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Denon DP-23F Troubleshooting

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Denon DP-23F Troubleshooting

Postby John Paul » 08 Feb 2018 01:31

I have a Denon DP-23F that I brought back to full working condition and I thought I would put together a couple common troubleshooting issues with this particular deck in one place. These three problems were not clear to me by reading the manuals.

1-You turn it on and press start and nothing happens.

Assuming you remembered to unlock the arm this can be caused by not balancing the tonearm first. It seems to be a bit of a safeguard for your needle. To balance the tonearm you must turn the machine off, move the arm in the space between the tonearm rest and the platter, and then adjust the counterweight until it floats. Return the arm and that is it. You do not need to adjust the tracking force before you do this and you cannot do it properly with the machine on as the electronic counterweights will be active.


2-How do you check and/or adjust the tracking force.

As the platter must be spinning in order for the electronic tracking to activate this seems to cause a lot of confusion. If you want to just do a quick check you can do that on the deck between the platter and the tonearm rest. You can press the lifter button, manually move the tonearm over the scale which will start the platter spinning, then press the lifter button again to let the needle glide down to the scale. If you want to adjust it or get a reading over the platter you must remove the platter and then find a way to raise your scale to what it would be if the platter, mat, and record were still in place. The rest you would do the same as I stated previously. If adjustments are needed they can be performed by rotating VR5 (It is in a labeled hole under the platter and is detailed in the service manual). Again the machine must be on and the motor spinning in order to have the electronic tracking force active.


3-The platter always spins and/or auto return doesn’t work (or is intermittent).

This deck uses a pair of LED lights, three CDS’s (cadmium sulfide Photoresistor) and a shutter attached to the tonearm to know where it’s located. These CDS’s are sensitive to temperature (which can cause an intermittent issue) and can also go out of spec over time. If you remove the bottom cover of your deck (make sure you remove the headshell and platter before turning it upside down) and turn the machine on you should be able to see two LED’s glowing in shrouds on a circuit board facing another circuit board above it that has three sensors attached along with the wiring for the audio signal. The CDS’s change their resistance depending on how much light they get and this deck is wired so that manafests itself in voltage changes presented to IC 2 on the main board. IC 2 is looking for >2.64v from the sensor. In my case my sensors had gotten out of spec to the point that they were only getting to 2.08v. If you have the service manual, a multimeter, and know how to read a schematic you can test it yourself but just changing them is probably a safe bet. As near as I can tell all three Photoresistors are 5-10KΩ and that worked for me. I just picked mine up in a cheap variety pack off Amazon for a couple bucks. It is worth noting that this system is unrelated to how it finds the start of the record (which is a mechanical not electronic design) and the adjustment for that is outlined in the service manual.


Although it is unrelated to troubleshooting I also replaced the capacitors in mine and found this post very helpful in that regard…
viewtopic.php?t=35176#p277397
I found similar discrepancies between what the service manual listed and what was actually there so I would recommend making a list of what is actually there before placing an order and changing them. Digikey does not stock some of the Panasonic part numbers listed in that post anymore but they had Nichicon substitutions for those that worked well for me.
John Paul
 
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Joined: 08 Feb 2018 01:18

United States of America

Re: Denon DP-23F Troubleshooting

Postby Clabur » 08 Feb 2018 04:26

Thanks for great info John. I was actually checking the cds’s on my DP-21F, which looks very similar to the 23F, earlier today. I have this problem: At start up, all functions work. After a while, the autostart only works if I choose the 17 cm size. And after a while the function to return the arm work but it keeps running the platter. Cds 2 and 3 measured very similar but the cds 1 gave quite different readings especially when I tested the dark resistance. For instance when testing in quite dark environment 1.8 MOhm for the cds 2 and 3 but only 0.01 MOhm for the cds 1. I was wondering, when the cds go bad, is it that they don’t give enough resistance in darkness or that they don’t go enough low in resistance when exposed to the LED? For example when your IC 2 only got 2.08 V, was it that the resistors didn’t go high enough in resistance or the opposite? My thought was that if the problem is that they don’t give enough resistance it could be enough to replace the cds1 for now.
Clabur
 
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Joined: 14 Jan 2018 11:59

Sweden

Re: Denon DP-23F Troubleshooting

Postby John Paul » 08 Feb 2018 04:39

The CDS have lower resistance determined by how much light they get. The less resistance the higher the voltage gets through. In this case the CDS are not giving a low enough resistance because they have aged and become less sensitive to light. You cannot test the resistance while they are still in circuit as you are measuring more than just the sensors. You also can't test the voltage at the sensors as there is other resistance in the circuit to get it to the voltage the controller chip is looking for and the service manual does not give required voltages at the sensors themselves. You have to check voltages at the controller chip if you want to test it as that is where the listed voltages are.

I would just replace them as they are cheap enough and seem to be a common failure point.
John Paul
 
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United States of America

Re: Denon DP-23F Troubleshooting

Postby Clabur » 08 Feb 2018 04:43

Ok sounds good. Good info and advice, thanks.
Clabur
 
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Sweden

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