Denon DP3500 Speed control

[GCP1001]

My Denon DP3500 turntable (1973) is not responding to speed control and just runs at high speed..any ideas?? thanks Graham

[chris@panteg]

Hi there

Welcome to AOS , Dave Cawley is probably best to help you here .

You need to post an introduction in the new members thread if you could:)

[Marco]

Hi 'GCP1001',

Welcome to AOS :)

Before we help with your query, could you please pop into the Welcome area and introduce yourself to our community by supplying your first name, basic geographical location, system details and music tastes, as this is the requirement for all new members joining AOS.

Cheers :cool:

Marco.

[GCP1001]

Hi, just to say welcome details posted .. thanks for the heads up..

[Mike]

Does it have a 'tape' and reader head on the inside of the platter?

I'm not 100% sure about the 3500 but I did have a similar problem with my 3000 when I first got it.

[kcc123]

One of my turntables, the JVC QL-7 had a speed issue last year, it also ran fast. So I replaced all the old caps on the circuit board and it has had no problem since.

[DSJR]

Old Denons as I recall do have a magnetic strip with a reading head which is adjustable in position. There should be minimal distance between head and strip and hopefully this will cure your probems.

Japanese capacitors were rather longer lived than many of the UK sourced ones back then. With any luck, you won't need to do wholesale replacements (I don't recall Denons or Technics decks being such afflicted).

[kcc123]

All Denon turntables use a magnetic speed detection system which controls the speed while comparing the phase of the output signals of the detector with the phase of the reference signal by the quartz oscillator. The inner rim of the platter is provided with a magnetic coating. As the turntable rotates, a magnetic head detects pulse signals and regulates the motor servo control. If the magnetic coating is damaged, I think, you are done with it.

[dale kid]

King, not strictly true in all cases of Denon turntables.

I take it that Graham in the first post here has the Denon DP-3000 motor installed in his DP-3500 system?

The Denon DP-3000 motor unit along with the DP-5000 motor unit used a 2 phase AC motor with the servo circuit controlled by the frequency generated from the pulses recorded on the magnetic strip through a comparator circuit fed with a reference voltage. These models were not quartz referenced. For an example the DP-2000 motor unit and DP-6000 motor unit were quartz referenced models and used 3 phase AC motors.

The comparator circuit is fed by the magnetic pickup head circuit and a reference voltage circuit, this can be checked for correct gap by placing a buisiness card between the head face and the rim when one of the platter access holes is positioned over the magnetic pickup head. Two other places to check are 1) the reference voltage being generated is correct and 2) that the compartor circuit is receiving the correct waveform from the pickup.

The Denon motor units perform well but can develop noisy bearings over time and can require some expert attention to sort out.

May your days be long and peaceful, Dale

[kcc123]

Hi Dale,

Thank you for correcting my mistakes!

My Denon DP80 is quartz referenced and driven by a 3 phase AC motor as well.

[GCP1001]

Thansk to all fo rthe suggestions..have checked the air gap between head and rim - is correct..like the idea of the caps replacements..any experts who can handle the work in the gloucester / south west area?

[Mike]

Give Vantage Audio a call and speak to Richard.

http://www.vantageaudio.com/

[Mike]

I've just realised what the DP-3500 is... Doh! :doh:

Here's mine!

http://img355.imageshack.us/img355/9028/p8011702ju9.jpg
By shian7 (http://profile.imageshack.us/user/shian7) at 2008-08-01

[GCP1001]

thanks Mike

will contact vantage..

Graham

[Mike]

You'll not regret it Graham, Richard gives good advice and does excellent work.

You can see pictures of mine being worked on HERE. (http://vantageaudio.com/info/KL60.htm)

Cheers...