Capacitor brand/type for NAD amp?

Hello,

I've had good luck with the Panasonic caps. I often order them from Digikey

I would not 'Shotgun' the entire amp, but I would replace the defective caps in both channels, even if only one of them was currently bad. I would not worry about the brand change. Though I'll warn you that discussing pros and cons of various brands of caps can lead to long boring threads on newsgroups.

Regards, Tim Schwartz Bristol Electronics

TDWesty wrote:

Panasonic FC capacitors are electrolytics. The high-value electrolytics you mentioned (50v 4700uF and 1000uF) will be used in the power supply section, which is working fine in your amplifier (I think you said your amplifier is working fine with CD and DVD inputs, but not with tuner and VCR inputs.)

For the problem you have - weak signal on left channel when using tuner or VCR inputs - you need to establish the cause. I'd guess it's a defective switch or connection somewhere.

It could be a very minor fault, but may take an engineer several hours to track down.

Tim

TDWesty: The best advice I can give you is to stay focused and fix the "Left Channel" problem.... then you can evaluate the overall performance and make a decision about a "shotgun" repair involving ALL of the caps..... personally, if the amp is working fine after your specific repair, I wouldn't fix it.....

-- Best Regards, Daniel Sofie Electronics Supply & Repair

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

I've got a '71 Quad system still working fine. The AM tuner has had a few sets of valves, and I've cleaned or replaced a few pots and switches. But not one cap...

--
*42.7% of statistics are made up. Sorry, that should read 47.2% *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

I agree brand doesn't matter. I use Xicon brand from either Parts Express or Mouser. Mouser's prices and selection of caps is better. The big caps are probably OK. I'd replace those in the amp and power supply. You better believe 30 year old caps are bad, or will be soon! If you replace capacitors, it's only the electrolytic caps that you need to replace.

(snip)

(snip)

Start with the switches, clean them thoroughly. I have fixed several recycled and junked stereo receivers from the 1970's an 80's and the most common fix is to clean the switches (next is dial lamps.) In one case the switch was damaged (no spares), so I jumpered the function on the board (only lost the tape-in option, no big deal, still have AUX.) Your problem does not suggest faulty electrolytic capacitors. Cheers, Roger

I've sprayed all the switches & pots with contact cleaner, and the resistance across the terminals off all the input switches are the same

- about 0.5 ohms. It is a bank of 4 switches (tape, cd, tuner, phono) soldered directly to the board, so without a desoldering tool, removal looks to be fairly tricky. Tape works fine, CD & tuner are bad in the left channel.

I may try to replace the transistor for the infrasonic filter, which is apparently bypassed for the tape input. I need to find one, it is not a common one - C1845.

Common as Dog Poo...MCM / Global has them. kip

"TDWesty" wrote in m

essage news: snipped-for-privacy@f14g2000cwb.googlegroups.com...

"TDWesty" bravely wrote to "All" (18 Jun 05 10:48:27) --- on the heady topic of "Re: Capacitor brand/type for NAD amp?"

TD> From: "TDWesty" TD> Xref: aeinews sci.electronics.repair:50953 rec.audio.tech:21300

TD> I've sprayed all the switches & pots with contact cleaner, and the TD> resistance across the terminals off all the input switches are the TD> same - about 0.5 ohms. It is a bank of 4 switches (tape, cd, tuner, TD> phono) soldered directly to the board, so without a desoldering tool, TD> removal looks to be fairly tricky. Tape works fine, CD & tuner are bad TD> in the left channel.

TD> I may try to replace the transistor for the infrasonic filter, which TD> is apparently bypassed for the tape input. I need to find one, it is TD> not a common one - C1845.

Add 2S prefix in front of C1845, you should find a 2SC1845 more easily. BTW the 2SC1845 is a "General Purpose" high gain transistor and it can be easily substituted by any with a suitable voltage that fits. Not that critical a part for audio usage.

A*s*i*m*o*v

... A stereo system is the altar to the god of music.

Hello,

Well, that transistor is a 2SC1845, and is really common.

--Tim

TDWesty wrote:

If you're not equipped for desoldering a switch, are you sure you should be contemplating a recap?

A fair point. :-)

But each cap can be done one at a time with minimal fuss and an iron. The switch bank has 24 pins and 4 switches clipped together in a rail, so I don't think it could be removed without a solder sucker. I've decided against a recap for now, at least until I get the left channel fixed and my speakers back in service so I can judge things better.

I'd normally remove a multipole switch by clipping the contacts etc to minimise damage to the pcb. Many are a pretty tight mechanical fit.

And I do have a desolder station.

--
*If a pig loses its voice, is it disgruntled? *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

I've only been able to find one manufacturer for the 2SC1845 - Fairchild, and Digi-Key doesn't carry this one for some reason (they have other Fairchild parts). Any tips on a substitution chart - I've been trying to match V, IC, and HFE closely, but haven't found anything DigiKey carries that is close enough. I would prefer to deal with a Canadian supplier to avoid border hassles. So far the NTE90 appears to be the only other close match.

I'm confused a bit by your comment about "any with a suitable voltage"

- isn't the gain significant? I can find some that match the 120V, 50ma rating, but very few with a gain of 600. I am assiming that I should replace both channels at once to avoid a mismatch, but wouldn't using a lower gain transistor cause problems? I don't have the schematic, so I don't know the exact function of this thing, but I do know it is in the infrasonic filter section. So I'm guessing the high gain is used to effect a sharp low freq roll off? In this case, perhaps the gain isn't that critical. Sorry if these are dumb questions...

In sci.electronics.repair sofie wrote: : TDWesty: : The best advice I can give you is to stay focused and fix the "Left Channel" : problem.... then you can evaluate the overall performance and make a : decision about a "shotgun" repair involving ALL of the caps..... : personally, if the amp is working fine after your specific repair, I : wouldn't fix it..... : -- : Best Regards, : Daniel Sofie : Electronics Supply & Repair

Agreed. I have a Marantz receiver that is 30 years old. No reason to go in and replace all of the capacitors. It works fine. Fix what is defective. Leave it at that.

b.

: The one problem my amp has (see earlier post) seems to be isolated to : the left channel infrasonic filter section. Assuming I can resolve this : be replacing the caps in that section, should I just quit there?

I'd suggest finding the source of the problem vs. shotgunning parts that are likely not to fix the problem. The "low impedence" capacitor is probably a low ESR capacitor. Impedance is a result of the value of the capacitor which is intrinsic, plus the inductive reactance of the leads/foils.

Most stereo equipment is "step and repeated" in their PC board designs. You have one working side and one with low signal. Compare (using an oscilloscope) the working side components vs. the nonworking side. It's helpful to have a schematic to see where the positions of the components are but a skilled technician/engineer can often follow the signal paths by the physical layout.

I have repaired electronic equipment for decades and have never seen a need to brute-force "every electrolytic capacitor" in any piece of equipment. It just seems foolish to me. Especially if the equipment has been in use (electrolytic capacitors do fail by "reversed polarity"

B.

I have, but the equipment was on the production line. :)

--
        If John McCain gets the 2008 Republican Presidential nomination,
           my vote for President will be a write-in for Jiang Zemin.

You should stop hanging around those wasted, commie, ex-hippie college professors.