Have a NAD s100 preamp that i like a lot but after 20yrs of use it needs some service.
Have replaced some aging Elna caps (down to half value..) also have some problems with the potentiometer and thinking just replacing it with a new one but hard to source (Alps 20x2 rk27 with motor) I can only find 10, 50 and 100k replacements.
I wonder what would happen if i replaced it with a 10K version? Or a 50K?
Input imp unbal. is 75ohm and balanced 100ohm according to another thread.
Another questions is about the psu and diodes, original it has the IN4003 and i happen to have some BYV26C old stock from Philips(vishay) https://www.vishay.com/docs/86040/byv26.pdf
laying around and what i can see it seems like a good replacement and maybe even some improvements? And something i haven't seen before it's the 2x ceramic caps they've placed before the diodes? Can i replace those with polyester caps i have. Bad feeling seeing ceramics that's all...
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Have replaced some aging Elna caps (down to half value..) also have some problems with the potentiometer and thinking just replacing it with a new one but hard to source (Alps 20x2 rk27 with motor) I can only find 10, 50 and 100k replacements.
I wonder what would happen if i replaced it with a 10K version? Or a 50K?
Input imp unbal. is 75ohm and balanced 100ohm according to another thread.
Another questions is about the psu and diodes, original it has the IN4003 and i happen to have some BYV26C old stock from Philips(vishay) https://www.vishay.com/docs/86040/byv26.pdf
laying around and what i can see it seems like a good replacement and maybe even some improvements? And something i haven't seen before it's the 2x ceramic caps they've placed before the diodes? Can i replace those with polyester caps i have. Bad feeling seeing ceramics that's all...
Servicemanual: Login - HiFi Engine
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Nothing wrong with ceramics there, they filter out high frequency noise and RF nicely. Your replacements would have far higher stray inductance I suspect.
I have some Ero Mkt 1817.. would they do worse you mean?
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Max
With regard to your potentiometer, I've found two sources in the U.K. that sell them.
Alps motorised | Hifi Collective
Alps RK27112MC030 20K Motorised Dual-gang Rotary Potentiometer | Rapid Online
With regard to your potentiometer, I've found two sources in the U.K. that sell them.
Alps motorised | Hifi Collective
Alps RK27112MC030 20K Motorised Dual-gang Rotary Potentiometer | Rapid Online
Thank you very much.
I see they both have straight round shaft while mine has a cut out. Would it work or i can with the help of a dremel grind it down?
I ordered that from Hificollective. I had an old RK27 without motor with same round shaft at home in my box, tried it on my Nad volumeknob and it seems to work ok too. If it later on struggles i will make a cut in it.
What i understand Alps doesn’t manufactured the rk27 with motor anymore so better hurry while supply lasts.
What i understand Alps doesn’t manufactured the rk27 with motor anymore so better hurry while supply lasts.
Max
Good to hear you ordered the replacement potentiometer. I just use a small file and make a flat section on the control shaft. It only needs to be small, just wide enough for the screw to make a purchase.
Good to hear you ordered the replacement potentiometer. I just use a small file and make a flat section on the control shaft. It only needs to be small, just wide enough for the screw to make a purchase.
After upgrading caps from 3x4700uf 50v to 3x6800uf 50v it sounds better and works well except when i turn it off i get a big ”thump” in my speakers. Not if i turn amps off first though.. why can that be? Also hear a slight hum.
2 caps are for audio and one for frontpanel/ relays/ etc so didnt have to upgrade that one but did it for cosmetic reason, just looked better if all caps looked the same.
I wonder if its because of that? The relays should cut the signal on the ouput when i press the power-button but it seems there’s a delay and the preamp let some crap out.
Anybody have a clue? Saw in a polish forum somebody that modified this and experinced same problem. There it was 3x10000uf caps..
2 caps are for audio and one for frontpanel/ relays/ etc so didnt have to upgrade that one but did it for cosmetic reason, just looked better if all caps looked the same.
I wonder if its because of that? The relays should cut the signal on the ouput when i press the power-button but it seems there’s a delay and the preamp let some crap out.
Anybody have a clue? Saw in a polish forum somebody that modified this and experinced same problem. There it was 3x10000uf caps..
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As the old caps were down to half value, you will have increased the stored charge 3 fold roughly. That's perhaps prolonging the turn-off transient sufficiently to end-stop the speakers whereas before they just moved silently?
The hum is likely higher current for the conduction pulses due to better capacitors, making the rectifier switching noise stronger. Perhaps some extra suppressor caps across the rectifiers, or small value resistor between rectifier and filter caps to lengthen conduction time?
The hum is likely higher current for the conduction pulses due to better capacitors, making the rectifier switching noise stronger. Perhaps some extra suppressor caps across the rectifiers, or small value resistor between rectifier and filter caps to lengthen conduction time?
I see and do agree with you that it can be the case But here comes the fun part, only one channel has the hum. I’ve been looking through the schematic and what i can understand all muting is done with relays except mute from remote is done by a transistor.
The left channel that has the problems getting about 3-4 degres warmer on the heatsinks and when checking diodes (D452 and D454) i see 2 of them are around 30 degres and 2 is 35 degress. Dont know if thats normal.
This hum i noticed first time after accidently turning preamp first, the bang was clearly disturbing cuz both my NAD 216 and Behringer NX6000 relays/ protection circuits went to mute/ protect and after a sec or two they came back and thats when i noticed the hum. Ive tried my amps with other preamp and they work fine. Ive switched opamps and no difference. With balanced output same noise but just stronger in level.
I suspect something in the regulator coukd have gone haywire..
From the regulator there is a ”tap” with a 100k resistor that goes to the controlboard, is this for sensing when its on/off. This pre you can also put in standby-mode.
Today i put back the orginal cap value (4700uf) for the regulator/ psu for controlboard but same issue. I double checked all soldering etc and couldn’t see anything wrong. I might hade ESD some zener/ transistor etc while doing this. Could be so. I’ve done a few capacitor upgrades, sometimes to twice the uF and have never caused any problems.
Another thing if NAD have tweaked it so that with capacitance, everything is set to some DC voltage ofset so if somethings off, i believe more capacitance will give slighty higher rail voltage? Then the relays acts folish. Or something..
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Have replaced all diodes in psu (7 totally) and measured all resistors and zeners and haven’t found anything yet. Hum is still present one ledt channel after the ”pop” i had..
The caps i’ve upgraded to is Nichicon LKG ”Gold Tune” and i wonder if they’re or one is faulty. My dmm can’t measure more than 200uF and not ESR... because of the double sided board it’s a hell to desolder and easy to rip of traces so i hope i dont have to desolder them again...
Any suggestions what i can check?
The caps i’ve upgraded to is Nichicon LKG ”Gold Tune” and i wonder if they’re or one is faulty. My dmm can’t measure more than 200uF and not ESR... because of the double sided board it’s a hell to desolder and easy to rip of traces so i hope i dont have to desolder them again...
Any suggestions what i can check?
Still debugging this.. with my limited skills.
Looking at the schematic i have hard time to undetsand why the toroid have 4 different voltages...11,12,21,22V. Strange why voltages are so close and seems opamps going with a very low voltage? after rectifying under 10V?
I'm not confident enough to start poke around with my dmm to find out voltages.
One bipolar transistor PNP (Tip127) seems faulty, get a beep between middle leg and emiiter collector but not on the the other (tip122) also this tip 127 from middle leg have connection not only to emiter but also to chassis.. hmm
Looking at the schematic i have hard time to undetsand why the toroid have 4 different voltages...11,12,21,22V. Strange why voltages are so close and seems opamps going with a very low voltage? after rectifying under 10V?
I'm not confident enough to start poke around with my dmm to find out voltages.
One bipolar transistor PNP (Tip127) seems faulty, get a beep between middle leg and emiiter collector but not on the the other (tip122) also this tip 127 from middle leg have connection not only to emiter but also to chassis.. hmm
A friend bought a NAD s100 pre-amplifier, the inputs from the front panel do not turn on only from the remote control, what could be the reason? Everything else is working correctly. Perhaps some function was included that he still does not know about and did not understand how to remove?
NAD S100 - Manual - Stereo Preamplifier - HiFi Engine
NAD S100 - Manual - Stereo Preamplifier - HiFi Engine
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Do you mean that when he switches input (push buttons) it doesn’t respond at all? Only from remote?