Nikko Beta 40 relay not click. Need help.
p4spooky
Active Member
Glad you figured it out. Troubleshooting vs shotgun replacement of parts is a worthy debate, but given the time it takes and relative low cost of parts I decided to do a blanket replacement of this area on mine to improve reliability. Don't remember now what part failed in mine but got the Nikko running in 15 mins.
The unit does sound excellent after a full recap. You may want to consider doing this to your Nikko 40 after you put the relay issue to rest.
The unit does sound excellent after a full recap. You may want to consider doing this to your Nikko 40 after you put the relay issue to rest.
I recapped my beta ii years ago with nichicon muse, totally blew away the elnas it had been loaded with. The caps in the x0 series are better, but can be improved. It's surprising, but years on these still fly under the radar of most folks and are still rationally priced.
Nikko designed some very nice preamps, and they respond fabulously to updating. Remote switches, partitioned cases, separate boards. Considering the number of transistor pairs in them, staying ahead of degrading caps is a must. They used good parts, but 40 years is starting to show on the caps.
Nikko designed some very nice preamps, and they respond fabulously to updating. Remote switches, partitioned cases, separate boards. Considering the number of transistor pairs in them, staying ahead of degrading caps is a must. They used good parts, but 40 years is starting to show on the caps.
Thanks for that. Didn't think about meter impedance. Even though I should have since I ran into a perfect example of it in my own Nikko project that you helped me with.
Glad @ReisDaddy got it fixed. Sounds like D902 was shorted.
At the risk of further digression, I'm thinking the reason the voltage on the collector of Q901 is not dropping to near zero is because it is operating it its "active" range as opposed to "on" (fully saturated)? So in this case hfe might be an important consideration in choosing a substitute? Is this correct?
Cheers...................................Todd
@Goldie99 @ivandezande @loudnoises @mbz @TConnelly @p4spooky @sregor
Thank you so much for your time guys.. i pray for you guys healthy, wealthy, and your families....
Yay.. she is singing bright like a diamond!
I like them paired better than Marantz 1180 DC alone, too much bass IMHO. Now its more flat. I think its become clinical. I like clinical sound.
Must test a view more running hours, im just afraid of fatigue. And not tested yet paired to Sansui AU-517.
Waiting to all the component arrive for recap.
But i did pull the diode D804 D901 D902 using DMM diode mode, usually i write them in excel, so i remember what was done.
So 0.55v is bad?
So many 1S2076 there, but the problematic there was 1S2076A (band with navy blue), the rest is 1S2076 (light blue)
Should i replaced them all?
Talking about fatigue, where is the subforum? i plan to discuss about fatigue, while most people think that the speaker that make fatigue, and in my experience it can be in pre amp or maybe amp, and before, i was not believe when people said about fatigue while discussing audio devices (i tought they are hyperbolic).
Sansui AU-517 was the first amplifier that make me fatigue, i like their sound character. the more time i listen to, the more my ear get tired. Very tired. That is strange.
Next day, i cannoy handle not even in 15 mnts. Next day again, 10 mnts is enough to make me fatigue. But, i bought one of Topping (china brand) pre-amp, the fatigue is gone! Strange.. I think if i continue the story it will be long hahaha...
Thank you so much for your time guys.. i pray for you guys healthy, wealthy, and your families....
Yay.. she is singing bright like a diamond!
I like them paired better than Marantz 1180 DC alone, too much bass IMHO. Now its more flat. I think its become clinical. I like clinical sound.
Must test a view more running hours, im just afraid of fatigue. And not tested yet paired to Sansui AU-517.
Waiting to all the component arrive for recap.
But i did pull the diode D804 D901 D902 using DMM diode mode, usually i write them in excel, so i remember what was done.
So 0.55v is bad?
So many 1S2076 there, but the problematic there was 1S2076A (band with navy blue), the rest is 1S2076 (light blue)
Should i replaced them all?
Talking about fatigue, where is the subforum? i plan to discuss about fatigue, while most people think that the speaker that make fatigue, and in my experience it can be in pre amp or maybe amp, and before, i was not believe when people said about fatigue while discussing audio devices (i tought they are hyperbolic).
Sansui AU-517 was the first amplifier that make me fatigue, i like their sound character. the more time i listen to, the more my ear get tired. Very tired. That is strange.
Next day, i cannoy handle not even in 15 mnts. Next day again, 10 mnts is enough to make me fatigue. But, i bought one of Topping (china brand) pre-amp, the fatigue is gone! Strange.. I think if i continue the story it will be long hahaha...
Interesting observation. If you calculate the base current 15 volts - 6.2 (zener)-.6 (Vbe) get 8.2 volts, dropped through a 150K resistor gets 54 uA or .054 mA base current. Multiply by 250 (hfe), get Ic of about 13 mA. The coil resistance was 819 ohms, so if it is 12 volts, should need about 14 mA (lot of fudging here about what is actually needed), so HFE is important. As long as IC is High enough to turn on relay, then circuit should work.
0.55v is a little lower than I normally see for a diode drop but not alarmingly so.
Hmmmmm, I remember you mentioned testing D901 and ZD901 and got 0.6xx, and OL with the leads reversed. Did you get OL on D902 with the leads reversed on this one as well? If so maybe my guess is off the mark. But if so, what did fix it?
Cheers...........................Todd
Goldie99
Super Member
@sregor @TConnelly - I think it's probably even a little more involved.
In LTSpice(#), I'm seeing a current thru' R902 (150k) varying between ca. 16 and 51 µA, at 50Hz (it's cap charging/discharging, not sinusoidal). Consequently, the Zener current also varies slightly, between about 32 & 36 µA. The exact values of the lower current levels depend upon the value of C826 (varying the supply voltage ripple), as well as the supply voltage frequency (50Hz vs. 60Hz, varying the charge/discharge times). The OP mentioned he's using a 240V step-down transformer so I'm guessing he's probably in Europe at 50Hz.
Q901 is in saturation only ca 20% of the time, with Ic varying from ca. 8.4 to 11.4mA, equivalent to very roughly 60 - 80% of the nominal 14.6mA expected for a 12V / 820R relay coil. I'd assume 80% would be enough to exceed the relay 'pull-in' value, and 60% would still exceed the 'drop-out' value.
I think it's probably been set up like that to give the fastest possible drop-out (muting) time when the unit's switched off; nobody cares if the start-up time is 5" or 10", as long as it's quiet, but to have a quiet shutdown it needs to be fast.
# - LTSpice using, 14.9 Vac, 50Hz, KSC1845 for Q901, 1N4148 diodes, a generic 6.2V Zener, and the OP's 820R for the relay coil
In LTSpice(#), I'm seeing a current thru' R902 (150k) varying between ca. 16 and 51 µA, at 50Hz (it's cap charging/discharging, not sinusoidal). Consequently, the Zener current also varies slightly, between about 32 & 36 µA. The exact values of the lower current levels depend upon the value of C826 (varying the supply voltage ripple), as well as the supply voltage frequency (50Hz vs. 60Hz, varying the charge/discharge times). The OP mentioned he's using a 240V step-down transformer so I'm guessing he's probably in Europe at 50Hz.
Q901 is in saturation only ca 20% of the time, with Ic varying from ca. 8.4 to 11.4mA, equivalent to very roughly 60 - 80% of the nominal 14.6mA expected for a 12V / 820R relay coil. I'd assume 80% would be enough to exceed the relay 'pull-in' value, and 60% would still exceed the 'drop-out' value.
I think it's probably been set up like that to give the fastest possible drop-out (muting) time when the unit's switched off; nobody cares if the start-up time is 5" or 10", as long as it's quiet, but to have a quiet shutdown it needs to be fast.
# - LTSpice using, 14.9 Vac, 50Hz, KSC1845 for Q901, 1N4148 diodes, a generic 6.2V Zener, and the OP's 820R for the relay coil
To bolster this theory, all my nikko gear does indeed have almost instantaneous relay drop when you switch it off.
Fabulous work here. Next time my beta ii goes on the bench in digging into that relay. Been jumpered for almost a decade now, it would be fantastic if the relays really weren't the issue.
Great stuff! Thanks for this guys. Clearly I need to embrace the horror and brush up on my ohms law. Math! Arghhhh!
Something is gnawing at me about this. @ReisDaddy, you said,
I’m hoping it’s just a language barrier thing and you meant “replace” rather than “remove”? I’m hoping you didn’t run it without the diode D902. @Goldie99, does LTSpice show what the voltage spike would be on shut down if D902 was removed. Am I correct in assuming this is the reason you cautioned against running it without it? Or is there another reason I’m not considering? Thank you all!
Cheers………………Todd
Goldie99
Super Member
@TConnelly - relay solenoid flyback was indeed my concern, but more from a perspective of not encouraging people to simply remove the diode, which as you know could potentially lead to other faults. I've simply used an 820R resistor to 'simulate' the relay coil, so in this case LTSpice had no inductance information to calculate flyback voltage.
Hahah.. yes you are right. replace. Sorry for bad english, since english is not my primary language.