[TechAssist] Re: RCA, G27304DT, CTC177AM2, Tuner problem UPDATE

  • From: daryls_tv@xxxxxxx
  • To: techassist@xxxxxxxxxxxxx
  • Date: Mon, 11 Oct 2004 21:52:05 -0600

Another day shot to Hell.....
I spent all day again on this dog.
It was mentioned several times to replace U7301.  This was the first part I 
replaced to no avail.  I didn't have another new one to try but I had the next 
best thing.  I had a working set to borrow parts from.  I replaced the IC again 
but still no change.  Thanks to Barry Thompson for the flow chart.  I followed 
it out and found nothing wrong.  I compared voltages to the working set and 
didn't find anything out of line.  I swapped out the varactor diodes without 
any help as well.  I figured I couldn't mess it up any more than what it was... 
so I played around with the coils and parameters.  Now I have some small gains 
but still not acceptable.  Channel 2 has lines and motor boating.  Ch. 3 
through 6 is acceptable but not great.  Ch. 7 through 10 is good.  Ch.11 has no 
picture and sound, just lines.  Ch. 12 through 18 are good.  Ch. 19 trough 22 
are ugly with lines.  Ch. 23 through 39 are great.  Ch. 40 through 48 has poor 
picture with lines and has noise in the sound.  Ch. 49
  & 50 has nothing but motor boating. Ch. 51 up is great until Ch. 99 which has 
lines and a poor picture.  That is the highest channel on the cable system.
I can still place my finger near some of the coils in the tuner and it will 
perk right up.
Any other ideas would be appreciated.
Thanks,
Daryl
Daryl's TV
2402 Wyoming Ave.
El Paso, TX  79903
915-565-9184 Voice/Fax
daryls_tv@xxxxxxx
www.angelfire.com/tv2/daryls_tv

----- Original Message -----
From: daryls_tv@xxxxxxx
Date: Sun, 10 Oct 2004 12:42:56 -0600
To: TechAssist@xxxxxxxxxxxxx
Subject: [TechAssist] RCA, G27304DT, CTC177AM2, Tuner problem

> 
> Hi,
> This RCA, model # G27304DT, ch. CTC177AM2, is really kicking my behind.
> It started with the complaint from the customer of losing some channels with 
> lines in the picture.  I pulled it into the shop and did the usual tuner 
> re-soldering job.  Set looked great and was delivered only to find out it was 
> doing the same thing.  Took it back to the shop where it worked great.  I 
> re-soldered everything again plus all of the connections on the smds.  
> Delivered it again and you guessed it...same thing.
> The channels from 40 through 50 were either missing or full of lines or motor 
> boating.  I played with some of the tuner parameters and it seemed to work 
> but not to my satisfaction.  The customer was pleased, so I left.  A week 
> later, same thing.
> I pulled it back to the shop where it worked fine.  BTW... the customer has 
> another set that works fine on the same cable line.  I put an attenuator on 
> my cable line and the trouble showed up and even worse.  It gave me channels 
> 2-6, 18-22, and 40-50 with the problems.  I re-soldered every smd in the 
> video section besides the tuner again and all of the grounds in the set... no 
> help.  Looked with a high power magnifier for cracks in the print (none 
> found).  Replaced IC7301, C7414(cracked), CR7102(didn't check the same as the 
> others), Q7102(RF amp), U3201(eeprom), & U1001(t-chip).  Did the tuner 
> alignments after each parts change but still no joy.  I found that if I would 
> place my finger over coils L7114 & L7112, the set would start to function 
> properly.  I got the same effect placing my finger over L7115, L7113 & L7111. 
>  I didn't have to touch the coils, just put my finger near the coils.  This 
> symptom reminds me of the old tube days when the grid neutralizer trimmer cap 
> was
  o
>  ut of adjustment on the RF amp tube.
> I really hope someone has encountered this and has a cure.... Help!!
> Sorry for the long post but I deemed it necessary to explain the problem.
> Thanks,
> Daryl
> Daryl's TV
> 2402 Wyoming Ave.
> El Paso, TX  79903
> 915-565-9184 Voice/Fax
> daryls_tv@xxxxxxx
> www.angelfire.com/tv2/daryls_tv
> 
> 
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