Denon DP1200 turntable speed fluctuation

[teknake]

I just hooked this table up today for the first time, as it was given to me when I purchased a record collection. The speed seemed to run fast and as I turned the adjusing knob it slowly got back to where it should have been then quickly slowed down to a point where it was way too slow. I played with the adjusting knob in this fashion for approx. 20 min. and was never able to get it to where the speed was running true. Not sure where to go from here

[paul401]

Hi,
sounds like a dirty pot! You'll need to give it a clean with some switch cleaner, something like 'Servisol' or similar. You need to get the cleaner right inside the actual pot, so a little dismantling may be needed to gain access, the 'straw' that comes with the cleaner is useful for this too. A couple of squirts and then turn the control through its full range of motion a few times. Make sure the unit is disconnected when cleaning. Hopefully this will fix it.

Paul

[leland1]

I just picked up a 1200 and want to clean the adjusting knob. Any tips on how to take the knob off before I just yank on it and break it? Do I need to go at it from the underside? Anything else I should use cleaner on while I am taking it apart?

[Alec124c41]

Manuals:
http://www.vinylengine.com/library/denon/dp-1200.shtml

Cheers,
Alec

[EdAInWestOC]

The DP-1200 turntable is pretty old and as far as speed control is concerned there are a couple of things to look out for.

First there is a brownish coloration on the inside edge of the platter. I hope that everything is OK with this because there is little you can do if it is damaged. That brownish color is like the oxide on a magnetic tape and there are speed pulses recorded in that oxide. These pulses are picked up by something that should look like a tape head.

The pulses will be used by the turntable's electronics to control the speed.

Now for the other potential bad news. The electronics on that table are over 30 years old...probably pushing 40 years old and were never designed to last that long. I'm not saying they cannot be fixed, they can but it requires you to box up the table and take it to an electroinics repair shop that will work on that old turntable.

If you are interested in fixing this turntable make some phone calls and find a place that will recap the electronics in that turntable. Electrolytic capacitors will not last 40 years very well and you can be fairly certain that the caps need replacing. Playing the game of waiting until the caps fail is pointless if you want something you can depend on. There is also the potential that a cap failure will damage something a lot harder to find than a capacitor.

DECISION TIME: The problem here is that there is no point recapping the turntable if anything is wrong with the servo information recorded under the platter. Its a tough call and only one you can make.

It depends how much you like that turntable and how attached you are to using it. If you go on the assumption that the servo information is OK the recapping and readjustment procedures listed in the service manual in this forum's library should be able to be done fairly cheaply. There isn't that much to the electronics of the DP-1200 and there isn't much to recapping the table.

Its up to you. You can go to the Library section of this forum, download the service manual for your turntable and print it out. Once you have that you can start calling around looking for an electronics repair shop that will work on your turntable.

Start by telling them you are pretty sure the turntable will need a recapping and readjustment. And also mention you have a copy of the service manual.

That may get you somewhere,
Ed

PS. That speed control you mentioned is probably not the issue. There is an outside chance it has something to do with the issue but Denon speed control circuitry is a servo feedback setup where the speed pulses mentioned before are read and used to control the platter speed. The control you mentioned is to allow a range of speeds outside the 33 & 45RPM absolute speeds and if you cannot get the table to lock onto speed no matter how much you rotate the control something else is probably up. Hopefully I am wrong.

[Jim Howard]

Like Ed mentions, there is a magnetic strip on the platter read by a magnetic reader as it spins. If the reader is misadjusted then simply follow the directions in the service manual to get this correct.

Electrolics are iffy when we get into 25 plus years of service. Even if they look fine on the outside they can be dried up or damaged inside.

It is fairly inexpensive to have these replaced and I would do so when you are sure everything else is good on the table.

This is not a quartz locked turntable so it is never going to have rock steady speed compared to those designs.

Look for a DP 6000 if you can find one. These are amazing turntables. I have owned a DP 60L and now own a DP 80. The better Denon motors make for simply amazing turntables.

Good luck and please report back.