Ickme
Newbie level 4
My hitachi v-1050f has an arc that comes and goes often a couple of times per second exiting the anode cap while powered on. Sometimes if it does not spark I can hear a fast crackling sound inside the oscope.
The covers are removed after I decided to attempt cleaning and checking the voltages. So, I don't think I had these symptoms before I purchased this scope.
The display will reduce in brightness when the spark jumps from the anode cap.
The intensity control is not changing the display. The traces on the screen are active but slightly reduced. But they are brighter than normal.
One resistor on the PSU & horizontal amplifier board (pef-499) sometimes will burn. It is R1101 valued at 10ohms and 1/4watt. It is between a power diode and a vertical deflector transistor TR1101 with a capacitor between them.
The resistor R1101 burns sometimes when the anode cap does not spark. I keep replacing it. I've tried even a 1/2watt. Right now I'm using a 10 ohm metal film one.
This resistor R1101 that sometimes burns is in the 55 volt line of TR1101 (which was already running hot at 270 degrees F before the arcing symptom according to my infrared thermometer.) The schematics say 55 volts then specifically shows (55.7). My reading I think was 54.3 or 53.4 volts.
The switches and pots all seemed to work normally and still seem to. However in trying to deduce where this arcing symptom originates, I have disconnected some cables between boards.
The display while the anode cap is arcing will show a pair of horizontal lines while my probe is connected to the calibrator at 1khz at .5v. It shows the horizontal lines but not the verticals quite brightly and the timing and voltage divisions are still making changes in the display.
I have not attempted to work on a high voltage crt system and am learning to play it safe. I've been around minor electronic repairs for awhile. But I'm getting stuck trying to determine the cause of these symptoms. I have been reading multiple websites for any useful information.
I do have a operator manual and a service manual for the v-1050 version. The v-1050f seems to have a few minor differences.
One difference is the board at the base of the crt of the v-1050f is different than the v-105.
I have checked the power supply voltages and they are within or close to the specs of schematics in the service manual. 12+ Is good. 12- is good.
100 volts (97) and 55 volts (53.4 or 54.3 can't remember)
While checking the voltages exiting the power supply I may have slipped my dmm probe at a vertical amplifier power board (peg-498 board) connector while checking the 55 and 100 volts at connector and causing the probe to touch both 55 and 100 volt pins at the same time. I just barely saw a spark at that junction. A few seconds later there was a spark from the anode cap jumping to a ground (I think) line close by the cap.
I do not yet have a way to check DC voltages over 1000.
Before this arcing symptom the scope was working mostly normal except for some dirty traces on the display and the vertical trace while connected to the calibrator square wave signal were not appearing.
The horizontal lines appeared normal on channel 1. On channel 2 there was a little bit of noise or interference when there was no connection to the probe. That was why I decided to examine the boards for blown capacitors check voltages and clean the contacts of the vertical preamplifier & vertical channel switch board.
The anode cap sparks.
The displayed image is significantly bright and unadjustable. Before the arcing symptom it was working normally.
A vertical deflection transistor TR1101 gets really hot. The schematics show this transistor is 2SD478C. I did replace it with a NTE375 but it still gets hot.
The 55 volt line is slightly down.
I cannot find any obvious blown components.
If any of you wish to offer any tips or suggestions I would like that.
I'm sorry for the repeat of some information. I'm trying to do this while using s smartphone.
I don't have a separate signal generator. I do have a cheap esr meter and a fluke dmm to use. I may try to get another scope to help me fix this one.
The covers are removed after I decided to attempt cleaning and checking the voltages. So, I don't think I had these symptoms before I purchased this scope.
The display will reduce in brightness when the spark jumps from the anode cap.
The intensity control is not changing the display. The traces on the screen are active but slightly reduced. But they are brighter than normal.
One resistor on the PSU & horizontal amplifier board (pef-499) sometimes will burn. It is R1101 valued at 10ohms and 1/4watt. It is between a power diode and a vertical deflector transistor TR1101 with a capacitor between them.
The resistor R1101 burns sometimes when the anode cap does not spark. I keep replacing it. I've tried even a 1/2watt. Right now I'm using a 10 ohm metal film one.
This resistor R1101 that sometimes burns is in the 55 volt line of TR1101 (which was already running hot at 270 degrees F before the arcing symptom according to my infrared thermometer.) The schematics say 55 volts then specifically shows (55.7). My reading I think was 54.3 or 53.4 volts.
The switches and pots all seemed to work normally and still seem to. However in trying to deduce where this arcing symptom originates, I have disconnected some cables between boards.
The display while the anode cap is arcing will show a pair of horizontal lines while my probe is connected to the calibrator at 1khz at .5v. It shows the horizontal lines but not the verticals quite brightly and the timing and voltage divisions are still making changes in the display.
I have not attempted to work on a high voltage crt system and am learning to play it safe. I've been around minor electronic repairs for awhile. But I'm getting stuck trying to determine the cause of these symptoms. I have been reading multiple websites for any useful information.
I do have a operator manual and a service manual for the v-1050 version. The v-1050f seems to have a few minor differences.
One difference is the board at the base of the crt of the v-1050f is different than the v-105.
I have checked the power supply voltages and they are within or close to the specs of schematics in the service manual. 12+ Is good. 12- is good.
100 volts (97) and 55 volts (53.4 or 54.3 can't remember)
While checking the voltages exiting the power supply I may have slipped my dmm probe at a vertical amplifier power board (peg-498 board) connector while checking the 55 and 100 volts at connector and causing the probe to touch both 55 and 100 volt pins at the same time. I just barely saw a spark at that junction. A few seconds later there was a spark from the anode cap jumping to a ground (I think) line close by the cap.
I do not yet have a way to check DC voltages over 1000.
Before this arcing symptom the scope was working mostly normal except for some dirty traces on the display and the vertical trace while connected to the calibrator square wave signal were not appearing.
The horizontal lines appeared normal on channel 1. On channel 2 there was a little bit of noise or interference when there was no connection to the probe. That was why I decided to examine the boards for blown capacitors check voltages and clean the contacts of the vertical preamplifier & vertical channel switch board.
The anode cap sparks.
The displayed image is significantly bright and unadjustable. Before the arcing symptom it was working normally.
A vertical deflection transistor TR1101 gets really hot. The schematics show this transistor is 2SD478C. I did replace it with a NTE375 but it still gets hot.
The 55 volt line is slightly down.
I cannot find any obvious blown components.
If any of you wish to offer any tips or suggestions I would like that.
I'm sorry for the repeat of some information. I'm trying to do this while using s smartphone.
I don't have a separate signal generator. I do have a cheap esr meter and a fluke dmm to use. I may try to get another scope to help me fix this one.