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@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@comcast.net

Tel/Cell: 248-961-2034

 

 

 

 

From: mrca-bounces@mailman.qth.net <mrca-bounces@mailman.qth.net> On Behalf Of Ray Fantini
Sent: Monday, November 21, 2022 11:16 AM
To: MMRCG@groups.io; MRCA <mrca@mailman.qth.net>; milsurplus@mailman <milsurplus@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

 

______________________________________________________________
MRCA mailing list
Home: http://mailman.qth.net/mailman/listinfo/mrca
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:MRCA@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html