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#4599374 - 12/09/17 08:36 PM Parasound Back On-line
sleddriver Offline


Registered: 02/06/10
Posts: 4311
Loc: Central Texas
A few years back, I noticed some increasingly LOUD buzzing from my surround sound set-up. One cause was the surround sound controller itself, the Citation 7. That reworking process was documented here several years back. Since the Citation 7 has been restored to service, it's worked perfectly ever since.

I peaked under to hood of the Parasound multi-channel amp and noticed the majority of the main PS caps were bulging. Well that's not good. So I removed it from service, ordered new caps with a higher Voltage rating, then began to disassemble the rectifier/filter board, replace the main caps and reassemble.

Here's one photo I found. Looking for the others. I discovered my disassembly notes while cleaning up the servicing bench, properly ordered the wiring, found the hardware and looking forward to getting it back on-line. This photo shows the height difference between the OEM 65V caps and the newer 80Vs. All six were replaced.




Recently had an unrelated problem with the HP amp cutting out. Thought perhaps the electrolytic caps in the DC protection ckt were out-of-spec. Then while listening last week, heard a faint 'crack' while one channel of the LP amp went silent.

So I dug into it last weekend and discovered a loose power switch and a loose bass level control on the custom active EQ/XO I built. I retightened, then checked by playing the cannon shot scene from "Master & Commander". No cut outs! Success!

Evidently the stereo control had become loose and vibration was sufficient to short the control wiring. This was the fault rather than the HP amp's DC protection ckt.

Sure makes a difference with respect to presence, depth, and spaciousness when BOTH subwoofers are functional. Each cabinet has a pair of 12" drivers. With both working, I'm back to four 12" drivers once again.

The cannons sound great!
_________________________
1998 Volvo V70 T5 224,823 mi. Original Owner.

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#4599493 - 12/10/17 01:24 AM Re: Parasound Back On-line [Re: sleddriver]
rubberchicken Offline


Registered: 07/07/08
Posts: 393
Loc: Maryland USA
Master and Commander: One of the finest movies ever ! What makes capacitors go bad ? This is a common problem on older PC motherboards.

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#4599515 - 12/10/17 04:04 AM Re: Parasound Back On-line [Re: sleddriver]
Motor_Boater Offline


Registered: 12/02/17
Posts: 22
Loc: Deutschland
Originally Posted By: sleddriver
...noticed the majority of the main PS caps were bulging... ...perhaps the electrolytic caps in the DC protection ckt were out-of-spec...
The electrolyte simply evaporates out. 20 years longevity is usually the max. I repaired the control board of my wash machine myself, following a youtube vid. The factory wanted a few hundred for a replacement board. I then replaced the offending 2 caps for only 1.15. You can just about repair any board inexpensively, as long as the programmable chip doesn't fail. As you see, none of the caps bloated yet. So, I had to run a test outside of the machine, heating up the chip with a hair dryer, to get the drum to spin:


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#4599826 - 12/10/17 11:49 AM Re: Parasound Back On-line [Re: rubberchicken]
sleddriver Offline


Registered: 02/06/10
Posts: 4311
Loc: Central Texas
Originally Posted By: rubberchicken
Master and Commander: One of the finest movies ever ! What makes capacitors go bad ? This is a common problem on older PC motherboards.
Yes it is. Being a sailor and loving boats, it's one of my favorites.

Electrolytic capacitors in particular are the type that experience problems with aging. Reason being they use electrolytic paste inside rather than a plastic film. Over time, this paste will slowly dry out, lowering the EC's value, meaning it no longer acts like a good capacitor. The internal AC impedence will also rise, which causes it to heat up. Over time this either dries/cooks the electrolite, causing the casing to expand or causing it to be vented externally.

Some ckts have local power filtering around them for stability; some don't. Once formerly steady DC voltage now has AC ripple mixed into it, causing power fluctuations, and noise to be fed into all other ckts.

Like batteries, the quality of EC's varies widely.
_________________________
1998 Volvo V70 T5 224,823 mi. Original Owner.

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#4599866 - 12/10/17 01:04 PM Re: Parasound Back On-line [Re: sleddriver]
kc8adu Offline


Registered: 08/02/05
Posts: 860
Loc: dayton oh
and even higher priced equipment tends to use garbage lytics.
do i see a group of lytics on the left board standing off the board by their leads?
very bad on things like a sub amp.they break off due to vibration.
and a sub by design creates lots of low freq vibration!
i see plenty of this sort of failure on industrial controls.
a common brand of cnc control often comes to me with caps rolling around in the case.
you think the designer would know better!
a blop of high temp hot glue would have prevented this.

Originally Posted By: sleddriver
Originally Posted By: rubberchicken
Master and Commander: One of the finest movies ever ! What makes capacitors go bad ? This is a common problem on older PC motherboards.
Yes it is. Being a sailor and loving boats, it's one of my favorites.

Electrolytic capacitors in particular are the type that experience problems with aging. Reason being they use electrolytic paste inside rather than a plastic film. Over time, this paste will slowly dry out, lowering the EC's value, meaning it no longer acts like a good capacitor. The internal AC impedence will also rise, which causes it to heat up. Over time this either dries/cooks the electrolite, causing the casing to expand or causing it to be vented externally.

Some ckts have local power filtering around them for stability; some don't. Once formerly steady DC voltage now has AC ripple mixed into it, causing power fluctuations, and noise to be fed into all other ckts.

Like batteries, the quality of EC's varies widely.

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#4599904 - 12/10/17 02:00 PM Re: Parasound Back On-line [Re: kc8adu]
sleddriver Offline


Registered: 02/06/10
Posts: 4311
Loc: Central Texas
Good eye. They are indeed floating above the pcb to make room for a tiny, small capacitance bypass cap. Solved a spring/mass problem producing a bad harmonic a few years ago in a loudspeaker woofer. Very puzzling until I saw it for what it was...

I concur this isn't good practice at all. Obviously they didn't want to put the small bypass caps on the opposite side of the board.

This isn't a sub amp though. Not connected to any cabinet. It powers the center spkr and both rear surrounds. 6ch's are bridged to three.
_________________________
1998 Volvo V70 T5 224,823 mi. Original Owner.

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#4600228 - 12/10/17 08:47 PM Re: Parasound Back On-line [Re: sleddriver]
sleddriver Offline


Registered: 02/06/10
Posts: 4311
Loc: Central Texas
Found the older photos I took before pulling the filter board out:

From this perspective, it's easy to see three of the EC's with bulging lids:


Here's another angle:


_________________________
1998 Volvo V70 T5 224,823 mi. Original Owner.

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#4600928 - 12/11/17 06:06 PM Re: Parasound Back On-line [Re: sleddriver]
kc8adu Offline


Registered: 08/02/05
Posts: 860
Loc: dayton oh
3 of them had open vents poking the plastic.
the higher voltage caps being a larger can means lower esr.
translates to lower ripple.
good job!

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#4601057 - 12/11/17 08:43 PM Re: Parasound Back On-line [Re: kc8adu]
sleddriver Offline


Registered: 02/06/10
Posts: 4311
Loc: Central Texas
  • I recently acquired a used ESR meter. I'll check each cap and report back.
  • I generally go with a higher V cap for that very reason...as long as they'll fit.
  • Lower ripple is always a good thing!
  • Thanks.
  • BTW, I'm interested in your flashlight hot-rodding. Have a few old Mag-lites laying around.

_________________________
1998 Volvo V70 T5 224,823 mi. Original Owner.

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#4602224 - 12/12/17 11:41 PM Re: Parasound Back On-line [Re: sleddriver]
rubberchicken Offline


Registered: 07/07/08
Posts: 393
Loc: Maryland USA
On the EC pics: thanks for pointing out the bulge- I would not have recognized that as being a problem: usually the caps I look at have silver tops with lines stamped in, so the bulge would be more noticeable.

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#4602574 - 12/13/17 01:12 PM Re: Parasound Back On-line [Re: rubberchicken]
sleddriver Offline


Registered: 02/06/10
Posts: 4311
Loc: Central Texas
You're welcome RC.

The EC's you're referring to are a different type & construction, if I understand your description correctly.
_________________________
1998 Volvo V70 T5 224,823 mi. Original Owner.

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#4632914 - 01/12/18 08:04 PM Re: Parasound Back On-line [Re: sleddriver]
Clausen Offline


Registered: 01/10/18
Posts: 2
Loc: FL
Hi. I have this same amp and I had to replace all the relays in it, which I did myself. I also have a hum that is especially noticeable if I turn up the gains. I was wondering what uf value these caps are and where to get them. It looks like in the picture they are 12,000 uf but it's hard to tell from that!

Thanks for this post!

BTW, is this the HCA-806a? I thought it said it was somewhere.

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#4633854 - 01/13/18 05:10 PM Re: Parasound Back On-line [Re: Clausen]
sleddriver Offline


Registered: 02/06/10
Posts: 4311
Loc: Central Texas
The originals are Elna LP5, 12,000uF 63V cans. I bought similar uF from Mouser, going with 80Vdc. 60Hz Hum & buzz are good signs caps are mis-behaving due to age.
_________________________
1998 Volvo V70 T5 224,823 mi. Original Owner.

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#4634027 - 01/13/18 09:09 PM Re: Parasound Back On-line [Re: sleddriver]
Clausen Offline


Registered: 01/10/18
Posts: 2
Loc: FL
OK...yeah that's where I bought the relays from,(Mouser). I'll crack it open to see what's there I guess, just being lazy. This is a huge relief for me though! I really like this amp. Its driving these...http://www.diyaudio.com/forums/multi-way/97043-elsinore-project-thread-203.html

Thanks again!

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