Author Topic: Magnavox Stereo Theater 1MR418M restoration  (Read 11515 times)

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #345 on: December 08, 2018, 03:34:38 PM »
I need an .0039 at 200 volt cap in the sweep section.  All I have been able to find is either .0033 or .0047.  Wonder how critical the value is.  Everything else I need Sal has.  I suppose Mouser's is my only option?
I don't need Google.  My wife says she knows everything.

TC Chris

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #346 on: December 08, 2018, 03:41:51 PM »
Or do a quick Google search to see what pops up.  Never can tell.

Chris Campbell

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #347 on: December 08, 2018, 04:11:41 PM »
I found some at Mouser's.  I need a break from their website.  Horrible.  The only word I know to describe it.  If I need to deal with them, I'll probably restuff with PZ's.  I love those things.  I'm referring to the PZ series of e-caps from Nichicon.  They are skinny enough I can restuff a four-section can, no problem.
I don't need Google.  My wife says she knows everything.

TC Chris

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #348 on: December 08, 2018, 08:28:14 PM »
The only reason I suggested Google is that I often overlook it as a way of finding odd things.  This spring my Mom's Subaru had not been run in a while and the battery was almost dead.  In trying to start it  we got the voltage below some critical minimum and all 4 parking lights started flashing.  Nothing would make them stop except disconnecting the battery.  Recharge, reconnect, and there they went, all 4 flashing no matter what I did.  So my sister did a quick cell-phone Google search on something like "Subaru lights flashing."  There was a quick tutorial.  It involved pushing a button on the underdash computer box while turning the ignition switch.  Damned if it didn't work.  Saved a trip to the Subaru dealer ($$).   Since then I've tried to remember just doing a Google search.  And for little components, eBay sometimes has them and it can be easier than a Mouser order.

Chris Campbell

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #349 on: December 09, 2018, 11:54:35 AM »
This chassis uses a 130Uf @200 volt ecap that appears to be an odd value.  It does not follow the rectifier, so I can increase it to 150uf @ 350 volts, which is a more common value.  I can get the coupling caps I need from Sal.  I prefer to give him my business whenever I can.  Part of the problem I was having with the .0039 was that I was looking in orange drops.  They do not make it in that value that is convenient to obtain.  I like simple.  Anything I perceive to be unnecessarily complicated I avoid.  I am being careful with component values in sweep areas and where I know exact values to be important.  I'm learning, albeit slowly......  "Gloriously Complicated".
I don't need Google.  My wife says she knows everything.

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #350 on: January 19, 2019, 05:30:53 PM »
I'm planning on recapping the chassis, then working with electrolytics.  That seems simpler.  I got all the caps I need so far at Sal's.  The electrolytics I will have to get at Mouser's or somewhere. 


I have not established a baseline on this chassis, due to obvious defects that will keep it from working.  I am working on the card table in my little den.  Much like restoring your '65 Mustang out in the backyard under the old oak tree!  Since this is my first TV repair, I don't have enough experience to be afraid of anything.  I have eight pages of notes made on this chassis.  Hopefully, if I have some type of issue when I get the chassis back in the cabinet, I'll be able to refer to my notes and figure out if I made a mistake, have a defective component, or if something I did not work on is the problem.  My goal is to get the picture tube to light and to hear some type of sound from the TV out of the speakers.  I am taking pictures as I progress, so stand by.  Here we go........ :)
I don't need Google.  My wife says she knows everything.

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #351 on: January 19, 2019, 07:54:12 PM »
While Chris is working on his radio on a table saw, I made progress working on my TV chassis on the card table.....


I got all the caps except one changed in the HV section.  No big deal so far.  I have been double-checking my work, one capacitor at a time.  After I get the lone holdout replaced, I'll run resistance checks in that section to make sure everything is okay.  I am retaining the old parts just in case. 
I don't need Google.  My wife says she knows everything.

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #352 on: January 21, 2019, 05:24:41 PM »
I have a question.


I have read on other forums that a B&K model 1076 TV analyzer is the bomb for working on old tube TV sets.  I see they are available on the 'bay for not too much money.  I also see a model 467 CRT tester like a guy I follow on YouTube uses.  I digress....


How does the 1076 work and how would it benefit me in my "relentless pursuit of perfection" on the Magnavox chassis I have been working with.  Or would there be little to no benefit.  The TV guys really like these things when working with a tube color set.  Are they of less benefit on black and white sets, or is their use overkill on black and white sets?


From what I have seen of these things, they are housed in a big box with maybe 12 to 15 tubes plus a CRT.  The CRT appears to be inside the box with no way to view it from the outside of the box.  The front of the cabinet just has controls on it.  I'd have to have a manual for one to figure out how to use it.  Anybody had any experience with one or knows how they work?
I don't need Google.  My wife says she knows everything.

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #353 on: January 22, 2019, 02:22:41 PM »
I have all the coupling caps changed, except one I could not see the value of.  I got a bigger cap out of the way, so now I can see the value.  .005 uf @ 200 volts.  I'll get one of those when I get the damper socket.  That project is next, followed by replacing all the electrolytic caps.  The one I could not see the value of is on the sweep board.  There is a shield soldered to the chassis over the back of the IF board.  I'll recheck the resistances again, then replace the shield.  I repaired the poor solder joints on the 6GC5 voltage divider/cathode follower tube on the sound board.  I'll recheck the resistances and see if I made any difference and/or if there are issues I caused by shotgunning all the caps.
I don't need Google.  My wife says she knows everything.

Motorola Minion

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #354 on: January 22, 2019, 04:18:51 PM »
Greg, The B&K 1076 and later 1077 are test pattern, color signal and sweep substitution generators from the 1970s. I used one in HS to confirm the flyback in a 1962 Silvertone color (RCA CTC11 clone) was fried. Back then, going into the supply house and asking for a 16 Y.O. part for a Sears would get general surliness and a $75 estimate to back-order one, no money back.

The TV Analyst IS the bomb when you have to trace out problems all through a BW or color TV. With the thoroughness you are restoring the Magnavox, you may not need it. I also have a Sencore VA-48 that is a similar help on anything pre-1980s, and even has a coil-ring test for flybacks and other transformers. It helps me check IF-video-color alignment and perform it without much fuss, as was the case if using marker adder and sweep generator. Less chance of un-dialing some slug that was OK IMHO

If you are testing CRT's the 467 is a more complicated and trouble-prone tester than a Sencore CR70 or an earlier BK, say a model 460. I like to keep my old 445 for the older sets, its more telling of condition.
Tubes - Magical - Tubes

Dave

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #355 on: January 22, 2019, 04:46:57 PM »
I have a B&K 445 CRT tester.  I don't know if it is accurate, nor really how to tell if it is/isn't.  I'm not even sure I know how to properly use it.  That said, I read about the analyzer, and, realizing that I am just starting out, wondered if it would do me any good to have one.  It's a neat looking contraption, full of tubes.  Thanks for your input.


I have run the resistances again after changing the caps.  Everything is what I would consider okay with the exception of pins 1,8, and 9 on the 6GC5 and pins 6 and 9 on the 6EM5.  I have fixed the opens on the 6GC5, but I'm not out of the woods yet.  I suspect an electrolytic cap may be the problem there.  The pins I mentioned on the 6EM5 test open.  I'll check the circuit involved with those pins and figure out what the deal is.  I'm getting close.  I want to figure this out before I do the e-caps.  I don't want to take the chance I may have introduced a fault.  I checked each cap after I changed it to make sure I had a good solder joint.  This is not the easiest PCB I have seen to solder on. 


I have several pages of documentation on the work I've done on this chassis.  Before and after resistance readings.  Readings on every resistor in the chassis.  I can't leave anything to memory.  I'm not sure how much good all this will do me, if any, but it sure looks impressive to see how much work I've put into a TV chassis that will still be obsolete after I put this much of myself into it.   :-[ ;) :)
I don't need Google.  My wife says she knows everything.

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #356 on: January 22, 2019, 05:09:15 PM »
Dave, what is the purpose of the picture tube in the 1076? 


I may have some shorted, or severely leaky electrolytic power supply capacitors in this chassis.  Pins 1,8, and 9 on the 6GC5 only have those caps between them and chassis ground.  This tube is used as an audio output tube in some versions of the C36 series chassis, but in this particular version, it is used as a voltage divider and cathode follower. 
I don't need Google.  My wife says she knows everything.

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #357 on: January 22, 2019, 07:16:07 PM »
Part of my problem was self-inflicted.  My notes have already bailed me out.   :)


I was going thru my notes on what I had done up to this point.  I saw a notation on the notes where I took resistance measurements "Tubes in place."  Oops.   :-[


I had taken several of the tubes out in order to give more room to work replacing the caps.  I had not put them back.  I noticed on the schematic that pins 3 and 6 on the 6EM5 were connected internally.  Putting the tube  back fixed that problem.  I read an open on pin 9 in my "before recap" resistance checks.  I read open on that same pin after the recap.  I wiggled the tube and found the needle on the ohmmeter bounced around when I wiggled the tube.  The spec on pin 9 is 450 ohms from that pin to the output of the rectifier.  I now have 16K ohms, which is way too much, but is less than having an open.  I won't worry about that at this point until after I have the filter caps changed.  And after I replace the 6EM5 with a new tube.  I still need to figure out the issue with the 6GC5,


I found this on the TV analyzer. 


https://antiqueradio.org/BK1077BTelevisionAnalyst.htm
I don't need Google.  My wife says she knows everything.

Motorola Minion

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #358 on: January 24, 2019, 10:50:37 AM »
The video is from Phil Nelson, a long-time member of videokarma, ARF and other forums. He like s the old stuff like us but also is a font of practical advice.

The CRT inside the analyst is a camera tube of sorts. The test patterns are on sheets that go against the face of the tube. The color bars are generated as in most of the color-bar generators like the RCA WR-64.

B&K was known for making equipment that allows for the flexibility to service not just TV but any type of monitor. Sencore equipment was geared more toward the TV repairman than AV techs and broadcast engineers.

For your 27" Magnavox BW that B&K 445 is perfect! It tests color also.
Tubes - Magical - Tubes

Dave

electra225

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Re: Magnavox Stereo Theater 1MR418M restoration
« Reply #359 on: January 24, 2019, 07:57:12 PM »
I have a friend with a 1077B for sale.  I may reach out after I get home in the spring.  It would be fun to play with if nothing else.  I don't have any way of making any kind of width or linearity adjustments.  I'm not convinced that this TV chassis has not had some "screw twisting" in its past. 


I learned something while I was servicing the PCB chassis.  Everybody else on this forum may have known this, but now I do too.  This particular chassis has the printed wiring on the back side with the components on the front side.  There is component nomenclature on both sides of the chassis, allegedly so it is easier to service.  All the printing on both sides makes the chassis look "busy" to me, making it actually harder to locate the components you want to work with.  I removed a capacitor, then could not find the holes in the PCB so I could put it back.  My wife was holding the flashlight and accidentally shined the light toward the chassis.  The holes I was looking for jumped out at me!  This make it very simple to locate the holes with all the junk on the chassis.  Shining the light from front to back makes it easy to follow the printed wiring in order to trace out the circuit.  It was recommended that I use a solder sucker when desoldering on a PCB.  On this particular chassis, I found it better to not use the solder sucker.  Leaving the little piles of solder from where the component was removed aids in finding the hole from the back of the chassis.  Magnavox's idea to put component nomenclature is good if you are trying to find a specific component.  It is not so helpful when removing components for replacement.  The first cap took 30 minutes, the rest of the chassis didn't take much longer than that.


I'm not going to try to clean any of the controls until I power up.  I have heard about "tinwhiskers" messing up controls and that, but I'm not going to worry about that now.  I'll deal with dirty controls after I get it going unless someone sees a good reason to change that plan.


Thanks, Dave, for the explanation of what the picture tube in the analyzer's purpose is.  That makes sense now.
I don't need Google.  My wife says she knows everything.