Much like this project, I'm an old dog, learning some new tricks. Over the last year, I parted out a couple of derelict consoles, and resurrected both a Magnavox 9300 6BQ5 push-pull tube amplifier and a Magnavox A531 solid state germanium amplifier and turned them into stand-alone (dare I say) "hi-fi" components. They both turned out amazingly well, and are two of my very favorite amps because of the amazingly good, yet different sound signature each of them has. Perhaps it was the lingering intoxication of striking gold in the bellies of Magnavox consoles that my judgement was impaired and I just had to do it . . .
"Oh Holy Geez!" my wife exclaims, "He's bought another one!"
Not a venerable 60's classic with a tube or germanium amp, but a sketchy, dubious, questionable-at-best solid state Magnavox R344 chassis in a very fine plastic and particle board offering from the not so golden year of 1978. And it was nasty- left out in the weather for at least a winter, covered in dirt, missing 3 wheels with steel scraping on the cement floor, top all bubbled and chipped, and at least a dozen wrinkled trucker and cowboy themed 8-tracks rattled around inside. The thrift store employee that helped me load it waved farewell with a suspiciously big grin as I drove off with it. What was I thinking! Probably just wasted another twenty bucks . . .
(A picture of the original console would have appeared here, but I forgot to take one. Doh!)
I was tearing this console down for parts (I was not seeing Hi-Fi gold) when I realized that the radio/amplifier chassis was actually designed to be built into a stand-alone cabinet. After an internet search I found it was used in multiple models mounted either vertically face up, and horizontally. In one model it came with it's own wooden case and the whole thing slid down into a cubby in the console. Suddenly I was inspired by the fond THC marinated memories of high end amplifier designs I had loved in the 70's- with broad deep brown toned wooden sides and top panels surrounding a shiny silver front face. I started thinking this might just make a fun retro project (That is if it didn't have a smoke of it's own when I tested it). I set the chassis up on my bench with some good test speakers, spray cleaned all of the pots and switches, checked everything over visually and gave it a try. Part of the front panel lit up nicely, (I miss that) and it actually worked and sounded pretty good- not excellent, but good. Surprised at the better than expected sound I was again reminded that it was the sketchy speakers and poor sources that were the weak links in these old consoles, and that the amp was usually a pearl in the oyster. Maybe, just maybe if I made some reasonable improvements, this might be a fun little retro receiver to play with. What do I have to lose?
Amazingly, I found the Sams photofact for the R344xx chassis on eBay for only $7.50. I scanned the important parts and added it to the Downloads area. If the link does not work search for "Magnavox R344":
1978 MAGNAVOX R344 Chassis Sams Photofact
The power amplifier portion was all on one modular plug-in card and heatsink, shown below. From my research into the literature, it appears to be about 12W per channel, using push-pull totem-pole TO-220 package NPN transistors on a 45V supply. Typical of a low-medium power amplifier, perfect for a single room or light listening (and about the same output as my Magnavox 9300 tube amp, and the germanium A531 amp). The bias adjustment trimmers were large black units next to the ceramic emitter resistors. The original output capacitors were an anemic 1000uF at 25V, I assume primarily limited by space on this small board. I upgraded to the dark blue 4700uF at 35V, and I can now hear a much better bass response at the lowest frequencies, with more punch, especially into my 4 Ohm speakers. You have to be careful going too big here too- This design does not have output relays, so I do get a bigger whump in the speakers when I power it on and off now. I considered putting some smaller value poly caps parallel the output electrolytics for higher frequencies, but I doubt my ears would hear any difference. I did reinforce some very long thin traces for a speaker output, supply, and ground on the amp board, and it made a placebo improvement in my mind at least.
After the output cap upgrades, I pulled every electrolytic capacitor one by one and checked it. I was at first inclined to change them all, but honestly it was not worth the expense to buy all new, and my junk stash had many older capacitors that weren't necessarily guaranteed to live any longer than those already there. These original caps were all Nichicon, so I only replaced the ones that were actually going bad. My LCR meter does not measure ESR, but it does measure capacity and leakage current. I found no cap had leaked or bulged, and all were within spec and had very low electrical leakage (Go Nichicon!) In the end I found only one bad cap, the only green one right next to the hot power resistor as you would expect. It had been replaced before some time in the past, with little wonder.
This design powers everything from one single-ended winding 45V supply, with a string of hot dropping resistors to generate a slightly lower bias supply, the 22V for the radio, and several others. Cheap and simple if you don't mind the heat, effective until it's not. Dial lamps come from a separate 6V winding. The primary filter capacitor was originally a tall aluminum can of 2000uF. It was still good, but I replaced that with the modern 4700uF of higher voltage that you see there in dark blue. I could have used a much larger value, but with diminishing returns- Even with the 2000uF there was no audible hum at maximum volume with this unregulated supply, and I really did not want to overtax the small poorly ventilated transformer with increased RMS heating from higher rectifier current peaks for little return. 4700uF should give additional dynamic response to the bass with little downside, so was a good balance.
Lots of other little upgrades were necessary- The boards had many thin and broken solder joints from thermal expansion- particularly near hot resistors, places where shields or metal frame was soldered to the ground, and around the board to board connectors. I wire bridged across the two connectors to the radio board rather than remove them, and opted to just clean the connector to the vertical amp board so I can continue to remove it for servicing. I removed the source input and speaker output plug-in connectors and soldered leads directly to the board. I replaced a dozen or so ceramic capacitors that were in the audio path through the volume and tone controls with poly type capacitors. The larger brown ones matched the wider lead spacing and are visible on top, and smaller flat green chiclets are connected pad to pad laying flat on the bottom as their lead spacing was much smaller. This too made a good improvement in the sound quality- better low bass from some increased values in signal coupling, and less distortion from the improved linearity of poly over ceramic in all of the filtering roles. I removed the simplified RIAA filter used for the ceramic cartridge phono input and converted it to be a third "aux" input. I had quite a chuckle when I discovered that the headphone jack was wired L-R backwards. (I doubt anybody noticed.)
The sound is now much more transparent and clean, and at least on par in quality with many of the "value" integrated amplifiers I have listened to in my life. The adjustment range of the tone controls is way too large for my taste (from super boomy to thin and flimsy), but when centered are reasonably flat. The loudness control is far too heavy- definitely cakes on the thick and boomy chocolate- I will probably never use it, but I do respect that it was part of the Magnavox console signature. The AM and FM radio come in strong and clear with a nice red stereo LED. Interesting having separate selector options for FM and FM-Stereo, but if the signal is weak that will be useful. I now have three inputs, Aux, Tape, and Phono. With all of the dial lamps replaced the whole dial has a nice blue glow and even a lit up signal strength tuning meter.
I built the cabinet from scraps I had around my garage. 3/8" plywood for the bottom with ventilation holes under key hot areas. The oak sides were cut from an old cabinet door from the local Habitat for Humanity- best $3 ever. The Mahogany top panel, perforated waffle-board back and brown screws came from a 1961 console- back when they used hardwood veneer on the sliding top panels. The big and only expense after the photofact was the set of Chinese RCA input and speaker binding posts, and machine screws from Walmart. The stain on the oak sides is Dark Walnut Watco Danish Oil - I love that stuff- nothing like a silky smooth rubbed oil finish on hardwood. Slather it on a couple of times to soak in, wipe off the excess, and it air dries hard inside the wood. Ever get a stain or scratch, lightly sand the area, re-coat with the Watco, and bam! like new- never shows. It definitely gives the oak that 70's dark brown look I was trying for. It badly needs labels on the back for all of the inputs and outputs. If anybody could suggest a reasonably easy way to do that I'm all ears.
Anyway, give it a looksie. It sounds great, it has a beautiful lit-up blue display, and a warm funk-a-lishous chocolate velvet vibe (Ron Burgundy approved! ) It's a lot of fun for a component receiver I have less than $50 invested in, and a great piece of Magnificent Magnavox history. What it lacks in pedigree or quality, it sure makes up for in soul. I have to say it again- It is fun! Really takes me back. I can see this taking an honored place in my den, driving mellow tunes through some large, equally vintage 3-way speakers. Maybe I'll don a smoking jacket, and sip some fine brandy . . .
1978 Magnavox Console R344 Chassis Goes Stand-Alone
- Hi-Fi-Mogul
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Re: 1978 Magnavox Console R344 Chassis Goes Stand-Alone
Wow !
Thanks for sharing such an amazing resurrection.
The new "component" is really beautiful.
Thanks for sharing such an amazing resurrection.
The new "component" is really beautiful.
Hi-Fi-Mogul
- William
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Re: 1978 Magnavox Console R344 Chassis Goes Stand-Alone
Wow is right, Warren, nice job. It looks like brand new and from what you stated it sounds better than new.
Bill
Bill
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Re: 1978 Magnavox Console R344 Chassis Goes Stand-Alone
Thank you for taking the time to describe your project, and for including the finished-product photos. I'm still a neophyte in transistor-land and always learn things from pieces like yours.
Chris Campbell
Chris Campbell
Re: 1978 Magnavox Console R344 Chassis Goes Stand-Alone
Thank you, I really appreciate it.
As I have mentioned elsewhere- I have another in-depth article I am working up on the Magnavox A531 germanium AB power amp chassis I bought on ebay. It will include cosmetic and electrical restoration, circuit walk-through, germanium output transistor matching, and tuning/measurement results. Since I don't see a lot of technical posts about germanium amplifier designs, how they work, and how to work on them, I thought it would be good to contribute what I have learned so that others can follow in my path if they want to explore this very interesting area. I have learned a lot about germanium, and about amplifiers in general, and while I am not an expert, I think I can lay bread crumbs that other hobbyists can follow on what has been a most enjoyable journey. I love how germanium sounds, as much as how tubes sound, and if others can use this information to either restore their historic consoles, or save and resurrect these otherwise landfill-bound amplifiers I know they will enjoy it too.
As I have mentioned elsewhere- I have another in-depth article I am working up on the Magnavox A531 germanium AB power amp chassis I bought on ebay. It will include cosmetic and electrical restoration, circuit walk-through, germanium output transistor matching, and tuning/measurement results. Since I don't see a lot of technical posts about germanium amplifier designs, how they work, and how to work on them, I thought it would be good to contribute what I have learned so that others can follow in my path if they want to explore this very interesting area. I have learned a lot about germanium, and about amplifiers in general, and while I am not an expert, I think I can lay bread crumbs that other hobbyists can follow on what has been a most enjoyable journey. I love how germanium sounds, as much as how tubes sound, and if others can use this information to either restore their historic consoles, or save and resurrect these otherwise landfill-bound amplifiers I know they will enjoy it too.
- hermitcrab
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Re: 1978 Magnavox Console R344 Chassis Goes Stand-Alone
Wow , nice restoration ... SS Magnavox circuit boards are built to give you room to actually get in and replace components... I wish the Japanese stuff was the same , currently working on a Sony TC-366 R2R all the caps are junk , and the whole record /playback board is the size of 2 sticks of butter side by side and the parts are jammed in crammed together ... Japanese workers must have small hands 

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