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: FT901dm & FT902dm - drift problem  (Read 4251 times)
W3HKK
Member

Posts: 621




Ignore
« on: March 04, 2011, 01:29:26 PM »

Both of these reliable, top notch rigs have  held up  wonderfully for the 30+ years Ive had them, but old age is catching up with them both, in the form of drift.  Over 2-3 hrs they will drift 500 hz, and over 5-6 hrs they will drift about 1000 hz.

As  mostly a cw operator, this is an issue, as  the guy Im rag chewing with has to chase me down the band.

Anyone familiar with  how best to correct the problem?
Logged
K6LO
Member

Posts: 226




Ignore
« Reply #1 on: March 04, 2011, 03:27:37 PM »

Before you start investigating the electronics, have you checked that it is not mechanical drift?    As the gearing lube warms up, it loses viscosity, and a 30 year old + dial mechanism tends to creep. This is exactly the case with my FT-102. Also you may want to check this product.  http://hone.comcast.net/~k4dpk  Looks interesting.

73,

Luke
Logged
W3HKK
Member

Posts: 621




Ignore
« Reply #2 on: March 05, 2011, 06:37:38 AM »

Never heard or thought of that...dial creep huh? 

How DO you check for it?

I started noticing it about 6-7  years ago and both drift about the same amount.
Logged
K6LO
Member

Posts: 226




Ignore
« Reply #3 on: March 05, 2011, 09:21:44 AM »

I placed one end of a Q-Tip between the knob and front panel to temporarily jam the works.  If that test fails then the compensating caps in the VFO probably need replacing.  The Jackson Brothers ball drives can develop flat spots with time.  How smooth is the rotation?
« Last Edit: March 05, 2011, 09:23:34 AM by K6LO » Logged
W3HKK
Member

Posts: 621




Ignore
« Reply #4 on: March 06, 2011, 02:09:08 PM »

rotation is fairly smooth, though now that you mention it, I can sense a slight counter rotation after I let go of the knob.
And as I turn the dial it is not uniformly smooth...some  spots are a bit tighter than others, altho it is not at all loose.  Its a firm snug dial, other than the above.
Logged
KB1GTX
Member

Posts: 462




Ignore
« Reply #5 on: March 07, 2011, 01:01:25 AM »

A trick that works for me is to monut a resistor/s on the housing that holds the tuning cap and power the resistor when the set is off.
It keeps the vfo nice and warm for instant on!

Take a little time to match the power diss to match the temp to the normal op temp of the set.   Oh you turn off the heater when you turn on the set..
Logged
M0WQR
Member

Posts: 3




Ignore
« Reply #6 on: March 15, 2011, 08:21:14 AM »

Try checking the 6 volt supply to the VFO. Mine started drifting 2 years ago and it took me a while to find it.
Later I found that other people have had the same problem. The 5 volt regulator was bad. I put a 78L06, as I
could not locate the orginal part.
Logged
N8YX
Member

Posts: 118




Ignore
« Reply #7 on: March 24, 2011, 06:42:17 AM »

Follow the info at this link:

http://www.dooleystreasurechest.com/wb5tka/yaesu.htm

And you should be good to go.

Repaired thusly, one of my '901's exhibits 300hz total drift from a cold start.
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!