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Ts-940s dots or display problem

Robalo

Well-Known Member
Aug 21, 2006
583
227
53
California
One of my locals got this radio on ebay with power supply problems and after fixing (avr) the power supply replacing Q13, Q6, D1, D2, D14, D3, and D9, the radio starts and after testing on a dummy loan the radio swings about 80 watts. but heres the trick, the radio transmits about 5-20 minutes and the frequency display goes out and all i see are dots. after a while the radio comes back sometimes/sometimes not. and then i decided to search online and i got some ideas on how to go about fixing this problem. after i started pinpointing, and testing all the connections, this is what i got. can someone help me out fixing this problem?

i think Q31 and 32 is the problem but i cant find it in any stores, what do you think?


kenwood ts-940s serie708xxxx
pll 50-2020-00 board

ic19>pin2=4.82v
ic8>pin2=1.37v not working (1.8vworking)
d16 ok
d8 ok
r75=2.34v (4.8v)
ic9>pin2=4.76v
ic9>pin3=1.46v
ic17>pin7=5.10v
ic17>pin1=2.28
ic19>pin3=1.59
d9=4.75v
con 5 pin4(ul)=0 (4.8v working )
con 2 pin5(ul)=2.49
d16 ok 2.50v/4.84v

Q 31 = DTC124ES NPN(NTE2357)
IN | OUT | GROUND |
3.90 V | 0.02 | GROUND | NOT WORKING
0 | 4.84 V | GROUND | WORKING


Q 32 = DTA124ES PNP(NTE3258) DIGITAL TR
IN | OUT | VCC |
2.49 | 4.92 | 4.9 V | NOT WORKING
4.91 | 0 | 4.95 | WORKING
 
Last edited:

ve7waz

Member
Mar 26, 2011
1
0
11
Please help!

I got a TS-940S in Serial # 603XXXX series that has the "dot" problem. When I turn it on, the freq. momentarily displays then disappears.

When I press the bandswitch buttons, the freq. shows again even when rotating the dial. But stopping, the "dots" displayed and PLL not locking.

Could you advise me what to do?


Skie
 

Shockwave

Sr. Member
Sep 19, 2009
3,779
3,270
273
I got a TS-940S in Serial # 603XXXX series that has the "dot" problem. When I turn it on, the freq. momentarily displays then disappears.

When I press the bandswitch buttons, the freq. shows again even when rotating the dial. But stopping, the "dots" displayed and PLL not locking.

Could you advise me what to do?


Skie

Search the internet a little more an you will find information about an IC chip mounted in a socket that often causes this problem. The socket itself will develop poor connection to the IC pins. They recommend removing the socket and soldering the IC directly to the board. Definitely not something to do unless you are very experienced with desoldering. An alternative may be to try and reseat the IC in it's socket while using contact cleaner.

These intermittent connections can also corrupt the information stored in the memory and may require a hard reset. Hold the A=B key on power up to clear any corrupt data. As I recall there are also two locations in this radio that require 3 volt lithium batteries. When they start going bad it can cause the display to do strange things.
 

TonyV225

W9WDX Amateur Radio Club Member
Apr 18, 2005
5,824
314
143
Wisconsin
The TS-440S also was known for the PLL not locking after time resulting in showing dots on the display. I repaired one that I had by reseating the chip. make sure if you do this that you ground yorself so any static on your body is cleared.

Radio Shack sells wrist straps for grounding and there inexpensive. All it takes is a simple shock or transfer of static in some of these chips and poof you have junk.
 

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