Ray Fantini
> *Sent:* Monday, November 21, 2022 11:16 AM
> *To:* MMRCG at groups.io; MRCA <mrca at mailman.qth.net>; milsurplus at mailman <
> milsurplus at mailman.qth.net>
> *Subject:* [MRCA] AN/PRC-70 continued
>
>
>
> Wow, just downloaded the TM 11-5820-553-23 and its way more useful then
> the TM 11-5820-553-34
>
> With that at least have an idea of the DC distribution in the radio, also
> starting to think maybe the two shelled cans that the book says are the
> Flyback/Trigger may indeed be that and I just that was not seeing any
> voltages on them. It appears that the radio never receives any DC from the
> battery unless the “X-Mode” connector is in place, wonder if that’s the
> problem? Will look and see if it’s in place.
>
>
>
>
>
> Ray F/KA3EKH
>
>
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