Magnavox 153B Hepplewhite.

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Re: Magnavox 153B Hepplewhite.

Post by Wildcat445 on Sun Jan 10, 2016 11:07 pm

That is true as well about pentagrid converters. About all a tube tester will tell you about those, reliably, is the condition of the filament. Substitution is the best way to test such a tube.

Is the 6H6, following the 6SH7 part of the discriminator circuit? I'm not sure I understand that part of it.

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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Mon Jan 11, 2016 10:11 am

The 6H6 is the ratio detector that provides the demodulated FM audio. The 6SH7 limits any amplitude variations in the signal, as amplitude has no place in the signals' detection. The audio amplitude is generated corresponding to the frequency variations in the signal, called deviation as opposed to modulation. The deviation level is expressed as a percentage of the unaltered carrier frequency.
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Re: Magnavox 153B Hepplewhite.

Post by Wildcat445 on Mon Jan 11, 2016 10:18 pm

You are Mr. FM, 75. I'm impressed. I never did understand how that worked. That is a good of an explanation as I have heard. When I get that little Howard FM converter back on the bench, I know who to ask to talk me thru it. Thanks for taking the time to bolster my understanding somewhat.

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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Mon Jan 11, 2016 10:41 pm

It's only scary because it is unfamiliar territory.  On my unit the alignment is essentially that of a CW receiver.
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Re: Magnavox 153B Hepplewhite.

Post by Wildcat445 on Mon Jan 11, 2016 11:12 pm

Your project and the comments you have made while working with it has certainly given me prospective when it comes to that Howard FM converter. As I recall, I had more-or-less correct element voltages and it was "kinda, sorta" working. Your comments about alignment make perfect sense and fill in some of the gaps. Again, as I recall, I had chased the problem to the discriminator stage. It is on my bench back home, so it will be spring before I see it again. Your comments have given me a next step, and that is more than I had. I appreciate that.

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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Tue Jan 12, 2016 12:13 am

No problem. You might also look up the service data on it as well and it may have the same rudimentary alignment procedure.
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Re: Magnavox 153B Hepplewhite.

Post by Wildcat445 on Tue Jan 12, 2016 12:10 pm

I have the service data for it. I'll have to review that and see what I need to do.

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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Sat Jan 16, 2016 12:31 pm

Well, I got a NOS Philco 6SH7 tube. I installed it and except for any trimmer and build shift, the microphonics are no more. I was worried for a few moments because the signal level would drift as I checked the trim on the unit, then I remembered the amplified dipole antenna drops out when moving in the room. Now it looks like getting the eye up and running.
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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Mon Jan 18, 2016 3:26 pm

Ran up the console with my laptop library. That thing really performs. I burned up some of the smells in the unit and really rattled the windows good. It played the newer stuff with nice fidelity and the old live and disc lifts well also.
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Re: Magnavox 153B Hepplewhite.

Post by Wildcat445 on Mon Jan 18, 2016 9:49 pm

It is good to hear it worked out well. Now you are hooked. ONE Magnavox is not NEARLY enough. Very Happy

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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Thu Jan 28, 2016 8:09 pm

Looks like the weather will be decent enough this weekend to finish up the antenna. I'm really hoping it will do well with distant stations.
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Re: Magnavox 153B Hepplewhite.

Post by Wildcat445 on Thu Jan 28, 2016 9:09 pm

I hope it works out as well as you hope.

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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Sun Jan 31, 2016 6:06 pm

I have finished with the antenna, and am now listening to one of the stations I can get well above the noise. The shortwave has improved greatly. I had thought the indicator function only worked with the broadcast band, but I get response on many shortwave stations now. I was able to get WWV on 10 and 15Mhz.
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Re: Magnavox 153B Hepplewhite.

Post by Wildcat445 on Sun Jan 31, 2016 6:13 pm

Did the antenna fix the eye tube issue, or did you do something about that that I missed?

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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Sun Jan 31, 2016 7:07 pm

The eye on the AM receiver had always worked on broadcast mode, but would not work in shortwave. Apparently there wasn't enough signal sensed in the shortwave mode to show on it. Now it at least during the day it will close halfway. I expect it will be doing some good stuff this evening. I am still going to have to pull the receiver and line it up for the antenna and maybe put some reject on the remaining RFI.
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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Sat Feb 06, 2016 11:11 pm

The antenna has been quite a addition to the console. the shortwave reception these past few nights have been quite impressive. I have gotten stations from China, Cuba, Australia, Romania and a number of other stations whose language I can't understand. Many of them have come in with enough strength to almost close the eye. It was also interesting to still hear FSK and NSK traffic and even a couple of fists making their messages out. I guess shortwave ain't quite as dead as some make it out to be.
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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Sat Mar 05, 2016 2:02 pm

After having used it for awhile, I thought I would pull the receiver and do some touch up tweeking and I guess running it has done some good. I brought the sensitivity up about 25%, reducing the RFI's influence. The eye is showing better capture and I can get more stations. I guess I'll finally be satisfied when I can pick WOWO out of the adjacent clutter.
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Re: Magnavox 153B Hepplewhite.

Post by Wildcat445 on Sat Mar 05, 2016 4:57 pm

Good luck with WOWO. I can't even get that station in MO anymore. Ever. Even with my longwire antenna.

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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Sat Mar 05, 2016 10:23 pm

I just got 'em. Broadcasting a Komets away game at rapid City and there is even a station in Atlanta that broadcasts on 1190. You gotta have faith.
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Re: Magnavox 153B Hepplewhite.

Post by Wildcat445 on Sat Mar 05, 2016 10:34 pm

In fairness, I live in a fringe area.  There are some evenings I can't get KCMO, less than 200 miles away.  I'm glad you can get WOWO.  You have a good antenna and you also have a Magnavox.  You can't lose.  Now that you are hooked, when may we look forward to your acquiring another Magnavox? Very Happy

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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Sat Mar 05, 2016 11:48 pm

Probably the next time a cheap unit catches me at a flush moment. Very Happy
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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Sun Mar 13, 2016 10:08 pm

I was pleasantly surprised to do a search for this type console on the Bing search engine. Here is what I found.

http://www.bing.com/images/search?q=magnavox+153b+hepplewhite&FORM=HDRSC2
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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Thu Mar 24, 2016 9:26 am

In order to reduce the amount of RFI noise in AM and Shortwave, I got a line filter like the one shown but for 10 amp rating. It has worked mighty well. I can get the English service of Radio Prague at about 6:30, a couple of hours before sundown.

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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Sat Jul 30, 2016 9:44 pm

I went through a realignment of the broadcast and shortwave receiver.  The SW oscillator trimmer had a very narrow window of operation and was quite microphonic.  I disconnected the capacitor gang from the circuit and used contact cleaner to attempt to get better function of the trimmer.  I was able to get a little extra action on it, and the shortwave sensitivity is slightly better than when I originally aligned it.  As it was, though the sensitivity was reduced by about a third.  This unit is hotter than the communications receivers I have.
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Re: Magnavox 153B Hepplewhite.

Post by Wildcat445 on Sat Jul 30, 2016 11:05 pm

Good old Magnavox! Very Happy

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Re: Magnavox 153B Hepplewhite.

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