DENON DP-60L: Speed Unstable- replace which caps?

davstev

Well-Known Member
Hi all,

I know there are a few threads already out there on this topic. I bought an awesome Denon DP-60L table yesterday. It's nearly mint, but the speed issue- it runs a bit fast in both 33 and 45 and this can't be easily adjusted on the table. It was unused for about 15 years and apparently that's a bad thing with these tables.

I already know about adjsuting the distance of the "tape head" to magnetic strip on the underside of the platter; did that and it seemed to make little difference.

So I am thinking of replacing caps. Instead of going through the whole unit and replacing all 30 or so, which would I target to replace to correct this issue?

All suggestions welcome. Maybe cap replacement is not necessary?

Still Troubleshooting....

thanks,
David
 
I recently acquired a DP-75 with speed issues, I opened her up and cleaned two speed adjustment pots and she synched right up. I don't know if your DP-60L has pots for speed adjustment or not, but it's worth a quick look! Good luck!
 
Clean any control pots, and on any unit like this I'd seriously consider a complete recap. At the very least, the power supply would be a good place to start.

If this thing has any of the demon VD1212 dual diodes in the drive circuits, follow Echowars' instructions to replace them with series pairs of diodes. Replacing those in my Sony PS-X70 finally got the last of the speed control demons out of it.
 
You need a serious work on it. Denon used custom chip to handle speed control with reference from quartz. Probably your table cannot lock feedback loop. You will need oscilloscope and service manual to start with. SM has a good explanation of how servo circuit works, which will help understand where and what to measure.
 
Thanks to you all. I am going to start with the simplest solution and work from there if it yields no results.

Thanks again. AK rules!

David
 
Buttercup, The speed issues that you stated for your DP 75..was it stable speed but too fast/slow, or was it unstable speed in general? Sounds to me like the former- too fast/slow.

Thanks,
David
 
Buttercup, The speed issues that you stated for your DP 75..was it stable speed but too fast/slow, or was it unstable speed in general? Sounds to me like the former- too fast/slow.

Thanks,
David

My speed issue was consistently and uniformly slow. I started with the adjustment for the 45 rpm and just moved it back and forth, then the 33 rpm adjustment pot and did the same... she locked right in and has been running correctly ever since.
 
Ok, so tonight I carefully removed the bottom plate on the DP-60L. I found the two potentiometers that relate to fine-tuning the 33 and 45. I fiddled with them a bit, moving them a bit this way and a bit that way, chasing the perfect spot. Simply cannot find it. The speed seems fairly stable, but I just can't chase that perfect spot so that the stroboscope shows it dead on. It's 1mm this way, and 1mm that way, then .5mm...etc...and it's never dead on. If I'd hit the perfect 33.3 or 45, would the quartz lock lock into place?

Then, just as I was giving up and thinking of just recapping, the stroboscope LED died- no light. I am just aiming for a recap and hoping for the best, hope i haven't fried the microprocessor.

Questions- a) if i've fried the microprocessor by running the table for 20 minutes while fiddling with the pots, how would i know if the processor is dead? Would this affect the LED? The table still turns.

b) There's a lot of talk in threads about the Denon microprocessor being unobtainable. Then, one thread i encountered from last year says that the SC3120A microprocessor is still available. I googled it. Seems it's still around in more than a few locations- looks exactly the same, same number.

http://www.datasheet-photos.com/Product/SC3120A.html

Thanks,
David
 
Ok, so tonight I carefully removed the bottom plate on the DP-60L. I found the two potentiometers that relate to fine-tuning the 33 and 45. I fiddled with them a bit, moving them a bit this way and a bit that way, chasing the perfect spot. Simply cannot find it. The speed seems fairly stable, but I just can't chase that perfect spot so that the stroboscope shows it dead on. It's 1mm this way, and 1mm that way, then .5mm...etc...and it's never dead on. If I'd hit the perfect 33.3 or 45, would the quartz lock lock into place?

Then, just as I was giving up and thinking of just recapping, the stroboscope LED died- no light. I am just aiming for a recap and hoping for the best, hope i haven't fried the microprocessor.

Questions- a) if i've fried the microprocessor by running the table for 20 minutes while fiddling with the pots, how would i know if the processor is dead? Would this affect the LED? The table still turns.

b) There's a lot of talk in threads about the Denon microprocessor being unobtainable. Then, one thread i encountered from last year says that the SC3120A microprocessor is still available. I googled it. Seems it's still around in more than a few locations- looks exactly the same, same number.

http://www.datasheet-photos.com/Product/SC3120A.html

Thanks,
David
Are you sure that you found actual part and not just print copy of data sheet? They not made for 15 years, but someone can have old stock left though.

If you want to fix your table, download service manual and check functions according to it. You will need oscilloscope for that. Manual is very good in explaining circuit design and functions.
 
Darn, I guess you are right. Maybe not the actual part.

As for an oscilloscope, I have never used one. I am reasonably good at figuring stuff out. I'll do whatever it takes to get this table running properly.
 
Try deoxiting those adjustment pots, likely that is the issue. I've seen it many times.
Not too hard to find replacement strobe lamps, digikey and mouser have them.
 
What is the best way to test the SC3120A microprocessor to see if it's dead? Oscilloscope the only option?
 
Try deoxiting those adjustment pots, likely that is the issue. I've seen it many times.
Not too hard to find replacement strobe lamps, digikey and mouser have them.

What is the best way to test the SC3120A microprocessor to see if it's dead? Oscilloscope the only option? I'm wondering (fearing) that that may be the issue. Can playing with the potentiometers let too much current through and fry it? I am doubtful that oxidation on the pots is the issue, because they look pretty clean, and i had been fiddling with them for awhile and able to make some fine adjustments to the speed, before the led lights stopped working and I got nervous about what was happening. I'm just paranoid about killing this gorgeous table by frying the SC3120A chip. I know there are some out there that will say "go no further. Recap at once".

The current plan is: recap all electrolytics (27 in total). Hope for the LED to come back to life. Hope for speed issues to rectify. Hope the SC3120A microprocessor is not dead.

I just bought this table. I can't let it go.
 
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What is the best way to test the SC3120A microprocessor to see if it's dead? Oscilloscope the only option? I'm wondering (fearing) that that may be the issue. Can playing with the potentiometers let too much current through and fry it? I am doubtful that oxidation on the pots is the issue, because they look pretty clean, and i had been fiddling with them for awhile and able to make some fine adjustments to the speed, before the led lights stopped working and I got nervous about what was happening. I'm just paranoid about killing this gorgeous table by frying the SC3120A chip. I know there are some out there that will say "go no further. Recap at once".

The current plan is: recap all electrolytics (27 in total). Hope for the LED to come back to life. Hope for speed issues to rectify. Hope the SC3120A microprocessor is not dead.

I just bought this table. I can't let it go.
If you do not want destroy good table - hire a pro for repair. Just make sure that "pro" is indeed knows what he is doing (not all do).
 
The microprocessors aren't available from that site, I tried to buy some and they came back with NLA. I was hoping to squirrel a couple away in case I needed them for my 60.
 
The microprocessors aren't available from that site, I tried to buy some and they came back with NLA. I was hoping to squirrel a couple away in case I needed them for my 60.

Thanks for the info. Is there a way to test the microprocessor to see if it's functioning properly before i recap the whole table? I'd rather not go to the effort of recapping only to find that the SC3120A is dead.

Thanks,
David
 
Thanks for the info. Is there a way to test the microprocessor to see if it's functioning properly before i recap the whole table? I'd rather not go to the effort of recapping only to find that the SC3120A is dead.

Thanks,
David


I'm no IC expert at all. I have no idea how to test an IC.
 
Why wouldn't anyone comment on the OP's response to deoxiting the pots. Who's ever trusted a visual examination of a pot?!?
 
Do try cleaning the trimpots.
Afaik the ICs are not stressed, iirc power transistors do the heavy lifting with throttling the spindle motor.

Sent from my SM-N900V using Tapatalk
 
Do try cleaning the trimpots.
Afaik the ICs are not stressed, iirc power transistors do the heavy lifting with throttling the spindle motor.

Sent from my SM-N900V using Tapatalk

Tried cleaning the trimpots with deoxit. Will give it another spritz. Also, there's an interesting message in there that I am having trouble interpereting. What are you saying about the IC (which i am assuming is the SC3120A?) Thanks for clarifying.

David
 
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