Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: HP 8640B expert needed  (Read 244 times)
N4UE
Member

Posts: 290




Ignore
« on: August 03, 2008, 05:16:55 PM »

Hi, I just acquired a pretty nice 8640B and it works FB, with ONE exception. The 'Fine Tune" is inoperative. The generator had a small label on the front, stating so.

I DO have ALL the HP Manuals for this beast (groan) and although I haven't yet found the exact section relating to the "Fine Tune", I have learned that it is mechanical. The knob rotates continously. The only reason I haven't had it apart, is that several of the front knobs have stripped out heads. Until I can find a suitabe "EZ-Out" or Left Handed drill bit, I'm holding off.

Has anone beem 'inside the cavity' and have a clue as to what I'm up against??


thanks in advance!

ron

N4UE
Logged
AC5UP
Member

Posts: 3822




Ignore
« Reply #1 on: August 03, 2008, 06:15:09 PM »

Different problem than yours, but the pics give a clue as to what's inside...

http://www.jvgavila.com/hp8640b.htm

http://www.jvgavila.com/wb1.htm

GL
Logged

Never change a password on a Friday                
WB2WIK
Member

Posts: 20542




Ignore
« Reply #2 on: August 04, 2008, 09:23:45 AM »

Mechanical?

Hmmmm.

The original 8460s I worked on during development had a "fine tuning" control that was purely electronic: It varied the bias on a varactor diode which was also part of the phase lock loop circuit.

I don't recall a mechanical "fine tune" on the 8640.  Maybe they changed the design later...

Does the generator function in the LOCK position (to engage the phase lock circuit), and does it work for FM (try modulating it with one of the tone frequencies and listen in an FM receiver to see if it's really modulating).

WB2WIK/6
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!