Hi everyone,
I have the same problem with my amp,
but when I checked the PCB and the relay on the board is not a Taiko DGX2-24M but an Omron G2R-2...
Does anybody knows if there is some special difference between those two? Or is it just an equivalent?
I'm looking for a replacement, and I'm wondering which one of the two I should be looking for...
Thanks
I have the same problem with my amp,
but when I checked the PCB and the relay on the board is not a Taiko DGX2-24M but an Omron G2R-2...
Does anybody knows if there is some special difference between those two? Or is it just an equivalent?
I'm looking for a replacement, and I'm wondering which one of the two I should be looking for...
Thanks
I cannot specifically answer your question.
(I primarily came back to this thread to give thanks)
This may or may not help. I used this post:
"Quote from post #13:
It is a very standard relay.
I use mostly JW2SN relays from Panasonic and i cut the two
unused lugs.
Try Omron too.
In Canada i obtain them from Digikey part no: 255-1118-ND
Best regards
__________________
Highspeed "
I just replaced the relay on my 304 an hour ago using the part listed above.
Thanks for all who contributed to this thread. Problem solved!
Rick
(I primarily came back to this thread to give thanks)
This may or may not help. I used this post:
"Quote from post #13:
It is a very standard relay.
I use mostly JW2SN relays from Panasonic and i cut the two
unused lugs.
Try Omron too.
In Canada i obtain them from Digikey part no: 255-1118-ND
Best regards
__________________
Highspeed "
I just replaced the relay on my 304 an hour ago using the part listed above.
Thanks for all who contributed to this thread. Problem solved!
Rick
I'd just like to say that I have a NAD 304 that was suffering from a faulty right channel. At low volumes it would it would drop out and crackle. At high volumes fine. Removing and refurbishing the relay mentioned in the thread seems to have solved the problem (I gave the copper contacts inside the relay a clean). Thanks for the informative thread guys.
Solved problem
Thanks a 1.000.000 times Highspeed, you saved my 304 (i was thinking of sell it!!)
Replaced the output relay with a really cheap one identical to the DEC i found in it (2 €) and now My NAD is singing again, better than my 3020 & 3120.
I love 304, what a damn good amp!!!
Thanks a 1.000.000 times Highspeed, you saved my 304 (i was thinking of sell it!!)
Replaced the output relay with a really cheap one identical to the DEC i found in it (2 €) and now My NAD is singing again, better than my 3020 & 3120.
I love 304, what a damn good amp!!!
Then you turn on yor 304, you hear a channell missing and crackling, sometimes the right, sometimes on the left, so you increase volume and "think" you fixed it
It's the same issue we all here have had on Nad 304,but just follow what HIghspedd says: just replace the output relay and your 304 will be OK.
Thanks Highspeed!
I had the fading problem on my NAD 304 and the problem was the relay!
I desoldered it, opened (the cover can be removed easily), cleaned the contact with extra fine sandpaper and contact cleaner and then resoldered it. Now it work!
I also checked the resistance beetween relay contact before and after the cleaning:
before was really impredictable, sometimes 6 ohm, sometimes 50 ohm, depending on luck
after cleaning always 0 ohm.
Thanks another time!
I had the fading problem on my NAD 304 and the problem was the relay!
I desoldered it, opened (the cover can be removed easily), cleaned the contact with extra fine sandpaper and contact cleaner and then resoldered it. Now it work!
I also checked the resistance beetween relay contact before and after the cleaning:
before was really impredictable, sometimes 6 ohm, sometimes 50 ohm, depending on luck
after cleaning always 0 ohm.
Thanks another time!
See this excellent article about repairing the NAD 304
http://www.condoraudio.com/wp-content/uploads/Projects/NAD-304-Restoration-Repair-Upgrade.pdf
http://www.condoraudio.com/wp-content/uploads/Projects/NAD-304-Restoration-Repair-Upgrade.pdf
Your 304 amplifier may perform better now that you replaced some failing components but you have made some odd part substitutions like those 3R3 power resistors used as base stoppers, yachadm. 1/2W is ample and likely better. Note that the emitter resistors you refer to are usually only ~ 0.22 ohms, not 3.3. There is only one such resistor here, in the collector of the upper power transistor and used for signal current sensing. I think you need to take a closer look at the schematic before telling us how excellent your upgrades and article are. Nice pics and composition, though.
Also, using larger, low noise resistors in the output stage is about as useful as power transistors at the input stage - pointless. The only benefit is to the manufacturer's income. Use low noise parts in the preamp and input stage, where you may get some measureable benefit in good designs that are already very quiet.
Also, using larger, low noise resistors in the output stage is about as useful as power transistors at the input stage - pointless. The only benefit is to the manufacturer's income. Use low noise parts in the preamp and input stage, where you may get some measureable benefit in good designs that are already very quiet.
Ian,
I didn't mention that I replaced the 0.22 ohm Bias resistors at all - there is no point in doing that - as long as they are in-spec, as you well know.
Those 3.3ohm's are not the Bias resistors. They were hot to touch, and one 3.3 ohm measured over 5 ohms. Too hot means that the original power spec was erroneous, and an up-rated replacement is in order.
Anyway, the originals were really crappy Chinese quality - I was surprised to see that in this NAD.
I did mention, and you can see clearly from the photo's, that ALL signal path resistors (including those in the preamp) were upgraded.
Comments are always welcome!
Menahem
I didn't mention that I replaced the 0.22 ohm Bias resistors at all - there is no point in doing that - as long as they are in-spec, as you well know.
Those 3.3ohm's are not the Bias resistors. They were hot to touch, and one 3.3 ohm measured over 5 ohms. Too hot means that the original power spec was erroneous, and an up-rated replacement is in order.
Anyway, the originals were really crappy Chinese quality - I was surprised to see that in this NAD.
I did mention, and you can see clearly from the photo's, that ALL signal path resistors (including those in the preamp) were upgraded.
Comments are always welcome!
Menahem
All NAD models uses crappy parts quality - ever since the original 3020, in my experience with them since around 1980. The price alone compared to up-market brands should tell us what to expect at such low prices for products primarily aimed at the European/North American markets.
Sure, there are no 0.22R "bias" resistors here. Just a single current sense resistor, as I said. Some folks do misread resistance codes, though. The only 3.3R resitors are base stoppers, for preventing oscillation also as I said, and also the output coil damping resistors, R423,4
I clearly described the 3.3R resistors as base stoppers and drew attention to there being no emitter resistors on the power out transistors, The original 3.3R resistors (assumed R353,4 and R357,8) were rated 0.5W flameproof and if they were hot to touch with no signal, it says there was a problem with excess DC current or oscillation from driver to output transistors.
Bias input current at the output transistor bases should be only in the order of a few milliamps, which amounts to about 1 mW resistor dissipation. The test points aren't identified on the schematic and illegible on the PCB layout, so it seems hard to identify what the actual bias current in the output pair will be, unfortunately. Being an EF triple, I imagine it will be around 120 mA or less, quiescent. Average audio signal input current through the stopper resistors may be in the region of 100 mA max. or around 50 mW.
So, if the stopper resistors ran hot, you were either running continuous sinewaves at high power or something was wrong with the output transistors, speakers or bias setting. Perhaps that's why the adjustment pots needed replacement.
I suggest you still scope the resistors to see what's going on or just measure the DC voltage drop across them and calculate the actual DC current. there's probably something still amiss if the oversize base stopper resistors still become more than just warm. Think about it, with Hfe >50, the quiescent base current of these Sanken LAPTs can't be much above a few mA. That means virtually cold.
Sure, there are no 0.22R "bias" resistors here. Just a single current sense resistor, as I said. Some folks do misread resistance codes, though. The only 3.3R resitors are base stoppers, for preventing oscillation also as I said, and also the output coil damping resistors, R423,4
I clearly described the 3.3R resistors as base stoppers and drew attention to there being no emitter resistors on the power out transistors, The original 3.3R resistors (assumed R353,4 and R357,8) were rated 0.5W flameproof and if they were hot to touch with no signal, it says there was a problem with excess DC current or oscillation from driver to output transistors.
Bias input current at the output transistor bases should be only in the order of a few milliamps, which amounts to about 1 mW resistor dissipation. The test points aren't identified on the schematic and illegible on the PCB layout, so it seems hard to identify what the actual bias current in the output pair will be, unfortunately. Being an EF triple, I imagine it will be around 120 mA or less, quiescent. Average audio signal input current through the stopper resistors may be in the region of 100 mA max. or around 50 mW.
So, if the stopper resistors ran hot, you were either running continuous sinewaves at high power or something was wrong with the output transistors, speakers or bias setting. Perhaps that's why the adjustment pots needed replacement.
I suggest you still scope the resistors to see what's going on or just measure the DC voltage drop across them and calculate the actual DC current. there's probably something still amiss if the oversize base stopper resistors still become more than just warm. Think about it, with Hfe >50, the quiescent base current of these Sanken LAPTs can't be much above a few mA. That means virtually cold.
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OK, so let's deal with the salient points:
1. The 3.3 ohm base stopper resistors were upgraded to 3W. They are running perfectly cool, so there is no problem.
2. The signal-generated waveform with a 1KHz signal is perfectly stable while monitoring the distortion on my 8903B (also stable), and the bias/emitter/ whatever voltage you want to call it - I choose to call it the bias-emitter voltage, for lack of a more precise term on this Class H amp (which has the 0.22 ohm resistor outside of the customary circuit region of the Class A or AB amps), is stable at 6mV. So I conclude that all is just fine, with no reason for concern, whatsoever.
3. I see no empirical significance of a small resistor being "likely better" than a larger one. If you have some solid objective evidence, I'd be pleased to learn about it, but in over 35 years of servicing electronics, I haven't yet seen any evidence of such.
4. I purposely use over-rated components in restorations, in circuit areas which I consider to be marginal, as a matter of conscious policy. It is the way I have always worked, and the long-term reliability of a restored machine, and consequently, the satisfaction of my customers, is my primary consideration. The original manufacturer already cut costs during initial production, and see where that got him. So, it will never bother me in the very least, should someone object to my using over-rated components.
Menahem
1. The 3.3 ohm base stopper resistors were upgraded to 3W. They are running perfectly cool, so there is no problem.
2. The signal-generated waveform with a 1KHz signal is perfectly stable while monitoring the distortion on my 8903B (also stable), and the bias/emitter/ whatever voltage you want to call it - I choose to call it the bias-emitter voltage, for lack of a more precise term on this Class H amp (which has the 0.22 ohm resistor outside of the customary circuit region of the Class A or AB amps), is stable at 6mV. So I conclude that all is just fine, with no reason for concern, whatsoever.
3. I see no empirical significance of a small resistor being "likely better" than a larger one. If you have some solid objective evidence, I'd be pleased to learn about it, but in over 35 years of servicing electronics, I haven't yet seen any evidence of such.
4. I purposely use over-rated components in restorations, in circuit areas which I consider to be marginal, as a matter of conscious policy. It is the way I have always worked, and the long-term reliability of a restored machine, and consequently, the satisfaction of my customers, is my primary consideration. The original manufacturer already cut costs during initial production, and see where that got him. So, it will never bother me in the very least, should someone object to my using over-rated components.
Menahem
Fine, you like big parts and expensive resistors. They are minor costs for a repairer, after all. I can understand that guys seeking "upgrades" for their amplifiers will think that tan resistors are wonderful too. Advanced DIYs and students of electronics will naturally see the inconsistencies from a technical point of view and see it as either window-dressing or lack of understanding where low noise components can be of use.
I'm sure you don't need the advice but there are a couple of issues that suggest the smallest possible component size is always the best. In an AB amplifier, it is about susceptibility to EMR which is literally everywhere and a huge problem for respectable noise and distortion figures. The reason is size and proximity of power supply, switching and output currents directly radiating to signal and feedback paths. Though mainly a PCB design and wiring issue, the size of components and leads does matter as you drop below 0.1% THD and -90dB noise.
Your systematic use of oversize resistors has also meant long leads where they are susceptible and would be questioned as a matter of principle by DIYs, designers and engineers everywhere.
BTW generally, large resistors have a nasty habit of outlasting components they might otherwise protect. I have occasionally replaced base stoppers in PA and stage amplifiers - some to my own design even - where they sometimes protect the transistors in disaster events. This has saved considerable cash and time when it came to repairs. Overkill may have a psychological advantage when substitutes are made but it can also run contrary to designed safe operation. For insurance reasons, I take that seriously and make certain I comply with design power ratings or use near equivalents where the originals are unavailable.
There are also quite a few errors in the article section 2 on resistor upgrades. Consider a rewrite. Whilst I think it's great that people prepare articles for others to read, touting your own work as excellent is really asking for close scrutiny.
For a little 35W NAD amplifier, why you would ever need more than a half watt rated resistor in the base of an output transistor is baffling to me though.
I'm sure you don't need the advice but there are a couple of issues that suggest the smallest possible component size is always the best. In an AB amplifier, it is about susceptibility to EMR which is literally everywhere and a huge problem for respectable noise and distortion figures. The reason is size and proximity of power supply, switching and output currents directly radiating to signal and feedback paths. Though mainly a PCB design and wiring issue, the size of components and leads does matter as you drop below 0.1% THD and -90dB noise.
Your systematic use of oversize resistors has also meant long leads where they are susceptible and would be questioned as a matter of principle by DIYs, designers and engineers everywhere.
BTW generally, large resistors have a nasty habit of outlasting components they might otherwise protect. I have occasionally replaced base stoppers in PA and stage amplifiers - some to my own design even - where they sometimes protect the transistors in disaster events. This has saved considerable cash and time when it came to repairs. Overkill may have a psychological advantage when substitutes are made but it can also run contrary to designed safe operation. For insurance reasons, I take that seriously and make certain I comply with design power ratings or use near equivalents where the originals are unavailable.
There are also quite a few errors in the article section 2 on resistor upgrades. Consider a rewrite. Whilst I think it's great that people prepare articles for others to read, touting your own work as excellent is really asking for close scrutiny.
For a little 35W NAD amplifier, why you would ever need more than a half watt rated resistor in the base of an output transistor is baffling to me though.
OK, Ian, I got your thread - what's really bothering you is the fact that I called my article "excellent".
That's fine, I have no problem with that - I even appreciate your comments, but I certainly detect your undertone to go overboard in your criticism, which largely is completely irrelevant.
EMR in THIS circuit is completely irrelevant, at the place where the base stopper resistor has long leads. It may be, and is "likely" certainly relevant in a circuit with high frequency, or at switching frequencies, but here, come on - what you're really doing is trying to apply a generality to a specific situation, and here, your "long-lead" EMR postulation has no merit whatsoever.
If you attempt to apply a generalized postulation to an irrelevant specific case, then be prepared to accept the rebuff from a different, but "likely" equally qualified and experienced engineer.
The Vishay-Dale resistors are well-known and acclaimed in the industry for their low-noise and wide application in audio circuits, so I don't understand what you have against these "tan" resistors, or is it only because I used them in my "excellent" restoration?
You don't have to agree with me at all; nobody requires that, and contrary to the dictates of this upside-down, diplomatically-correct world, where dissent among the sheeple is frowned upon, engineers have always thrived on dissent as a matter of lifeblood. I enjoy it, and commend it, and I am qualified to give as good as I get.
You've beaten this to death, not 100% honestly, so quit while you're ahead.
If your motivation is to criticize, because I got your goat, go ahead, but in the interests of technical accuracy and excellence, keep it absolutely on topic and 100% relevant to the situation at hand, or it becomes an degrading exercise in foolishness.
That's fine, I have no problem with that - I even appreciate your comments, but I certainly detect your undertone to go overboard in your criticism, which largely is completely irrelevant.
EMR in THIS circuit is completely irrelevant, at the place where the base stopper resistor has long leads. It may be, and is "likely" certainly relevant in a circuit with high frequency, or at switching frequencies, but here, come on - what you're really doing is trying to apply a generality to a specific situation, and here, your "long-lead" EMR postulation has no merit whatsoever.
If you attempt to apply a generalized postulation to an irrelevant specific case, then be prepared to accept the rebuff from a different, but "likely" equally qualified and experienced engineer.
The Vishay-Dale resistors are well-known and acclaimed in the industry for their low-noise and wide application in audio circuits, so I don't understand what you have against these "tan" resistors, or is it only because I used them in my "excellent" restoration?
You don't have to agree with me at all; nobody requires that, and contrary to the dictates of this upside-down, diplomatically-correct world, where dissent among the sheeple is frowned upon, engineers have always thrived on dissent as a matter of lifeblood. I enjoy it, and commend it, and I am qualified to give as good as I get.
You've beaten this to death, not 100% honestly, so quit while you're ahead.
If your motivation is to criticize, because I got your goat, go ahead, but in the interests of technical accuracy and excellence, keep it absolutely on topic and 100% relevant to the situation at hand, or it becomes an degrading exercise in foolishness.
OK Menahem, just as you wish, though I have been gentler in tone than you seem to think. I have no desire to thrash this out beyond having drawn your attention to what I believe to be either wrong or unjustified. What you do about it is your concern but I think that if you apply the same rigor to some statements made in your article as those made here, you will gain more of the respect you deserve for your effort.
I've been lurking here for a few months learning how to repair my 304 and it's finally in working order.
I'd like to make some additional changes not mentioned in this thread. Can I replace the 1N4003 and 1N5402 rectifier diodes in the power supply with uf4007? The reason I ask is because I was given 100 of these and don't know what to do with them. I was also considering swapping out the four 10,000uf caps with 15,000uf caps. What are the pro's and con's to what I want to do? Thanks in advance.
I'd like to make some additional changes not mentioned in this thread. Can I replace the 1N4003 and 1N5402 rectifier diodes in the power supply with uf4007? The reason I ask is because I was given 100 of these and don't know what to do with them. I was also considering swapping out the four 10,000uf caps with 15,000uf caps. What are the pro's and con's to what I want to do? Thanks in advance.
Hi Everyone,
After 20 years of sterling service my beloved 304 has started to exhibit the problems mentioned in this thread. Particularly one week channel (not always the same one) volume control not always working correctly and very occasionally jumping into red light safe mode.
Normally I'd think 20 years is a pretty good run and replace with a younger model but its such a great little amp that after reading this and similar threads and realising that these are well known 304 quirks with known fixes i've decided to make my first foray into the innards of any amplifier and have a go at getting it sorted.
I'm planning on:
replacing the relay with this JW2ASN-DC24V Panasonic Industrial Devices | Mouser
Replacing R333 and 334 with 1 watt versions
and possibly replacing the volume pot. I've given it a good squirt of contact cleaner but it still sounds scratchy. This did work a treat on the balance and tone controls.
Because I'm such a novice I've got a couple of embarrassingly basic questions;
1. Whats the best way of getting to the underneath of the pcb to desolder the components? I could just start undoing screws but it would be reassuring to have some guidance..
2. Where on the board are R333 and 334? (its a bit dirty and can't read all the numbers)
3. Has anyone changed the volume pot and if so what component did you use
4. Does this plan sound sensible?
As you can tell I'm totally knew to this so any advice would be gratefully received. Fab site too.
Thanks, alexis
After 20 years of sterling service my beloved 304 has started to exhibit the problems mentioned in this thread. Particularly one week channel (not always the same one) volume control not always working correctly and very occasionally jumping into red light safe mode.
Normally I'd think 20 years is a pretty good run and replace with a younger model but its such a great little amp that after reading this and similar threads and realising that these are well known 304 quirks with known fixes i've decided to make my first foray into the innards of any amplifier and have a go at getting it sorted.
I'm planning on:
replacing the relay with this JW2ASN-DC24V Panasonic Industrial Devices | Mouser
Replacing R333 and 334 with 1 watt versions
and possibly replacing the volume pot. I've given it a good squirt of contact cleaner but it still sounds scratchy. This did work a treat on the balance and tone controls.
Because I'm such a novice I've got a couple of embarrassingly basic questions;
1. Whats the best way of getting to the underneath of the pcb to desolder the components? I could just start undoing screws but it would be reassuring to have some guidance..
2. Where on the board are R333 and 334? (its a bit dirty and can't read all the numbers)
3. Has anyone changed the volume pot and if so what component did you use
4. Does this plan sound sensible?
As you can tell I'm totally knew to this so any advice would be gratefully received. Fab site too.
Thanks, alexis
I see you've had no replies so this is how it looks to me...
1/ If there is no access plate on the amp chassis then removing screws, knobs, control fixing nuts, rear socket fixings etc is probably the quickest way of pulling it all apart. It looks an easy amp to work on and it takes longer wondering than just to disassemble it all fully. Some "cheapo" music centres of the 90's had upward of 60 or more screws to be removed to access certain parts of the unit... the NAD is a piece of cake.
2/ The resistors should be easily locatable with reference to the service manual and/or print designators on/under the PCB.
3/ The secret with pots is finding one physically similar. If the NAD as a four pin (so eight in total) arrangement then you may struggle to find a replacement. The fourth pin would be a tapped loudness control... I don't know if it has that or not.
4/ Sounds reasonable to me
Make sure the relay is the correct coil voltage. The coil resistance looks pretty high on the replacement so there shouldn't be any issues there. And make sure the pin outs are correct physically to fit the board.
R333 and 334. If it is a known fault then yes, replace with what I assume are higher wattage parts.
1/ If there is no access plate on the amp chassis then removing screws, knobs, control fixing nuts, rear socket fixings etc is probably the quickest way of pulling it all apart. It looks an easy amp to work on and it takes longer wondering than just to disassemble it all fully. Some "cheapo" music centres of the 90's had upward of 60 or more screws to be removed to access certain parts of the unit... the NAD is a piece of cake.
2/ The resistors should be easily locatable with reference to the service manual and/or print designators on/under the PCB.
3/ The secret with pots is finding one physically similar. If the NAD as a four pin (so eight in total) arrangement then you may struggle to find a replacement. The fourth pin would be a tapped loudness control... I don't know if it has that or not.
4/ Sounds reasonable to me
Make sure the relay is the correct coil voltage. The coil resistance looks pretty high on the replacement so there shouldn't be any issues there. And make sure the pin outs are correct physically to fit the board.
R333 and 334. If it is a known fault then yes, replace with what I assume are higher wattage parts.
Hi Mooly,
Thanks for encouraging me to carry out the plan and in answer to question 1 to start undoing things and just take it apart!
I found the service manual online so things are gradually becoming clearer.
If anyone has done this before it would be great to here your advice.
Thanks,
Alexis
Thanks for encouraging me to carry out the plan and in answer to question 1 to start undoing things and just take it apart!
I found the service manual online so things are gradually becoming clearer.
If anyone has done this before it would be great to here your advice.
Thanks,
Alexis
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