Opinions on a Dual 721 problem?

There was a time when I considered myself an audiophile. I fell away from the affliction for a good many years, but it’s slowly coming back (blame SACD). Now, I have a Dual 721 turntable, but it spins slightly faster than 33-1/3 even after maximum adjustment of the pitch control. It worked fine when I was stationed in Germany in the late ’70s, but never behaved properly in the U.S. (I’m convinced it has something to do with the power conversion). Is it salvageable? Could the thing be fixed with something as simple as a new pitch control? Anybody?

 

This may be too obvious but... aren't there two lines to choose from for pitch control, depending on the current you're running the turntable on. The adjustment line for 331/3 will be a different one now that you're back in the States.

sorry if I'm way off

http://www.compassnet.com/concept/

 

I own a Dual 1229 which I picked up at an estate sale. It worked but had a few problems, but I thought it would be a great backup turntable.

It was very easy to find someone to repair it. A quick phone call and $40 later, and it was lubed, tuned up, and running nicely.

So yeah, it should be reasonably easy to find someone to fix it.

And welcome back to hi-fi!

 

Re: Re: Opinions on a Dual 721 problem?

Thanks! It’s a rewarding, if financially punishing interest. ’Fraid I don’t have the means to get back into the highest of fi’s anymore, so I’m largely relegated to the mid-fi world (champagne tastes, beer…). But every little piece makes a difference. And thanks for the help!

 

I don't remember this model specifically, but I doubt it's too hard to fix. The rim-drive models used a "pulley" that had a smoothly varying diameter (actually four steps, one for each speed, but smoothly varying on each step). To speed up it moves the rubber inter-idler wheel down, to a slightly wider place on the capstan. If you can't get it into adjustment you just have to loosen a set screw and reposition the pulley.

The later belt drive models were unusual. They had a segmented "pulley" and a gizmo that pushed down to expand the segments slightly, making the effective diameter larger, and thus increasing the speed. It probably sounds more complicated than it really is, probably just needs to have a slight mechanical alignment (I don't remember *exactly* how it works, but I'm sure it's simple.)

 

The 721 can operate on 50 Hz or 60 Hz without modification.

However, to switch from "110" to "220", you have to open the unit and UNSOLDER the mains wire connected to the "220" terminal, and then SOLDER that same wire to the "110" terminal, which is right next to the "220" terminal.

If this change was already made, and the unit is still running so fast, something would indeed seem to be wrong...

FWIW, if you need a copy of the schematic, I can supply it. If that's turns out to be not enough, supposedly the whole service manual is available for download (not free) at http://www.manualgenius.com/cgi-bin...g&uid=default&Series=0700&view_products_700=1. (At least, that's what their web page says - I don't know these guys and can only assume that they might be helpful if and when.)


FFF

'small world sometimes innit

 

Sometimes they do things that don't make a lot of sense, looking back...

In this case, the early 721 platters had a "combined" 50/60 Hz strobe pattern for 33 1/3 RPM, so there was just one "line" to watch. You can see how unusual (irregular) the bottom edge of the platter looks here: http://www.compassnet.com/concept/tables/721.htm. Worse yet, there was no pattern at all for 45 RPM.

As seen in the 2nd picture, the later platters have the usual multiple strobe "lines", as one would expect.

FFF

 

Yup, that’s the beast —the “early model,” anyway. Thanks for everybody’s help, but I think this story is coming to a quick end.

I couldn’t find my 721 instruction manual or schematics earlier today. It wasn’t in the drawer housing the rest of the equipment manuals, and I thought to look for it on top of the turntable stored on the top shelf of a closet. Nor was the turntable where I left it last. My wife isn't certain, but it might have been given away. Experience has taught me that her lack of recall marks some form of misfortune. Blast! The cartridge was more valuable than the turntable!

Maybe it’s still around somewhere, I was tinkering with it as recently as this year. I’ll keep looking for it… but this is double-plus ungood.

 

Well if it's lost now seems the perfect time to buy a dual...on ebay that is.

 

Hmmm? I have that same situation here.



mud-

 

More distressing than losing the turntable is the loss of the cartridge that went with. I don’t remember the model number, but it was a limited edition Audio Technica with a berserk frequency response, circa ’78 or ’79. It was a thing of beauty… and I haven’t seen any hint of the setup. After all this time, well, this truly bites.

 

Sorry to hear that all is lost.

Hey, look at the bright side - now you can spend a lot of money on a new 'table and cartridge!!!