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Messages - TC Chris

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1
Magnificent Magnavox / Re: Magnavox 1ST278R Information
« on: Today at 10:50:39 PM »
If the old dial cord is still there, note how many turns it has around the tuning shaft, and the direction they run.  You can often figure out routing of the cord just by staring at the device for a while.  Usually there's a spring somewhere to keep the cord tight--often on the big pulley that drives the tuning capacitor.  Getting the cord in the right direction on the tuning shaft is important so the dial pointer goes right when you turn the knob clockwise and vice-versa.

Chris Campbell

2
Introductions / Re: New member from SE WI
« on: September 13, 2019, 03:04:01 PM »
Welcome!  And please add questions, comments, advice, descriptions of your experiences with these devices.  More participation is better for everybody.

Chris Campbell

3
Magnificent Magnavox / Re: Magnavox Stereo Theater 1MR418M restoration
« on: September 12, 2019, 07:09:31 PM »
Here's another suggestion.  Doesn't all the power to the TV chassis have to go through its own power transformer?  Why not just disconnect the TV power transformer primary and wire a cord to it, with maybe a switch and fuse, and power it up independently?  That would be a way of determining if the video circuits were doing anything, or perhaps if there were some internal TV-only short.  It's possible that something could have got wired just exactly wrong. Not that I've ever done anything dumb like that, of course....

Chris Campbell

4
Magnificent Magnavox / Re: 1947 Magnavox Contemporary - 148B (CR-197D)
« on: September 12, 2019, 07:02:33 PM »
Do you know any history of ownership of your device?  During WW II (before yours was built), it was considered patriotic for Americans of German extraction to have the SW bands of their radios disconnected so there could be no suspicion of them listening to German propaganda.  I've got  Sparton prewar console radio with this done, and it came from a part of the community with lots of people with German background.  Maybe it remained fashionable after the war too.

Chris Campbell

5
Electronics / Re: Power transformer fuse
« on: September 11, 2019, 10:14:34 PM »
The point of one of the suggestions was that the 125 VAC glass fuse could conduct via vaporized metal deposits on the glass, when used in a high voltage application.  The wire would just fizz into the atmosphere.

Chris Campbell

6
Magnificent Magnavox / Re: Magnavox Stereo Theater 1MR418M restoration
« on: September 11, 2019, 07:49:00 PM »
I can't recall seeing a circuit breaker on consumer goods in anything but  a primary circuit.  I doubt it's in a HV circuit.  In places like that they would likely have a non-user-serviceable device, one requiring the service guy to come out and fix the underlying problem.  But those are just semi-ignorant guesses. 

Chris Campbell

7
Electronics / Power transformer fuse
« on: September 11, 2019, 06:44:09 PM »
I'll answer my own question about a power transformer fuse, discussed under another topic recently. While filing away some info I had printed out, I found the file on that subject.  One guy said he used #47 lamps on the PT center tap.  "This acts as a fuse with a 150 MA trigger."  I suppose you could consult tables of lamp currents to select another value. Another guy worried about using fuses rated for 125 VAC at higher voltages because when they blow, the vaporized metal can coat the fuse inside and conduct.  He said that HV fuses are longer & larger.  He uses an inch of #30 wire ( a single strand from an 18 gauge line cord is #34) across a terminal strip, or larger sizes for more current.  Interesting ideas.  These were both ham radio guys discussing their receivers.

Chris Campbell

8
Sightings / Re: Craig's List Ad!
« on: September 11, 2019, 06:31:46 PM »
I have a VM tape recorder that has a 6CA4, 12AX7 a 6EU7 and P-P 6BQ5's powering a 6X9 speaker.  Plus the eye tube which I can't remember the number of.  The more I see of VM's products, the more respect I have for it.

Which V-M tape recorder?  I've always had an irrational fondness for those.

Chris Campbell

9
Sightings / Re: Craig's List Ad!
« on: September 10, 2019, 09:48:37 PM »
Here's the schematic, which I think I also posted in downloads.  Note the extra taps on the output transformer primary, back to the screen grid (?).  It's a form of local feedback and not expected on a not-so-high-end device  But there it is, so V-M must have decided it would improve things.

Chris Campbell

10
Sightings / Re: Craig's List Ad!
« on: September 10, 2019, 06:34:09 PM »
I'm guessing from that YouTube video that the 562 is the same device n a tabletop configuration as my Model 566.  And the same Sams seems to cover both.  6BQ5 P-P output?  And notably an "ultralinear" output stage arrangement.

Chris Campbell

11
General Discussion / Re: Bumblebee capacitor
« on: September 10, 2019, 06:27:34 PM »
Here's a link to a color code chart:
http://www.angelfire.com/electronic/funwithtubes/How_To-Reading_Codes.html

Chris Campbell

12
Magnificent Magnavox / Re: Magnavox Stereo Theater 1MR418M restoration
« on: September 10, 2019, 06:20:05 PM »
That's a valuable lesson for all of us, and thank you for sharing it.  I have not been adding fuses in the primary in my restorations, mostly because it requires mental effort and I can be lazy sometimes after work.

Maybe somebody can give us a short tutorial  on sizing fuses for the power transformer? 

There's the whole issue of inrush current as filaments are cold and the filter caps charge up, and maybe a new issue of higher current draw at higher modern line voltages.  Is it enough to just take wattage from the label or schematic and add 50%?

One last point--most light bulbs fail either when brand new or when very old.  It's a bell-shaped curve with few failures once you get past "youth."  Maybe it's otherwise in those AA5 sets where the dial light looks like it's going to self-destruct at turn-on.

Chris Campbell

13
Music / Re: A Mercury disc
« on: September 10, 2019, 06:10:18 PM »
My mother kept trying to get me to take piano lessons, but I shared the bias that it was too girly and successfully deflected all the urging.  Of course, I have regretted it ever since.  I was watching the Aretha Franklin gospel music documentary a while back and was terribly jealous of those people who could just sit down and make the most beautiful sounds.  I have to look at the keyboard to type, for goodness' sake. 

I did like making music in the band--marching and concert, and can still remember the trombone parts of many of the pieces we played.  I could probably sing them better than I ever could play them.  Some day when I retire I intend to seek a few lessons and see if it comes easier as an old guy who has listened to lots of music and knows what it should sound like.  Credit goes to the band teacher, a kind, tolerant, generous man named Walter Cramer.  I like to spell out his name as a way of honoring teachers, those people who affect our lives in so many ways.

Chris Campbell

14
Sightings / Re: Grommes-Phillips, Oak Park Il. $70.00
« on: September 09, 2019, 10:39:48 PM »
Grommes built good stuff, and this one has a Collaro changer!

Chris Campbell

15
Magnificent Magnavox / Re: That cheesy sticker
« on: September 09, 2019, 10:37:22 PM »
The light is the device in the right back corner.  A rod actuates the switch when the lid is lifted.  And I also forgot to add that the cabinet was made in Saginaw, MI, just a few miles from where this one lives.

Chris Campbell

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