I landed my next Magnavox console, a newer 1963 unit. One of the last tube architecture models and a stereo console. It has 6 speakers, including 2 12 inchers. I am starting to sift the components out of the dirt inside.
Sounds very cool! We'd love to see a pic or two.....
It'll be a few days, I have it in the garage and can't get a proper picture just yet.
I have come to the last chassis in the console to perform a replacement of the capacitors in. Two of the capacitors have ruptured and of all places, in the stereo demodulator. This is what can happen when one must play a 54 year old tube architecture console. It must've went from a bothersome hum to a loud 60Hz buzz. They were in exactly the values I don't have, and owing to the nature of the circuit, I want a replacement of the same value. This will be the 3rd set of capacitors I've had to get for it.
Are these electrolytic capacitors? Are they rated for a high enough voltage for the application? Were they connected with the correct polarity?
Larry
These were OEM capacitors. One was an electrolytic, the other was what appeared to be a paper wound. Each were correct according to the parts list. It was just what sometimes happens when the unit is operated with aged capacitors. Before I could advise them not to, they turned it on to show me the horrible noise it made. That was probably those failed components doing their thing. Soon as I get the last two replaced, it will have current, safer capacitors and the quiet parts will be quiet and the music will be loud.
I know it's been a while, The weather hasn't been cooperating, either. I've been able to do some more cleaning and finishing on the cabinet and I have each component recapped. I will now have to install and reconnect the components and when I disassembled the unit I took detailed close ops of everything as it was. Now, in going to review the pics, I find the SD card has failed. So I am awaiting the assistance of a very knowledgeable person to help me with integrating the added FM demultiplexer assembly into the system. The unit also had some bad staining on the top sliding covers, and I have been working on those to get them at least looking like they haven't been saturated in adult beverages. At least none infiltrated the unit in any critical areas.
I have put the unit back together as best I could and I can't get audio. Not a scratch, click nor pop. I am getting meter deflection on the receiver, so I know it is receiving. The amp is getting at least the filament voltage, as is each of the other assemblies. I have completed the check back of the work I have done to insure it is correct to schematic. I also found the heavily obscured the teeny tiny tag that confirms it's model number. There is a bit of complexity as there is a harness of interconnects for the power circuits as opposed to the signal circuits, the former being conveyed by molex connectors and the latter by RCA plug cables. I can't find a schematic of the receiver to match my unit. It's always something, as Rosanne Rosanadanna used to say.
I am sure a schematic is out there somewhere. Maybe try to find a forum on these things and ask there.
I'll get it straightened out one way or the other.
I went back through the unit, toned out the speakers, put an Mp3 player on the amplifier inputs to test through to the speakers and eliminated all but the receiver assembly. I finally found it was the dual audio amplifier output tube. The filament opened up. I ordered a new one from a seller in Valparaiso IN and I have found the post office is taking it on a traveling holiday along the roads of north Georgia. Just what a tube with a double long filament needs. I am also getting space for the console in the living room, on Saturday. Maybe I will have a functioning tube in hand by then.
Well, the filament hadn't opened up. I found that my tube tester would not work with 6EU7 tubes. So I had to wait on another tube tester that is working quite well. The problem still remains with the tuner/ receiver. It will not even pass audio to it's output to the amplifier. The amp also sets up the B+ voltages, that are trunked through the system between assemblies. I want to make sure those potentials are correct before tracing through the tuner.
Did a quick search on it and found a forum with lots of info. Audiokarma.org
Thanks, I'm a member.
OK, that makes sense!
Another good forum is vintagehifi.net . They have a lot of reference material as well.
Well, I finally got it up and running. An excrescence sitting in the middle of my living room. I've set it up with the music library and it is shaking the walls and rattling the windows.
I meant to say it was an excrescence before it was up and running.
Over a period of operation, the FM receiver has gone off frequency. Way off frequency. It is missing 1/3 of it's bandspread. I had bought another receiver a few weeks ago, so I set it up to use in this console. It's closer to being on frequency and has the entire bandspread. I gave the unit a application of orange oil. It is looking better.
I got the original receiver out, and set it up to connect into the system while having it fully accessible on a panavise base on a small stand. I can get some movement on the received stations but I am going to have to get an indicator of my alignment of it. It looks like a digital oscilloscope interface for a PC/Laptop would come cheaper than a VTVM. I prefer a scope anyway. I have a conventional scope, but it is only 10 Mhz, below the FM IF for this unit. The alignment relies on both symmetry as well as amplitude as the indicator of correct alignment.
I've ordered a 20 Mhz digital scope interface and some ceramic caps and some metal film resistors. I should have something going on soon.
these old sets are expensive to restore and near impossible to find a needle for the turntable. My cousin has an old 1950's stereo and the tuner in in the shop....at $70.00/Hr for labor, you'd better really want these units to work....
That's where doing your own repair work makes things much more affordable. There are a number of businesses that carry needles, drive parts and other bits for phonographs. There are a few places still manufacturing the vacuum tubes (valves) for these units as well. This console will play recorded music very well, it's just the FM receiver that is having some problems.
I had ordered a set of ceramic alignment screwdrivers to use when the oscilloscope finally gets here. The metal film resistors came from China and spent over a week in customs in Frisco. The ceramic capacitors came from Amazon and was here in 2 days.
Got the oscilloscope and couldn't get any useful function out of it, so had to lug out the CRT oscilloscope and set up to align the unit. The original receiver wouldn't correct from the strange condition that it had. the spare that i ordered was able to center up for much of the bandspread with the last 10-15 Mhz off scale. The unit does sound quite nice. I can strongly recommend a set of ceramic alignment tools for RF alignment work, as they performed quite well here. I have a return request initiated on the new oscilloscope.
The receiver has been tweaked and peaked up for a while now. It appears the next problem with it is my being in a non line of sight area out of town. I have ordered a amplifies AM/FM antenna for it. My vehicles' radios seem to work well in the driveway, so I should be able to get a decent signal at home. The console just has a time with the afc hunting and MPX locking.