Author Topic: Need Schematic for Magnavox Portable  (Read 160 times)

AstroSonic100

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Need Schematic for Magnavox Portable
« on: September 19, 2018, 11:32:50 AM »
I just acquired a 1965 Magnavox 1-SC237 portable.  Basically their bottom of the line model.  At least it has the Micromatic changer in white.
I'm having trouble finding the schematic for the amp.  The label says AP9901.  Date code 7/65.  Tube lineup is 12AX7 and two 50EH5.  Sams does not have a listing for that amp model.

I was going to keep it for the changer and scrap the rest of it, but thought it might be fun to try and restore it.

Fabric on cabinet is in fair shape with small tears that show wood cabinet underneath.  Don't know whether to try and paint over it or if there is a way to remove the covering and recover it. 

I'm going to need to service the changer.  Change cycle is slow and the two styli are missing.  It uses the EV 26 cartrfidge.

The good news is the amp works with no hum, but I still want to put new filter caps in it.

Ray

electra225

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Re: Need Schematic for Magnavox Portable
« Reply #1 on: September 19, 2018, 12:13:58 PM »
I was not aware of Magnavox making tube instruments past 1963.  I'd be interested in seeing more documentation on this one.   :) 
I'm great at multi-tasking.  I can listen, ignore, and forget all at the same time.

Motorola Minion

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Re: Need Schematic for Magnavox Portable
« Reply #2 on: September 19, 2018, 01:57:33 PM »
Ill see if there is a listing in my older Sams indexes, which were simpler. The EV-26 cartridge was used on many if not all 1959-61 Magnavox record changers, so a tube amp is a good match.

I have a suspicion low-power transistor amps were avoided in favor of "tried and true" tubes, based on price points in 1964-65. A few years later, no tubes were used in anything US-made.
Tubes - Magical - Tubes

Dave

electra225

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Re: Need Schematic for Magnavox Portable
« Reply #3 on: September 19, 2018, 02:39:07 PM »
Euphonics E and U series cartridges were also used in Magnavox during the time you cited.  When did Magnavox discontinue use of the EV 26?  I thought it was 1962, but I could be wrong on that. 
I'm great at multi-tasking.  I can listen, ignore, and forget all at the same time.

AstroSonic100

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Re: Need Schematic for Magnavox Portable
« Reply #4 on: September 19, 2018, 05:46:52 PM »
Euphonics E and U series cartridges were also used in Magnavox during the time you cited.  When did Magnavox discontinue use of the EV 26?  I thought it was 1962, but I could be wrong on that.


I have one of those Euphonics cartridges for my 1957 Wedgewood. The console has factory stereo conversion kit installed near the end of the mono era so it wouldn't become obsolete.  Originally had an EV 26 which was bad. Euphonics is mounted on the long mounting bracket with two screws.
Ray

electra225

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Re: Need Schematic for Magnavox Portable
« Reply #5 on: September 19, 2018, 07:34:52 PM »
I believe the EV 26 was one of the best ceramic cartridges ever made. 
I'm great at multi-tasking.  I can listen, ignore, and forget all at the same time.

TC Chris

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Re: Need Schematic for Magnavox Portable
« Reply #6 on: September 19, 2018, 08:26:00 PM »
As to the new filter caps, it's much less crucial because your little portable doesn't have a power transformer.  Big devices with power transformers are vulnerable to shorted filter caps that take out the very expensive power transformer when they short out.  But without the power transformer, you lose a rectifier, apparently solid-state in yours.  If it's a selenium rectifier (one with stacked metal plates) the smell is awful when they die.  But if it's a little silicon rectifier, they die peaceful deaths and they're really cheap anyway.

Chris Campbell

Ken Doyle

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Re: Need Schematic for Magnavox Portable
« Reply #7 on: October 04, 2018, 10:06:13 AM »
I've read that the EV-26 was the first stereo cartridge available to the public. 


Late in the tube era, Magnavox began using the EV-150 cartridge, which lowered the tracking force to an advertised "1/10 of an ounce", but continued using the EV-26 on less expensive sets into the mid-1960s.  Sadly, the EV-150 is long out of production, and age has taken it's toll on most of the original ones.

AstroSonic100

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Re: Need Schematic for Magnavox Portable
« Reply #8 on: October 04, 2018, 03:32:10 PM »
Astatic also made cartridges that used Magnavox mounts.  The Astatic 461 (an Astatic 133D) has the mount for the Micromatic changer I have.  I have good luck with the Astatic cartridge.  Seems NOS are still working.  The yoke where the stylus shaft sits seems to be made out of nylon or plastic instead of the rubber that EV used.  I"m currently using an Astatic 459 cartridge (an Astatic 133D) which is the 2 hole mount for the older Collaro changers.  It works very well in my '57 Wedgewood.
Ray

Motorola Minion

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Re: Need Schematic for Magnavox Portable
« Reply #9 on: October 05, 2018, 08:11:29 AM »
The Astatic 133 was a workhorse used on the lower-priced Motorola-branded V-M record changers 1961-64. The Pfanstiehl 164 stylus it uses looks very much like the EV150/Pfanstiehl 365. I found a 133D in my spare parts and it to, played OK. The more expensive Motorola-VM used a Sonotone 9t.

I also agree that the EV-26 was simple but perfect for consoles, as ceramic cartridges go. My 1960 1ST208 has one as do my other two pre-62 Magnavox consoles with Collaro conquest changers. The sound could hardly be improved.
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Dave

AstroSonic100

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Re: Need Schematic for Magnavox Portable
« Reply #10 on: October 05, 2018, 10:40:58 AM »
The Sonotone cartridges are very good performers.  I have a Sonotone 16T in my Garrard RC121 changer which I have installed in a 1950 Philco console.  The Sonotone sounds great considering the frequency response limitations in a 1950 console with a single 12" speaker. i'm hearing highs I didn't think was possible on that model.
The Sonotone 8TA4 cartridge was also used on some of the Magnavox Collaro changers.
I bought an Astatic 197 to replace the EV257 cartridge for my 1966 Astrosonic 100 which has the straight tone arm.  It performs great.  It also has the nylon/plastic yoke vs. the rubber yoke on the EV 257 cartridge.  The Astatic was a vast improvement.
For my small portable, I'll try the EV26 and if it's bad, I'll go ahead and try the Astatic 461.
Ray