I second Jaycee's opinion that replacing resistors is both a lot of work and unlikely to make much difference as they dont seem to age badly in my experiance.
If you want to make work for your self, you could take out a resistor (start with any looking burnt) and see if its in tolerance.
I also suggest that the preset variable resistors look nice and modern and you dont need to replace them.
If you want to make work for your self, you could take out a resistor (start with any looking burnt) and see if its in tolerance.
I also suggest that the preset variable resistors look nice and modern and you dont need to replace them.
Rob,
Don't over think this! You have a perfectly decent amp that needs some refurb. Do that. You are worrying about the 1% problem. Fix the first 99%.
Then, if you are as sick as some of us, you have something to listen to while you read the books from Cordell and Self, all the Pass and Didden papers, Leach, Jung and others. Learn how to use Spice. A couple terms at the local trade school in electronics, Then start prototyping stage by stage. Oh yea, about a a grand in test equipment. About 3 or 4 grand later, you will come out with a very decent amp, about like you could have bought used for $150 US.
You could find yourself very happy with having repaired your amp, something a lot of folks cannot do.
Its an NE5532N opamp. The phonostage is something I would like to get the very best out of, or would it be better going for a external one? The bits in this amp seem to be of a decent quality, all the caps are rubycon , apart from the two red ones, alps pot and possibly switches,big BHC caps in power supply. I intend to replace all the caps with Rubycon Zl apart from the two big BHC caps which I have been thinking perhaps using two more BHC caps, but if you could advise differently as to what would be best where it would be appreciated, I just figured they are decent parts anyway so why not change like for like.
Here are the values, I hope you can make this out.
I can segragate it into the four different circuits if you wish.
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Do yourself a favor and don't buy low ESR caps, particularly if you don't have the schematic.
No ZL, no FM, no FC, no PW, etc.
Some years ago I've recapped a NAD AV receiver with Rubycon ZLs, sounded great but guess what?
After few months it literally started to burn (real flames)
I've repaired it, adjusted bias and after a few months burned again...
Use good quality standard elcos like Nichicon VR, Vishay BC038/046, same value and higher voltage rating that fits.
If you want to use audiograde caps use Nichicon FW, they're economic and good sounding industrial caps.
No ZL, no FM, no FC, no PW, etc.
Some years ago I've recapped a NAD AV receiver with Rubycon ZLs, sounded great but guess what?
After few months it literally started to burn (real flames)
I've repaired it, adjusted bias and after a few months burned again...
Use good quality standard elcos like Nichicon VR, Vishay BC038/046, same value and higher voltage rating that fits.
If you want to use audiograde caps use Nichicon FW, they're economic and good sounding industrial caps.
Do yourself a favor and don't buy low ESR caps, particularly if you don't have the schematic.
No ZL, no FM, no FC, no PW, etc.
Some years ago I've recapped a NAD AV receiver with Rubycon ZLs, sounded great but guess what?
After few months it literally started to burn (real flames)
I've repaired it, adjusted bias and after a few months burned again...
Use good quality standard elcos like Nichicon VR, Vishay BC038/046, same value and higher voltage rating that fits.
If you want to use audiograde caps use Nichicon FW, they're economic and good sounding industrial caps.
ESR doesn't become flammable, even if you don't have a schematic.
Something else was your problem.
If the circuit was designed expecting a minimum ESR from a capacitor, using a low-esr one could lead to oscillation or other problems...
Think about low-esr caps at the output of most three terminal regulators...
BTW it's a free world...
The 2.2uF electrolytics in my amp are small (5mm dia 10mm length). Can you recommend any small dia film cap replacements?
Then it will be difficult if not impossible to find a manufacturer who builds film caps with 0.1" pin pitch.
You are likely to have to use a 0.2" film cap and pre-bend the leads to fit the PCB.
Do you want to do that?
I replaced a 10uF electro with a 1uF film yesterday (RC in a timer) doing this and I cannot see from the top or from the bottom that I have bent each of the legs to an offset of 0.05". But any knowledgeable builder will realise what has been done.
You are likely to have to use a 0.2" film cap and pre-bend the leads to fit the PCB.
Do you want to do that?
I replaced a 10uF electro with a 1uF film yesterday (RC in a timer) doing this and I cannot see from the top or from the bottom that I have bent each of the legs to an offset of 0.05". But any knowledgeable builder will realise what has been done.
Replace all the small electrolytics with Elna Silmics with as high a voltage rating as will fit, change the main diodes to IR hexfets, replace the volume control, change the 2 main electrolytics to the largest value 105C rated Panasonic or Nichicon cap that fits - ( small chance you may have to increase the AC input fuse to handle the increased inrush currrent).
This is the best trade off for cost versus value - improved sonics and reliability.
Bass control and resolution will improve for the first 50 to 100 hours of runnning time, but you'll hear an improvement at first turn on.
This is the best trade off for cost versus value - improved sonics and reliability.
Bass control and resolution will improve for the first 50 to 100 hours of runnning time, but you'll hear an improvement at first turn on.
Thanks Ticknpop.
I am compiling a shopping list but wanted to set the bias before I did anything. My multimeter arrived today AM- TECH DIGITAL MULTIMETER COMPLETE WITH 9V BATTERY AND LEADS on eBay! Ive never used one before so can anybody please explain what to do? I need to set it to 5 mV.
I am compiling a shopping list but wanted to set the bias before I did anything. My multimeter arrived today AM- TECH DIGITAL MULTIMETER COMPLETE WITH 9V BATTERY AND LEADS on eBay! Ive never used one before so can anybody please explain what to do? I need to set it to 5 mV.
Usually service manuals clearly state that bias should be adjsuted when you power on the amp and fine tuned after it stabilize.
BTW, after components changes you'll have to readjust.
Cheers , it says on my amp set to 5mV when warm.
So I take it i have to let the amp warm up first.
Done , thank you. Both channels are down to 5mV, well , between 4.9 and 5.2, those trim pots are very sensitive and I cant do it on the fly as my probes cannot fix to the pins in anyway.
I also checked the DC offset , left is 0.04, it starts at around 2.5 ish then settles to 0.004.
Right settles at 21, thats a big difference , not huge readings so is there anything here that needs seeing to?
edit - forgot to add , both tests done when warm with no source or speakers connected, volume down to zero.
I also checked the DC offset , left is 0.04, it starts at around 2.5 ish then settles to 0.004.
Right settles at 21, thats a big difference , not huge readings so is there anything here that needs seeing to?
edit - forgot to add , both tests done when warm with no source or speakers connected, volume down to zero.
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