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Old 1st February 2009, 12:53 AM   #1
izools is offline izools  United Kingdom
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Unhappy NAD 3020A Issues

Hi all!

Newbie here just needed some advice.

Used to be the proud owner of some B&W S3 600 Range 5.1 system & Onkyo TX-SR 606 beautifulness but I had to give that and and my house up a few months ago (damn economy!)

I've had to go el' cheapo, el' second-hando for my current audio -

I think I did quite well, one of the pieces of kit I've picked up is a NAD 3020A Amplifier (Mission 700 Speakers, the later ones). The first 24 horus of use, brilliant. Warm, rich, inviting soundstage with a certain richness that makes one feel almost smothered in undertones of low-end subtlety.

VERY different sound to what I've been used to, gone is the light and detaled extended high end unfortunately, but it's still a very good sound for such cheap kit.

Phono stage is good also, Rotel RP-830 with a new Ortofon OM10 cartridge sings along nicely. I like this combination as the OM10 cart can be bias toward the high end, and the amp can be a bit dark. Marry the two and they seem to cancel out their differences and portray a rather open and light sound.


......UNFORTUNATELY the amp has developed issues.

After approx 10 seconds of being powered on the right speaker begins to hiss and crackle. This crackle is continuous and notably unchanged irrespective of which input is selected, or whether the volume is being adjusted. Same counds for Mono and Loudness buttons - doesn't impact the crackly hiss. Tested bass, treble, and balance controls, also. Nada.

I disconnected the Pre-Power links, and the hiss is gone. It is definitely an issue in the Preamp section.

The crackle gets louder and louder progressively over approx 30 second period. The left speaker is unaffected.

This was not an issue until I left the amp on continuously for about two hours or so. I read that the 3020 needs to warm up for an hour or two before it provides a less dark, more detailed and transparent soundstage. So I left him to warm up (nothing playing) and came back to the hissy crackle.

Any ideas?

OH, and it continue after I disconnect the turntable and it's GND cable.
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Old 1st February 2009, 02:40 AM   #2
frugal-phile(tm)
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I always left my 3020s on 24/7.

Here is the service manual.

http://p10hifi.net/planet10/manuals/...viceManual.pdf

dave
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Old 1st February 2009, 05:39 PM   #3
izools is offline izools  United Kingdom
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Thank you!

Question: How simililar in design to the 3020 is the 3020A?

Interestingly the scratchy hiss doesn't seem to be an issue today. Happened for a few seconds during warm up but has now gone.

It sounds like wind blowing over a stylus... very strange.

At some point I will be re-capping this amp, I think it deserves it, and I'll take the oppourtunity to look out for any dry solder joints or corroded coponent legs (was a bit damp when it arrived).

Probs just a combination of dampness and age taking their toll on some miniscule solder joint somewhere.

On the subject of caps - Elna or Nichicon?

I've not used a soldering iron sincce High school, so the task is a bit daunting...
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Old 2nd February 2009, 04:46 AM   #4
izools is offline izools  United Kingdom
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crackle is back again... no sign of it going away... any pointers what I should be looking out for?
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Old 2nd February 2009, 05:17 AM   #5
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I had a nasty intermittent crackle in a NAD 701 in the power amp section, the solution was to reflow every solder joint.

Given the age of the unit, replacing the electrolytic caps would be a good idea - not a lot of work or $ to do, and one of them may be the source of the problem.

I also suggest that you modify the power amp section to add emitter resistors on the outputs, otherwise the design is at risk for thermal runaway - that's what happened to mine.
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Old 2nd February 2009, 05:27 AM   #6
sangram is offline sangram  India
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I would suggest a blowdryer after you remove all the caps. We have a problem with humidity in some parts of our country, and warming up the board helps a lot. I've seen older boards actually absorb moisture - resulting in a few failed joints and cracks sometimes.

After removing the caps I use my hot air station to get the board heated up to about 60 degrees, cool and repeat the process. Overnight with a few packs of silica gel in a ziplock pouch, and two days later the board is fit for recapping. I've actually restored a computer motherboard for myself like this.
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Old 2nd February 2009, 05:32 AM   #7
lineup is offline lineup  Sweden
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Potentiometers
are one thing to check and possibly replace.
But your previous post indicates maybe isnt a worn out pot.
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Old 2nd February 2009, 07:03 AM   #8
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Solder joints, resistors, capacitors. You have lots to check. Curious why you use a Rotel phono stage in preference to the Nad.
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Old 2nd February 2009, 12:18 PM   #9
izools is offline izools  United Kingdom
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Quote:
Curious why you use a Rotel phono stage in preference to the Nad
Sorry maybe I wasn't clear - I use a Rotel Deck, the NAD stage is renowned so I'll stick to that!

And many thanks to everyone else for the hints and tips.

From the looks of things several joints had to be re-flowed at some point in the past, there is evidence of this, there is also evidence of track repair by means of copious amounts of solder, rather than jumpering the worn track... someone seems not to have been very good at soldering me thinks!

Off to the stores this weekend methinks... get some caps and a soldering iron... better practice on an old PC Motherboard or something to start with

I've looked at the schematic and narrowed the fault down to just over a dozen different components, as the crackle is affected when I turn the balance to the left, it fades, but it isn't affected by the volume control, so it's between the Bal. pot and the Vol. pot.

I'll stick a bit of contaact cleaner on them for good measure but I'm confident this isn't a scratchy pot issue (I wish it was... so much easier!)

Watch this space
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Old 2nd February 2009, 03:09 PM   #10
izools is offline izools  United Kingdom
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I came up with this shortlist:

Electrolytic Capacitor Kit (To replace various caps in preamp) 4.49
4x 2200uF 35V Caps (To replace PSU Reg. Caps) 2.20
2x 35W 0.25Ohm Resistors to replace Speaker Thermal Fuses 3.90
2x Heatsinks for the Speaker Protection Resistors 2.60
2x Retaining Clips for Heatsinks 0.15
Thermal Pads for bonding Power Resistors to Heatsinks 1.60
Servisol 10 Contact Cleaner / Lubricant 2.95
20W Soldering Iron with 0.8mm Bit 14.95
Lead Free Solder with 4% Silver content 4M 1.45

Add VAT and Shipping and it's pretty much 40. Really worth spending that much on this old amp? Think I'm looking to buy the right parts?

very new to this
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