AVS Forum banner

Status
Not open for further replies.
1 - 12 of 12 Posts

·
Registered
Joined
·
10 Posts
Discussion Starter #1
Gentlefolks,


How do you determine if the GP-5000 has entered into a protection state?


How do you get out of it?


My projector shut down (fans run, filaments in the tube glow, but no picture) when I was increasing the vertical height (too much) of the image. It has been pointed out that there is auto protection to prevent damage to the CRTs in such a situation.


Any help is greatly appreciated.


Thanks, Vinay
 

·
Registered
Joined
·
1,030 Posts
Surely your pj entered in a protection state.


All the pjs are protected against a lot of things, like anode overcurrent and overvoltage, too low cathode voltage, almost all are protected against the too big raster (the tube may implode and the HT power supply may be damaged, if the electron beam reaches directly the anode zone...), a deflection board malfunction that could stop the electron beam in a certain position on the centre of the tube surface... and so on.


Open the pj and locate a small pot (trimmer) on the right big board (on the right of the two big fans), look for the V size trimmer, and lower it, in order to shrink the image vertically.

Look if a red led, on the front side of the same board, is lighted. In that case, your pj could have entered one of the protection state, that turns off the HT anode voltage. It could have been happened that you've damaged the final transistor of that board (the deflection board).


If the led is light, I'd turn opff the pj and check the 2SC4288A transistor with a normal tester... if it's shorted, surely you've to replace it and the pj will start again to work... in the 90% of the cases there are no other damages.




Romano
 

·
Registered
Joined
·
1,481 Posts
For your reference: Romano and I worked on remote (can you measure Rome/Cuba' s distance?) on my PJ, that had a similar problem. LED D5023 was on, and symptoms were the same. Don't worry: with 15 minutes and an appropriate solder, you'll fix it. just be careful in doing everything from below the board, and you'll be through. Good luck!

Andrea
 

·
Registered
Joined
·
10 Posts
Discussion Starter #4
Rorox & Andrea,


Thanks for your reply. I did find the trimmer pot for the vertical size previously. I did not fool with it.


Ca you tell me which direction the pots need to be turned to reduce the size (I guess it does not matter, since it already is in the protection state, increasing will not effect any response).


Both the red LEDs light up momentarily during power on, but remain off thereafter.


The distance from Rome (Lat-41:52:00N Long-12:37:00E) and Habana (Lat-23:08:00N Long-82:23:00W) is 5421 miles (8724 km) or (4711 nautical miles).


Regards.


Vinay
 

·
Registered
Joined
·
1,481 Posts
Vinay,

as a simple rule of thumb: start checking if the 2SC4288A is down: connect a cheap multimeter and see if EBC are shorted (any short on any combination of the three will reveal if the transistor is gone). If it's so, change and GP-5000 will resurrect!

If I don't make a mistake, the pot should go down turning it counterclockwise (i.e. towards the pj's frame).

Hope this helps,

Andrea


P.S. Distance: wrong answer: my house has a different Lat (-23:08:34) and Long (-82:23:28W) 'cause I don't live in the center of La Habana... ;=))) Thanks, appreciated the time you've spent for a joke!
 

·
Registered
Joined
·
10 Posts
Discussion Starter #6
I tried adjusting the v-height pots (there are more than one), did not have any luck.


Checked the specified transistor, there are no shorts between the pins.


I finally got the service and user manual, so what next?


Vinay
 

·
Registered
Joined
·
1,481 Posts
Vinay,

let’s see together what the service manual can tell us (pag. 93, No horizontal deflection circuit).

i) Check Q5007 on DEF PWB: NO: defective Q5007; YES: Confirm the waveform (approx. 2V p-p) at pin 8 of T5901 on DEF PWB (same location where the Q507 is, 5 is DEF PWB on right side)

ii) YES: confirm the voltage (approx. 35V) at TP5009 and the voltage (approx. 1.5 V) at TP5008 on DEF PWB. YES: defective deflection yoke; NO: defective PS unit, IC 5010 on DEF PWB or its peripheral circuit

iii) NO: confirm the waveform (approx. 10 V p-p) at TP 5004 on DEF PWB. NO: defective IC 4001 or its peripheral circuit on DEF PWB; YES: confirm the voltage at TP5015 on DEF PWB

iv) NO: defective IC5202, Q5209 or their peripheral circuit on DEF PWB; YES: defective H.PRE DRIVE circuit or H.DRIVE circuit on DEF PWB


I can’t write the whole service manual, but would suggest reading around page 84, (NO HIGH VOLTAGE OUTPUT). If you don’t have same version I have (but guess the source is the same Aussie that helped me…), while I don’t have a scanner, I’ll take a shot with my digital camera and send it.

Let me know if this can help, and don’t hesitate in writing: I know how much is terrible feeling alone with a broken PJ…. ([email protected]).

Ciao,

Andrea
 

·
Registered
Joined
·
10 Posts
Discussion Starter #8
Andrea,


Will check out the stuff you hi-lited.


I did some random checks from the manual, checking for voltages at the test points, talked about in the service manuals. For the most part (I think) things checked out OK. But ofcourse, there was no method to my madness.


I think my manual is probably the same as yours, although the "3. No High Voltage Output" is on page 87. Mine are originals, not scanned or copied.


I will spend some time on this over the long weekend.

Regards,


Vinay
 

·
Registered
Joined
·
1,481 Posts
Vinay, let's keep in touch, I'll do the same on this short weekend (here the word "vacation"is practically unknown...)

Ciao

Andrea
 

·
Registered
Joined
·
1,030 Posts
Vinay and Andrea,


If both the led turn on for a while, and then shut off, after a second, it means that the deflection field is correctly working on the tubes. Very probably the 2SC4288A is perfectly working.


If you've a scope, use the 10x probe and connect it to the def yoke coil. If you see a perfect sawtooth, go further, excluding any problem on the def board.


If the anode voltage is correct, you may investigate immediatly on the cathode voltage (140V at the pedestal level, with 20V of upper peaks, like almost all the other pjs). Again, use the scope.



just an opinion


Romano
 

·
Registered
Joined
·
10 Posts
Discussion Starter #11
Rorox/Andrea,


I never got a chance to work on the PJ during Thanksgiving or since (work is turning out to be a hindrance). Rorox, I do have a scope so from your previous message can you answer the questions, see bold items below.


If you've a scope, use the 10x probe and connect it to the def yoke coil where is this coil . If you see a perfect sawtooth, go further, excluding any problem on the def board.


If the anode voltage is correct, you may investigate immediatly on the cathode voltage (140V at the pedestal level, with 20V of upper peaks, like almost all the other pjs). Again, use the scope. Where do I check for the anode and cathode voltages?


Please bear with my ignorance.


Thanks, Vinay
 

·
Registered
Joined
·
1,481 Posts
Vinay,

we're in good company! My GP-5000 broke once again, same transistor, same problem...

I think I'll be checking every voltage, just to be sure...

Not a solution, but a shared problem is more affordable!

Ciao,

Andrea
 
1 - 12 of 12 Posts
Status
Not open for further replies.
Top