Can anyone identify this monitor from a picture of the chassis. From 1976 Sea Wolf

learpilot2

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Can anyone identify this monitor from a picture of the chassis. From 1976 Sea Wolf

Trying to get a monitor ID so I can find a High Voltage diode for it...

I have attached a couple photos

Thanks
 

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Motorola XM702. Just like the tag in the bottom of the first picture says :D

-Ian

I have a Gun Fight it has the Midway monitor in it not the Motorola, Does anyone know where i can find a Schematic for it?

thx,
 
Oops

Yea, I guess it does say the model number right on there. How about that...

Now that we cleared that up, the next question gets harder...

What HV diode does it take and where can I get one?

All I see for sale is one for B/W vector monitors like asteroids.

Anyone know where to download a manual?

Thanks
 
Thanks for the manual..

Do I measure +73V DC on pin 2 on the outer edge of the chassis board?

I just connect one lead of VM to pin 2, and the other lead to chassis ground?

If the voltage is off, I assume the adjustment is on R74?

Thanks
 
No luck..

I removed the HV Diode. It looked like a long black fuse with metal ends. The holder had no di-electric grease. It was clean and dry. No spring holders either.

I put lots of di-electric grease on each end, and re installed. It made no difference in the blooming picture.

I measured B+ at pin 2 on the outer edge of the chassis board on the XM702-10. It showed 100.6 Volts. If I am measuring the correct pin, that should be B+. Should it be 73.0 VDC? I turned the R74 resistor slightly counter clockwise, and it made no change in the voltage on pin 2. Does that mean I screwed up some other setting on R74?

I am measuring with a DVM on DC scale from lead on pin 2 of the outer edge of the chassis board, and the other DVM lead on chassis ground. I get 100.6 VDC

The HV Diode must be bad. It had a label on it that said:

VARO 7604 H386C

Any ideas where to get one???

Thanks,

Rick
 
Thanks for the diagram!

I wish I was smart enough to read the wire diagram better. I am still having trouble finding the measuring point for B+ on the chassis, and the pot to adjust it. Anybody good at wire diagrams?

I tried measuring Pin 2, and got way too high voltage (100.6VDC vs. 73VDC). I adjusted R74, and it made no change to the reading. Not sure if I am measuring or adjusting the right things.

Thanks for the help.

Rick
 
Do I measure +73V DC on pin 2 on the outer edge of the chassis board?

I just connect one lead of VM to pin 2, and the other lead to chassis ground?

If the voltage is off, I assume the adjustment is on R74?

Thanks

Yes, DC voltmeter red lead to pin two on the circuit board pins as shown in the manual. Black DC voltmeter lead goes to chassis (frame) ground. You are measuring on the DC volts scale of your meter and need to read the +73 volts. Be sure your voltmeter has known fresh batteries as weak/old batteries will affect accuracy or readings on your meter.

As shown in the manual, R74 adjusts the +73 volts output. The location of R74 is also shown in the manual.
 
I did do that and here is what I got...

I checked voltage on pin2, and got a whopping 106.0 VDC. I moved the R74 pot counterclockwise slightly with little or no effect on the voltage of pin 2. Is it pin 2 or 22?

Do I keep turning the R74 pot a large amount to bring down the B+ voltage, or is something else likely wrong. I am not sure there is enough turns on R74 to bring down pin 2 voltage 30+ volts. What do you think? I am used to making small adjustments like on power supply pots.

Could this high B+ voltage cause monitor blooming, or is that more the need of a new HV diode. The HV diode I pulled out look in good shape, but untested.

Thanks,

Rick
 
new NTE505 stick rectifier did not work...

I installed a NTE 505 stick rectifier in place of the Varo H386C HV diode. The NTE 505 was slightly smaller in diameter, and it had a "+" on one end, no line. I installed it with the "+" toward the flyback. I turned it on, and no picture, just blind play. Before it had good picture, just enlarged off the screen edges. Did I put in the stick rectifier backwards?

Also, I adjust R74 both directions with no effect of B+ on pin 2. B+ is still high (104.0 VDC instead of 73VDC). Any idea where to go from here?

Thanks,

Rick
 
To me you have to start at the beginning of the power supply circuit....it is pretty straight forward. First thing to check is for 90.0vdc coming out of your bridge (@ R79 or + side of C43A)....once that looks good then it is on to Q16, Q15, Q14, etc....to find out where your B+ voltage gets screwy. If you don't have 90.0vdc coming out then you don't have to worry about your power supply circuit and can jump on that bridge rectifier....
 
I will check those voltages...

The BR is hard to find, as are the R79 and C43A. I think they are hidden on the back side of the chassis frame. The Q14,15,16 are usually chassis mounted. Do you know how to check these transistors to see if they operate correctly. Do I check the transistors with power on? I have a DMM, and am new to this.

Thanks for the help

Rick
 
Checked Transformer voltage at R79

The voltage at R79 was 101VDC. I think you said it should be 90VDC. Is that a problem?

The B+ voltage is showing 100.5 on pin 2. I assume that means Q14,15, or 16 is not regulating the voltage properly.

I am not sure how to test them. I tried looking for parts, and cannot find them.

They are labled:

Q14 - A2J M721
Q15 - M624
Q16 - ECG130
185-7926

Cannot find any of the replacement transistors anywhere. Any ideas?
 
The voltage at R79 was 101VDC. I think you said it should be 90VDC. Is that a problem?

The B+ voltage is showing 100.5 on pin 2. I assume that means Q14,15, or 16 is not regulating the voltage properly.

I am not sure how to test them. I tried looking for parts, and cannot find them.

They are labled:

Q14 - A2J M721
Q15 - M624
Q16 - ECG130
185-7926

Cannot find any of the replacement transistors anywhere. Any ideas?

Q14 = A2J = 48S134952 = 2N4400 = NTE123AP...I'm sure there's more

Q15 = B2N = 48S137574....I'll have to do some digging on this one

Q16 = A8W = 48S137368 = NTE130 = 2N3442.....I'm sure there's more

Edward
 
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