Repair of a 1965 Magnavox Astro-Sonic console stereo (I think it's fixed) - part 4
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- Опубликовано: 2 окт 2013
- OK, I think it's finally fixed and ready for service.
Here's a 1965 Magnavox "Astro-Sonic" solid state console stereo, using the R204 series chassis. In previous videos; we performed routine repair work on the chassis and the record changer. However, we had an issue with poor FM performance. I thought I had the problem fixed; until I reassembled the stereo, was listening to a station, and it suddenly faded to near nothing. One thing is for sure, if something is going to mess up, it's going to wait until you have it all put back together to misbehave.
So, in this video, I took the chassis back out of the cabinet and found that the FM RF amp transistor, a germanium device, was intermittent. At first, It checked open. Then, I physically stimulated the transistor and got a reading. Then, one of the leads pulled out of the bottom of the transistor; so, that pretty much sealed the deal with that transistor being bad.
Early solid state equipment used germanium transistors and it wasn't until the later part of the '60's that silicon transistors became popular. Unfortunately, germanium transistors are not aging well and new production germanium transistors are getting hard to find and expensive. In fact, the NTE126 that's listed as a substitute for the original transistor in this stereo is almost $10 + shipping, while silicon transistors that serve in the same application are normally not over a dollar.
One might ask, why not simply replace a defective germanium transistor with a silicon device? In some cases, that will work; but, in other cases, the difference in bias voltage will not allow a silicon device to work in place of a germanium device. In some cases, it's possible to redesign the circuit to accept a silicon device. A germanium transistor conducts at around .2-.3 volts, while a silicon device conducts at .6-.7 volts. That may not seem like much of a difference; but, it's a big enough difference that it can cause a silicon transistor not to work in a circuit that was originally designed for a germanium transistor.
Digging through my junk stash, I found a '70's (or earlier) Archer-brand (Radio Shack) universal PNP silicon transistor. I installed this silicon device directly in place of the germanium device; and, fortunately, there wasn't any organ rejection and the chassis seems to be happy with the silicon transistor. Actually, the FM performance is now better than it ever was during my ownership of this unit.
This stereo also has an aux. input; but, the jacks are on the chassis. I don't know why they didn't place the jacks on the rear of the unit; but, since they didn't, I ran an RCA cable from the inside jacks out the back cover of the stereo. Now, this stereo can be used with modern playback devices.
The only thing left to do is clean/polish the cabinet and find an automatic 45 rpm adapter, so that I don't have to use the little yellow and red snap-in adapters. 
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The last 45 record was the best
Love the old Clint Eastwood westerns
The actors from that time were great
The good,the bad and the ugly Hugo Montenegro (spaghetti Westerns)
Congrats on another job well done, Sir! Your magnificent Magnavox console is a beauty!
that record deck is spot on well done
That Would Be A Good For Someone
Who Really Needs A Stereo For Their Livingroom
It's true what you said that it's rare to find anything from Radio Shack made in USA. Back in the 60's through the early 80's they sold their own bra nd of tubes guaranteed for "life." The tubes were mostly made in Japan but I did come across some that were made by RCA, GE and Sylvania. The Japanese ones were crap! If I got a Tv in the shop that had one, I would change it and 9 times out of 10, that would cure the problem. Thay were like Good All capacitors. They were junk from the start.
great job it sounds wonderful you really show in great detail how to repair the faulty parts and I really enjoy all the videos
Great restore and a nice set which sounds terrific. I enjoyed following along.
Cheers, John
As everyone else has said, really enjoy your videos....wish I had soldering skills!
You sure have a great collection of records.
Nice work! I'm not surprised it was one of the germaniums, they didn't age very well compared to silicon...I"m glad you didn't have to rebias the new silicon transistor. That's a fine stereo....wish I had room for consoles....
I have a sort of working ($20.00 investment), 1RP622...made 6/67. Cabinet is in great shape. Until I can afford for someone to do repair work, I will probably hook it up to my existing stereo. Really cleaned up nice, left channel very weak....doesn't seem to be a needle in the tone arm, but the little brush is there.
Nice unit, I'd like to find one from 1970-1972 as we used to have one from that ear. One of these days maybe I'll find a good ole magnavox astro sonic, they seem to be so rare now. The Magnavox Console TV's from that era are almost non-existent now, you can find Zenith's but the Magnavox's are gone. I think they made some of the nicest ones with pretty cool features back in those days. I remember the Magnavox Stores, we used to have one here in Greenville, SC.
Hey wow thanks for your video! I have a 65 magnavox console 60" from my grand parents wow I hope to fix it. Wow I am so happy I found you
Another job well done! Sounds AWESOME!
Great Job As always.
Travis
very nice, I hope someone that knows quality will buy it, it sound terrific.
I think that did it my friend, good job. Could be that 4 lead NTE had the Tin Whisker problem or the seal was gone, had a lot of British Mullard Germaium transistors with similar issues. Must say that works more than VERY WELL now.
love the videos...i am using your tutorials to fix a seized platter on a Zenith console
I'm surprised that the FM side worked so well with such a substitution--and apparently with no realignment needed. Besides the differing bias with a silicon transistor; at the frequencies that an FM RF amp works at, the *transition frequency* or *alpha cutoff*--the highest frequency the transistor can amplify--is very important. It would have been interesting to see the specs on that transistor, because if it was a "general purpose" part, it was rated VERY conservatively. Good job sir!
I've run into dead RF amps before. One was in a CB that some idiot went through with the golden screwdriver and attempted an alignment on. Took me a good while to align it to spec so I could even find out what was wrong with it. Would have taken about 10 minutes to fix if not for the hackjob attempt at a fix. I subbed something I had in a parts rig, soldered right to the bottom of the board since the leads were too short. Works fine now!
Nice work, it looks and sounds great!
I would love to own one of those Magnavox console stereos now, the newer stuff is junk. When I was a kid, my parents had a Magnavox console that was a little bit newer than that one, it had the same turntable, but it had the silver tone arm. I think it was made around 1968 and had the 200 watt amp in it. That old thing would rattle the walls if you played something with lots of bass in it and it had great sound quality.
Great repair there!!
The Animals and Donovan LPs. Perfect on a 60s Magnavox stereo.
Your Amazing Nice Work On The Magnavox Stereo
Great Job ! Thank you for sharing.
I love the song playing at 6:29! :D
I enjoy your videos Thank you
A tip on the 7" set down - for as good as the Micromatics are, they never seemed to set down correctly at 7" when the 12" set down position was correct. Just one adjustment for all 3 sizes - the rest are dictated by the locating cam wheel and it's cast grooves. At least they error on the side of going in too far vs. out too far.
More than likely the greatest hits from the May Day parade, like Maoist revolutionary songs and the Internationale, stuff that suits his view of the world.
Wow,59 cents; had to be a LONG time ago
This appears to be the exact same as the one in our living room, with two horn tweeters (they called them "exponential horns", as I recall) and two side firing 12 inch woofers. Sure would like for you to repair it for us, if you would take it on. I can truck it to you myself anywhere in the southern US, I reckon. I am in Western North Carolina. The cabinet seems exactly the same finish and style, from what I see here. The unit looks new, as it has not been moved since we got it new around 66 or so.
why did these old speakers sound so good!
They were very efficient. For one thing. And was quality.
i wish i did too i am learning them slowly
Like the Tonecrest 1964 stereo you did a video of I had a cheap Crosley recorded player someone gave me I ELO It I have Expensive records and I wound u
With a technics direct Drive Turn table
I have a console like that one side is dead other side works my fm is ok and the turntable works great
I'm pretty sure it's Van Halen - Panama
That sounds like some bad electrolytic capacitors, in transistor/solid state units from the 1950s through the 70s they used electrolytics as coupling capacitors. The electrolytics dry out and you either end up with low audio, distorted audio, or no audio on one channel.
I would buy that off you if it could be shipped to Australia!
Anyone know the name of the song that starts at 9:26? I've tried Googleing the lyrics but have come up with nada.
That's Devo's "Theme from Doctor Detroit."
what brand of capacitors did you use to re-cap the small audio board?
so you never mentioned, was the silicone transistor a drop in? or did you have to adjust bias for it?
I like mine a Box console stereos as long as they have a dual turntable and on other now I think that magnavox is that they made earlier are not all that great thats My opinion but they're probably better but I never like the early magnavox is but right everybody's got their own opinion in this world
I wonder what the output power is on this i have one close to this one that needs some repair's
Ugh what setting on the dial are you turning to skip songs on the record and bringing down the top record?
Ever teach at Aberdeen Woods.....or Melbourne?
Hey there. The radio & TV stations you're able to get. What city & state are they located?
+Mark Covington MS.
Can anyone point out where on the chassis the aux input is? Total newby here and would appreciate the help.
+IEatPandas203 the input is right next to phono inputs on the chassis... ( rca jacks)
what causes the one speaker to crack and pop when turning the volume up?
Typically dirty potentiometers are the cause. When you turn the volume (or bass, treble, etc) it moves a wiper across an element that increases in resistance in one direction and decreases in the other. Over time, the element and wiper become dirty and hence the static. Some contact cleaner usually fixes it.
Radio Shack is no More.
One thing leads to another..
10 year diamond stylus warranty???
Ashley Cox Panama by Van Halen.
I wish to know... what is the song played at 8:55?
TheSkullArmyMC panama by Van Halen
1 "Panama "-Van Halen
2 "One Night In Bangkok "-Murry Head
what was that first 45?
How often do you get to hear Murray Head and One Night in Bangkok?
Or Theme From Doctor Detroit by Devo? It was one of the 45s!
3Cr15w311 - I think that was the third one played.
I have an automatic 45 rpm adapter for your player.
Are you for hire?