DIY Hi-Fi: Vintage Receiver Repair and Modification

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Introduction: DIY Hi-Fi: Vintage Receiver Repair and Modification

About: Why fix it if it ain't broken? Because it's fun.

The amplifier in an audio system serves as the central command unit in a way, as it takes the audio from the source, amplifies it, and sends it to the speakers. A receiver, or integrated amplifier, is even more involved in its role, as it has source selectors, speaker selectors, equalizers, and often a radio receiver, as well as other functions. For ultimate simplicity, and cost effectiveness, an integrated amp of receiver is recommended over obtaining and using the individual components. When it comes to receiver choice, there's two main categories: new and vintage. Vintage is generally preferable, as long as you don't need satellite radio, an iPod dock, wireless streaming or other superfluous features. Vintage receivers are better than modern receivers with the same features for a few reasons:
Build quality: vintage receivers are solidly built. They use high quality materials (often all metal) and wood too.
Sound quality: vintage receivers often have very low harmonic distortion that often rivals modern receivers. Beyond that, the sound is often thought of as being more lifelike, dynamic, or full by some.
Repairability: a vintage receiver will last a lifetime. Literally. They require maintenance, but so do modern receivers. But often, modern receivers are unrepairable with surface mount components and other construction methods. Vintage receivers were usually built with the intention of being repaired when they break. Not thrown out.
Value: A high end, restored vintage receiver will run you between 100 an 350 dollars usually. A modern receiver with that level of sound quality is near impossible to find at that price. But a vintage receiver in need of repair will run you about 30 bucks, and can be brought back to better-than-factory condition for about 50 to 70 dollars, plus a couple hours of your time.
This Instructable serves as a basic guide to selecting of a vintage receiver and general repairs that need to be done to bring it back on line. A word to the wise: this Instructable, as I said, is a general guide. There may be questions or issues that you stumble upon specific to your receiver. RESEARCH RESEARCH RESEARCH. audiokarma.org and diyaudio.com are both great resources, but a simple google search can turn up much information. Also, try finding a repair manual on Google. If you find a free download, or even one for a couple bucks, it might just save your project from the scrap heap. 

Step 1: Find a Receiver

When it comes to selecting a vintage receiver, there are a few considerations to make. The first is the age. The golden age of receiver quality is often thought of as being from 1970 to 1985 (ish). The second major consideration is brand. Some good brands to be on the lookout for include: McIntosh, Sansui, Pioneer, Sherwood, Marantz, Kenwood, Onkyo, and Yamaha. There are other great brands out there so do your research. A third consideration is condition. If there is a bad transformer in the power supply, walk away. Bad caps and scratchy controls, however, are not a major problem and are easy to repair. Blown bulbs are also expected, and should not lend much to the decision. Also, burned out components can sometimes be an issue. Burned resistors are no biggy, but burned transistors can be a complete roadblock, with certain transistors no longer being available and equivalents being hard to determine. When it comes to where to find a receiver, there are many options. eBay is probably the most obvious choice, thought for a good value take a look at local thrift shops and antique shops. Many have old audio equipment kicking around. Since they often don't deal with vintage audio equipment, it can be purchased at a good price.
Here, I'm going to use the rebuilding of my Sherwood S-8900 as an example. This receiver was op of the line in 1974, with a list price of $399 dollars. About $1800 today. It's well built and easy to work on. I picked it up in working condition for 30 dollars from a local antique store.

Step 2: Diagnose Potential Issues

There are a few issues that almost any old receiver will have, even if they had been well taken care of by the previous owner. These issues stem from the limited lifespan of certain components. Three main issues are:
Old capacitors: electrolytic and paper capacitors degrade with age. Paper capacitors tend to change their values, while electrolytics break down chemically and essentially turn into a resistor. When power is put through them, they heat up, boil the liquids inside, and go boom. For this reason NEVER PLUG IN AN OLD RECEIVER RIGHT AWAY. Capacitors have a shelf life of anywhere from 10 to 30 years, but a usable life of 1000 to 5000 hours, depending on application and quality. For those reasons it can be assumed a receiver from the 1970s has bad capacitors.
Scratchy controls: the potentiometers that control volume, balance, and EQ need maintenance to function properly that almost was certainly never done. Dirt collects inside of the pots and wipers and traces (depending on material) corrode. Also, the lubricant inside the pot can gunk up with use and needs to be cleaned out and reapplied. If a bad pot is turned, the audio from the speaker often crackles and pops, or even cuts out. While the effect of a bad pot is dramatic, often a cleaning is all it needs and that is easy enough.
Blown bulbs: most receivers that fall into the vintage category preceded widespread use of LEDs. For this reason, small incandescent bulbs were the source of illumination. Being incandescent, they burn out over time. Thankfully, replacement is easy if you can find a bulb, but if you can't an LED conversion is possible.

Step 3: Capacitor Replacement

The most overlooked issue by newcomers to vintage audio is the capacitors. But a bad capacitor has the potential to fail catastrophically, as a quick search of YouTube will demonstrate. But with vintage receivers, they were built to be repaired and used indefinitely, so capacitor replacement is easy enough. First step is to open your receiver and have a look around. Marvel at the vintage construction techniques, and then start numbering the capacitors. Make a list of all the capacitors, with their numbers and values, because it will make ordering replacements easier. While you are in the receiver, also mark capacitor polarity directly on the circuit board. Also, take note of the capacitor markings and can design. Many of the larger value capacitors, often labeled "computer grade" are two capacitors in one, where the two leads on the cap are in fact both positive and the can a common ground. Both caps are usually the same value, though this is not always the case. The values of each cap are listed separately with a D or a triangle between them.
As to where to order your capacitors, there is one only one place I can recommend, due to their selection, service, and prices, and that is Parts Connexion. They also have many other replacement audio components, but they keep a large stock of many audio grade capacitors that are hard to find anywhere else. And as to what kind of capacitor to order...thats an area of personal preference and hot debate. The sky's the limit with capacitor prices, and many people don't want to buy the most expensive capacitors. Some recommended brand for their sound quality and price are:
Elna Silmic II: said to have very clear, smooth mids and highs, and strong bass. Some feel the bass can be unrealistic however. This is my preferred capacitor.
Nichicon Muze Kz: said to be relatively neutral in tone, and having great clarity. Some say the highs can be harsh.
Some other brands to look into include Mundorf and Sanyo Oscon. When it comes to selecting replacements, make sure the voltage rating of the new cap is higher than the old, as well as capacitance value. But that being said, if the old cap is 250uf, the new one can be 220uf. Power caps can be upgraded to larger values, but not by too much, as it can over stress the power supply. For my receiver, there are 25 electrolytic capacitors. The 3300 uf main power cap was changed to a 4700 uf, as were the 4000uf output caps. Here I used Nichicon Gold Tune, since they are priced well and come in the required values and voltages. Some of the other power supply capacitors that were 500uf were changed to 470uf to balance out the increase of the main capacitor. These, as well as all the smaller value caps, were almost all Elnas. My bill from Parts Connexion for all 25 capacitors plus shipping was about $60.00

Step 4: Fix Scratchy Controls

Scratchy controls go hand in hand with old equipment. The contacts in switches and buttons need to be cleaned, but the biggest issues lie in the potentiometers. The metal wipers tend to corrode, and the carbon contacts become scratched and dirty. Thankfully, potentiometers and switches are easy enough to clean. To clean a potentiometer can be done two ways. One is the more drastic method of opening it up and using a pencil eraser to clean the carbon contacts, remove corrosion from the wiper, lubricate and reassemble. This is risky, so the way I would recommend to start with us a chemical cleaning. It's a multiple step process but with positive results:
Dust removal: use an air duster to spray the dust out from in the pot. Put the straw in the space by the leads and give a couple sprays. Deoxidation: use a chemical cleaner to remove any tough dirt and oxidation. For this I recommend Caig Deoxit, which is available with Caig Deoxit Gold at RadioShack. Caig products are also available at Parts Connexion. There are many types, but I recommend the airosol spray type, since it more effective at reaching into the pot.
Lubrication: this is a necessary step to preserve the life of the pot. For this step Caig FaderLube is probably the best, though I have used WD40 with success. Many hate the idea of using WD40, but if the pots on the receiver were as bad as mine the WD40 also helps break up the tougher corrosion that the Caig products did not. The lubricating properties also preserve the pot and prevent further corrosion.
When cleaning the potentiometers, they can be left in the receiver if you are able to still stick the straw of the spray in the space by the leads. Just try not to make a massive mess, and keep the pot surrounded by paper towels so the spray does not end up coating the inside of the receiver or circuit boards. 

Step 5: Replace Bulbs

It can be guaranteed that your receiver has blown bulbs. But do not despair; it's an easy fix. The most obvious route is to replace the bulbs with new ones. This is certainly possible, though it can require a bit of legwork finding replacements. A good place to start is dgwojo.com. If that does not appeal to you, or you want to to change the color of the lights on your receiver, an LED replacement is possible.
The LEDs should usually be wired in series with a resistor, since the voltage supplied to them by the receiver can be around 12 volts. You can also figure 3 ultrabright LEDs to replace one bulb and ensure they are equal or greater brightness. However, when it comes to figuring out the number of LEDs and resistor, it's up to the stats of your receiver, making it hard to provide specific instructions. Often, by googling the type of bulb used in the receiver, the specs of the bulb allow you to determine the voltage that will be suppled to the LEDs. You can also just measure the voltage being supplied to the socket with the receiver switched on.
When replacing the bulbs with LEDs, also try to preserve the connections for the bulbs so if you ever want to go back to bulbs it is possible without too much extra work.
For my receiver, the bulbs were GE53, which is a 14v bulb. I smashed the glass of the bulb and soldered the series resistors and LEDs to the filament support wires in the bulb. The space in the bulb was then filled with hot glue. This allowed the LEDs to be inserted into the stock bulb sockets. Blue LEDs were used to light up the glass, green for the FM signal dial, and red for the stereo light. Since my bulbs are bayonet base, it's important to make sure that the LEDs face the right way when the bulbs are rotated and locked into position. The LEDs are powered of AC, which the LEDs I used can be powered off of safely. Some LEDs have poor reverse polarity strength, but the LEDs I used are the high dispersion type from Christmas lights, which also handle reverse polarity well. Some receivers, however, for things like stereo lights used DC electricity, so heed the polarity. My stereo light operates on DC, so the LED had to be soldered on with the polarity correct.

Step 6: Finishing Touches and Use

While you have the Deoxit out, it is a good idea to use it to clean some of the input/output jacks on the back of the receiver. Cotton balls and swabs are good for this. After an initial cleaning with Deoxit, apply Deoxit Gold to preserve the metal and prevent more corrosion. Cleaning the case of the receiver should also be done. A mild soap and water solution can be used on tough dirt on wood and metal surfaces; just make sure it isn't dripping into the circuit or controls. Windex is also an old standby. Sometimes plastics for knobs and switches can become discolored. These can be cleaned, thought I'm not going to recommend it due to the chemicals and effort.
Now it's time to use it! It's a good idea to power the receiver on with the case apart, and leave it one for a couple minutes. This is just incase you installed a cap backward, and it bursts, you don't have to tear it apart to replace that cap (it's happened to the best of us). Also, many feel that caps have a break/burn in period, others do not. The Silmics have incredibly strong bass immediately after installation, and it is my experience that this does recede with time; so don't judge the sound immediately. Break in can take up to 40 hours of listening time. 
My results were exceptionally positive. Over my old 1990's Pioneer receiver, the sound is much more full, with bass that is cleaner and more controlled. Highs don't screech, but they aren't mellowed out too much either. The mids are very clear, but don't shout on complex music like the Pioneer did.  Plus, the silver front and glowing blue tuning dial look retro but not outdated. For 90 bucks, it can't be beat!

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    67 Discussions

    0
    user
    phredd

    Question 7 days ago

    Hi, I have an old Yamaha CR-620 receiver bought new in 1977. Recently, I often do not get any sound when I turn the power on. The lights and gauges work but but I do not hear the surge protector click off when this occurs. If I leave the power on, the sound will sometimes come on later by itself. Can you give me an idea of what the problem might be and how I might remedy it? Thanks.

    Hello , I just found your site and I'm hoping you may be able to help . I just purchased an "excellent" working Monarch STA-100X Push-Pull receiver (1960-65) off of C/L ,,, it isn't . According to what I have found it is an entry level tube reciever . I hooked up the unit and let it warm up for several minutes while I tinkered about . Then ,, I selected PHONO , (it has an MPX board , (is that a phono pre-amp out ?) , the sound is VERY faint in STEREO mode , I switch over to MONO and there is sound albeit not a lot , the FM /AM section are the same . All of the tubes are lit and glowing from what I can see , also no evident burning of resistors and Cap's . Is this unit worth repairing ? I paid $80.00 and it is actually in VGC cosmetically , and it is also my first Tube unit . If it is a viable candidate I'd like to increase its output . It is currently 8-10wpc. The output transformers are Hammond 125D (push-pull by their p/n ) . I hope you can help me on this one . I do have a list of all tubes , the output tubes are 7189's . Thanks for your time , Dusty Dawg

    I am replacing a bad power cord on a JVC receiver rx-554v the factory cord is split 2 (ul)E ll9098 105degree .May I use a split 2 105 degree (ul) c e322507 cord

    Pioneer VSX-4900S ..looking for troubleshooting guide for the '90's receiver. Unit worked when stored 20 years ago, now no sound.

    Hi. I have a Sansui 6060 that has some distortion on the right channel. Also in between songs you can hear a put put sound from the right channel too. Can you offer any help on this ? Thank You !!

    hello, I have a vintage pioneer amp sa608. When starting it up it makes a buzzing noise. After a minute thats gone and the amp plays great. What could be the problem?

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    2 replies

    Replace the speaker relay, and this problem should go away, if you still have the receiver, two years later LOL.

    does it still have the stock capacitors? If so all the electrolytics have to be replaced. start with the big main power caps then the smaller ones

    I just received a quote of 900.00 to restore my Pioneer SX 5580. There has to be somebody out there that can fix this for MUCH less than that. I think because it is so rare they are trying to make money off me. I just want it fixed. Lights up, heats up but no sound. Any leads as to somebody that can fix it? Thanks so much.

    Hi, thanks for a good and thorough, how-to article on amp repair. I have an old Mark Levinson No. 336 amp that has no sound coming from one channel. I swapped in a functioning amp and both channels work, so I assume the ML amp does have a compromised channel. I got an estimate that was very costly to repair it (not including price of new caps). I was also told it is rare for a ML amp to lose a channel. I am curious if a simple fuse may be the culprit or worse, something dire.

    I'd like to keep the amp as it sounds amazing. I contacted Cornell Dubilier to see if a custom set of caps could be made - but no word back. C-D caps are supposed to be well made and better sounding. Phillips and Chemicon caps were original. Where do I go from here? Thanks.

    I recently bought a vintage receiver/amplifier from Goodwill and I tested out the receiver to try and give it a diagnosis, and luckily, according to this article, I came to the conclusion that it may be in need of minor repair. The first thing I tried was to plug it into was a turntable (turned all the way down). But the turntable isn't fancy, it doesn't have too many controls... I got back really crackly and distorted sound... when I plug speakers in, it sounds like the sound has been heavily bitcrushed, or worse. (video demonstration here https://goo.gl/w6dTu5)

    The indicator lights also don't seem to be fully functional. This suggested that it'd be a good idea to clean the pots... but inexperienced me is trying to figure out where those are. I'm assuming they're the volume controls, but I wouldn't know how to go about properly cleaning them despite the article providing such good information.

    Any help you could provide would be super helpful!

    IMG_20170819_164440842.jpgIMG_20170819_164450482.jpgIMG_20170823_181421732.jpgIMG_20170823_181431570.jpg

    Any advice for an NAD T 762? One of the channels is completely dead, even though the others, and the unit overall, work fine!!

    Hi can you help? I have a JVC RX111 whose GND button broke off leaving a stub in the machine. I can´t screw it out with pliers. Is there some way to fix this? Thanks

    Have an old Realistic that works great. Has to be dated pre-1993. Only trouble is that recently the on/off button won't let me turn the unit off. It stays on all the time when I push the button. Was wondering if it might just be dirty?

    Don't want to take it apart and mess it up.

    0
    user
    mlm101

    1 year ago

    Hi -Great article! I have about half dozen wonderful pieces that I got over the years including my first integrated amp when i was in 6th grade, a Kenwood KA 5700. "A vintage receiver in need of repair will run you about 30 bucks, and can be brought back to better-than-factory condition for about 50 to 70 dollars, plus a couple hours of your time." That's nice to hear. A local shop has a minimum price of 185 for repair! I have another KA 5500 that runs a pair of GNPs (mid & tweeter) on "A", and then the matching 2x8 GNP subwoofer on "B"....Clicked to "A" the speakers sound fine (although not much bass), when I click "B" I hear the mid & lower frequencies, somewhat odd sounding, coming from the sub. When I click A & B, it's sounds terrible, no high frequencies, just a bunch of mid and low mid. I'm not an electronics expert, but I'm pretty technical. Is this an easy fix? Thanks for your time!

    1 reply

    I have a pair of GNP Valkyrie (trianglar tops) with bass modules, Model 20 (square top) with bass modules, and Model 10 (bookshelf) speakers. The 'bass modules' consist of 2 6.5" drivers in one acoustic suspension cabinet. That cabinet has a set of speaker input jacks, which are the lowest on the rear cabinet. Above those are another set of speaker jack-these are output only. You run speaker wire from the amp/receiver to the bass module bottom speaker jacks. Then run another pair of speaker wire (18" or so) from the top set of output speaker jacks to the mid/tweeter cabinet input speaker jacks. The bass modules have an internal relay or crossover for the upper speakers. Using them as separates doesn't work as you found out.

    If your using a real Subwoofer versus the bass modules then that's different.

    Note: I'm using a subwoofer with input/output jacks that go to the GNP speakers input on the bass modules. Even though GNP loudspeakers can go very deep, 8-12" woofers can do magic that dual 6.5" woofers can't, hence the additional sub that lets the GNP do their own magic.

    Hope this helps.

    I am hoping you could help me or direct me.

    I just bought a Marconi 1003 record player in a case, after inspection it has a stamp underneath that reads Audio Tool and Engineering 950a.

    Do you think the name is different because parts have been changed?
    when I turn it on to play a record I have to initiate the spin with my hand. There is a loud hum coming from what might be the motor, the box on the right.
    Lastly, I get needle sound from the needle on the record, but nothing from the speakers. the tube lights up, maybe an amplifier problem? I did a visual check of the wire and soders and they seem to be okay.
    Thoughts?

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    Very helpful. Thank you for taking the time to create this instructable!

    Hello, I also need help with my stereo receiver. I have a MCS Series 3236. I hear sound from the right channel only. The watt meter for the speakers, only indicates signal from the right side.

    I was using MCS speakers and I have changed those out with other known to be good speakers ( tested on my friends JVC stereo system) Still no sound from the left side. Out of curiosity, I plugged my stereo head phones into the head phone jack of the 3236, and the head phones mimic the speaker problem.

    Out of curiosity, I attached a stereo cassette tape deck to the MCS receiver. and Surprisingly, the recording meters indicate sound levels on both left and right channels.! Also the tape deck records sound from both channels! I recorded stereo music onto a cassette from the FM receiver of the MCS 3236. !???? Can you tell me what is causing the problem and where I will find that problem inside? Or give me tips/ suggestions/ direction to direct me to the problem? please. I thank you in advance.

    1 reply

    Hello. I am a musician and not an expert by any means on HIFI but I had exactly the same problem as you with my KLH receiver, and I struggled for days checking and switching on and off but no luck. I did an awful lot of research but finallly telephoned to purchase a new amp when my brother, a computer engineer, suggested that on such an amp it is probably dirt\corrosion on the potentiometers. These can be cleaned he said with contact cleaner. I used WD40 and also squirted some at the knobs and push buttons at the front. Nothing happened but the next day I began to listen to a talk through the one speaker and after 5 minutes they both worked again. I cancelled my order for a new amp and one week later they still work perfectly. i love the sound from my KLH speakers and receiver and would, after forty years, be heartbroken to lose such a sound.