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Denon DP-790

thefragger

thefragger

Certified Crazy.
Today was a beautiful, sunny, and sorta-kinda warm day-- the kind of day that made me want to tear down a TT and clean every last tar-coated part of it.

I'll post more photos as I take them, but I've got a lot of homework to catch up on now :nono:

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Short list of problems;

-The balancing mechanism doesn't work at all, if anything, setting it up to the max puts the arm in equilibrium, with the stylus hovering over the record. I used a penny for a bit then switch to two bus tokens (aluminum, much much lighter) to keep the stylus on the record.

-The original cart is in pretty bad condition (no output), so I took the headset from my Toshiba for testing. I found that the arm doesn't swing to the centre of the record and this causes tracking problems past half-way... can this be fixed by aligning the cart at an angle inside the head shell?


Since the original cart is toast, does anyone have any suggestions about what I should replace it with (under $50 for a cart and stylus, I want to use the Denon shell)? Maybe upgrade the tonearm as well (at a MUCH later date)? I'll come up with more questions as I think of them. Does anyone have any info on this TT for me?


Thanks!
Philip.
 

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Try putting the good cart in the Denon headshell. It may be heavier which will allow you to set tracking force. The pennies make me cringe. :no:

It also looks as if the arm base is twisted towards the outside of the table, gently turn it towards the center, making sure you have a good grip on the base of the arm, maybe a slight loosening of the hold down nut will be needed underneath the deck, just lift the front or side gently and loosen it, usually fingers will do it, then turn slowly, retighten and see if it is fixed.

I am assuming it is a manual tonearm? If turning it doesn't work, then it is possible that the tonearm wires are twisted up, though that is unlikely, as they would break if you put too much force on them..... so be gentle while investigating. This may be the case, but it is also possible that with the arm turned, you hit a rise in the tonearm lift and it causes it to sit in one place, this may be the most likely culprit as to your tracking problem.

Also the antiskate may be sticking, causing it to jam up at the middle of it's travel. Is it hard to move over, or just won't travel on it's own?

The most important thing to remember.... be gentle, tonearm wires are pretty tiny and no fun to redo.
 
VinylHanger said:
Try putting the good cart in the Denon headshell. It may be heavier which will allow you to set tracking force. The pennies make me cringe. :no:

It also looks as if the arm base is twisted towards the outside of the table, gently turn it towards the center, making sure you have a good grip on the base of the arm, maybe a slight loosening of the hold down nut will be needed underneath the deck, just lift the front or side gently and loosen it, usually fingers will do it, then turn slowly, retighten and see if it is fixed.
Click to expand...

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I remounted the tonearm like that, but I'll try your suggestion out. Why would it make a difference?

I am assuming it is a manual tonearm? If turning it doesn't work, then it is possible that the tonearm wires are twisted up, though that is unlikely, as they would break if you put too much force on them..... so be gentle while investigating. This may be the case, but it is also possible that with the arm turned, you hit a rise in the tonearm lift and it causes it to sit in one place, this may be the most likely culprit as to your tracking problem.

Also the antiskate may be sticking, causing it to jam up at the middle of it's travel. Is it hard to move over, or just won't travel on it's own?

The most important thing to remember.... be gentle, tonearm wires are pretty tiny and no fun to redo.
Click to expand...

Yup, it's a full manual table. There's a five-prong plug whose male side us on the underside of the tonearm and the female goes to the RCA cable, so I'm assuming the tiny wires are all inside the tonearm assembly. How tiny are they? Wire-wrap awg (30)?

What happens in that at the half-point it looses tracking. Maybe one and a half rotations will play, it'll skip back one track, play the 1.5, skip back etc. Manually setting it past the middle point runs find until it gets closer to the end of the record, when it completely loses tracking-- I think this is because the stylus isn't parallel to the tracks and the geometry of the needle doesn't help.

When the antiskate is set to zero, it completely disengages from the tonearm; I took note of that while I was cleaning it up.


Philip.
 

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I was trying a couple more records today to make sure that it wasn't the vinyl, and I noticed something... the arm is resisting movement. The needle starts to flew in with the track, then skips back. Moving the arm back and fourth I could feel that it was resisting. I tried to put some fine oil in and it's slowly working in, so we'll see if that does anything.

Did I make a boo-boo? Is it, in actuality, a simple adjustment?


Philip.
 
While I'm not familiar with your Denon, something is wrong. I have 2 LP's with no grooves on one side that are good for a General anti-skate setting, I guess you could iron a throw away LP smooth to set it up that way, the penny thing bothers me more, you need to get to the Denon site to see what cart weight you need to balance it properly, unless someone else here has one and can tell you. I would not play another LP untill I got it set up properly.What was the old cart that was toast?

Craig
 
stuwee said:
While I'm not familiar with your Denon, something is wrong. I have 2 LP's with no grooves on one side that are good for a General anti-skate setting, I guess you could iron a throw away LP smooth to set it up that way, the penny thing bothers me more, you need to get to the Denon site to see what cart weight you need to balance it properly, unless someone else here has one and can tell you. I would not play another LP untill I got it set up properly.What was the old cart that was toast?

Craig
Click to expand...

I've thrown out the penny-- the proper Denon headshell has the correct weight to counterbalance everything into equilibrium.

What's bugging me is that even with anti-skate at 0, it just doesn't feel like it's moving right... I think I'm going to take the entire assembly apart when I have time and see where the metal-on-metal wear pattern is and take it from there.

Can't beat free :thmbsp:



... :tears:
 
I think the lube helped it a bit... it still has trouble now and then, rarely in the same spot twice, but usually on female vocal highs. I couldn't find my Allen key set so I couldn't tear the arm completely down.
 
It's a nice table. Go slow, take pictures as you go and don't let any parts fly off into the other room or never-never land :(

The arm should move buttery smooth across the whole playing arc. Antiskate only get's up to a few grams of lateral force. If you feel a sticky spot - that is well above a couple of grams resistance and will completely negate any tuning settings, anti-skate, whatever. You need to get around that issue first.

Have you gone to Vinylengine.com to see if they have copies of your owners manual or service manual?
 
BrocLuno said:
It's a nice table. Go slow, take pictures as you go and don't let any parts fly off into the other room or never-never land :(

The arm should move buttery smooth across the whole playing arc. Antiskate only get's up to a few grams of lateral force. If you feel a sticky spot - that is well above a couple of grams resistance and will completely negate any tuning settings, anti-skate, whatever. You need to get around that issue first.

Have you gone to Vinylengine.com to see if they have copies of your owners manual or service manual?
Click to expand...

I was very careful when I tore the table apart in the garage-- laundry detergent lids work great for holding / washing little parts-- and even more careful while washing all the tar off. I want to disassemble it one more time to oil up the wood a bit more.

There's more than a few grams in spots along the arc; sometimes they go away, but they come back. I've got the owners manual, which covers some troubleshooting (states that it'll never need lubrication!), but haven't found much beyond that.


Philip.
 
It could be bad tonearm bearings. With anti-skate off, balance the arm so that it floats horizontally and move it to the center of the platter. It should stay there.
 
hakaplan said:
It could be bad tonearm bearings. With anti-skate off, balance the arm so that it floats horizontally and move it to the center of the platter. It should stay there.
Click to expand...

I thought there might be a bearing in there, but I can't find some of my tools (aaargh). The bearings could very well be gummed up with tar; that stuff gets everywhere.

When I balance the arm so it's horizontal and move it to the centre of the platter, it moves out roughly an eighth of an inch (0.125") and stays.


Philip.
 
AWESOME

So I found my Allen key set and proceeded to open up the collar... it was a little difficult pulling the arm out so I firmly pulled on it a little more until *SNAP*

I broke all the tonearm wires :( Time to trace out the RCA cables... what colour wire corresponds with which channel?

Red
Green
White
Blue
Black
Shorter Black (possibly never hooked up)


It's my own damn fault. I think I need to get new wires because the red is now definitely shorter by an inch.


Philip.

P.S. on the plus side, oiling the bearings got them running smooth again.
 
You mean the collar where the headshell attaches? Don't feel too bad. I did the same thing.

Red = right signal
Green = right ground
White = left signal
Blue = left ground
Black = electrical ground and probably attached to a screw inside the arm --maybe at the collar and/or maybe further up toward the pivot. That might be why there are two.

Glad to hear that the arm is moving smoothly, though.
 
Alright, I replaced the wire with the same gauge, but solid core.

Balancing the arm horizontally and positioning it to the centre of the platter, it swings almost all the way out on its own. Live and learn, I guess.

Now I really have to hunt down the good stuff. It was a good break from working on my thesis defence, though.


Philip.
 
If I were to extend the old tonearm wires would I expect any degradation in the audio signal?

Should I just replace them with one straight run?
 
It runs well. There's a low rumble and I think I need to apply some thin machine oil to the main bearing to get rid of that.
 
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