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Bolt down NAP160 bolt size ?

Discussion in 'd.i.y.' started by istari_knight, Sep 5, 2010.

  1. istari_knight

    istari_knight pfm Member

    I've got myself a bolt-down NAP160 & need to get inside but some bugger has already tried & rounded off the heads on the bolts ! Not a big deal getting them out but I'd like to replace them.... Does anyone know the correct size replacements ? I thought M4 x 8 but not sure.

    Thanks for the help :)
  2. misterc6

    misterc6 Wasted and wounded, it ain’t what the moon did

    M4 x 8, countersunk with Allen key head,


    Correction: M4 x 6, but I don't think 8 mm would be a problem.
  3. istari_knight

    istari_knight pfm Member

    Spot on Malcolm ! Thanks for that.

  4. misterc6

    misterc6 Wasted and wounded, it ain’t what the moon did

  5. istari_knight

    istari_knight pfm Member

    Hehe those are the exactly ones I bought five minutes ago !

    I also need some new ones for a NAC12 as they originals are rusty - Just on the off chance you might know ?

  6. misterc6

    misterc6 Wasted and wounded, it ain’t what the moon did

    The ones in the NAC12 are M3, again countersunk but with Phillips or Posidrive heads. I remember that there were two different lengths but I can't get at them all without removing the NAC12 from the rack. The length didn't seem to be important. The one I have removed is M3 x 7 so I think M3 x 8 would be fine for them all,

  7. istari_knight

    istari_knight pfm Member

    Your a gent Malcolm :)

    Thanks for the help, James.
  8. misterc6

    misterc6 Wasted and wounded, it ain’t what the moon did

    No problem James, glad to have been of help. I've recently serviced a BD NAP160 which is for sale in the classifieds forum and a NAC12 that I'm keeping for now. If you need more help just ask!

    p.s. I've bought screws from that eBayer before and was very happy with his service and products,

  9. AussiePete

    AussiePete pfm Member

    whilst on the subject of bolt sizes - does anyone know what size the bolts on a 250 holding the heatsinks to the case are?
  10. neiljadman

    neiljadman Senior Member

    M5 with a 4mm hex key needed...if you mean the big ones going right through the case. If you mean the smaller ones holding the heat sink to the inner tray they are M4 again....
  11. AussiePete

    AussiePete pfm Member

    Thanks Neil, I appreciate it.
  12. istari_knight

    istari_knight pfm Member

    Yes I did notice that in the classifieds, a bargain if you ask me....Recently paid £390 for my BD NAP160 / NAC 12 which are both unserviced & a bit tatty.

    I intend to pretty much replicate what you have done to yours - The S/N on mine is 492 which dates it to '74 I think so parts / build may be slightly different... I'll have to take a peek inside & see.

    How are you finding the NAC 12 ? Its pleasantly suprised me so far after pulling the MC boards & running in a few days.
  13. misterc6

    misterc6 Wasted and wounded, it ain’t what the moon did

    Firstly a word of caution. If you are replacing the feet on the 160, which is a good idea on a product of this age, be aware that the earth strap connects to the chassis through the bolt attaching the foot closest to the mains input socket. I didn't realise this and removed and replaced the foot leaving the earth strap and nut floating around inside the case. Luckily I spotted the error before any damage was done.

    Serial number 0492 dates your 160 to the second half of 1976.

    The NAC12 is an excellent and under-rated pre-amplifier. The weakest points are the basic quality controls. You owe to yourself to replace the volume control with an Alps Blue ( or better. If you don't need the balance control, replace it with two fixed resistors. If you do need it, find a better potentiometer. I also replaced all the sockets on the rear panel.

    There are three versions of the 12. Version 1 has all the components on a single board (with the possible exception of the phono boards) like the NAC42, Version 2 has six daughter boards (2 x 324, 2 x 321 and 2 x phono (322 or 323)) with the relay circuit on the motherboard. Version 3 also has the relay circuit on a 325 daughter board making seven in all.

    Versions 2 and 3 are very little different to the NAC32. The performance can be further improved by replacing the 324 boards with the 729s as fitted to the NAC72.

    You will probably find that the tantalum beads are all rated at 25 V, Naim had a program of replacing these with the 35 V types when units came in for service.

    I have a future project to fit individual regulators for each board. The layout makes this extremely simple. A strip of regulators would easily fit onto a side panel and you could feed in 37 Vdc or so from a printer brick or, alternatively, you could wire out the pre-amp regulator in the 160 to get a similar raw dc supply.


    p.s. Having checked I remember that the NAC12 Version 2 has different edge connectors to those used in the later preamps so more modern boards will not fit. The Version 3 has the same edge connectors as the NAC32 - NAC72 and is, therefore, somewhat easier to upgrade.
  14. istari_knight

    istari_knight pfm Member

    Fantastic info Malcolm !

    It turns out I bought mine from this forums own RCook...

    From your decription my NAC12 is a Mk.2 but not entirely sure - I'll be starting work on them Wednesday anyway so I'll have a look then.

    First job is to make a parts list !

    NAC12 :

    20K Alps Blue pot.
    Elma selector switch
    Not sure what balance pot to buy (would rather not bypass it)
    Recap all boards
    Replace the old & decrepid DIN sockets with some nice new ones
    Fit inline attenuator (couple of R's) to the tuner input
    New feet

    NAP160 :

    Kendeil psu caps
    Full recap / maybe bypass the preamp cap with a film or teflon
    Disable SOA - May need a wee bit of guidance when the time comes !
    Fit some new 4mm Binding posts as current ones need a wire brush & some elbow grease...
    Bias / DC offset
    New feet....Also need to replace the power switch bulb.

    Looking at getting a mate of mine that owns a car bodyshop to sandblast the cases & fill / respray them, need to get some preamp controls machined too... One of mine is cracked :(

    After that little lot They will be sorted for another 20 years all for the price of a s/h nait5i ..... I wonder which would sound better ? :D

    If you can think of anything else I'd be glad to add it to the worklist !

    Cheers, James.
  15. misterc6

    misterc6 Wasted and wounded, it ain’t what the moon did

    The 12/160 would beat a 5i any day of the week for me :)

    My 160 already had a film capacitor across the 3,300 uF electrolytic in the pre-amp supply.

    If you're having the re-spray I'd be interested in having the four main panels of my NAC12 done at the same time.

    I replaced the BNCs on the phono input with RCA phonos which fitted the holes exactly. Are you keeping your phono boards in, or by-passing them to give another line level input?

  16. istari_knight

    istari_knight pfm Member

    I couldnt agree more, new Naim just doesnt do it for me until you get to the £££ level.

    I removed the 323 boards & replaced them with 328's ... I know they are apparently terrible but they are O.K for the minute & buy me an extra input. The other four boards I havent bothered identifying yet.

    I'll let you know once I've seen him & get back to you although I doubt he'll charge anything for spraying / refinishing them....never has yet anyway.

    Cheers, James.
  17. misterc6

    misterc6 Wasted and wounded, it ain’t what the moon did

    Take out the dreadful 328s and replace them with simple link wires - instant improvement. I can let you have a couple of link wires but they would only suit the version 3 edge connectors. I'd need to see the connectors on a version 2 to suggest the best way to go.

  18. istari_knight

    istari_knight pfm Member

    Okay, sounds like something else to do ! I'll take a few pictures on Wednesday & get your opinion on the best approach.

    Looking at the 323/3 boards the pins look identical to the ones in the attched picture.... So possibly a Mk.3 ?

    Cheers, James.

  19. istari_knight

    istari_knight pfm Member

    Its quite handy to read all in one place so....

    Received the bolts & replacement bulb today so started work on the amps..... All of the top cover bolts on the nap160 had rusted and already been stripped so it was fun getting them out, only took 2 hours ! Anyway upon opening it I found a couple of interesting things.Firstly, the PSU filter caps are BHC & dated to 1987 so maybe this has been recapped in the past ? All of the tants in both pre/power are rated at 35v too, i'm sure the originals are supposed to be 25v might be wrong though.

    However, onto the nac12..... As you can see in the attached pictures it is a Mk.2 with the 6 daughter boards (2xNA112 / 2xNA114) I have now removed the evil 328 cards & fitted cartridge tags in place on the pins which fit perfectly giving a real improvement in SQ when using the phono input.

    I've sent Naim an email to find out if they has been serviced in the past & just need to order the new pots / connectors / caps etc.....



  20. misterc6

    misterc6 Wasted and wounded, it ain’t what the moon did

    Hi James,

    you'll need to host the photos somewhere in order to get them up on here!

    If the psu caps are 1987 and the tants 35V the amps have both been re-capped. Best of luck with Naim, they are very good with stuff built after 1982 (when they moved to Southampton Road) but get a bit vague with anything earlier. They should have a record if they did the service. Must have been a caring first owner if they were re-capped after just eleven years.

    The NAC12 is definitely a Version 2. Did the 328s fit easily onto the pins?

    Carry on with the good work,


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