Denon DP-51F Repair

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airslashfury
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Denon DP-51F Repair

Post by airslashfury » 28 Oct 2019 06:15

Hi All

Just got a Denon DP-51F passed down. Used to be working about a year ago but now when I turn it on, everything lights up, platter seems to spin at the proper RPM when a vinyl is placed on top but the tone arm just stays parked when start is pressed. I do notice the arm lift slightly when the unit is powered on but that's about it. I have tried moving it manually but it swings back to the resting location. I have checked that it is leveled but nevertheless issue continues. The lifter button doesn't seem to be doing anything. I have experience working with electronics, just new to Record Players and their nuanced. Any tips on what to look for and troubleshoot are appreciated.

Bluesnote
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Re: Denon DP-51F Repair

Post by Bluesnote » 28 Oct 2019 07:50

airslashfury wrote:
28 Oct 2019 06:15
Hi All

Just got a Denon DP-51F passed down. Used to be working about a year ago but now when I turn it on, everything lights up, platter seems to spin at the proper RPM when a vinyl is placed on top but the tone arm just stays parked when start is pressed. I do notice the arm lift slightly when the unit is powered on but that's about it. I have tried moving it manually but it swings back to the resting location. I have checked that it is leveled but nevertheless issue continues. The lifter button doesn't seem to be doing anything. I have experience working with electronics, just new to Record Players and their nuanced. Any tips on what to look for and troubleshoot are appreciated.
You can download the service manual here. . .
https://www.vinylengine.com/library/denon/dp-51f.shtml

I have a DP-47F working nicely but did have a similar experience, on close inspection the album I was trying to play was not opaque - it looked black but when held to the light it was quite transparent, the sensor couldn't determine there was a disc so refused to play ball. May not be your problem directly but may indicate a 33/45 sensor issue?

Chris

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Re: Denon DP-51F Repair

Post by airslashfury » 28 Oct 2019 13:02

I think it does detect the vinyl size properly and such i tried both 33 and 45. Went through the manual, didn't see anything that would jump at me as a probable cause. I'm going to try to clean the position Sensor/LED and see if that helps. Don't know if that would cause the Lifter button to not work.

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Re: Denon DP-51F Repair

Post by Bluesnote » 28 Oct 2019 22:15

airslashfury wrote:
28 Oct 2019 13:02
I think it does detect the vinyl size properly and such i tried both 33 and 45. Went through the manual, didn't see anything that would jump at me as a probable cause. I'm going to try to clean the position Sensor/LED and see if that helps. Don't know if that would cause the Lifter button to not work.
I can't remember if I tried the lift button, but I always go to the easy fix first - be aware that that sensor can be tricked by direct strong light too, so best to place the TT in a shaded space. The slight lifting of the tone arm when powered on is normal. Make sure you have the arm balanced and stylus force set 1.8g (check with scales if you have one) - too much weight will affect the lift.

Silly question but, have you removed the transport screws? I don't know if they would give your symptoms but worth checking?

Chris

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Re: Denon DP-51F Repair

Post by Bluesnote » 28 Oct 2019 23:17

. . .another thought, you can override the automatic operation by turning the rubber mat 90 degrees effectively taking the sensor out of the equation - you now have a manual TT. Set your LP, set speed and manually place the arm?

If that works you have narrowed down the possible issue.

Chris

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Re: Denon DP-51F Repair

Post by airslashfury » 02 Nov 2019 00:52

Bluesnote wrote:
28 Oct 2019 23:17
. . .another thought, you can override the automatic operation by turning the rubber mat 90 degrees effectively taking the sensor out of the equation - you now have a manual TT. Set your LP, set speed and manually place the arm?

If that works you have narrowed down the possible issue.

Chris

That's interesting, I will try that and get back. At least to see if the arm is able to lower. I do know that rubber mat has got some dimples underneath that lock it into the correct position which will probably make it tricky to sit level when i turn it. nevertheless i'll what happens.

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Re: Denon DP-51F Repair

Post by Bluesnote » 02 Nov 2019 00:58

airslashfury wrote:
02 Nov 2019 00:52
Bluesnote wrote:
28 Oct 2019 23:17
. . .another thought, you can override the automatic operation by turning the rubber mat 90 degrees effectively taking the sensor out of the equation - you now have a manual TT. Set your LP, set speed and manually place the arm?

If that works you have narrowed down the possible issue.

Chris

That's interesting, I will try that and get back. At least to see if the arm is able to lower. I do know that rubber mat has got some dimples underneath that lock it into the correct position which will probably make it tricky to sit level when i turn it. nevertheless i'll what happens.
No, it's a design feature to allow the playing of transparent vinyl where the sensor can't read disc size. You'll find the mat will sit down flat when rotated 90 degrees.

Chris

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Re: Denon DP-51F Repair

Post by airslashfury » 02 Nov 2019 02:15

Bluesnote wrote:
02 Nov 2019 00:58
airslashfury wrote:
02 Nov 2019 00:52
Bluesnote wrote:
28 Oct 2019 23:17
. . .another thought, you can override the automatic operation by turning the rubber mat 90 degrees effectively taking the sensor out of the equation - you now have a manual TT. Set your LP, set speed and manually place the arm?

If that works you have narrowed down the possible issue.

Chris

That's interesting, I will try that and get back. At least to see if the arm is able to lower. I do know that rubber mat has got some dimples underneath that lock it into the correct position which will probably make it tricky to sit level when i turn it. nevertheless i'll what happens.
No, it's a design feature to allow the playing of transparent vinyl where the sensor can't read disc size. You'll find the mat will sit down flat when rotated 90 degrees.

Chris
I see what you mean, I was able to rotate the rubber mat so that it covers the slots on the aluminum plate. However the issue still remains that the ToneArm still stays elevated. I can swing it all the way to the inner part of the vinyl but it will return to the rest as if it where springloaded. It seems that something is keeping the arm actuated to the rest position.

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Re: Denon DP-51F Repair

Post by lenjack » 02 Nov 2019 03:19

These are fabulous tables when they are working right, but are a bear when they get like this. My Dp-52 acted up 2 years ago after 32 years. It was the pots. I think yours is the electronics.

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Re: Denon DP-51F Repair

Post by airslashfury » 02 Nov 2019 04:19

lenjack wrote:
02 Nov 2019 03:19
These are fabulous tables when they are working right, but are a bear when they get like this. My Dp-52 acted up 2 years ago after 32 years. It was the pots. I think yours is the electronics.
It did sound great when the old man had it as a daily user a few years ago. Automatic movement was spot on. I do know \ the issue seems to be with is being stuck on rest mode but can't exactly figure out why.

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Re: Denon DP-51F Repair

Post by airslashfury » 02 Nov 2019 04:40

I did notice that the arm is capable of moving to the lead in position if I remove the mat and press the start button(As it is shown for the lead in adjustment on the manual). So while a mat is present it will continue spinning at the proper RPM but no movement from the tonearm. I assume whatever the issue is, it is also the reason the Lifter button doesn't seem to be working.

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Re: Denon DP-51F Repair

Post by Bluesnote » 02 Nov 2019 04:49

airslashfury wrote:
02 Nov 2019 02:15

I see what you mean, I was able to rotate the rubber mat so that it covers the slots on the aluminum plate. However the issue still remains that the ToneArm still stays elevated. I can swing it all the way to the inner part of the vinyl but it will return to the rest as if it where springloaded. It seems that something is keeping the arm actuated to the rest position.
As Lenjack has alluded, it's going to be tricky to diagnose remotely - they certainly are worth persevering with though, mine is a slightly different model (DP47F) but has much the same function.

Reading back over you original post, we may need to take it a step at a time :D

When my TT is in the off status, the arm is able to float nicely balanced over the platter. Once I press the power button, the only indication that it is powered on is the red sensor is now lit - nothing else (the DP51F may show DENON lit?) - the arm no longer floats but can be weighed at 1.8g.

If your arm still floats when powered on this is not normal. My understanding is this is magnetically controlled?
If you are comfortable reading the diagrams/ testing and re-setting, the 'service manual' has all this detail. (link in my first reply). May be a starting point for diagnosis?

Chris

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Re: Denon DP-51F Repair

Post by airslashfury » 02 Nov 2019 05:10

Bluesnote wrote:
02 Nov 2019 04:49
airslashfury wrote:
02 Nov 2019 02:15

I see what you mean, I was able to rotate the rubber mat so that it covers the slots on the aluminum plate. However the issue still remains that the ToneArm still stays elevated. I can swing it all the way to the inner part of the vinyl but it will return to the rest as if it where springloaded. It seems that something is keeping the arm actuated to the rest position.
As Lenjack has alluded, it's going to be tricky to diagnose remotely - they certainly are worth persevering with though, mine is a slightly different model (DP47F) but has much the same function.

Reading back over you original post, we may need to take it a step at a time :D

When my TT is in the off status, the arm is able to float nicely balanced over the platter. Once I press the power button, the only indication that it is powered on is the red sensor is now lit - nothing else (the DP51F may show DENON lit?) - the arm no longer floats but can be weighed at 1.8g.

If your arm still floats when powered on this is not normal. My understanding is this is magnetically controlled?
If you are comfortable reading the diagrams/ testing and re-setting, the 'service manual' has all this detail. (link in my first reply). May be a starting point for diagnosis?

Chris
So yes, It does float when off and I did balance it to the proper force. Issue is that when it is powered on (Yes, the Denon light powers on) it will automatically lift a little above the balanced point and return to the rest. If you move the tonearm, even if it's stopped it will always return to the arm rest so it seems voltage is constantly being applied to the arm servo so that it recoils back to the rest position(you can feel resistance if you try to move the arm when stopped) .

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Re: Denon DP-51F Repair

Post by Bluesnote » 02 Nov 2019 06:37

airslashfury wrote:
02 Nov 2019 05:10

So yes, It does float when off and I did balance it to the proper force. Issue is that when it is powered on (Yes, the Denon light powers on) it will automatically lift a little above the balanced point and return to the rest. If you move the tonearm, even if it's stopped it will always return to the arm rest so it seems voltage is constantly being applied to the arm servo so that it recoils back to the rest position(you can feel resistance if you try to move the arm when stopped) .
OK, Floats when off (normal with correct cartridge and rear weight adjusted), the tone arm should be in balance and parallel to the platter, but you say it continues to float when switched on i.e. no weight has been applied to the tone arm? That shouldn't be the case. With mine, when powered on if you manually lift the tone arm it is no longer balanced and has the set 1.8g down force, so now can be moved to the record and set down. You can't rely on the 'stylus force' adjustment, it will get you close but scales will get you on the mark.

If you don't have scales, experiment with stylus force, maybe err on the heavy side to see if the arm takes on some weight?
Denon DP47F weight.jpg
(67.86 KiB) Downloaded 35 times
Chris

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Re: Denon DP-51F Repair

Post by airslashfury » 02 Nov 2019 06:55

https://www.youtube.com/watch?v=oglpb7c ... e=youtu.be

Here's a vid of how it's behaving. Sorry for the poor quality.

As you will see. When you power it on it does a slight lift of where the balance height is. I'd say about a good 3mm above the balance point and then moves to the rest point, which is constant. Even when it is on STOP.

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