Nakamichi TA2A - "vented" caps on PS board? - diyAudio
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Old Yesterday, 05:26 PM   #1
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Join Date: May 2010
Location: Skokie Il
Default Nakamichi TA2A - "vented" caps on PS board?

I've had to do some minor repairs to this unit a couple of times. Last time I replaced a leaky capacitor on the power supply board. I just slapped a new one in and replaced another large cap associated with the 30 volt voltage doubling circuit. It worked fine for a year but recently it started to make a buzzing noise in the tuner again. The noise is different this time and it comes and goes. Anyway, there's another cap that blew its goo all over the board.

Of course I'm going to recap the whole power supply board this time. I notice that there's about 5 different brands of caps on this board, which makes me think that it was repaired before. One of the caps is a Taicon cap which I found out was popular on some motherboards made in the late 90s. It's bulging and the sleeve is discolored by heat.

Anyway, the latest offender says "vented" on the sleeve. The board has two large holes under the cap, I guess for the vents. I look closer and I see that both caps I replaced last time have the same vent holes under them. The oddball Taicon cap has the same holes underneath it. Every oddball cap on the board has the holes under it. So you know where I'm going with this logic - apparently every vented cap has blown its wad on the board at one time or another.

So my question is this - are vented caps an outdated technology, or will my Nichicon PW(M) replacements fail in this application? Does anybody have any experience with vented caps? It seems like they all blew out the vents, and partially melted the sleeves. Some of the adjacent parts have been barbequed too. The unit always has run hot, but it has provided years of wonderful service too. The amplifier board and power transformers are still original save for a couple of bias resistors I replaced in the power amp.
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Old Yesterday, 05:42 PM   #2
rayma is offline rayma  United States
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Join Date: Apr 2011
Location: Upper midwest
Quote:
Originally Posted by Fast Eddie D View Post
So my question is this - are vented caps an outdated technology, or will my Nichicon PW(M) replacements fail in this application? Does anybody have any experience with vented caps? It seems like they all blew out the vents, and partially melted the sleeves. Some of the adjacent parts have been barbequed too. The unit always has run hot, but it has provided years of wonderful service too. The amplifier board and power transformers are still original save for a couple of bias resistors I replaced in the power amp.
Use 105C rated caps, with low ESR and plenty of voltage rating, and there shouldn't be a problem.
If there's a voltage doubler, that would probably be a weak point in the power supply.

If you want to lower the failure rate further, you could use a ventilation fan.
That worked wonders on a Dyna FM-3 for me. It runs cold now.
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Old Yesterday, 05:57 PM   #3
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Join Date: May 2010
Location: Skokie Il
Quote:
Originally Posted by rayma View Post
Use 105C rated caps, with low ESR and plenty of voltage rating, and there shouldn't be a problem.
If there's a voltage doubler, that would probably be a weak point in the power supply.

If you want to lower the failure rate further, you could use a ventilation fan.
That worked wonders on a Dyna FM-3 for me. It runs cold now.
They are rated 105C, low esr.

I think the voltage doubler is cheesy too, for such a nice unit.

I have a box of computer fans of all sizes and configurations. I'll see what I can find.

I'm not looking to mod this unit; I feel like it will affect its value. These units are still very popular, and I've seen reconditioned units offered on fleabay for $300-500. Non working units are offered at $80-125. A lesser unit I would mod away or just scavenge parts. And there are some really nice parts to be scavenged.

Thanks.
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