The AM Forum
March 28, 2024, 10:17:17 AM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1]   Go Down
  Print  
Author Topic: Racal 6790GM Low sensitivity help  (Read 2551 times)
0 Members and 1 Guest are viewing this topic.
KL7OF
Member

Offline Offline

Posts: 2313



« on: June 15, 2017, 11:08:30 AM »

I left my 6790 hooked to an antenna whilst operating a high power TX....It still plays but the sensitivity is way down...This happened once before and I sent the first mixer card to Gary Wingerd for repair......I can't find Gary anymore.(is he still doing Racal repair?)  It looks like he replaced a 16 pin chip on the antenna input...I read SP1 50001 and 80 44 printed on the chip..If this is the problem,I can replace the chip if I can find one..  I would appreciate any advice on this RX repair...Thanx..Steve KL7OF
Logged
WB6NVH
Member

Offline Offline

Posts: 266


WWW
« Reply #1 on: June 29, 2017, 09:12:27 PM »

There is a Racal Yahoo Group which at least a few years ago had traffic on this subject and I believe Gary is/was a member.  If you search the back traffic from the 2007-2009 era this was a popular subject.

As you point out, the front end of the 6790 is as robust as a canary and even precipitation static can blow it out as it was originally supplied.  These were never intended to be hooked directly to an antenna (so I was told) but rather were intended to be downstream from a multicoupler.  Common suggestions today are to feed the set from something like an Ameco preamp just to insert a buffer between antenna and receiver.

Working from memory, there is a generic part you can use for that chip, and some precautions you can take to protect the front end, by adding.  What those were, I don't remember - - neon lamps, back to back diodes, ?
Logged

Geoff Fors
Monterey, California
KL7OF
Member

Offline Offline

Posts: 2313



« Reply #2 on: June 30, 2017, 08:36:31 AM »

I rec'd several replies to this query...Thank you...I was able to contact Gary Wingerd and ordered  a new SD50001 chip assy. If I can get it installed properly, I will be happy...
Logged
KL7OF
Member

Offline Offline

Posts: 2313



« Reply #3 on: July 09, 2017, 08:43:03 AM »

I rec'd the chip and pc board mounting card from Gary .......Installed it yesterday....Receiver works as it should......
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone © 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.064 seconds with 18 queries.