Nakamichi 670ZX Restore

[derek92994]

This 670 ZX needed a lot of work. Mechanism was seized due to hardened grease on pinch roller pivot points. To my Horror the heads look terrible, only left channel works, right is dead. Most Likely the head, tested the deck electronics and it has output, just not getting signal from the head. I will try resoldering the leads on the head, if I'm lucky that may make a change but not so sure.

First time I have worked on a ZX deck, took some time to figure out, quite a few frustrating moments, happy ending though, at least got it going.

I contacted the seller and he is going to give me a 660 ZX Parts deck for free which has good heads, not a bad deal at all. Will transplant good heads into the 670.

In the future there may be some mods done to OP Amps, electrolytic and orange cap replacements etc.

 

[derek92994]

It took quite some time to get this deck right. Heads have been replaced from a Donor 660zx deck, fixed the main sound issue. It was difficult getting the alignment correct after the seized pinch roller arms were removed cleaned and re lubed, but I got there in the end. This unit also seemed fussy with the type of belt used, that had to be right.

Heads replaced:

Capacitor Stocktake time:

Re cap and calibrate:

Need to track down a few caps which have strange values. All polyester caps at 100 volts 560pf, 680pf, and 3000pf. Mouser didn't seem to have them. Deck is performing well, however recording is not 100%, I do wonder if its something to do with caps on the switch PCB. Time will tell.

 

[TapeHeadOne]

You don't need polyester per se. You can use micas. Don't forget to do the ones around that tone generator. The mouser selection system for caps is a bit akward sometimes. Just start of with 5% or better and see what's left. I think Nak prescribed 2%, but that may be a bit of a challenge. Just don't goo too far of the reservation with the voltage. It does have some averse effects when the rated voltage is several magnitudes larger of what's specified.

What did you use as calibration tapes ? The 1K cal tape from Nak is a really weird one.

 

[derek92994]

You don't need polyester per se. You can use micas. Don't forget to do the ones around that tone generator. The mouser selection system for caps is a bit akward sometimes. Just start of with 5% or better and see what's left. I think Nak prescribed 2%, but that may be a bit of a challenge. Just don't goo too far of the reservation with the voltage. It does have some averse effects when the rated voltage is several magnitudes larger of what's specified.

What did you use as calibration tapes ? The 1K cal tape from Nak is a really weird one.

When I bought my 1st restored BX-300 the tech made a test tape with all tones required for calibration. It was done on a Sony XR Metal with the 3khz tone section recorded on a Dragon.

Never heard of Micas, will look into it. Do those white coloured caps around the tone generator need replacing as well?

 

[TapeHeadOne]

I'd need some numbers as I don't have a 670 manual handy, but there are two or three next to that signal generator. They are responsible for a lot of problems with Nak decks, and seem to suffer the most for some reason.

 

[derek92994]

I'd need some numbers as I don't have a 670 manual handy, but there are two or three next to that signal generator. They are responsible for a lot of problems with Nak decks, and seem to suffer the most for some reason.

I'm assuming this is the tone generator section:

 

[TapeHeadOne]

There's a 'tone' generator, which from memory has 1 pp cap, and there's a 'bias' oscillator which has 3 (this seems to vary, sometimes 2). It's the ones on tha bias that cause the most problems. I think you need to look at C316, C321 and C322 (orr close tot those). They're clearly marked in the parts list as PP capacitors. Also, when you remove parts, check the part designation. There were 'updates' over the years that sometimes didn't make it into the manual.

 

[derek92994]

Thank you for the info, before caps are ordered next time I will check to see if those are replaced.

 

[TapeHeadOne]

Remember that some of those caps have short leads, unlike PP caps. Sou you would have to measure pin hole distance before ordering. For what they cost I would replace them regardless. I had a deck serviced by an eminent repair source in the community and even he didn't get it right.