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#77
07-06-2022, 09:50 PM
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as mentioned, make sure the voltages are OK, AND, if the paper caps in the area have not been replaced, DO IT...
Leaky caps are the fastest way to kill audio output, and they are hard to test w/o a leakage tester.
__________________
=^-^= Yasashii yoru ni hitori utau uta. Asu wa kimi to utaou. Yume no tsubasa ni notte. いとおしい人のために 
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#78
07-06-2022, 09:51 PM
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#79
07-07-2022, 06:09 AM
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#80
07-07-2022, 09:24 AM
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The voltages you measured around the 6K6 seem pretty good. Have you tested and replaced tubes in this set?
What about the voltages on the 6AT6 pins. A bit of clarification on how the sound stages work. 6K6 is the audio output tube, it is responsible with developing the power to operate the speaker. Most of the 6AT6 is used as a audio amplifier, it increases the voltage size (amplitude) of the audio signal. The 6AL5 is the FM discriminator (detector or demodulator). Before the 6AL5 the signal is 21.25 MHz with FM audio modulation, after the discriminator the sound is in the audio range. That makes the volume control a good place to try injecting audio. The audio stages are easier to troubleshoot than the IF. You need a bigger audio signal at the grid of the 6K6 than the 6AT6 grid to hear the same volume. The general way to determine the wattage required for a resistor is to use the resistor value and the voltage difference across it. That 1K resistor that feeds the screen of the 6K6 and then feeds the plate through the output transformer has 25 volts across it. Voltage squared, divided by the resistance is the wattage given off (dissipated), that come out to 0.625W. You always want to use a resistor rated two or more times the dissipated wattage so it stays fairly cool. So a 2W should be OK.
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#81
07-07-2022, 09:44 AM
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I have not seen that he has made the voltage tests yet, are the all in spec?
__________________
=^-^= Yasashii yoru ni hitori utau uta. Asu wa kimi to utaou. Yume no tsubasa ni notte. いとおしい人のために
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#82
07-07-2022, 09:57 AM
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The description of the roles of both tubes makes sense to me now. I work on the east coast of the US and live just outside Philadelphia PA in the suburbs. I'm at my day job right now, cheating my employer out of some time and money monitoring VK!!! I will check and report on the voltages on all pins of both tubes tonight. Both of them are tested old stock replacements I purchased from Antique Electronic Supply so they tested as strong tubes worthy of resale by AES in fact, I replaced almost all of the tubes in the set as well as all the wax/foil/paper caps and the electrolytics...and, as I said previously, some of the mica caps with exact value and voltage replacements...not an inexpensive change. The resistor we are discussing is an original as I have not replaced any resistors yet except for the large, ceramic, dual bleeder resistor(s) on the back of the chassis. The 1K measures within 10% and it is considerably larger than most of the other resistors. I believe the Riders has no 1K resistors, other than the bleeders, listed at more than 1 watt. I'll do the voltage drop measuring and the calculation you described and see what I get. The ceramic bleeder resistor was fascinating and beautiful but, unfortunately, one side was open. It's actually 2 resistors and not a strip with terminals coming off at resistive values along its length. The values are 510 ohms and 700 ohms by the Sams and 1125 and 610 by Riders. I went with the Sams resistance specs because the working side of the original gave me a reading of 507 ohms, a lot closer to 510 than to 610. The Sams lists them at 10 watts and the Riders lists them at 20 watts. I mounted 10 watt resistors at the Sams resistance values and the 700 kept blowing out. I did not mount it to the resistor housing however so there was no heat sink. 20 watt wirerwounds are hard to come by in exact values so I purchased two 15 watt resistors with matching values (Sams 700 and 510) from Mouser and flush mounted them directly to the large resistor box with heat conducting paste. The box gets hot but it seems to be doing its job as a heat sink adequately and I've had no issues with the bleeders. Sorry for the long post! I'm stealing money by the letter! 
Last edited by Chris K; 07-07-2022 at 10:11 AM.
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#83
07-07-2022, 09:58 AM
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#84
07-07-2022, 07:29 PM
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OK...here we go. Man, is this screwed up! First I measured all of the resistors in the schematic in around the 6K6, 6AT6 and the 6AL5. All 3 tubes are fresh replacements testing good. I'm using the Riders parts list for identification. I won't list the rated resistance, just what I get. The ratings are on the schematic.
R179 496k R180 8 Megs R181 103k R184 484k R185 1.1k Now the pin voltages. This is where it's a mess. All volts are DC unless AC is indicated. The pins will be identified as P1 or P2 for Pin 1 or Pin 2. 6K6: P1 No Pin P2 6.3V AC P3 -67.4V P4 -67.5V P5 -14.3V P6 -15.1V P7 No Volts P8 No Volts. Oy Veh! 6AT6: P1 through P3 No volts P4 6.2V AC P5 -3.1V P6 -0.67V P7 58.7V 6AL5: No volts on any pin except 6.3V AC on pin 3 Jesus...what a mess. Maybe I should just throw it out and restore another Philco! Thanks Chris
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#87
07-07-2022, 09:34 PM
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this is the tube voltage chart from the SAMs for the RCA 630ts which is very close.
http://suzaku.live-evil.org/sound-volt.jpg Ref V14 15 16 it's normal to see almost no voltage aside from heater on the 6AL5 the 6AT6 also seems OK, pin 7 may be lower than what is said, but mot likely not an issue. what is WEIRD here is the 6K6GT,, You should be only be seeing negative voltage on pin 5, if pins 3 & 4 are negative then something is VERY wrong, especially if you have a good strong +225 bias on the far side of that 1k power resistor feeding it.
__________________
=^-^= Yasashii yoru ni hitori utau uta. Asu wa kimi to utaou. Yume no tsubasa ni notte. いとおしい人のために
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#88
07-07-2022, 10:09 PM
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#89
07-07-2022, 11:10 PM
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then you should have a dead set :O
gonna have to trace the main bias path from the 5U4 heater through the filter -> horz center pot -> vert center pot -> focus coil - > bleeder network to try to see where it's getting lost, and hope that it's not a unreplaceable part like an open focus coil. 
__________________
=^-^= Yasashii yoru ni hitori utau uta. Asu wa kimi to utaou. Yume no tsubasa ni notte. いとおしい人のために
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#90
07-08-2022, 05:51 AM
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I don't think the focus coil is open because moving it does what it's supposed to do on the CRT but, as I've displayed here several times in this thread, what the hell do I know  So my plan is to meticulously retrace the 5U4 DC output checking voltages along the line until I find my screw up. My wife and I are leaving for a well deserved vacation tomorrow so, unless I act on an insane instinct to bring the TV and all of my equipment to Cape Cod, I probably won't have anything to post on this project for the next 8 or 9 days. I appreciate all of the help the forum members have offered to this point and I hope everyone who have been so generous so far will stand by until I pick this up again in a week or so. At least now I know, thanks to you, it's a major and possibly single issue of a miswiring or something easily corrected. I hope!
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Linear Mode
