Restoration
of the Sony ICF-6800W - nr 6 (1979)
1. OLD
I bought this ICF-6800W on Ebay. This unit had seen serious use -
it had approval stickers for naval use from the German FCC and ownership stickers from an (Arabic?) country.
Problems:
- mode switch not working
- no lights, except for the MEMO-LITE
- no meter response
- on SW no counter movement when spinning the dial, LO stuck "high"
- the usual dirt and small scratches
2. NEW
Radio China on shortwave
a. Clean with water and soap (I dont like to work on a dirty radio).
b. Start disassembly.
c. Contact clean all switches and pots.
d. So now we are ready for the PLL problem: see Technical Note 1.
In
this case Q32, Q33, Q34, Q35 and Q36 have been replaced. Once you take
off the cap assembly, it is best to change all these suspect
transistors. I measuref hFE 20-25 on these. In the picture one can see
the PCB underneath the cap assembly with the transistors to be removed (Q34-36 are under the lid next to the 2 black trim caps).
These replacements gave a nice functioning PLL, but a the high end
lock was still inadequate because of low VFO input power to the
squarer. So Q23 on the MW board was suspect.
It is very important to
have good contact on the MW board between the PCB and the chassis using
the screw shown. If contact is not good, the ferrite antenna will
not work well, and the MW antenna gain does not function since the PIN
-style diode is not to ground.
e. Other problems.
For the mode switch, the problem is mostly just mechanical... the screw needs to be adjusted correctly and fixed well.
Pilot lamps are getting hard to obtain. I replaced the meter lamp with
a mini-LED (3mm) and a 180 ohm series resistor. For the dial lamp, I
used 3 LED in series. This seems to work well.
The meter problem was just a loose wire.
Some hints for restringing the FM dial cord since this is not in the service manual.
f. Alignment as per service manual.
3. OPEN ISSUES
None, except some lettering on the front panel faded. Also, this radio is missing the side handles. These are on my wanted list.
4. SUMMARY
About 2 hours cleaning, 6 hours repair and 1 hour alignment.
Sensivity: MDS at 14,1 MHz -128dBm using the signal generator on the PL input.
5. DOCUMENTATION
Good service documentation can be found on mods.dk. But i am still
looking for GOOD scans of the PCB. Anybody with a service manual
original?
Serial number 13579.
back
