2950 TX issues

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31
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Joined: Sunday 20th Jul 2008, 23:48
Location: Hawaii

2950 TX issues

Post by 31 »

I bought the radio with issues. I had low TX , 1-2 watts AM. I swapped the AM regulator to an 2SB817, still same problem. I adjusted the PLL via L17 and voila I got 25-30 watts TX. 1 week later I noticed that when I turn the power on I get little RX then a minute or so later it would kick in and normal RX. I also notice soon after I turn the radio on I would be able to get 25-30, out of no where I drop down to 10 watts TX.
My question is the PLL losing the voltage somehow and I'm out of "lock"? As Doc Electronics is the man for 2510's , where is the shop to send my 2950 to?Thanks
ramblingman
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Post by ramblingman »

If the pll was going out of lock..you would have no rx and no tx at
all..I would be looking in the area of the voltage regulator chip..
I believe it is ic-4 in this radio,not certain on that number however.
But it should be the first chip on the right side rail of radio.
It could also be a shunt component off this chip.Or a poor solder
connection in this area..Does the face plate L.E.D.s go dim when
this happens????
31
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Joined: Sunday 20th Jul 2008, 23:48
Location: Hawaii

Post by 31 »

I have no dimming . however I have noticed that the area on the middle of the radio near the voltage regulator gets real warm on the chassis. I made a homebrew rf probe but I can't get it to work right so really I'm shooting in the dark. I have a parts radio to pull from but not to many IC chips to pull from. Thanks
ramblingman
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Location: mississippi

Post by ramblingman »

I would suggest starting taking some voltage readings and relay
them to us...Take readings while the radio is in fault mode.
And we can compare them with our voltage chart..Like i said start
by giving your readings around the voltage regulator chip..And
B.T.W. I wouldnt worry about the Am Mod Amp getting warm, they
will do that. Just as long as it doesnt get real hot.
ramblingman
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Post by ramblingman »

After taking a look at schematic..IC-4 is the 5 volt regulator.
And the 8 volt regulators are IC-6 AND IC-15 these are along
the right chassis rail,the 2 ics closes to the front of radio.
They should be 7808s and the 5 volt reg. should be a 7805.
James Unit 198
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Post by James Unit 198 »

Try setting up the PLL section as per http://www.cbtricks.com/radios/rci/rci_ ... ll_adj.htm

James.
Unit 67
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Post by Unit 67 »

31:Can you check your 2SC2312 Final transistors?

It is because this is a very common problem in this type of radio when you have one bad or leaked of the 2SC2312 Final transistors!!!!
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