Recommendations re Nakamichi IA-2 maintenance

[ftpols]

NAKAMICHI IA-2 AMP HELP

Hi,

I just purchased a used Nakamichi IA-2 amp. Nice piece of gear but there is a very loud hum from LH channel when switched to Phono and there is no signal source. (All other selection are silent.)

Also, the trouble and strife says the reproduction is metallic...

Could somebody kindly advise about troubleshooting?

Many thanks!

Ftpols

 

[Mooly]

To evaluate the phono input you must apply shorting plugs. If the input is floating then hum/noise pickup is normal although both channels would usually be similar. Short the inputs and see if the hum remains. If it is faulty then you will need a circuit diagram to see what is going on. It sounds an odd fault (if it is faulty) and could even be something like broken or cracked print somewhere (transit damage).

 

[ftpols]

NAKAMICHI IA-2 AMP HELP + SERVICE MANUAL

To evaluate the phono input you must apply shorting plugs. If the input is floating then hum/noise pickup is normal although both channels would usually be similar. Short the inputs and see if the hum remains. If it is faulty then you will need a circuit diagram to see what is going on. It sounds an odd fault (if it is faulty) and could even be something like broken or cracked print somewhere (transit damage).

Many thanks for your kind advice, Mooly.

I connected the shorting plugs and a cable from the GND terminal to grounded mains socket. I also sprayed Electrolube in the MM/MC phono selector switch and operated it 20 times.

With the phono MM/MC selector switched to MM, there is a whisper of white noise/pink noise from the left channel at full volume. When the phono selector is switched to MC, however, white noise/pink noise is very prominent on left channel at low volume.
Otherwise the amp is fine. It's years since I used an MC tone arm and turntable, so I guess it's no big deal.

Unfortunately, I can't upload the service manual because the file size is excessive.

TX.

 

[Mooly]

So the hum has gone under these conditions. It should be silent (for hum) with just the shorting plugs and no separate wire.

White/pink noise will be "electronic" in nature with differences between channels caused primarily by differing semiconductors L vs R. There should not be any great difference though... first thought is to check whether the MM/MC switch really is functional and changing the gain on the channel that stays quietest. A large increase in noise is normal in the MC position.

 

[ftpols]

NAKAMICHI IA-2 AMP HELP + SERVICE MANUAL

So the hum has gone under these conditions. It should be silent (for hum) with just the shorting plugs and no separate wire.

White/pink noise will be "electronic" in nature with differences between channels caused primarily by differing semiconductors L vs R. There should not be any great difference though... first thought is to check whether the MM/MC switch really is functional and changing the gain on the channel that stays quietest. A large increase in noise is normal in the MC position.

Many thanks again, Mooly.

I will check the MM/MC switch next weekend.

Best regards,

 

[Mooly]

OK, good luck

 

[ftpols]

The passives in my amp are 25 years old. But none of the caps (mostly Nichicon) are bulging or leaking - photos attached. The amp sounds fine.

I was thinking about preventative maintenance but don't have the time to replace the scores of transistors. And I excluded the phono PCB because I don't use it. Apart from replacing the other electrolytic caps are there any other parts that I should be focusing on, for example, the MOSFETS?

Also, I noticed that the heat sink never gets warm and wondered how effective are the TIM sheets between the MOSFETS and heat sink. I wonder if 3M 8810-2X36 Thermal Interface Material I have would be better.
Amazon.com: 3M 8810 Thermally Conductive Double-Sided Bonding Tape, 0.010" Thick, 2" Wide x 36 yards, 1 Roll: Industrial & Scientific

Many thanks for your recommendations, especially regarding manufacturers and part #s.

 

[Ian Finch]

The only components that will need replacing are those that deteriorate. The only components that will consistently deteriorate (whether you hear or see it or not) are electrolytic capacitors. After 25 years, replace them - replace them all methodically, one channel at a time so you always have a working reference amplifier in case of problems.

Replacing other components without good reason, such as you may find in other brand amplifiers that have a reputation for early failure, would just be window-dressing.

 

[JonSnell Electronic]

Is it faulty? If not leave it alone. Components chosen by the manufacturer are of excellent quality and last year after year after year. Semiconductors fail from time to time and until then, leave as it is. The conductive insulator pads used exceed the 3m stuff that you have your eye on.

 

[ftpols]

Hi, Ian.

Many thanks for your kind support. Further questions if you don't mind.
1. Would I need to change those two big beasts in the fuzzy photo of the Power Supply PCB?
2. Any recommendations re swapping the Power Supply and Power Amp electrolytics from Nichicon->Panasonic?
3. Re my comments about the heat sink not getting warm, the interfacing MOSFETS should be OK?

Have a nice day in Coffs Harbour.

 

[ftpols]

Hi, JonSnell.

Not sure where you are but Cruden Bay was the closest I have been to the Jurassic Coast...
Many thanks for your sound advice. I am still inclined to replace the electrolytic caps, though. And many thanks for the feedback about the 3M TIM. When working on computers I used Arctic MX-2 between the CPU and heat sink with excellent results.

 

[Ian Finch]

1. Would I need to change those two big beasts in the fuzzy photo of the Power Supply PCB?

These are the principal power supply smoothing caps and the obvious first parts to replace (both of course). Where possible, use original grade equivalents of similar capacitance. If necessary where exact vales are not available, values up to 50% more capacitance are not likely to cause problems. Modern caps will be much smaller, and that can be difficult when you try to fit the replacements.

I realise these are expensive and hard to source but if you want to replace parts, there isn't much point to replacing a few little ones which may be fine in their non-audio application.

2. Any recommendations re swapping the Power Supply and Power Amp electrolytics from Nichicon->Panasonic?

Panasonic have a popular high ripple current grade (TSHA)( that I find good for audio use but many people have a traditional trust in certain grades of Nichicon brand. The grade you may need to use though, may be dictated by the few types available in that size/style. Actually, many manufacturers have equivalent or similar grades but nobody can afford to test them all - It's your choice or you can just read the most enthusiastic opinions

Smaller caps will need to be in different grades such as moderately low ESR type Panasonic FC. There are lower ESR grades like FM and FR but don't assume lowest ESR is better in all situations. It isn't best for smoothing, for example.

- Thanks for your good wishes. It was another beautiful day here

 

[DSJR]

For those that don't know, the IA1 and IA2 were good quality mid priced integrateds, the IA2 sold at similar prices to the UK-popular Audiolab 8000A and capable of very good sound indeed I thought. I don't think Nakamichi were into skimping on components back then, if ever, and the amp ran fairly cool I remember, so you may find everything's as it should be, in which case leave well alone.

I'm very fond of Crown's 'D' series power amps from the early to mid 70's. Even thrashed examples in terrible physical condition are still working on original capacitors and Ken Rockwell confirmed it on slightly less care-worn examples he measured in 2015. Seriously, I'd leave the IA2 alone myself

 

[ftpols]

Hi, DSJR.
Suffolk is a nice part of the country. (I went to school near Ipswich.)
Many thanks for your feedback. Yes, the IA-2 delivers very good sound. I heard that Nakamichi only built 200.

 

[ftpols]

These are the principal power supply smoothing caps and the obvious first parts to replace (both of course). Where possible, use original grade equivalents of similar capacitance. If necessary where exact vales are not available, values up to 50% more capacitance are not likely to cause problems. Modern caps will be much smaller, and that can be difficult when you try to fit the replacements.

I realise these are expensive and hard to source but if you want to replace parts, there isn't much point to replacing a few little ones which may be fine in their non-audio application.
Panasonic have a popular high ripple current grade (TSHA)( that I find good for audio use but many people have a traditional trust in certain grades of Nichicon brand. The grade you may need to use though, may be dictated by the few types available in that size/style. Actually, many manufacturers have equivalent or similar grades but nobody can afford to test them all - It's your choice or you can just read the most enthusiastic opinions

Smaller caps will need to be in different grades such as moderately low ESR type Panasonic FC. There are lower ESR grades like FM and FR but don't assume lowest ESR is better in all situations. It isn't best for smoothing, for example.

- Thanks for your good wishes. It was another beautiful day here

Hi, Ian.

Many thanks for your expertise. And my apologies for taking up so much of your time. A couple of more questions, please.

1. The power supply smoothing caps are anchored with hot glue. I was planning to slice it off and bond the new caps with this adhesive:

Bostik Soft Plastics Adhesive - A water resistant adhesive

2. I was thinking to use Panasonic FCs for the smaller caps on the Power Supply PCB and all caps on the Power Amp PCB. For the Front PCB, I was going to use Silmic 2s Does that make sense?

Glad to hear you are having good weather. Rains every day where I am and looks like another year with no Spring

 

[Ian Finch]

Elna Silmic 2 are also good but I have little experience with them. They are an exotic type, allegedly using silk fibre paper as spacing between the foil electrodes. While Elna and reviewers may claim unique sound quality benefits, the caps can only be of benefit in a few locations that are directly involved with signal processing. At the price, I think using them is a choice you make in hope of improvement rather than with any guarantee.

The glue used to bond the large caps is not critical so long as it isn't water based or corrosive when aged. Any moisture retained in the glue may become conductive or initiate corrosion of the terminals or copper foil if the glue is applied to more than just the outer edge. Polyurethane types like the Bostlk example should be ok, as would butyl mastic, neutral-cure silicone RTV and hot melt types are usually fine too in cool running amps.

 

[mario2005]

Hi ftpols , I have here Nakamichi IA-2 with output transistor failure .
Can you upload service manual part where is output power stage on ?
thank you .

 

[ftpols]

Hi ftpols , I have here Nakamichi IA-2 with output transistor failure .
Can you upload service manual part where is output power stage on ?
thank you .

Hi, Mario.

Sorry to hear about your IA-2. Attached are the heat sink assembly details with transistor part numbers. Let me know if you wanted something else.

The IA-2 Service Manual is only 11 pages, and says:

"Reference Service Manual

The base Model of IA·2 is Amplifier 2. In this Service Manual, identical sections/items are omitted. So, please refer to the
Service Manual of Amplifier 2 (OQ06142A)."

Unfortunately, I haven't sourced the Amplifier 2 SM.

Best of luck repairing a great amp!

 

[mario2005]

Thank you , i need schematic from power amplifier Nakamichi IA-2 .
I have had luck with this amplifier , only output transistor i must change and amplifier work now perfect . I have original Sanken from some old Yamaha 5.1

I have before Nakamichi IA-1. That is one of the best integrated amplifier i listen .

I think all is the same only Nakamichi IA-1 have double output transistor and have 80 watt , and support 4 ohm speakers .

do you know something about Nakamichi's unique Harmonic Time Alignment circuitry ?
I dont see difference in schematic from some clasic amplifier .

 

[ftpols]

Hi, Mario.
I posted the only schematic I have in my 5th April post. (Nakamichi IA-2 SM(p4).pdf.)
I don't know the technical details of Harmonic Time Alignment circuitry.
Try posting a new thread for this subject. Somebody else may be able to help you.
Cheers.