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Having some issues with a nak 700...

J

Jinkies!

New Member
Brand new here to AK.

I recently bought a nak 700 with the box and manual for a decent price and it has been having some random issues

The rewind and fast forward make a clunking type of noise when engaged

I have a video here reproducing the issue


The deck has some other random issues like a pop sound coming from the tape type button, the source button, and the dolby B button but I think Deoxit might be able to fix that... possibly

Another thing that this guy mentioned on his craigslist but didn't really explain to me in person was he apparently changed the counter belt and I actually notice that the button feels kind of tight when pressing it

I appreciate any help, as I really love this machine and it just sounds so fantastic
 
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I have referred these deck to Nakmandan in norther IL for repair in the past and he has done a good job but these deck are old and can have multiple problems and the noise you hear as a pop is usually a DC on the switch that does not belong there due to a leaking electrolytic cap. The deck if you want it restored will need a full recap. I don't know if Dan is taking in repairs again but at some point he might. All tape deck technicians are all overloaded and UI have 184 units here myself.
Gerhard in FL can do the deck as he has all the tapes required. IF you want his contact info send me a PM as they don't want me selling anything here like service.
 
Thanks man PM me!

How could a bad cap cause the rewind to have that noise? I haven't taken the case off yet because Ive been waiting to get a bottle of Deoxit
 
Ohhhhh I just realized you meant my popping noise from the buttons, yea definitely it could be a bad cap considering the machine is from 1973, my brother and I have so many projects rn, not only the nakamichi, but we have a pair of KLH 22A, KLH 5s, and 12s that all need recapping right now
 
I had a popping noise with a Tascam 32 1/2 track deck. The problem was a defective 2SK68A FET but there can be a number of reasons a change of mode can pop but it is most certainly a DC introduction to where it does not belong. In old equipment a pop is most likely a leaking cap but it can be other things as well- if you want to find out get the scope and meter in there and you will know. Everyone seems to want the easy answer these days and don't want to work to find it. Well the easy answer does not always come.
 
Most of your issues sound like caps, but hard to tell unless in person. Don’t waste your time with Deoxit to solve any pops. Scratchy pots maybe, but not hum or pops.

There are 6 belts and 2 tires on the deck. All require a fair amount of disassembly to replace. The tightness of the button has nothing to do with the belt itself.

The 700 is a royal PITA to work on, electrically especially but also mechanically. Replacing caps will be more expensive than on newer decks. First, because there are so dang many, with many jammed against other components, since most all circuits are discrete components. Only the switching logic of the buttons uses some ancient logic ICs. None of them are easy to get to, requiring disassembly to get to them.

There are 8 major PCBs interconnected by edge connector boards and 6 umbilical cords. Makes signal tracing a nightmare. Then to top it off, either because of age or solder type used, the original solder requires more heat and time to liquify and remove. Hard as a rock.

Then, just to add insult to injury, the traces lift off fairly easily AND the PCB design is old school, with no labeling on the solder side like most other Naks, and common leads all mechanically intertwined and soldered at a large common junction, like old tube amps used to. Very time consuming.

The design makes “in place” troubleshooting about impossible. Access to both solder and components side of the PC boards except the main junction board is impossible because of vertical slot inserted cards, or cards inserted in to the mechanics. No longer available umbilical extension cards were required.

Then, just to add one more level of frustration, there are two versions of the 700 even before the 700II, with different boards and heads and the Service Manuals only vaguely resemble either one. When I recapped my own 700, while the green gumdrop caps were fine, every single electrolytic cap except the tantalums were out of spec. Surprisingly, the old style rolled foil huge polypropylene caps were also all still good. The 1uf/50V weren’t too bad, mostly within 20%, but all others were 30,40,50% or more high, & slow to stabilize; indicators of leakage. And by leakage, I do not mean physical chemical leakage, but electrical loss of maintained charge leakage. All the electrolytic caps used are Shoei generic caps and the fact that they have stood up as well as they have for 45 plus years is a testament to the Japanese quality. Caps by many other makes like Frako, ATE, & Philips would have self destructed long before then.

I do not service the 1000/II, 700/II, 600/II and 500 because of these issues unless you have very deep pockets.
 
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The noises from the video are both solenoid chatter, likely cap related to low power supply voltage and or pull up logic, and a combination of loose capstan, reel belts, and hardened idler tire rubber (2) along with what possibly sounds like the reel motor needing lubrication. The popping from Dolby is most likely caps in the Dolby Play board. Dolby on the 700 is entirely discrete components and their is a separate Record Dolby board, a separate play head board, a separate line amp etc, etc.

As an FYI, as you know, the deck weighs a ton, about 30lbs and should never be shipped in the wooden case. Sorry, I don’t want to be a Debbie Downer, but those are likely to be expensive repairs unless you are a very, very competent cassette DIYer. Does the serial number start with 370 or 371?

Just an FYI, Deoxit is a series name, there are different types of Deoxit, for contacts & pots, just for cleaning just for coating contacts for improved conductivity, etc. Most people refer to it to mean potentiometer cleaner and lubricant and has nothing to do with your issues. They come in spray cans of different sizes.

The piano keys for the different 700 versions all used a heavily advertised “soft touch, no movement, futuristic” membrane switch, that evolved over the series and was eliminated in the 700II, for micro contacts. The original ones were known to collapse over time. They should never be lubricated. Since your keys appear to work, I will guess your SN starts with 371. The other pushbuttons are sealed self cleaning slider types, and may or may not benefit from Deoxit.
There are about 1000 better decks that can be purchased for what that deck will sell for, depending on the S/N, even for parts.
 
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