Hello Gentleman,
A friend of mine(don't be so surprised that I have a friend)picked up a minty clean little 15 watt per channel Pioneer SX-450 for his son to use while off at school. It worked fine for while although now the right channel sounds quite good and the left channel is very distorted. While I am no technician(I didn't even stay in a Holiday Inn Express last night)I suspect that it is a bad output transistor. I may be wildly off base. Any ideas?
The original devices are three legged packages like a to220 and labeled as D 313 EHD My conclusion is that this is an NPN epitaxial planar transistor that at one time was produced by Unisonic Technologies and there seemed to be at one time a Sanyo produced equivalent under the designation of 2SD 313.
Does anyone know of something equivalent that would be able to replace these devices? Again I am not sure this is even the problem and would be open to suggestions.
My friend has such a small amount of money in the receiver that taking it to a technician is out of the question and he has one son already attending college and two more soon on their way. Money is an issue in these matters as I remember when I started attending a state university it was $18 a credit hour. This is, as you already know, not the case any longer.
It's a shame to see such a nice clean little piece of gear go into the waste bin or just sit a collect a lot of dust at the very least.
Thanks for taking the time to read this. I hope someone has some helpful suggestions.
Keith Lockwood
A friend of mine(don't be so surprised that I have a friend)picked up a minty clean little 15 watt per channel Pioneer SX-450 for his son to use while off at school. It worked fine for while although now the right channel sounds quite good and the left channel is very distorted. While I am no technician(I didn't even stay in a Holiday Inn Express last night)I suspect that it is a bad output transistor. I may be wildly off base. Any ideas?
The original devices are three legged packages like a to220 and labeled as D 313 EHD My conclusion is that this is an NPN epitaxial planar transistor that at one time was produced by Unisonic Technologies and there seemed to be at one time a Sanyo produced equivalent under the designation of 2SD 313.
Does anyone know of something equivalent that would be able to replace these devices? Again I am not sure this is even the problem and would be open to suggestions.
My friend has such a small amount of money in the receiver that taking it to a technician is out of the question and he has one son already attending college and two more soon on their way. Money is an issue in these matters as I remember when I started attending a state university it was $18 a credit hour. This is, as you already know, not the case any longer.
It's a shame to see such a nice clean little piece of gear go into the waste bin or just sit a collect a lot of dust at the very least.
Thanks for taking the time to read this. I hope someone has some helpful suggestions.
Keith Lockwood
Does the distortion go away if you crank up the volume? If so, I'm betting the Vbe multiplier transistor is fried and the output stage is biased in zero bias class B. You should be able to find the Vbe multiplier on the same heat sink as the main output devices. It'll be connected between the bases of the output pair.
I think your guess of D313 = 2SD313 is correct. If you're having trouble locating it, try outfits like B&D Enterprises.
~Tom
I think your guess of D313 = 2SD313 is correct. If you're having trouble locating it, try outfits like B&D Enterprises.
~Tom
Thanks Tom,
I didn't try really cranking on it since it sounded so bad. I had it hooked up to my pair of AR 4x's I drug out of the basement, circa 1968 very low efficiency but still a good suggestion since even 15 watts would get them going pretty well. I will check it out.
Are schematics available for such a dinosaur?
Keith
I didn't try really cranking on it since it sounded so bad. I had it hooked up to my pair of AR 4x's I drug out of the basement, circa 1968 very low efficiency but still a good suggestion since even 15 watts would get them going pretty well. I will check it out.
Are schematics available for such a dinosaur?
Keith
Tom,
No such luck. The distortion is still there when really cranked in that channel, just of course, louder. So I thank you for your suggestion but I don't think that is the answer in this case.
Does that point evidence more to the output devices themselves in that scenario?
Thanks again,
Keith Lockwood
No such luck. The distortion is still there when really cranked in that channel, just of course, louder. So I thank you for your suggestion but I don't think that is the answer in this case.
Does that point evidence more to the output devices themselves in that scenario?
Thanks again,
Keith Lockwood
I just got one of these too.
Mine is got a flashing light when turning it on. Anywhere from 1 sec to 2 mins the light seems to shimmer. Then it lights up and works great. Of course its playing great the whole time. Anyone know what it could be.
Man I love the 70's stuff. It even looks classy, the knobs and all of it with their machined aluminum look and feel just scream class.
Anyway, you guys think a cleaning of the potentiometer will do it ?
Cool.
Srinath.
Mine is got a flashing light when turning it on. Anywhere from 1 sec to 2 mins the light seems to shimmer. Then it lights up and works great. Of course its playing great the whole time. Anyone know what it could be.
Man I love the 70's stuff. It even looks classy, the knobs and all of it with their machined aluminum look and feel just scream class.
Anyway, you guys think a cleaning of the potentiometer will do it ?
Cool.
Srinath.
Thank you so much RJM1 for the suggestion and for supplying the portion of the schematic.
I will do just that.
You guys are around here are very helpful.
Keith Lockwood
I will do just that.
You guys are around here are very helpful.
Keith Lockwood
Srinath,
I doubt that cleaning the volume pot would have anyy effect on the shimmering lights. Perhaps a seance would be about as helpful for that issue, but a good cleaning of an old carbon pot is never a bad thing.
I would suspect that power switch before anything else since it seems to be playing fine. try cleaning that and see what happens. A little Caig DeoxIt might do the trick. By the way Caig makes a product that works wonders on old carbon level controls. It used to be called CaliLube and I would have to do a little looking at their site to remind me what they changed the name to caig.com - Home of DeoxIT - CAIG Laboratories, Inc.
I think they call it DeoxIt Fader lube now.
Keith
I doubt that cleaning the volume pot would have anyy effect on the shimmering lights. Perhaps a seance would be about as helpful for that issue, but a good cleaning of an old carbon pot is never a bad thing.
I would suspect that power switch before anything else since it seems to be playing fine. try cleaning that and see what happens. A little Caig DeoxIt might do the trick. By the way Caig makes a product that works wonders on old carbon level controls. It used to be called CaliLube and I would have to do a little looking at their site to remind me what they changed the name to caig.com - Home of DeoxIT - CAIG Laboratories, Inc.
I think they call it DeoxIt Fader lube now.
Keith
srinath - the flashing is due to the power switch arcing. Replace power switch if you can find one, and problem is solved.
Thanks much for the replies guys, and this amp has gorgeous knobs and I am afraid of breaking something.
But the on/off potentiometer is removed by first pulling the knob off the front, then unscrewing the nut that retains it and removing it right ?
Now do I stand a snowball's chance in hell of finding a Potentiometer that will take that knob and match it with the rest of it ?
I would rather keep it all original looking, there is a guy in town who has parts out the ears for these things. he'd trade me some cool speakers/parts for it if it was all original.
Cool.
Srinath.
But the on/off potentiometer is removed by first pulling the knob off the front, then unscrewing the nut that retains it and removing it right ?
Now do I stand a snowball's chance in hell of finding a Potentiometer that will take that knob and match it with the rest of it ?
I would rather keep it all original looking, there is a guy in town who has parts out the ears for these things. he'd trade me some cool speakers/parts for it if it was all original.
Cool.
Srinath.
srinath,
I don't have the cover off of the unit I have her e at the moment but you may not have to take the knob off of the switch to get some cleaner in there. It may be the case that you need a new switch as has been suggested previously but I would be worth a try to give some DeoxIt a try first.
Keith
I don't have the cover off of the unit I have her e at the moment but you may not have to take the knob off of the switch to get some cleaner in there. It may be the case that you need a new switch as has been suggested previously but I would be worth a try to give some DeoxIt a try first.
Keith
RJM1,
The 1/2 ohm 2 Watt resistors you are referring to are on the schematic as R233, R234,R235, and R236?
being an idiot electronically speaking and with a chronic brain infection to boot, what would be the color band coding to I.D. these little gems?
I have been testing resistors with my VOM. I just need to locate these bad boys and check them out. All the parts are mounted to the top of the beard if I remember right as I have had the bottom cover off within the last few weeks but my memory is not for S***.
The 1/2 ohm 2 Watt resistors you are referring to are on the schematic as R233, R234,R235, and R236?
being an idiot electronically speaking and with a chronic brain infection to boot, what would be the color band coding to I.D. these little gems?
I have been testing resistors with my VOM. I just need to locate these bad boys and check them out. All the parts are mounted to the top of the beard if I remember right as I have had the bottom cover off within the last few weeks but my memory is not for S***.
I think I have I.D.'d the .5 ohm resistors in question as largish green units. They all seem to have continuity.
Time to look elsewhere.
By the way, you don't need to remove the front knob to clean the power switch as it has an extension on it and the switch is mounted further back on the circuit board out in the open where you could easily spray some contact cleaner on it and work it a bit. It could as previously suggested just be plain worn out contacts, but you don't have to take the knob off.
Thanks everyone,
Keith Lockwood
Time to look elsewhere.
By the way, you don't need to remove the front knob to clean the power switch as it has an extension on it and the switch is mounted further back on the circuit board out in the open where you could easily spray some contact cleaner on it and work it a bit. It could as previously suggested just be plain worn out contacts, but you don't have to take the knob off.
Thanks everyone,
Keith Lockwood
Well If you try using just headphones on the receiver and it sounds ok then you probably have an open output transistor if those resistors are ok, Check the resistance readings on your meter on diode check between both channels on the transistors to find which one has opened. If anything had shorted you would have a large amount of DC at the output.
hth
Bob
hth
Bob
Bob,
Thanks I don't have a pair of phones around. I will get a hold of a pair to try that with.
DC at the output is the kiss of death for speakers isn't it?
Isn't that why they called the old big Crown amp the "DC" 300A? Seems it took down more drivers that even Bob Carver's "Flame"linear 400.
Maxgain
Thanks I don't have a pair of phones around. I will get a hold of a pair to try that with.
DC at the output is the kiss of death for speakers isn't it?
Isn't that why they called the old big Crown amp the "DC" 300A? Seems it took down more drivers that even Bob Carver's "Flame"linear 400.
Maxgain
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