Re: 1973 Magnavox. One dead channel.
Found them on Mouser....
JunkForLess
Member
Last Activity: 12-08-2021, 07:54 PM
Joined: 11-01-2021
Location: Midwest
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Re: 1973 Magnavox. One dead channel.
Thanks a lot for all your help. Learned a bunch. I'll be making a demo video of the console soon.
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Re: 1973 Magnavox. One dead channel.
Well well well.. got her running perfect now. See attached.
[ATTACH]248975[/ATTACH]...Leave a comment:
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Re: 1973 Magnavox. One dead channel.
So, it was working PERFECT... then I removed it from the cabinet to clean up a few things and noticed the right channel was a bit odd again.
This is starting to come together like a CSI episode...
I believe there might be a bad solder joint between the back panel board and the main board. The speaker output passes through that board first, along with a bunch of BS, then comes back down. If you lightly press on that board the channel comes back. The volume knob is located on the edge of the main board and that rear...Leave a comment:
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Re: 1973 Magnavox. One dead channel.
The parts show up tomorrow
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Re: 1973 Magnavox. One dead channel.
Great news:
With PC3 removed, the factory pot works. It's still only a single channel, but that confirmed that PC3 does something that I might not even care about.
Using jumper wires, I connected the factory pot in like a standard three lug pot (works like a 100k pot) No extra taps. It works as it should and I moved it between the two channels.
When I posted the other night saying it didn't work, I had it wired it the same way except I was using a cheap pot I had laying around. Something that most...Leave a comment:
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Re: 1973 Magnavox. One dead channel.
Best I can tell, the bass section of the diagram is correct, but it's placed in the wrong order. The correct order is Timbre, Treble, Bass, Loudness. So I don't feel as crazy now.Leave a comment:
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Re: 1973 Magnavox. One dead channel.
It only has what is outlined in both. So, 7 total pins, 1,2,3,4 for the left channel 4,5,6,7 for the right channel, pin 4 is a shared ground pin.
Either way, it was easy to remove so I left it out for now. I hooked up the 100K pot up and it doesn't work. Tried it on left and right. To make it even harder, it seems the diagram doesn't match the board 100%. My best bet might be to draw out the physical board and confirm I am not blind.Leave a comment:
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Re: 1973 Magnavox. One dead channel.
Got it, I have a few cheap ones laying around, I'll try a few values first.
I freaked out a bit when I saw how crazy the stock pot was, I thought I was stuck after all this work. The old non-tube stereo consoles aren't worth much of anything, but I wanted to get it working. I need to practice on this cheap stuff first.
Think I should remove PC3? I wonder if it will do anything odd left floating....Last edited by JunkForLess; 11-11-2021, 02:30 PM.Leave a comment:
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Re: 1973 Magnavox. One dead channel.
100% correct, I just want to play some Christmas records and maybe some Dean Martin
. It will most likely live most of it's life at mid-low volume, I don't mind adjusting the knobs to get the sound right.
What factors do I need to look out for with pot sizes? For example, if the pot doesn't have a high enough range would that mean I wouldn't be able to mute it? The face of the radio doesn't have any sort of volume scale printed on it, so I don't mind if "max" comes before a full turn. EDIT: I am a...Last edited by JunkForLess; 11-11-2021, 12:30 PM.Leave a comment:
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Re: 1973 Magnavox. One dead channel.
Left channel is just as strong as before. Right is very strong when the loudness pot isn't causing it to kick out
Can I skip the stuff tied in at 150,151 and 152,153 and just tie in a audio pot? The pot also bolts onto the front, so I could put another pot in there and rotate it so the pins face up, then wire it to the PCB however I wish.
For example:
PC3b pin 1 > pot > point 93
PC3a pin 7 > pot > point 112
What does all the stuff in PC3b and PC3a seem to do?Last edited by JunkForLess; 11-11-2021, 10:52 AM.Leave a comment:
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Re: 1973 Magnavox. One dead channel.
I need to step away for the night.
Even after cleaning the volume pot I still need to screw around with the volume knob to keep the right channel working. Sometimes you have to press it a bit to one side, or pull up a bit.. I don't believe there is anything I could replace it with since it has all the extra taps?
When working, everything sounds great. The thing can get pretty dang loud, so I would be up for ideas on how to replace it even if I have to give up the top half of the volume range.
...Leave a comment:
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Re: 1973 Magnavox. One dead channel.
Well... it kind of worked. I noticed the right channel was kind of there now, not 100% dead like before. I pushed down on the volume knob a bit and the right channel came around loud. A month ago, before I took this thing apart, I sprayed all the pots with D5. I know for SURE this wasn't the case before, but I don't think I would have been able to tell since the right channel was 100% dead. Its kind of like a double stacked pot. The pot nearest the knob is the right channel, I was brave enough to take that half apart and found...Leave a comment:
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Re: 1973 Magnavox. One dead channel.
The new transistors test correctly.
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Re: 1973 Magnavox. One dead channel.
I have been told this is a 50 watt model. So I would think that means 25/25?Leave a comment:
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Re: 1973 Magnavox. One dead channel.
I figured that will allow me to adjust it to stock, then see what it sounds like going up or down a bit....Leave a comment:
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Re: 1973 Magnavox. One dead channel.
I ordered some Nichicon UDBs. Set of 2x 6.8s and 2x 3.3s and 2x 4.7 I'll try both ways a try. "Designed specifically for crossover networks in Hi-Fi sound systems." Good enough for my neighborhood.....Leave a comment:
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Re: 1973 Magnavox. One dead channel.
I don't mind if its the exact shape or whatever, I just wasn't sure what I can use as a replacement. For example, the current cap for the crossover is a rather large electrolytic, but could I use a gum drop capacitor of the same value, or a film? I also read that since its 10%, I could use something like a 6.x mfd instead of a 8?...Leave a comment:
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Re: 1973 Magnavox. One dead channel.
I wasn't sure if the G at the end meant anything, the specs are spot on tho..
I got the NTEs for the same price, that's why I was happy to find them in sets.. but I should have known better...
So, I also need the caps for the speaker crossovers, it has a 8mfd 25v. By the look of it, it seems to be a non-polarized with the leads out either end, but it doesn't seem to be a common value.. parts sites always point me to the really little Radial Polyesters.....Leave a comment:
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Re: 1973 Magnavox. One dead channel.
On Mouser is a MJ2955G and 2N3055G made by onsemi. Yay/Nay?Leave a comment:
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