Free but stuffed! Naim Nac32/160/SNAPS
- Thread starter SPH
- Start date
I'm using a pair of bc549c's. The only matching that's been done is checkin that they both have bc549c printed on the flat side.
I did know previously that these were supposed to be a matched pair but I have no way (that I know of) to test the values. I could reuse the originals I guess, I'd have to confirm that they were in a usable state.
OMG I spent hours last week scanning and making PCB board layouts for these cards!
Did you do reg boards as well? edit: scratch that yours is 160 so no reg!
I just finished complete rebuilds of 3 X NAP 250 boltups. Have changed every component except for transformers.
I have some leftover parts like switches, lenscaps etc. I've "modernized" mine with a blue switch.
Also I have a bunch of Kemet milspec 47uf wet tantalums that I've used for feedback caps and am happy with the sound.
Did you do reg boards as well? edit: scratch that yours is 160 so no reg!
I just finished complete rebuilds of 3 X NAP 250 boltups. Have changed every component except for transformers.
I have some leftover parts like switches, lenscaps etc. I've "modernized" mine with a blue switch.
Also I have a bunch of Kemet milspec 47uf wet tantalums that I've used for feedback caps and am happy with the sound.
Got any pictures of the rebuilds? I'd love to see one of them!
I'm still chasing wire wound resistors and some ZTX753's. I need to get the hfe checked on my transistor pairs too. I might need to order a bunch and get someone local to check them. Or check the originals for that matter.
I also need to check out my output transistors (TR11 & 12 in the diagram) as I have no idea if they're any good. Any suggestions? Accoustica suggests MJ15003 (Or BUV20's but stuff that, $30 each!).
Will post pics shortly.
I used MJ15003. Most of the BDY58/NA001's I pulled are probably still good. I am super happy with the sound but I have to admit that I consider myself and audiophool... I am well aware that when I change parts out I am likely to think they sound better. My ears/brain probably cannot actually tell.
For the ZYX753s I subbed for another part will post when I get home.
Wire wounds should be easy to find at mouser or newark/e14 let me know if still stuck.
Yeah, easy to get. I just had to wait and see which parts turned up from the local supplier. They were a bit of a lucky dip. They seemed to have a knack for not finding direct replacements on E14 (where most of their parts come from). I got silver mica caps instead of styrene's, for instance. E14 had the right parts, I found out after they turned up, but oh well. They should work.
I've never heard this amp work so any sound will be ok as a starting point. I'm really just hoping it doesn't burn up when I hit the power button.
I've never heard this amp work so any sound will be ok as a starting point. I'm really just hoping it doesn't burn up when I hit the power button.
This was my first effort rebuilding anything. Had good help from neilj and martin. I also had many mistakes, zapped myself good, melted a tool to the chassis, smoke, cap explosion. Some causes of faults were backwards transistors, and hooking up wrong amp pins.
I re-used the existing boards, new boards are just for standbys in case any fry so I can quickly swap without musical downtime over the next 10 yrs
If you want we could do a sanity check of measuring resistances at different board points and compare to mine. This is one way I saved myself frying more parts (at one point I blew 2 sets of boards consecutively
)I would try these people (see link to the ZTX753 below, AU$1.23
), I have ordered stuff from South Korea where I was working recently and they delivered very fast, they also have a superb free schematic builder software you can use, just need to register with them same as Farnell/Element 14.http://www.digikey.com.au/product-search/en?keywords=ZTX753
I also looked up on Alldatasheet.com and they quoted alternatives for the BDY56 as follows :
http://www.alldatasheet.com/datasheet-pdf/pdf/82700/ETC/BDY56.html
A quick look on Digikey brought this up for the fairchild alternative :
http://www.digikey.com.au/product-search/en?keywords=MJE170 (all less than 1USD each)
Edit: just remembered that T11 and 12 are TO-3 style and are mounted outside the case, had another look for an alternative and found these ..... just checking the various specifications they look reasonably similar generally.
http://www.digikey.com.au/product-s...t=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25
Mike
colasblue
pfm Member
They aren't actually schottky diodes, they're just really old fashioned silicon diodes. the Naim rectifier arrangement is very unorthodox in that it uses one traffo winding to charge the positive res cap and the other winding to charge the negative res cap.
You can substitute two normal bridge rectifiers like the one you've suggested.
Naim use International Rectifier units rather than Fairchild but I doubt there's any difference.
This is the circuit, and you implement it by effectively using only half of each bridge rectifier.
http://www.circuitstoday.com/centre-tap-full-wave-rectifier
You can also get direct replacements for the originals if you prefer and they're widely available
http://docs-europe.electrocomponents.com/webdocs/0026/0900766b800266f9.pdf
You can substitute two normal bridge rectifiers like the one you've suggested.
Naim use International Rectifier units rather than Fairchild but I doubt there's any difference.
This is the circuit, and you implement it by effectively using only half of each bridge rectifier.
http://www.circuitstoday.com/centre-tap-full-wave-rectifier
You can also get direct replacements for the originals if you prefer and they're widely available
http://docs-europe.electrocomponents.com/webdocs/0026/0900766b800266f9.pdf
PigletsDad
My intelligence test came back negative.
Is there anything wrong with the rectifier? If not, why change it?
It won't wear out and a new one will be no better than the old one.
It won't wear out and a new one will be no better than the old one.
colasblue
pfm Member
Indeed but the amp came with a blown mains fuse, leaky (as in goo) res cap and dead output stage so not improbable that a rectifier diode has been taken out.
This seems to me to be a ridiculously complex job due to the OP's inability to actually diagnose the problems, ie no way would I have been re-engineering PCB's in this case, but none the less nice restoration.
This seems to me to be a ridiculously complex job due to the OP's inability to actually diagnose the problems, ie no way would I have been re-engineering PCB's in this case, but none the less nice restoration.