CTC175-CTC176-CTC177


Date Chassis Symptom  Cure
4/21/98 CTC175L 19GT352TX1 CTC175L chassis. Unit acts dead. Unit has standby voltages. But has continous activity on the data and clock lines of the EPROM U3102(5 & 6) Tech wants to use the Chipper Checker to try to reload the initial software from the vendor. Instructed the tech to use the Chipper Checker and verified the software is upgraded with the latest software that wil support the CTC175 chassis. This would be Chipper Check II at least version 1.0. Tech will need to Resolder the tuner grounds, and initialize the EPROM using the 8 pin clothes pin clip adapter that I made for the Chipper Checker interface box. This proceedure corrected the fault. Fixed unit without using any parts.
10/20/97 CTC177 F27252FE1 CTC177 chassis with broken F-59 connector on rear of chassis for tuner. Needs to replace connector part number Part number 215543 from manual.
12/17/97 CTC177 25GT520 CTC177 Buzz in audio for channel 7 only. Does not show up in mono or SAP mode. Only Stereo. Symptom also shows up with a MTS stereoonly. A VCR is connected to the Aux inputs of television. The VCR is a stereo type but not MTS stereo only HIFI. Based on the fact the symptom is only noticeable channel 7 stereo on the TV and VCR It puts the problem within the CAT , mainly the channel 7 L-R signal. Problem was in CATV system. 
1/5/98 CTC177 CTC177 Unit will blank on and off, After resoldering the tuner section the set no longer turn on. Asked tech to check the data at pins 5 and 6 of the EPROM. It is very possible That in the process of resoldering the tuner, a solder splash could have contacted the data or clock line and prevent the unit from turning on. Tech did find a solder splash on the Data line touching next to the newly soldered shield.
2/12/98 CTC177 G27303 CTC177AM Collector of Horizontal out measure shorted to ground.  After Removing all active components in the Horizontal output circuit the short was still present. Had tech float pins 1,2,& 3 on primary of the transfomer and measure from these pins to cold ground. Tech found that the resistance to ground from these pins top the secondary of the transformer was less the an ohm. Tech needs flyback. T4401
4/1/98 CTC177 CTC177. Unit shuts off as soon as the TV is turned on with the front panel controls or with the remote.  Putting the unit on a variac it would not stay running if line voltage was lowered to 90 volts. In fact when voltage was dropped to below 90 volts the TV blows the line fuse. Replaced the regulator (U4101) fixed trouble.
8/8/98 CTC177 G27343BK . Unit has a bright screen with retrace lines I had tech check the cathode of the CRT and relay the voltage. It was only 100 volts. This is too low. It should have a dynamic range from dark to bright screen 190=black to 150=bright. This voltage is measured at the collector of each video drivers on the CRT socket. Unit had defective C4703 47 mfd @ 250 vdc.
9/2/98 CTC177 G27302 CTC177 Unit has no stand by power supply voltage.  I had tech check for raw B+ at U4101(7) which was 166 vdc. But the soft start input U4101(4) was almost 25 volts. This pin is typically not this high. No excessive loads on secondary of power supply. Unit has defective U4101. 
9/17/98 CTC177 F27253. Unit does not receive any reception. All snow on all VHF channels. UHF works fine Band 1 covers channels 2 through 17(CATV), band 2 covers 18 through 50(CATV) , and band 3 covers 51 through 125(CATV) or 14 through 69 (UHF). Further checking of Quad op amp U7501(7, 8,&14), while in band 3 the voltage would rise when the next higher channel is selected. However in band 1 and 2 (2 ~ 13) the voltage was always 33 vdc no matter what channel was selected. All other band switching was occurring normally. This indicated the local oscillator (VHF) for band 1 and 2 is not running. It is recommended to replace the U7301 the UHF/VHF mixer oscillator.U7301 was defective.


Last Updated on 3/11/99
By Dennis Viereck
Email: wa6ati@mindspring.com