Need help with possible receiver repair

Keith Lockwood · 10th March 2010, 11:20 PM

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

tomchr · 10th March 2010, 11:27 PM

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

Keith Lockwood · 10th March 2010, 11:41 PM

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

Keith Lockwood · 11th March 2010, 04:13 AM

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

srinath · 11th March 2010, 05:52 AM

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.

RJM1 · 11th March 2010, 07:07 AM

Check the .5 ohm 2W resistors by the output transistors, they often open.

Keith Lockwood · 11th March 2010, 11:34 AM

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

Keith Lockwood · 11th March 2010, 03:46 PM

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

sregor · 11th March 2010, 03:50 PM

srinath - the flashing is due to the power switch arcing. Replace power switch if you can find one, and problem is solved.

srinath · 11th March 2010, 08:53 PM

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.

10th March 2010, 11:20 PM	#1
Keith Lockwood diyAudio Member Join Date: Jun 2004 Location: Michigan	Need help with possible receiver repair 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

11th March 2010, 03:50 PM	#9
sregor diyAudio Member Join Date: Jan 2006 Location: massachusetts	srinath - the flashing is due to the power switch arcing. Replace power switch if you can find one, and problem is solved. __________________ Steve

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Marantz SR-50 receiver repair	Stuey	Solid State	18	10th October 2009 06:08 PM
A receiver I'd like to see	preiter	Everything Else	0	3rd April 2007 05:55 PM
A / V Receiver	janderson	Everything Else	0	24th May 2005 07:14 PM
Marantz receiver repair	SoundQuest	Parts	0	4th June 2004 06:24 AM
Hey i need help with receiver........EXPERTS HELP(two channel receiver)	Andre Baptiste	Parts	1	1st May 2004 11:20 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

10th March 2010, 11:27 PM	#2
tomchr diyAudio Member Join Date: Feb 2009 Location: Greater Seattle Area	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

10th March 2010, 11:41 PM	#3
Keith Lockwood diyAudio Member Join Date: Jun 2004 Location: Michigan	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

11th March 2010, 04:13 AM	#4
Keith Lockwood diyAudio Member Join Date: Jun 2004 Location: Michigan	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

11th March 2010, 05:52 AM	#5
srinath diyAudio Member Join Date: Feb 2010	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.

11th March 2010, 11:34 AM	#7
Keith Lockwood diyAudio Member Join Date: Jun 2004 Location: Michigan	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

11th March 2010, 03:46 PM	#8
Keith Lockwood diyAudio Member Join Date: Jun 2004 Location: Michigan	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

11th March 2010, 08:53 PM	#10
srinath diyAudio Member Join Date: Feb 2010	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.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)