DC motors and outboard power supplies...


For those of you with analog rigs that utilize a DC motor and outboard power supply....I'm wondering:

1. How often do you check to see if the platter is at correct speed?

2. How often do you have to fine tune the speed adjustment?

3. Once fine tuned, does it stay throughout the listening session, or do you need to make adjustments throughout?

4. Would you be willing to comment on which table you are using?

Thank you for your comments.
no_regrets
Hi Dan ed,

"No_regrets, how do you get the controller to work properly again after one of these slow down episodes?"

I shut the supply down, pour myself a drink to calm my frustrations, and after a period of time, sometimes a couple of hours later or the next day I go back turn and turn it on. Many times it works just fine, but sometimes not. That's the thing about it. I don't do anything to it.

One of my thoughts was that something may be drawing too much current and causing one of the many regulator chips to go into thermal overload. But then why is it that I can literally listen for up to 8 strait hours without a problem one day and the next day not even make it 1 hour?

Raul brought up the trimmer pots may be going out of spec. I don't know a lot about electronics but that could be an option. I can't seem to find the exact model number anymore, but I would think as long as I replace with like values it should be fine. I found some for as little as 79 cents. Worth a try at least.

Thanks for your question. I'm sorry I don't have a more technical answer for you though.
No regrets, This is just my 2 cents, but if you don't know how the motor control circuit works, I would advise against random parts replacement. That can lead to confusing the issue, if you make an error. Anyway, I am sticking with the idea that you should measure some voltages during full function vs during problematic moments. It sounds like the problem IS localized to the motor or its upstream circuit.
Hi Lewm,

I just got home from listening to a 17 piece jazz band playing charts from Count Basie, Duke Ellington, and the like. Great fun! I'm going to spin a few albums now and try and take some measurements as you suggested and see what happens.

I appreciate your words of caution as well.

No Regrets
I'd have to guess that you have a thermally related issue - power on, current draw, and component 'X' drifts out of spec. Tracking this proverbial needle in a haystack can be very frustrating without a working knowledge of electronics. That said, in most cases semiconductors either work or they don't; it is pretty rare to see a fixed regulator, for example, start drifting wildly on its own - if that occurs they simply self-destruct. I'd look to passive components first - capacitors and carbon comp resistors, especially on the raw power supply/rectification side of things. Good luck.

-Richard
Along the lines of what Palasr suggests, can you swap another DC source for the battery? I am able to do this with my controller by using a 12-vdc wall wart. The wall wart isn't as quiet but it is great for emergencies and troubleshooting. It does sound like the controller is fine, but the supply is questionable. What battery are you using? How often do you charge it?