68 mono radio
05-23-2014, 12:39 AM
#1
Burning Brakes
Thread Starter
68 mono radio
Ive searched the forum and didnt find much and I know this may be kind of a long shot but I'll ask anyways. The factory radio in my 68 has very low volume, I can hear stations but barely, even with the volume all the way up. Anyone here had this problem before and what ended up being the fix. I'm guessing the fix is gonna be send it out to be repaired but I figured I'd ask just in case there is a DIY fix out there. Thanks for any input.
05-23-2014, 10:33 AM
#2
you could try removing the radio, opening the chasis and using some electronic spray cleaner try to get some in the volume control potentiometer while turning the **** from full off to full volume and back. At the same time make sure all connections to the radio are clean.
05-23-2014, 02:18 PM
#3
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Sounds like you may have a dead or dying transistor in the convector assembly.
It's a DS-501 transistor.
I've seen them on eBay.
It's a DS-501 transistor.
I've seen them on eBay.
05-23-2014, 08:39 PM
#4
Instructor
And here's another take on the problem and another solution.
Go to RadioShack and buy a can of DEOXIT (NOT tuner cleaner - that stuff turns the deposited carbon tracks in the controls to black mush and the metal wiper drags the carbon off over time destroying the control!). Then you will have no or low volume for sure.
Locate the variable nichrome wire wound bias control on the audio sub-board and spray it with the shortest squirt you can deliver. Turn the control back and forth and reset it exactly where you started from.
If that does not bring the audio back up, replace the two 100 microfarad and the 10 microfarad axial electrolytic capacitors on the audio sub-board. You can get those at RadioShack too.
And if the sound you are hearing is extremely low and appears to be coming from the radio itself when you have turned the volume up full, hook up another speaker as a test. It is possible to hear sound from the loose laminations in the speaker loading coil inside the radio. This is the same loading coil that was finally moved from the speaker frame on 58-67 vette speakers to the radio itself.
If it's still not working, you should send it to someone. It's playing and that means the problem is not serious. Just old age related.
_Jerry_
Go to RadioShack and buy a can of DEOXIT (NOT tuner cleaner - that stuff turns the deposited carbon tracks in the controls to black mush and the metal wiper drags the carbon off over time destroying the control!). Then you will have no or low volume for sure.
Locate the variable nichrome wire wound bias control on the audio sub-board and spray it with the shortest squirt you can deliver. Turn the control back and forth and reset it exactly where you started from.
If that does not bring the audio back up, replace the two 100 microfarad and the 10 microfarad axial electrolytic capacitors on the audio sub-board. You can get those at RadioShack too.
And if the sound you are hearing is extremely low and appears to be coming from the radio itself when you have turned the volume up full, hook up another speaker as a test. It is possible to hear sound from the loose laminations in the speaker loading coil inside the radio. This is the same loading coil that was finally moved from the speaker frame on 58-67 vette speakers to the radio itself.
If it's still not working, you should send it to someone. It's playing and that means the problem is not serious. Just old age related.
_Jerry_
05-26-2014, 08:41 PM
#6
Burning Brakes
Thread Starter
Wow, thanks for the replies guys, glad I asked. Bought the deoxit and will do a bit further diagnosing possibly this coming up weekend. Will check speaker resistance first and try them out on a different source. If they check out good I will remove the radio and try some suggestions. Thanks again!
05-27-2014, 10:12 PM
#7
Instructor
Wow, thanks for the replies guys, glad I asked. Bought the deoxit and will do a bit further diagnosing possibly this coming up weekend. Will check speaker resistance first and try them out on a different source. If they check out good I will remove the radio and try some suggestions. Thanks again!
You can find the wire wound bias control recessed under the hole in the bottom cover of the radio towards the front on the left (volume control side). The tiny coiled nichrome wire runs around the outside under the shell so spray at an angle. A little bit is plenty. Bet that does it... (fingers crossed).
05-28-2014, 12:25 PM
#8
I have a 68 with a similar issue.....radio will play fine for a time, then have the same results as the OP. I have been thinking about re-capping the radio, as Jerry has suggested.
Jerry, any write up on this (with pictures)? I know it seems pretty straight forward, but I have yet to find a write up and it seems it may help a few people out.
~Rich
Jerry, any write up on this (with pictures)? I know it seems pretty straight forward, but I have yet to find a write up and it seems it may help a few people out.
~Rich
05-28-2014, 04:13 PM
#9
Instructor
Ive searched the forum and didnt find much and I know this may be kind of a long shot but I'll ask anyways. The factory radio in my 68 has very low volume, I can hear stations but barely, even with the volume all the way up. Anyone here had this problem before and what ended up being the fix. I'm guessing the fix is gonna be send it out to be repaired but I figured I'd ask just in case there is a DIY fix out there. Thanks for any input.
It would take a lot of work to document even that little bit because so few guys have an auto radio background (including most techs based on what I see arriving here). And so many others would need a course on soldering and parts type identification before they could even start. I guess it's like a carburetor; you either know how to rebuild/repair build one, are willing to invest the time to learn to rebuild one or shouldn't be rebuilding one.
Life's just too short to master - literally!
But whatta ride...
05-31-2014, 08:25 PM
#10
Burning Brakes
Thread Starter
Jerry, cant thank you enough! Did what you said w/ the deoxit and worked like a charm. Radio works great now, also replaced the burnt out bulb in the radio. Now I have a working radio with a working back light. Once agian, cant thank you enough, if youre ever in the southern California area Id like to buy you a beer!
06-01-2014, 10:44 AM
#11
Instructor
Jerry, cant thank you enough! Did what you said w/ the deoxit and worked like a charm. Radio works great now, also replaced the burnt out bulb in the radio. Now I have a working radio with a working back light. Once agian, cant thank you enough, if youre ever in the southern California area Id like to buy you a beer!
Excellent news! There are other age related problems lurking in there so anticipate another decrease in volume as a couple of the electrolytics degrade further. With luck it will take several more years to happen. Enjoy!!
PS: the deoxit is a magic wand where corroded electrical connection points are concerned especially if you have a 6 volt (53/54) car. It's good in the home too. And it sure beats sandpapering relay contacts (which reduces the surface contact area and encourages arcing).
11-05-2014, 09:25 PM
#13
Intermediate
You can find the wire wound bias control recessed under the hole in the bottom cover of the radio towards the front on the left (volume control side). The tiny coiled nichrome wire runs around the outside under the shell so spray at an angle. A little bit is plenty. Bet that does it... (fingers crossed).
11-05-2014, 09:27 PM
#14
Intermediate
Jerry, cant thank you enough! Did what you said w/ the deoxit and worked like a charm. Radio works great now, also replaced the burnt out bulb in the radio. Now I have a working radio with a working back light. Once agian, cant thank you enough, if youre ever in the southern California area Id like to buy you a beer!
Thank you! (Pole) barn found 69 vert here, so everything needs some TLC (but it's all there! and i'm hoping to keep it all there). Thanks!
11-06-2014, 12:39 AM
#15
Burning Brakes
Thread Starter
I ended up removing the radio and taking to top and bottom cover off. Getting it out is kind of a PITA but Jerry said its pretty important to put the adjuster back in its original location so I didnt want to risk it. Not sure if yours works but Id go ahead and change the backlight bulb also while youre in there.
11-06-2014, 06:40 AM
#16
Instructor
When you have a moment, can you share what you wound up having to do w/ the deoxit (in terms of "did you have to pull the radio out, and then apart" or were you able to just spray up (a bit) into the radio itself)?
Thank you! (Pole) barn found 69 vert here, so everything needs some TLC (but it's all there! and i'm hoping to keep it all there). Thanks!
Thank you! (Pole) barn found 69 vert here, so everything needs some TLC (but it's all there! and i'm hoping to keep it all there). Thanks!
The wound wire is shielded by its containing case, you must have clear access when you spray. The "blast everything with tuner cleaner and WD40" mentality doesn't apply to radios.
One other tip, if the sound you hear is only coming from the radio itself and not the speakers, check the speakers first. A pole barn environment will encourage dry rot of the paper cones. And if it was a 70 and later with 4X6 Delco speakers, you can bet the speakers are shot!
The speaker loading coil was moved inside the radio in 68 and later vettes. The inductor laminations were loose and the audio power creates an AC magnetic field that shakes them - thus, with dead speakers, you can hear the radio itself with the volume turned up.
The DC voltage measured across the green and black speaker wires in a mono radio car should be close to 1.25 (two 8 ohm speakers wired in parallel). The wire wound bias control will allow you to set this value using only a voltmeter.
Someone in the other thread said to switch to 4 ohm speakers for some reason. Wrong! This audio amplifier is very touchy about the impedance it sees and loves to distort the sound without a pair of 8 ohm devices. Engineers back then knew what they were doing and did it for a reason. Modern speakers are for modern radios - use ones made for these radios (www.turnswitch.com/speakers.htm).
11-06-2014, 07:55 PM
#17
Intermediate
_____
The wound wire is shielded by its containing case, you must have clear access when you spray. The "blast everything with tuner cleaner and WD40" mentality doesn't apply to radios.
One other tip, if the sound you hear is only coming from the radio itself and not the speakers, check the speakers first. A pole barn environment will encourage dry rot of the paper cones. And if it was a 70 and later with 4X6 Delco speakers, you can bet the speakers are shot!
The speaker loading coil was moved inside the radio in 68 and later vettes. The inductor laminations were loose and the audio power creates an AC magnetic field that shakes them - thus, with dead speakers, you can hear the radio itself with the volume turned up.
The DC voltage measured across the green and black speaker wires in a mono radio car should be close to 1.25 (two 8 ohm speakers wired in parallel). The wire wound bias control will allow you to set this value using only a voltmeter.
Someone in the other thread said to switch to 4 ohm speakers for some reason. Wrong! This audio amplifier is very touchy about the impedance it sees and loves to distort the sound without a pair of 8 ohm devices. Engineers back then knew what they were doing and did it for a reason. Modern speakers are for modern radios - use ones made for these radios (www.turnswitch.com/speakers.htm).
The wound wire is shielded by its containing case, you must have clear access when you spray. The "blast everything with tuner cleaner and WD40" mentality doesn't apply to radios.
One other tip, if the sound you hear is only coming from the radio itself and not the speakers, check the speakers first. A pole barn environment will encourage dry rot of the paper cones. And if it was a 70 and later with 4X6 Delco speakers, you can bet the speakers are shot!
The speaker loading coil was moved inside the radio in 68 and later vettes. The inductor laminations were loose and the audio power creates an AC magnetic field that shakes them - thus, with dead speakers, you can hear the radio itself with the volume turned up.
The DC voltage measured across the green and black speaker wires in a mono radio car should be close to 1.25 (two 8 ohm speakers wired in parallel). The wire wound bias control will allow you to set this value using only a voltmeter.
Someone in the other thread said to switch to 4 ohm speakers for some reason. Wrong! This audio amplifier is very touchy about the impedance it sees and loves to distort the sound without a pair of 8 ohm devices. Engineers back then knew what they were doing and did it for a reason. Modern speakers are for modern radios - use ones made for these radios (www.turnswitch.com/speakers.htm).
I'll def take everything apart and approach the task in a targeted way vs. a spray everything way. And as an earlier post suggested, while I'm in there, may as well check out the bulb as well
I'll re-try my test tomorrow before taking everything apart (have to replace the clock, as well, so good excuse to address the radio too), but seems the sound is coming from the radio vs. the speakers, though with some **** turning, I think some faint sound comes from speakers as well. Ever so faint, and it's one of those "if I turn volume all the way up, then turn tuner back and forth over strongest station in town, as I pass over top, I can hear it faintly, and then it fades out as I continue to turn - and I can't stop on the station and have the sound stay either).
So hoping it's just a case of contacts and old gunk in the works
11-06-2014, 08:25 PM
#18
Instructor
Can of DEOXIT in hand from a shopping jaunt to Radio Shack today. They had *no* idea what i was talking about - lol - but when I said "spray", they took me over to the "spray stuff" section - and I found it there
I'll def take everything apart and approach the task in a targeted way vs. a spray everything way. And as an earlier post suggested, while I'm in there, may as well check out the bulb as well
I'll re-try my test tomorrow before taking everything apart (have to replace the clock, as well, so good excuse to address the radio too), but seems the sound is coming from the radio vs. the speakers, though with some **** turning, I think some faint sound comes from speakers as well. Ever so faint, and it's one of those "if I turn volume all the way up, then turn tuner back and forth over strongest station in town, as I pass over top, I can hear it faintly, and then it fades out as I continue to turn - and I can't stop on the station and have the sound stay either).
So hoping it's just a case of contacts and old gunk in the works
I'll def take everything apart and approach the task in a targeted way vs. a spray everything way. And as an earlier post suggested, while I'm in there, may as well check out the bulb as well
I'll re-try my test tomorrow before taking everything apart (have to replace the clock, as well, so good excuse to address the radio too), but seems the sound is coming from the radio vs. the speakers, though with some **** turning, I think some faint sound comes from speakers as well. Ever so faint, and it's one of those "if I turn volume all the way up, then turn tuner back and forth over strongest station in town, as I pass over top, I can hear it faintly, and then it fades out as I continue to turn - and I can't stop on the station and have the sound stay either).
So hoping it's just a case of contacts and old gunk in the works
And just to make this arduous process even more meaningful for you, have a few Q-Tips handy and spray them one at a time and clean all 9 contacts on the AM/FM switch. They were all a shiny silver color when new. I bet they aren't now.
You can find it by moving the selector bar back and forth and the interconnecting linkage will slide the switch contact bar in the center to the left and right. Like Brylcreem, a little dab'l do ya.
Good show! My fingers are crossed but I can assure you that since you are hearing stations, you have a very good chance of fixing this yourself.
11-06-2014, 10:55 PM
#19
Burning Brakes
Thread Starter
Can of DEOXIT in hand from a shopping jaunt to Radio Shack today. They had *no* idea what i was talking about - lol - but when I said "spray", they took me over to the "spray stuff" section - and I found it there
And just to make this arduous process even more meaningful for you, have a few Q-Tips handy and spray them one at a time and clean all 9 contacts on the AM/FM switch. They were all a shiny silver color when new. I bet they aren't now.
You can find it by moving the selector bar back and forth and the interconnecting linkage will slide the switch contact bar in the center to the left and right. Like Brylcreem, a little dab'l do ya.
You can find it by moving the selector bar back and forth and the interconnecting linkage will slide the switch contact bar in the center to the left and right. Like Brylcreem, a little dab'l do ya.