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NAD 1300 Recap/Restoration

j!m said:
I feel like an EE right now trying to explain this, but (first of all, I'm not an EE), if it seems too daunting, perhaps step back and having a qualified repair center do the upgrades for you is the right answer.
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Ha, well no harm in asking. You don't have to feel obligated to answer. I appreciate you and those who have chimed in with knowledge and experience. Nothing too daunting but also don't want to go into something under-informed. Similar to some of your previous posts I'd rather ask folks who've been there before instead of going in blind.

The opamps I linked are both 4562 but mouser has two different part no's hence the question (no difference in specs). FWIW, after a bit of back and forth with mouser only difference in the part numbers I listed above is packaging.

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Yes, I've run into parts being out of stock only to find identical replacements in a different packaging... Some packaging matters with automated populators.
 
ccrnnr9 said:
Thanks for this - but for C605/606 you upped capacitance to 2200uf from 440 and stayed with stock on all others? In my past projects I've upped capacitance on the main power supply caps by rec of some experience forum members.

I'm hoping my 1300 arrives today so I can see what's already in there. Supposedly a hum coming from the phono stage...
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I went with 2200uF on mine, but mine has an 80VA toroidal transformer as well.

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This thread has been super helpful. Got mine desoldered and a few questions come up before installing new parts:

1. In the parts list, all 9 op amps are listed as 2043D - on mine the op amps in IC203-206 are JRC8214 and the other 5 are JRC8220 - both have 2043DD stamped across the top. I assume it's okay to replace all 9 with identical LM4562NA?
2. Based on others feedback I purchased a couple different 16V .5W Zeners - 2% and 5% - is there a preferred spec?
3. Only replace the Zeners at 602 & 603 - D601 can remain stock?
4. Lastly what is the best way to test voltage at the opamps? I assume I'll be okay but would prefer to check without assuming (I opted to stick with largely identical capacitance values throughout the power supply as what was in from the factory with only bumps in V)

Thank you!
 
ccrnnr9 said:
4. Lastly what is the best way to test voltage at the opamps? I assume I'll be okay but would prefer to check without assuming (I opted to stick with largely identical capacitance values throughout the power supply as what was in from the factory with only bumps in V)
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Use sockets, and measure the voltage at the sockets before installing the op-amps.
 
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pwauk12 said:
yes pin 4 -ve voltage and pin 8 +ve voltage- all reference to ground (chassis)
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I’ll go grab some sockets today from the local spot and try this out? Im reading conflicting information on whether or not it’s okay to power up and test on sockets without op amps installed.
 
it IS ok to power up without IC's installed- bring the unit up on a dim bulb tester if you have one and before powering up check that there are no shorts on the power rails (DMM set to ohms, measure from pin 4 and 8 to chassis)
 
I tested with empty sockets. Nothing to harm if they're not installed...

Going over-voltage on fresh op amps? Sub-optimal.
 
Recap mainly completed last night except the tight spacing at C117/118 prevented me from using the MKS2's I'd ordered.

Would it be alright to bump up from 2.2uF/50v to 4.7uF 50v or 63v in this slot? Otherwise I'll wait on the order...
 
Finally got around to getting back at this one with some time off before the holidays. Caps and all new components went in without issue.

Used these Vishay 16V 0.5W 2% zeners - looking at the readout for pins 4 & 8 on all the ICs I'm getting -4.4V and -1.2V respectively. Unit passed the DBT test - all caps oriented correctly. Any ideas what could cause readings this far off?

FWIW I stuck with the same capacitance value on all caps except C605/6 where I bumped up to some UPW 680/50V as that's what I had in stock.
 
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