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#91
10-07-2015, 01:14 PM
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The Bias control should increrase the brightness. that IS worth a try.
The controls above the HV adj. are for vertical and pin cuhsion and will NOT help you... I STILL...thik you have a video drive problem... 
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#92
10-07-2015, 01:59 PM
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I think there's a video drive problem as well.
I don't know what shape the CRT is in but I doubt it's screwed to the point where it can barely produce an image. Adjusting the screen controls do nothing, but the voltage is there. The brightness control has some effect. EDIT: Strike that the tubes are all glowing, it's just hard to see. And when shutting the set off, the image brightens as it shuts off. I think what I might try next is replacing the tube or tubes that are most likely related to the issue. The 12HL7 is a good suspect as it's for "VIDEO OUTPUT" also it looks to be the oldest tube in the set. It is glowing but could it be weak or have another issue? Last edited by MRX37; 10-07-2015 at 02:13 PM.
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#93
10-07-2015, 02:22 PM
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When you turned off the set it was brite white for
a sec so lets assume the CRT is OK G-2 ( white w/ stripes ) are OK so boost OK G-1 ( yellow ) are high BUT they only carry color info. Cathodes ( solid colors) high, should be abt 140 VDC. This is the B&W info. Cathode high= pix dark. Cathode low = brite. Measure the 12HL7 voltages. Count pins CW from under, CCW from top. Usually you can get it from the top. Bias is in color part but try anyhows also. 73 Zeno 
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#94
10-07-2015, 03:07 PM
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Okay, just measured the voltages for the 12HL7 tube. The gap in the tube socket is at the 12 o'clock position, so I took the measurements starting clockwise. Positive lead of multimeter connected to tube pin and negative to chassis frame:
Pin 1: 0 volts. Pin 2: 355 volts on startup, dropping to 305 after warm up. Pin 3: 355 volts, dropping to 320 Pin 4:50mV building up to ~150 mV before dropping back to zero and climbing again. Pin 5: Much the same, gets to about 200mV, then drops back to 0 and starts climbing again. Pin 6: fluctuating readings, but never leaving the mV range. (maybe 200 mV max.) Pin 7: Same as Pin 5 Pin 8: started out at 4.2 volts positive, then went to negative 13 volts after warm up Pin 9: Same as Pin 5 and 7
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#95
10-07-2015, 05:12 PM
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I THINK...you are measuring BACKWARDS...Otherwise...you have NO plate voltage----and I do NOT think that would result in a no-brightness condition. but--maybe I am wrong.
let's asume you ARE measuring backwards..This makes more sense. THEN...you are getting 320 colts on the PLATE-----and that is likely WAY too high. I see only - 8 volts on pin 3 (8). this sounds WAY too high to me....tube would NOT draw any current and WILL keen cathode of CRT cut-off. HERE...accd. to Sams is what your voltages SHOULD be..on that tube.: Pin 1--cathode--.5 volts pin 2--control grid--- -2.5 volts.. pin 3-, pin 9--grounded. pin 4, 5 --filamant. pin 6-ground pin 7--plate--235 volts. you are measuring WAY too much here. pin 8--screen grid--115 volts. There is a 22K resistor here--r-70. CHeck to see if it is open or high in value. Off of the grid pin--pin 2--there is a choke--l15--should read 10 ohms. Ths is paralleled by a resistor--R65, shoukd be 4.7K. SOMETHING..is OPEN here. ALSO..On the OTHER SIDE of L-15 is the delay line. COUld be open. if not...on the other sid eof it...is ANOTHER choke--L-12. 5.2 ohms. Then...it goes to a transsitor--Q5--the 2ND video amp, collector pin. SHould read 11.6 voilts or so. ,Base should read 16 volts, emitter 16.5 volts. lThis is a PNP transsitor---it relies on a differential i voltages on base to collector--toi conduct. base goes CONTRAST control--which is connected to 21 volt line.through R-61 18K. Last edited by rca2000; 10-07-2015 at 05:17 PM.
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#96
10-07-2015, 05:55 PM
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Quote:
Last edited by MRX37; 10-07-2015 at 05:59 PM.
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#97
10-07-2015, 06:02 PM
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This set is a TRUE definition of a HYBRID set.
Here you have a set with most of the low-level stages SOLID_STATE--including an IC_-for sound det-pre-amp and a power transistor for the output. ALL of the IF and AGC is SS. Most of the video is SS..--save for that 12HL7 V-out tube.. Most of the chroma stage--Except fot the 6MD8 chroma amp tube is SS too. Only the horiz and vert stages are mostly tube. Tuners are SS too. The FINAL Hybrid Sylvania color set--the D-16, evidently dispensed with the HV rect and shunt reg tube..replacing them with a TRIPLER
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#98
10-07-2015, 06:06 PM
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Scratch the part about the TV not having a contrast control. i just discovered that what i thought was just a missing nameplate is a door with 4 more controls I'm going to try adjusting those and see what I get.
Edit: adjusting the contrast control makes a slight difference. Last edited by MRX37; 10-07-2015 at 06:11 PM.
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#99
10-07-2015, 06:20 PM
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Looking at sams for D-12-8. VERY likely to have same video layout as yours.
in FACT...I SEE 2 of the resistors now.. R65..next to l-15--left side of that coil--L-15, maybe in FRONT of it.. R-70--in FRONT of 12HL7 tube--to the RIGHT of it.. R-61 is on SS board--FRONT of set...behind a little black transistor.. Your delay line is M4...should be on the side of the board with the 12Hl7. If it is open or shorted...it WILL kill the video..and NOT overload anything. Check it..it COULD have been broken off or such. if OPEN...you CAN bypass it--it's purpose is to delay the video a few microseconds...to ensure it does not get to the CRt before the chroma--which takes longer to process. If bypassed...it will NOT look quite right...but WILL tell you what you need to know... Last edited by rca2000; 10-07-2015 at 06:35 PM. Reason: add. info
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#101
10-07-2015, 07:08 PM
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Indeed it is. It should show continuity between the sides....NOT to ground. I do not have an ohms value--but I do not expect it will be over 100 ohms or so...but it should NOT show low to ground..
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#103
10-07-2015, 07:37 PM
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Hey! That helped! The picture is still dim and blurry, and the focus control doesn't help, but I was able to connect my DTV box and get the horizontal and vertical adjusted.
You can see in the attached image how blurry it is. That's supposed to be a box that says "No Signal"
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#104
10-07-2015, 08:07 PM
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Ok....so you have an open delay line. not the most uncommon thing to see.
Your tube likely is not too bad. BUT...you sem to have A focus voltage problem too... Focus comes from the flyback--is rectified by diode X6---and then goes through a couple of resistors--including one to GROUND_-to keep it from going too HIGH-..-R-155, a 66 meg resistor. There is also R-154, a 4.7 meg resistor--in line to the focus pin to the tube. Sams says 4KV for focus...but this is an AVERAGE voltage...it may be higher or lower depending on the CRT. The focus control is a coil--tied between boost and boosted boost ans the focus voltage...there are a oair of resistors that parallel the windings--if these are off much---it WILL mess up the focus. R-161, 162. 8.2K. There is a cap, c-110, in line to that focus coil--likely ceramic--130PF, if shorted--it would mess up focus too. Last edited by rca2000; 10-07-2015 at 08:08 PM. Reason: Mistake
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