Denon DP 47-F does not lock to 33 but locks on 45

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alanmeyne
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Denon DP 47-F does not lock to 33 but locks on 45

Post by alanmeyne » 10 Apr 2019 14:37

Hello, I have recently bought a Denon DP-47 F. The TT does not lock to 33 RPM. if i engage 45 rpm it locks and thereafter go to 33 rpm it locks steady. similarly in 33 rpm, if i assist the platter by spinning it a bit, it locks to 33. though a recap is on the cards, i don't know if that will resolve this...in the service manual it mentions the pulse position adjustment for 33 and 45 rpm. Can the above issue be resolved with some readjustment of the trim pots? Please advise! Thanks.

lenjack
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Re: Denon DP 47-F does not lock to 33 but locks on 45

Post by lenjack » 10 Apr 2019 16:31

Does the service manual show internal trim pots? If so, you can probably clean them with Deoxit. These Denons were fabulous, but after 35 years of electronically controlled arm and speeds, some of the IC's and capacitors may have drifted out of spec. I don't know if even Denon can fix it if that's the problem.

alanmeyne
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Re: Denon DP 47-F does not lock to 33 but locks on 45

Post by alanmeyne » 10 Apr 2019 18:16

Thank you lenjack, I will try the deoxit and the cap change...the manual does show trim pots

lenjack
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Re: Denon DP 47-F does not lock to 33 but locks on 45

Post by lenjack » 10 Apr 2019 19:04

Trimpots first. If that works, you may not need to do the caps, unless you want to. I had a dp-52F with external tracking force and antiskate/damping pots, that constantly needing deoxing after 32 years. Never did the caps, but finally sold it, for fear it would eventually get too much to handle.

alanmeyne
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Re: Denon DP 47-F does not lock to 33 but locks on 45

Post by alanmeyne » 11 Apr 2019 04:16

Thank you lenjack, will share how that went once i have done that.

captmark
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Re: Denon DP 47-F does not lock to 33 but locks on 45

Post by captmark » 11 Apr 2019 08:55

Your issue is most likely a bad resistor R12 if 45 is locked and 33 isn't. The 33 speed is stepped down from 45 by a fixed ratio with that resistor. A recap, though highly recommended will not fix this issue, but will keep 90% of other issues from happening down the short road. You will need an oscilloscope to do the adjustment correctly to get the waveforms right. You can always do it wrong and just turn VR1 to change the 33 speed till you lock and forego 45 locking, but that is a very short term fix. You will need some kind of a stobe disc as doing this will get it to lock to something, but not necessarily 33.3rpm.

alanmeyne
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Re: Denon DP 47-F does not lock to 33 but locks on 45

Post by alanmeyne » 11 Apr 2019 17:53

Hi captmark, Really appreciate explaining how the circuit works. Will try to get my hands on an oscilloscope and do the job right as I intent keep this TT for good. Will reach out to you for further guidance...Thank you once again

alanmeyne
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Re: Denon DP 47-F does not lock to 33 but locks on 45

Post by alanmeyne » 27 Apr 2019 07:06

Hi Captmark, I recapped with no resolution (as suspected) to the 33 locking problem... Am trying to understand the circuit. The manual says to adjust VR1 to set the pulse position from TP1 to be at the 50% position of the traingular wave form from TP2 for 45 rpm. This means, there is only one correct physical position for VR1. This is understood. But for adjusting the 33 rpm lock, it says to switch to 33 rpm and do the same, ensuring that the pulse from TP1 is now between 40 to 80% of the wave form from TP2. this may or may not coincide with the 50% position already set for 45 rpm. If VR1 is to be turned to accomplish 33 lock, then it will also mean that the previous adjustment for 45 is upset... your thoughts? Thanks.

alanmeyne
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Re: Denon DP 47-F does not lock to 33 but locks on 45

Post by alanmeyne » 27 Apr 2019 07:08

I must confess that i have not checked the health of R12 (22k)...I will do this soon.

captmark
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Re: Denon DP 47-F does not lock to 33 but locks on 45

Post by captmark » 28 Apr 2019 05:16

Make sure you have a 60hz strobe disc before proceeding. I am going to guess that R12 is not your culprit, and that you are on the far edge of tolerance (off the 50% center-wave on the 45 rpm reading) so it still locks there yet be too far off to have the quartz circuit compensate on the 33 setting. Before doing any VR-1 adjustments with the scope, check both speeds and make sure you are grounding to the right spot (I don't have the manual in front of me but is specifies the pin on the outside edge of the PCB). You're on the right track and almost have it sussed...

alanmeyne
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Re: Denon DP 47-F does not lock to 33 but locks on 45

Post by alanmeyne » 28 Apr 2019 19:08

That sounds very sensible deduction...Thank you so much captmark. Really appreciate.

captmark
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Re: Denon DP 47-F does not lock to 33 but locks on 45

Post by captmark » 29 Apr 2019 08:16

I just realized you may not have 60hz electric where you are-small world! Just make sure you have the right strobe disc for your wall voltage. Good Luck!

Rajkumar
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Re: Denon DP 47-F does not lock to 33 but locks on 45

Post by Rajkumar » 11 Oct 2019 05:18

Hi alanmeyne, do you have any update on this issue, I have same issue 33 flashing, if I switch 45 than 33 it lock. If switch to direct 33 not lock flashing. I have lubricate bearing not help.

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