Author Topic: Magnavox Micromatic Model: 2ST647 New Needle - No Sound  (Read 3574 times)

John B

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Re: Magnavox Micromatic Model: 2ST647 New Needle - No Sound
« Reply #105 on: March 29, 2018, 07:07:46 PM »
Steve,

Thanks for the warning.  I haven't touched them.  No luck with the volume.  I'll try more Google searches read up on the schematics.  Many forums suggest replacing all the capacitors and on one forum some guy changed all of his and it didn't help.

Thanks,

John B

SeniorSteve

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Re: Magnavox Micromatic Model: 2ST647 New Needle - No Sound
« Reply #106 on: March 29, 2018, 07:15:37 PM »
There has to be something simple that I'm missing.  With the voltages near normal and you do get the stereo indicator, I'm sure the tuner is working. 

What doesn't make sense is the fact that you have near normal voltages and you don't have output on the Magnavox.  Then more interesting or should I say confusing is the fact that the tape record out doesn't produce anything in the Pioneer. 

Do you have an external device you can connect the RCA cables up to.  Something like a cd player.  I'm really trying to find out if the cables are working.  You should be able to connect a CD player or tape deck to them (the RCA cables) and hear it at the Pioneer.

John B

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Re: Magnavox Micromatic Model: 2ST647 New Needle - No Sound
« Reply #107 on: March 29, 2018, 08:05:57 PM »
Steve,

Well, it looks like the wire that goes from the living room, under the house, to the TV room is the culprit.  I also have a couple of RCA's that have an open end are also bad.  What I could do is take my workshop into the TV room and configure things out from there.

Thanks,

John B

John B

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Re: Magnavox Micromatic Model: 2ST647 New Needle - No Sound
« Reply #108 on: March 29, 2018, 08:24:41 PM »
Steve,

I moved the Magnavox to the top of the Pioneer and I can hear sound nicely.  The volume is controlled by the Pioneer.

John B

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Re: Magnavox Micromatic Model: 2ST647 New Needle - No Sound
« Reply #109 on: March 29, 2018, 08:38:51 PM »
John, that is great news!  I now know where to concentrate on working  on the Magnavox.  The one thing you don't want to do is to leave that Magnavox chassis on top of the Pioneer.  It's blocking the heat vents and solid state equipment does NOT like too be overheated. 
A lot has been accomplished today!  Thanks for your time and patience.  The problem is limited to the driver and output stages on the Magnavox.  Take a breather.

Steve

John B

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Re: Magnavox Micromatic Model: 2ST647 New Needle - No Sound
« Reply #110 on: March 29, 2018, 08:41:49 PM »
Steve,

Thanks,

John B

John B

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Re: Magnavox Micromatic Model: 2ST647 New Needle - No Sound
« Reply #111 on: April 11, 2018, 04:32:04 PM »
I DID IT!!! 

I have successfully fixed my radio!  I'm hearing it!  AM and FM!  Loud and clear!  Today I installed a dozen new capacitors ending with C6 and C7.  In total, I've replaced twenty-one paper capacitors.  Two caps were blown.  From what I measured, the caps were more than twice the MFD rating.  The new soldering station (Hakko 936) was a big help.  When I put the radio back into the console, I'll find out if I need a new phono cartridge or not.
Thanks for all the help from the VintageHiFi Forum.

John B

John B

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Re: Magnavox Micromatic Model: 2ST647 New Needle - No Sound
« Reply #112 on: April 21, 2018, 01:12:31 AM »
Unfortunately, it went silent on me again and I can't figure out why.  I don't know a lot about radios.  Today I heard an AM station for a while but nothing else.  The panel lights go on, I can hear static when I change bands, and I hear a hum when I touch a couple of the wires.  I was really excited but now not so much.

John B

John B

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Re: Magnavox Micromatic Model: 2ST647 New Needle - No Sound
« Reply #113 on: April 22, 2018, 11:16:02 AM »
Unfortunately, it went silent on me again and I can't figure out why.  I don't know a lot about radios.  Today I heard an AM station for a while but nothing else.  The panel lights go on, I can hear static when I change bands, and I hear a hum when I touch a couple of the wires.  I was really excited but now not so much.

John B

Basically, I cannot get AM and FM radio to work. It had worked. The last time I had the chassis in the console the record player worked and I could hear it even without the radio and this morning I connected a portable CD player to the RCA jacks in the chassis and I could hear music from it. I've changed all the electrolytic capacitors and two bumble bee caps and cleaned the pots. The two panel lights work.

Thanks for any help,

John B

John B

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Re: Magnavox Micromatic Model: 2ST647 New Needle - No Sound
« Reply #114 on: May 12, 2018, 12:34:47 PM »
I took out the Base leg of Q17 (transistor, Sam's 841-6) and measured it.  I set the DMM at Diode and at 20KΩ and got different results.  I pasted them here and I need to know if
I have a good transistor?  I'll check all the transistors that I can get to as long as I know what I'm doing.

Q17 PNP   
DMM @ Diode
B-E 3.04, 0.21
B-C 3.04, 0.21
C-E 2.84, 2.64

DMM @ 20KΩ
B-E OL, 5.94
B-C OL, 5.45
C-E OL, 4.04

John B

John B

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Re: Magnavox Micromatic Model: 2ST647 New Needle - No Sound
« Reply #115 on: August 04, 2018, 07:05:38 PM »
I finished the console work.  I changed a couple of transistors and several resistors and most all of the capacitors and a diode.  I cleaned the pots with Deoxit F5 and rubbing alcohol.  It was a lot of hard work and a learn as you go experience.

Thanks for all the help,

John B