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  #1  
Old 02-03-2015, 12:26 PM
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timmy timmy is offline
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65 maggie

hi all, i am certainly not looking to run up another thread like the last one, but this 65 maggie roundie had a new crt in it but i since traded with another set but the problem i have is the screen is very dark with the new crt and the one i put in. the bias is a switch and if in the min position no screen at all if in the middle i can start to see the screen bearly but with the switch up i have a screen but its very dark. the thing here is the crt thats in it now seems to have a problem with the green gun heater not heating up sometimes and if i tap the neck the blue sparks happen and then its good but i would like to maybe correct whats happening with the lack of brightness and can only get just that with the bias maxed out. i changed the boost diode that was bad, and checked all the high wattage resistors. the voltage at the hot is around 172 volts i dont think it should be that high but then again i dont have a schematic that gives voltages. i was told the chassis was a 16 clone by moyers as i had bought a new fly for a spare and it is correct for the chassis but the rca schematic dont show voltages. maybe this is a simple fix, dont know but at least the chassis will be ok if the crt takes a final dump and if i come across another crt then ill be all set to go. the crt now does work but how long the heater will last i dont know. i feel bad asking for any help since the last thread, lol,lol im sure everyone wants me to fade away, lol...;
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Old 02-03-2015, 01:25 PM
DaveWM DaveWM is offline
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check HV should be 23-25kv, check focus voltage should be 4-5kv
check crt voltages should be about 280v on the cathodes, 180v on the G1 and 700v on the G2. From there you know where to look.

Last edited by DaveWM; 02-03-2015 at 01:31 PM.
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Old 02-03-2015, 01:33 PM
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hv is up where it should be so ill check those crt voltages. "from there i know where to look" lol,lol ok ill see what i can confuse myself with,lol lol... thanks dave.
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Old 02-03-2015, 01:57 PM
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DavGoodlin DavGoodlin is offline
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Timmy, PM me with you email and Ill scan a schematic for you. Does the mag chassis sticker say its a U43 or U45?
I have the Tab Magnavox Color TV service manual by Stan Prentiss, and it helped alot on the 64-70 Mags I ve seen over the years.
I recall having issues in the Video amp stage.
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Old 02-03-2015, 02:00 PM
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Quote:
Originally Posted by DavGoodlin View Post
Timmy, PM me with you email and Ill scan a schematic for you. Does the mag chassis sticker say its a U43 or U45?
I have the Tab Magnavox Color TV service manual by Stan Prentiss, and it helped alot on the 64-70 Mags I ve seen over the years.
I recall having issues in the Video amp stage.
ok ill get the back off and see what it says, this is a combo so ill have like 25 screws,lol.
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Old 02-03-2015, 02:15 PM
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ok all there is on the chassis is 10- 65 g date, and stamped in black ink is , 5 45 5 thats it unless there was more to the tag but its gone. and the model says on the cabinet 20t567k
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Old 02-03-2015, 09:30 PM
Bill R Bill R is offline
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If it has automatic degausing it will be a 45 series chassis. Thats whats in my 65 combo.
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Old 02-04-2015, 07:37 AM
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yes it has auto degausing and instant on but i dont use that.
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Old 02-04-2015, 02:09 PM
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well im not sure if the problem here is in the blanker circuit but the g1 is 159v bright up and bias ccw. otherwise the voltages are close depending where the rgb drives are. but i cant set it up unless the bias is maxed, thats not right, so im looking...
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Old 02-04-2015, 03:37 PM
DaveWM DaveWM is offline
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thats a bit on the low side, but you need to find out what the cathodes are, those are directly coupled to the video out tube. You want approx 100v difference in the cathodes to G1 voltage (cathode should be higher).
the greater the difference the more cut off the tube will be (darker). It does not take a lot of change to go from dark to bright.
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Old 02-04-2015, 04:43 PM
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well it turns out that the g1 159 v is the red the others are 165v the g2 900-1000v and the cathodes 305-318v
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Old 02-04-2015, 04:54 PM
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well it turns out that the g1 159v the cathodes 305-318v
well there is the problem cut off due to bias of CRT well over 100v
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Old 02-04-2015, 04:58 PM
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i tested these with the crt cap off because its difficult to test with it on , hope it dont matter. and this was again bright up bias ccw.
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Old 02-04-2015, 05:01 PM
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I would start by trying a new video out to see if you can drop the cathodes down. if a known good tube does not help then you are back to checking voltages.

The g1 seem a little low as well. so checking the difference amps voltages would be in order, does the CRT bias have any effect?
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Old 02-04-2015, 05:04 PM
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the crt bias does raise the voltages on the g1.
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