• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Denon DP-7F Turntable - arm horizontal movement issue

redpackman

redpackman

Active Member
I just picked up a DP-7f turntable off CL. Everything works on it except the horizontal movement on start-up when in the 30 cm (regular sized LP) mode. When I press "Start" the tone arm raises and perhaps moves a few MM toward the LP. Then it lowers (toward the turntable deck, of course, not onto the LP). It doesn't even go far enough for the LP to start turning.

** This is NOT a problem with the "lead-in" setting. I'll show you why later.***

If I manually place the arm on the LP and then hit the "stop" button, OR if the arm reaches the end of the LP, the arm happily and promptly moves at "regular speed" back to the arm rest and the TT shuts off.

(I hope you're still reading because this is where it gets weird).

If I select the 17 cm setting (for 45 rpm records) and press Start the tone arm raises, and makes its way at regular speed, joyfully to the proper size and sets down. No hesitation, no feeble movement. Why does it work on the 17 cm setting and NOT on the 30 cm setting?

Weirder. If I place the tone arm on the LP and then press the "replay" button and then the tone arm reaches the end of the LP the tone arm lifts makes its way to the proper spot on the outer rim of the LP and starts to repeat the LP as it should. This is why I know the "lead in" setting is correct.

If, in the 30 cm setting, I press start the tone arm rises and makes its feeble move toward the LP AND I KEEP MY FINGER ON START as the tone arm continues to SLOWLY make its way in the proper direction eventually the turntable begins to spin....and the tone arm SLOWLY continues on its way toward the LP. If I let up pressure on the Start button the tone arm lowers toward the table deck because it's not yet overt the LP. So I re-press the start button and the tone arm raises and continues on its SLOW progress toward the LP's edge. Then at an appropriate spot I let up on the button and the tone arm lowers on the turning LP and it plays.

So, why the SLOW movement inward in the 30 cm setting when it moves normally (INWARD) in the 17 cm setting?

I've got he service manual from HiFi Engine and this problem is not addressed (or I'm not smart enough figure it out) in the manual.
 
Register to hide this ad
G'day..
haven't scanned the manual Might check in manual mode checking the auto return at end of travel point in 33 mode. Perhaps a dirty switch or contact switches or controller timing? also manually check arm horz for starting the platter rotation.
just throwing darts. usual cleaning is standard.

ttps://www.vinylengine.com/turntable_forum/viewtopic.php?t=72865 gives some hints... really an intro p' mount model on other reviews.

edit read that switches are an issue as it's all cpu controlled.
 
Last edited:
Binkman said:
G'day..
haven't scanned the manual Might check in manual mode checking the auto return at end of travel point in 33 mode. Perhaps a dirty switch or contact switches or controller timing? also manually check arm horz for starting the platter rotation.
just throwing darts. usual cleaning is standard.

ttps://www.vinylengine.com/turntable_forum/viewtopic.php?t=72865 gives some hints... really an intro p' mount model on other reviews.

edit read that switches are an issue as it's all cpu controlled.
Click to expand...

OK. I checked the switches and gave them another shot of De-Oxit. Still the same symptoms. I've checked some of the voltages on the board. Where it says I'm supposed to have +5v DC and -5v DC, I've got that, no problem. But where it says I'm supposed to have +10v DC and -10v DC, I've got +14v DC and -14 v DC. I've checked the power transformer and the two yellow leads each have 12.65 v. AC. But as soon as you get to the ends of the rectifier diodes it's +/- 14v DC. I'm assuming that can cause some major issues. Both on the board and in the schematic it says those areas are supposed to have +/- 10 v DC.

Yes, I'm a newbie at this, so the answer(s) as to how that happens is not obvious to me. What would be the origin of that anomaly?
 
redpackman said:
OK. I checked the switches and gave them another shot of De-Oxit. Still the same symptoms. I've checked some of the voltages on the board. Where it says I'm supposed to have +5v DC and -5v DC, I've got that, no problem. But where it says I'm supposed to have +10v DC and -10v DC, I've got +14v DC and -14 v DC. I've checked the power transformer and the two yellow leads each have 12.65 v. AC. But as soon as you get to the ends of the rectifier diodes it's +/- 14v DC. I'm assuming that can cause some major issues. Both on the board and in the schematic it says those areas are supposed to have +/- 10 v DC.

Yes, I'm a newbie at this, so the answer(s) as to how that happens is not obvious to me. What would be the origin of that anomaly?
Click to expand...
I don't see that as an issue. The only place I see +/- 10V is going into the +5V regulators IC 8 and IC 9. The correct +5V is coming out of the regulators, so I don't believe this is causing your arm malfunction.
 
Yes, Blnkman, I realized this. Thank you for posting and contributing to this discussion. I DO expect to press the start button once and expect the tone arm to then move to the correct position at normal "Denon speed" to the proper point on the LP, lower and play.

What happens now when i have the size selector set on "30" cm (the regular LP size)? I press the start button once and immediately let up, the arm raises, it moves maybe three mm toward the lp and lowers....way short of the LP in the no man's land between the LP and the arm rest.

IF i press and continue to hold down the start button the arm will VERY VERY slowly move toward the LP and will lower when I cease holding the start button down. So I can, if I'm patient, get the tone arm in the right position by holding it down probably for 20 seconds and then releasing it at the proper time.

"Well," you say, "your horizontal movement (inward at least) is messed up/broken. That's your problem."

Yes, that would seem to be true except when the Size selector is set on 17 cm (45rpm size) and I press the start button the arm raises and moves at normal "Denon speed" to the spot on the record that corresponds to 45 rpm size and then lowers. In other words, the horizontal movement "Motor" works perfectly then. The $64,000 question: Why not when the "size" button is set at 30 cm?

Furthermore, If I press the repeat button when an LP is playing, and the LP reaches the end of the side, the arm will return to precisely the spot where it should lower on the LP to play it again. It once again operates perfectly. So the stylus placement adjustment isn't off. It knows where the edge of the LP is for repeat play. And if repeat is not selected it moves horizontally wonderfully at the end of the LP to the tone arm rest and lowers.

So movement outward is always perfect. Movement inward is perfect if the 17cm size selector is operative, but when the 30 cm is elected the horizontal INWARD movement is faulty.

For those of you who can read schematics better than i, Is this likely a failure of the IC controlling all this (the part of the iC that moves the arm horizontally inward) is broken when in the normal position but functions fine in the repeat mode? Or is this more likely a failure of the repeat/normal play switch (which I've blasted with De-Oxit a number of times.

I haven't tested it because doing so is a bit tricky, but I'd guess in the repeat, return and 17 cm modes the motor is receiving a normal amount of DC current, either + or - depending on the direction desired, in or out, but for some reason (the mystery outlined above) it is receiving only a fraction of that when the repeat switch is in the normal play mode, inward motion is desired and only when I keep my finger on the start switch is it receiving any voltage at all.

Insights very very welcome.
 
redpackman said:
The $64,000 question: Why not when the "size" button is set at 30 cm?
Click to expand...
More Darts....
Can you check the selector switch for continuity in both both 17 and 30cm settings? perhaps the sw contacts in 30cm are flakey, why you have to hold down the button? one other test... while powered on, set to 30cm. shut power off and pull the AC cord. then plug in and retest the start button. generally a cpu resets itself.
 
Binkman said:
More Darts....
Can you check the selector switch for continuity in both both 17 and 30cm settings? perhaps the sw contacts in 30cm are flakey, why you have to hold down the button? one other test... while powered on, set to 30cm. shut power off and pull the AC cord. then plug in and retest the start button. generally a cpu resets itself.
Click to expand...


Yes, there is continuity on the switch, so that's not the problem. I've also pulled the plug and then "reset" things electronically, too. No difference.

Is the problem then, most likely then in IC6 or IC2? Does IC6 determine whether the horizontal motor will receive + or - DC current and thus the direction of the tone arm. But as I stated above the tone arm works well when the size selector is in the 17 cm position but NOT (when moving in) when the size selector switch is in the 30 cm position, i.e. the tone arm will move IN Very, very slowly and only if the start switch is held down. Even in the 30 cm OR 17 cm position the tone arm moves out fine.

Are both the IC2 and IC 6 proprietary chips? I don't have what it take s to switch out the IC2, I'd probably destroy the whole mother board. I may be able to switch the IC6 chip since it has only 8 legs.
 
Last edited:
Ok, tested out the voltages at 33 on the schematic (output to the horizontal motor). There were similar voltages but positive DC (inward) and negative DC (outward movement) for both.

The weird thing is that when the size switch is at 17 cm the voltage reading is the same as it is when it's at 30 cm. INWARD MOVEMENT: The arm moves inward at normal speed when the size switch is at 17 cm and it doesn't move or moves at a snail's pace inward when the switch is at 30 cm (AND the start switch is held down continuously). But the voltages are the same!

What??

The arm moves out toward the arm rest at the normal speed no matter what the size switch is set on.

Again, in all cases the voltage applied is roughly the same, just one is +volts and the outward is - voltage.
 
redpackman said:
What??
Click to expand...
It's not the ic's because they are performing normal in 45rpm mode.
https://www.vinylengine.com/turntable_forum/viewtopic.php?t=35974
https://www.vinylengine.com/turntable_forum/viewtopic.php?t=35974
describes the issue maybe in the horz. arm pot adjustments and one poster explained the 45 was normal but same issue in 33 as you have. Adjusting these pots is in the service manual. however a scope is used in the directions. however a member describes not using a scope but imo that's a gamble. (note use of deoxit or contact cleaner on the pots)
If you attempt to adjust w/o a scope.. you need to mark the pots so you can find the orig. position.

note the sm doesn't make clear which VR pot adjusts which function feature.. i.e. platter rpm, tone arm action?

might just consider recapping the electrolytics (oft. done on servo TT's), also might be a problematic diode in that motor control?
 
Last edited:
Binkman said:
It's not the ic's because they are performing normal in 45rpm mode.


https://www.vinylengine.com/turntable_forum/viewtopic.php?t=35974
describes the issue maybe in the horz. arm pot adjustments and one poster explained the 45 was normal but same issue in 33 as you have. Adjusting these pots is in the service manual. however a scope is used in the directions. however a member describes not using a scope but imo that's a gamble. (note use of deoxit or contact cleaner on the pots)
If you attempt to adjust w/o a scope.. you need to mark the pots so you can find the orig. position.

note the sm doesn't make clear which VR pot adjusts which function feature.. i.e. platter rpm, tone arm action?

might just consider recapping the electrolytics (oft. done on servo TT's), also might be a problematic diode in that motor control?
Click to expand...


Binkman, I think you may have put me on the right track. As you stated someone else had the same problem: horizontal IN works in 17 cm size mode but now in 30 cm size mode. mode. They put it down to a bad light sensor. there's one for the 17 and one for the 30. If the 30 is bad the arm won't work. I've got parts on the way and we'll see, but I think this was the problem. Thanks for putting me on the right track!

Here is the thread: https://www.vinylengine.com/turntab...f=98&t=123824&p=1119184&hilit=GL5516#p1119184

Thanks too, to captmark who had the gem of a suggestion.
 
Got the GL5516 sensors today. Still not working. Tried adjusting the horizontal OP amp offset voltage mentioned in captmark's post and in the manual as well as adjusting the lifter op amp offset voltage. Still not working. It says in the service manual to use an oscilloscope. I don't have a scope. I use a VOM.
Put the old GL5516 that was in the 17 cm circuit back in and the old GL5516 back in the 30 cm circuit.

Back where I started. Starting from 17 cm setting works but from the 30 cm setting ....no movement of the arm OR platter.

I'm assuming the 5516's I got are the wrong specs for this turntable. Am I right in assuming that GL5516's don't all have the same specs.....apparently?
 
Last edited:
Binkman you are right the GL5516 I got today work!!

As to my problem of the tone arm operating in the 17cm setting but not the 30 cm setting (regular LP size). I'd ordered the 5516 CDS sensors and the first ones I got were the wrong specs apparently (when exposed to light the ohm reading was STILL way too high) and didn't work with my machine. I got some others today which when exposed to light drop their ohm rating much lower than the original batch. My turntable now works!!!

These are the ones I got:
https://www.adafruit.com/product/161

When exposed to bright light (probably brighter than they get on the turntable) the ohm ring drops to <1000 ohms.

Thanks Captmark and Binkman!!!!!
 
You must log in or register to reply here.
Back
Top Bottom