REPAIRING AND NOT THROWING AWAY

REPAIRING AND NOT THROWING AWAY

Richtige Fernseher haben Röhren!

Richtige Fernseher haben Röhren!

In Brief: On this site you will find pictures and technical information about Service Modes, Circuit Diagrams, Firmware Update procedure, Disassemble procedure, Universal remote control set-up codes, Troubleshooting and more....

If you go into the profession, you will obtain or have access to a variety of tech tips databases HERE IT IS Master Electronics Repair !.

These are an excellent investment where the saying: 'time-is-money' rules. However, to learn, you need to develop a general troubleshooting approach - a logical, methodical, method of narrowing down the problem. A tech tip database might suggest: 'Replace C536' for a particular symptom. This is good advice for a specific problem on one model. However, what you really want to understand is why C536 was the cause and how to pinpoint the culprit in general even if you don't have a service manual or schematic and your tech tip database doesn't have an entry for your sick TV or VCR.

While schematics are nice, you won't always have them or be able to justify the purchase for a one-of repair. Therefore, in many cases, some reverse engineering will be necessary. The time will be well spent since even if you don't see another instance of the same model in your entire lifetime, you will have learned something in the process that can be applied to other equipment problems.
As always, when you get stuck, checking out a tech-tips database may quickly identify your problem and solution.In that case, you can greatly simplify your troubleshooting or at least confirm a diagnosis before ordering parts.

Happy repairing!
Today, the West is headed for the abyss. For the ultimate fate of our disposable society is for that society itself to be disposed of. And this will happen sooner, rather than later.

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..............The bitterness of poor quality is remembered long after the sweetness of todays funny gadgets low price has faded from memory........ . . . . . .....
Don't forget the past, the end of the world is upon us! Pretty soon it will all turn to dust!

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All posts are presented here for informative, historical and educative purposes as applicable within fair use. NOTHING HERE IS FOR SALE !

Tuesday 5 February 2019

SONY HCD-GTX777/GTX787/GTX888 - ELECTRICAL ADJUSTMENTS

Sony HCD-GTX777/GTX787/GTX888 - ELECTRICAL ADJUSTMENTS

TUNER SECTION [0 dB = 1 µV]
1. Turn the power on.
2. Input the following signal from Signal Generator to FM antenna input directly.
Carrier Freq : A = 87.5 MHz, B = 98 MHz, C = 108 MHz
Deviation : 75 kHz
Modulation : 1 kHz
ANT input : 35 dBu (EMF)
[Use 75 ohm “coaxial cable” to connect SG and the set. You cannot use video cable for checking.  Use SG whose output impedance is 75 ohm.]
3. Set to FM tuner function and tune A, B and C signals.
4. Confirm “TUNED” is lit on the display for A, B and C signals.
[The mark of “TUNED” means “The selected station signal is received in good condition.”]
DECK SECTION [0 dB = 0.775 V]
Demagnetize the record/playback head with a head demagnetizer.
2. Do not use a magnetized screwdriver for the adjustments.
3. After the adjustments, apply suitable locking compound to the parts adjust.
4. The adjustments should be performed with the rated power supply voltage unless otherwise noted.
5. The adjustments should be performed in the order given in this service manual. (As a general rule, playback circuit adjustment should be completed before performing recording circuit adjustment.)
6. The adjustments should be performed for both L-CH and RCH.
7. Switches and controls should be set as follows unless otherwise specified.
RECORD/PLAYBACK HEAD AZIMUTH ADJUSTMENT
1. Perform these adjustments for Single deck
Mode: Playback
2. Turn the adjustment screw and check output peaks. If the peaks do not match for L-CH and R-CH, turn the adjustment screw so that outputs match within 1dB of peak.
4. After the adjustments, apply suitable locking compound to the parts adjusted.
Adjustment Location: Playback Head (Deck).
CD SECTION
TEST DISC LIST
Use the following test disc on test mode.
• CD: YEDS-18 (PART No. 3-702-101-01) or PATD-012 (PART No. 4-225-203-01)
1.CD Block is basically designed to operate without adjustment.  Therefore, check each item in order given.
2. Use YEDS-18 (3-702-101-01) unless otherwise indicated.
3. Use an oscilloscope with more than 10MW impedance.
4. Clean the object lens by an applicator with neutral detergent when the signal level is low than specified value with the following checks.
S-CURVE CHECK
1. Connect an oscilloscope to TP106 (FE) and TP124 (VC).
2. Turn the power on.
3. Load a disc (YEDS-18) and actuate the focus search. (In consequence of open and close the disc tray, actuate the focus search)
4. Confirm that the oscilloscope waveform (S-curve) is symmetrical between A and B and confirm peak to peak level within 3 ± 0.5 Vp-p.
Note: • Try to measure several times to make sure that the ratio of A : B or B : A is more than 10 : 7.  • Take sweep time as long as possible and light up the brightness to obtain best waveform.
RF LEVEL CHECK
1. Connect an oscilloscope to TP123 (RFO) and TP124 (VC).
2. Turn the power on.
3. Load a disc (YEDS-18) and playback.
4. Confirm that oscilloscope waveform is clear and check if RF signal level is correct or not.
Clear RF signal waveform means that the shape can be clearly distinguished at the center of the waveform
Posted By: FRANK at 09:01
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