NAIM Audio NAP 110 restoration

[Extreme_Boky]

I forgot we were talking about an audio amplifier here...

 

[Oleg Turbin]

you can understand why they gave it to me...

View attachment 1106814 View attachment 1106815 View attachment 1106816

Wow some like burned chicken
So
black burn places on the amp board have of parasites resistance. You need check black burn places with multimeter (ohms meter).
Bast way replace amp board to new (diy in fabric or buy original )

 

[Jasnochytron]

Good day
Nap

And NAC
Also if you have of original boards you need correct few resistors in nap and NAC schematics

Thank you!

 

[huggygood]

Wow some like burned chicken
So
black burn places on the amp board have of parasites resistance. You need check black burn places with multimeter (ohms meter).
Bast way replace amp board to new (diy in fabric or buy original )

Hi Oleg.
I got your PM, I'll take one or two front / back photos if I take out the pcb of the preamp and I'll send them to you.

 

[Oleg Turbin]

Hi Oleg.
I got your PM, I'll take one or two front / back photos if I take out the pcb of the preamp and I'll send them to you.

Thanks a lot my friend !!!
I try make gerber for PCBs from yours photos after receive

 

[asroma]

Good morning and happy Sunday.
I worked for a few days on the nap110 replacing the power transistors, some diodes and the 47uF or 10uF tantalum capacitors and some resistors, following the nap 250 scheme as suggested.
the bias is set after 30 minutes on both channels about 8 mv and the outputs are not equal one marks 16 mv the other about 30 mv.
connected to my nac 102 one channel works and the other plays very slowly. When I turn the balance to the soft part, it sounds but slightly distorted if I increase the volume.
To exclude cables and preamplifier I reversed the boards and the problem moves in the same way to the other side.

the card so confirms to have problems and I ask can you show me the way.
Observing the various components and equating the two boards, I see on the interested side a ztx 752 combined with a ztx 653.
The abbreviations of the other transistors are then the same.
I await your opinion

 

[asroma]

The MJ15003Gs were purchased online from Mouser as were the capacitors.

 

[huggygood]

I already see that you have a mixture of "BCxxx or 2Nxxxx" transistors on one card and almost only ZTXs on the other.
Which of the two cards is the problem? the upper or the lower (on the photo of the amp)

 

[asroma]

the board is the upper one in front of the toroidal transformer

 

[asroma]

 

[huggygood]

if I understand correctly, since the last time, you only changed the power transistors?

 

[asroma]

not only that, a 47k resistor, a 100 ohm resistor and all tantalum capacitors, plus two 1n4148 diodes in series

 

[jpk73]

Jeff Young has listed recommended transistor substitutes in his NAP250 threads, iirc you can use BC547/550 in the LTP, ZTX and MPSA are still available, for the ZTX108 you can use what Avondale uses in the NCC200/220. In the recent NAP clone thread you can read about resistor values needed for the 15003s. Good luck!

 

[asroma]

my reference scheme is this,the alternative to the ztx is interesting because it is not easy to find, instead of the BC55 I bought the BC 239C.

 

[huggygood]

have you checked the direction of the pinout? ZTX and BC can have different pinouts (EBC vs CEB or CBE)

 

[huggygood]

I repeat my request about your source of purchase of your MJ 15003

 

[asroma]

I repeat my request about your source of purchase of your MJ 15003

you mean where did I buy them? on the mouser.DE site
Is it wrong to mount those transistors on the Nap110?

 

[huggygood]

do you have the old transistors? to give it a try?

 

[asroma]

honestly its not like testing a resistor or transistor. The old pair of naim originals are present of course.
Do you think the new ones are defective?

 

[huggygood]

let's just say that I'm very suspicious of everything that concerns old TO3s, even from Mouser.