NAD 7020i sudden death - Page 8

mjona · Today, 01:13 AM

The debate is an extension of much the same as a thread last year only with fire breathing in my direction.

Anyway that caused me to do more searching to find this that thread - see Hometaxial 2n3055/mj2955 and read post 2 and the work background of the member responsible.

I have looked at a variety of NAD amplifier models which omitted the emitter resistors and these were produced over two decades and selling on the second hand market.

I have a contact who runs a shop selling used Hi-Fi equipment I will ask him to keep a lookout for me on any model coming into his shop. These are not selling for silly money in this country - maybe owners are mostly hanging on to them.

indianajo · Today, 02:48 AM

Nice work zenzaman. A custom PC board! I'm impressed.

Ian Finch · Today, 04:24 AM

Quote:

Originally Posted by mjona

.........Anyway that caused me to do more searching to find this that thread - see Hometaxial 2n3055/mj2955 and read post 2 and the work background of the member responsible......

I would give some weight to the author of #5 there, who's CV I think, includes some acknowledged expertise in the field as well as a personal interest.

zenzaman · Today, 07:48 AM

Quote:

Originally Posted by indianajo

Nice work zenzaman. A custom PC board! I'm impressed.

Thanks!

What about base stoppers? Do I need them?
Now I'm sorry I didn't include some traces for them on the diy pcb just in case...

zenzaman · Today, 08:22 AM

also, are the 0.56ohm resistors ok in value or too much? (I didn't go for the 0.33 3W I had because I have no idea what make they are. If a smaller value is needed I might be able to find a couple from the same local seller that had these .56 ones)

mjona · Today, 08:34 AM

I had amicable contact with John Ellis two years ago. John had started a thread for a new amplifier circuit he had built. He was using other than LTSpice software for simulations. I was able to do those in LTSpice for him.

Anyway there were two points in post #5.

You have skipped John's first one which supported my contention that the 7020 output transistors are epitaxial devices. In a way I have already acknowledge his expertise on that score.

The outputs that came out of zenzaman's amplifier are clearly Motorola 2N3055 and MJ2955 which are epitaxial according to datasheets and the Motorola Selection Guide

The year code in the images give the year code as 1990 so they were not old stock at the time of manufacture and the NAD 7020 company part numbers end with M.

What have you got to say about this.

Today, 02:48 AM	#72
indianajo diyAudio Member Join Date: Jan 2010 Location: Jeffersonville, Indiana USA	Nice work zenzaman. A custom PC board! I'm impressed. __________________ Dynakit ST70, ST120, PAS2,Hammond H182(2 ea),H112,A100,10-82TC,Peavey PV-1.3K, MMA-81502, Herald RA88a mixer, Steinway console, Wurlitzer 4500, 4300

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Today, 01:13 AM	#71
mjona diyAudio Member Join Date: Jul 2007 Location: Upper Hutt	The debate is an extension of much the same as a thread last year only with fire breathing in my direction. Anyway that caused me to do more searching to find this that thread - see Hometaxial 2n3055/mj2955 and read post 2 and the work background of the member responsible. I have looked at a variety of NAD amplifier models which omitted the emitter resistors and these were produced over two decades and selling on the second hand market. I have a contact who runs a shop selling used Hi-Fi equipment I will ask him to keep a lookout for me on any model coming into his shop. These are not selling for silly money in this country - maybe owners are mostly hanging on to them.

Today, 08:22 AM	#75
zenzaman diyAudio Member Join Date: Nov 2018 Location: Sibiu	also, are the 0.56ohm resistors ok in value or too much? (I didn't go for the 0.33 3W I had because I have no idea what make they are. If a smaller value is needed I might be able to find a couple from the same local seller that had these .56 ones)

Today, 08:34 AM	#76
mjona diyAudio Member Join Date: Jul 2007 Location: Upper Hutt	I had amicable contact with John Ellis two years ago. John had started a thread for a new amplifier circuit he had built. He was using other than LTSpice software for simulations. I was able to do those in LTSpice for him. Anyway there were two points in post #5. You have skipped John's first one which supported my contention that the 7020 output transistors are epitaxial devices. In a way I have already acknowledge his expertise on that score. The outputs that came out of zenzaman's amplifier are clearly Motorola 2N3055 and MJ2955 which are epitaxial according to datasheets and the Motorola Selection Guide The year code in the images give the year code as 1990 so they were not old stock at the time of manufacture and the NAD 7020 company part numbers end with M. What have you got to say about this.