Spectra D37 A5 VCO unlock.
Posted: Wed Mar 23, 2011 10:22 pm
Here is my problem...
D37 A5 900 Mhz Spectra that has been in my possession for nearly 20 years.
Working fine and used a lot until about 7 years ago.
Last year or so I have only used it a little, now 900 activity is picking up a lot.
Started to get that "thump" in the speaker on mode or volume change.
So, today decided I better do the re-cap.
( I have been carefully inspecting the caps periodically, no leakage seen )
Changed all the electrolytics, very little leakage hidden under the caps when removed.
Cleaned per the usual.
Fired up the radio, Rx good, TX on DIRECT is good, but not Rpt. FAIL 001 instantly.
Opened the case, removed the RF board shield to take a look, radio worked fine for about two minutes.
VCO is around 4.3 v on RX, same on TX Direct.
VCO basically Zero ( .16 v ) when unlocked.
Freqs are all in the 902 range.
Again, this radio has worked fine for years.
Compared the voltages at all the new caps with a working "sister" radio on same freqs, and those voltages are nearly the same.
Same with OSC voltage.
Any body have an idea.
These have the resistor VCO mod ( 150 ohm )
D37 A5 900 Mhz Spectra that has been in my possession for nearly 20 years.
Working fine and used a lot until about 7 years ago.
Last year or so I have only used it a little, now 900 activity is picking up a lot.
Started to get that "thump" in the speaker on mode or volume change.
So, today decided I better do the re-cap.
( I have been carefully inspecting the caps periodically, no leakage seen )
Changed all the electrolytics, very little leakage hidden under the caps when removed.
Cleaned per the usual.
Fired up the radio, Rx good, TX on DIRECT is good, but not Rpt. FAIL 001 instantly.
Opened the case, removed the RF board shield to take a look, radio worked fine for about two minutes.
VCO is around 4.3 v on RX, same on TX Direct.
VCO basically Zero ( .16 v ) when unlocked.
Freqs are all in the 902 range.
Again, this radio has worked fine for years.
Compared the voltages at all the new caps with a working "sister" radio on same freqs, and those voltages are nearly the same.
Same with OSC voltage.
Any body have an idea.
These have the resistor VCO mod ( 150 ohm )