Nakamichi Stasis ?'s-balance issue - diyAudio
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Old 28th May 2005, 08:23 AM   #1
Heiney9 is offline Heiney9  United States
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Question Nakamichi Stasis ?'s-balance issue

Iíve been lurking around here for awhile. Trying to absorb as much goodwill and knowledge as possible. Forum members are very helpful and respectful to each other. Thatís one of the reasons I read so often, even the threads that are way over my head. I have an interest in learning why things work and sound the way they do, but as far a practical application Iím a pure novice.

Iím looking for some advice on a problem Iím having with a Nakamichi SR-3A receiver which uses the Stasis output topology licensed from Threshold. I really have no means of checking or measuring anything, my purpose is more for understanding/advice than DIY repair. I know some of you on this forum have worked on many brands/models of equipment.

I recently purchased the unit for use in a 2nd system. When I got it, it was pretty dusty and the switches and attenuators were crackly so I disassembled the front panel and cleaned all the contacts and switches with Deoxit. Fixed that problem. After several months of listening I notice that on all source material one channel is louder than the other. Iíve swapped cables; speakers (L to R & R to L); swapped speaker cables and still the same problem. What could be causing this? I now listen with the balance control set to the left about ľ turn and that seems to be acceptable.

Also; I used this unit in place of my main rig for awhile and noticed it was quite a bit brighter sounding than my separates (Adcom 545 & Nak CA-5) also the bass was bloated and uncontrolled. Again this was compared to the separates in my main rig. All other components were the same. Is this typical of these units or is there a problem? I used to sell these when they were new in ~1986 and always thought they were a nice sounding unit, but now Iím not so sure. Could it be way out of spec? If so what could be causing the problems?

For a 2nd system I can live the SQ issues (if itís typical of the way this unit sounds), but Iíd like to get some idea of why the balance is so far off. Also what's the availibilty of parts for this unit? I purchased a service manual so if I need to get it repaired and the repair shop doesn't have a manual I can provide it. But if parts aren't avail, no use trying to have someone repair it.

Thanks in advance for any information/experiences you can share. Itís much appreciated and I look forward to some discussion.

Brock

P.S. Sorry for thr lengthy post
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Old 28th May 2005, 07:32 PM   #2
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Could be a variety of things, but without an oscillator and
a multimeter, it's going to be tough to track down.
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Old 28th May 2005, 07:53 PM   #3
Heiney9 is offline Heiney9  United States
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Quote:
Originally posted by Nelson Pass
Could be a variety of things, but without an oscillator and
a multimeter, it's going to be tough to track down.

Thanks for replying Nelson. I realize with my limited /non-exsistant repair experience it's a tough call. But I'm just looking for some ballpark idea's of some things that might cause this. Do you have any idea's considering they used part or all of your original Stasis design? And are parts going to be an issue?

Any input is greatly appreciated.

Regards

Brock
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Old 28th May 2005, 09:20 PM   #4
djk is offline djk
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Loosely speaking your schematic looks like this:

http://sound.westhost.com/p3a-f1.gif

20 year old electrolytics tend to dry up and change value. When C3 dries up the gain of the amplifier will reduce dramatically. Replace C3 and C1 in both channels, use as high a quality electrolytic as you can find, and/or tack a 0.1ĶF film cap in parallel.

See the power supply bypass caps marked C+ and C- ? , I'm not sure what the Nak has there. For tighter bass these should be around 22ĶF.

I really like the sound of these.
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Old 29th May 2005, 02:02 AM   #5
anatech is offline anatech  Canada
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Hi Brock,
I used to repair these under warranty, and still have a TA-2. This is in my bedroom and sounds very nice. I would operate the switches and controls to see if that fixes it (bad contacts - I know you cleaned them).

As I recall, there is a resistor from the positive rail in the current source circuit. It tends to overheat and increase value. Check it and replace with at least double the wattage. If you can send the schematic I can help more.

I have noticed that these sets sound better with an 8R load than a 4R load.

Last note, leave lots of room (5~6" minimum) above the unit for ventillation. The cooler it runs, the better off you are. I think there are some mods related to transistors in the tuner (might be for TA series).

Good choice, I hope you have many years of enjoyment with it. Also, a really good preamp. Wish I had one (well, CA-7).

-Chris
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Old 31st May 2005, 09:38 PM   #6
Heiney9 is offline Heiney9  United States
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Chris,

Thanks for the reply. I know these are good sounding units and this just seems a bit off to me. I will try to get a scan of the schematic if you are still interested in taking a look at it. I purchased a service manual but to be honest there are all kinds of schematics and block diagram. Which 1 would help? Considering my limited knowledge maybe you could give me an idea of which schematic you would need? Apparently there were several versions of Nak equipment for each market and this manual covers them all.

I do really like my CA-5 also. The CA-7 was long on my wish list, mainly for the remote. However as this stuff gets older it seems to me to be harder & harder to get parts, so I havenít pursued a purchase of a CA-7.

Again thanks for the input. Iíve seen many other posts of yours and always seem to go out of your way to help. If you are still interested in looking at the schematic I can get it scanned inÖlet me know

Regards

Brock
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Old 31st May 2005, 09:38 PM   #7
Heiney9 is offline Heiney9  United States
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djk,

Thanks for input as well

Brock
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Old 31st May 2005, 10:21 PM   #8
anatech is offline anatech  Canada
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Hi Brock,
I would like to see the amplifier section, "A" series (US and Canada). A scan of the preamp / power supply and tuner section would be nice later. No problem with helping you out with this.

While running the receiver, push and operate each control slowly while listening for static or cut outs. With the cover off, try to locate the speaker relay. Tap it lightly at low volume and listen for a change in the sound. I'll advise further after I have looked at the schematics.

-Chris
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Old 2nd June 2005, 01:35 PM   #9
Heiney9 is offline Heiney9  United States
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Quote:
Originally posted by anatech
Hi Brock,
I would like to see the amplifier section, "A" series (US and Canada). A scan of the preamp / power supply and tuner section would be nice later. No problem with helping you out with this.

While running the receiver, push and operate each control slowly while listening for static or cut outs. With the cover off, try to locate the speaker relay. Tap it lightly at low volume and listen for a change in the sound. I'll advise further after I have looked at the schematics.

-Chris
Ok Chris will run these tests you mentioned. Sorry fo the delay I've been under a few deadlines on my end. I will post the schematic in a day or two when I can get it scanned in. Thanks again

Brock
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