Systemdek iv 33 rpm motor fault

[Mooly]

Lets take it one step at a time

The original fault was that one speed (33 rpm) failed such that the platter stopped turning.

Is the numbering on those chips identical in every way?

If so and if one was faulty then we would expect the fault to now be that the 45 rpm speed fails... and yet that isn't what seems to be happening.

 

[Kdt6452]

Hi,

Both chips are identical. When I swapped the chips around the motor didn't run at the 45-speed setting but it did run at the 33-speed setting - This is the reverse of the original fault. Swapping them back to their original positions the motor ran at the 45-speed setting but not at the 33 speed.

Cheers
kgt6452

 

[Arch Stanton]

Keep the 33 RPM, who cares the 45.

 

[Kdt6452]

I tend to agree, but just out of interest and in case the motor isn't running at the correct speed. Would you know where I can get one of these chips.

cheers
kdt6452

 

[Mooly]

OK, it was just the way I was reading it... so looks like the chip is duff. I've tried to find useful info on these and failed, however it looks like they are pretty much unobtainable

Read somewhere the Xerxes uses these.

 

[Arch Stanton]

Get a stroboscope somewhere in the web, print it and test the speed.

 

[Mooly]

So Nikko (Dalbani) list them:

M706B1 INTEGRATED CIRCUIT DIP-8 | eBay

It might be worth contacting them. Heck of a price but I guess its supply and demand.

 

[Arch Stanton]

Before ordering that part, ask what is it made for.
Because with the name M706 you can get a power manager for microcontroller.

 

[Mooly]

The newer PSU supervisor chips seem to be SMD small outline only and cost peanuts. The Nikko one does say 8 pin DIL and does quote the full correct device number.

Its not good to use such similar descriptors though. The other totally different chips are STM706T/S/R and STM706P.

 

[Arch Stanton]

You are right but there is not a photo on the eBay link, only a 3D model.

 

[Kdt6452]

Thanks guys,

I found this datasheet for the M706B1 chip on the web. Not sure if its the same as mine.

cheers
kdt6452

 

[Arch Stanton]

Good, yes it's your IC.

 

[Kdt6452]

Thanks,

How does this help me? I think it's an old document.

Cheers
kdt6452

 

[Arch Stanton]

It is absolutely helpless, only an information.

 

[Kdt6452]

Ok thanks,

If I buy the chip on molly's message. Could I damage the PCB if it's not quite the same spec.

Cheers
kdt6452

 

[Arch Stanton]

I wrote a silly thing, the clock divider give 50Hz with the lower frequency quartz and 67Hz with the higher. That is absolutely correct for 33 and 45 RPM.

 

[Arch Stanton]

Ok thanks,

If I buy the chip on molly's message. Could I damage the PCB if it's not quite the same spec.

Cheers
kdt6452

Don't worry it's exactly what you need.

 

[Kdt6452]

I Can't thank everyone enough for their help. I'll get everything back together and put the pully back onto the motor. I'll leave the 33rpm setting working until I get the new chip. (may not bother - it is a hell of a price).

Will post update when all connected up and tried out.

cheers
kdt6452

 

[Mooly]

You're doing well finding that data sheet such as it is... all should be good with that chip.

 

[Mooly]

I'll leave the 33rpm setting working until I get the new chip. (may not bother - it is a hell of a price)....

I guess one way of looking at it would be to think of it as worthwhile to both restore functionality and also to have as a spare.

Small IC's are usually ultra reliable and always the last suspect... unless there happens to be a known issue with them.

This is just my thoughts now... I once built a preamp with all electronic switching using discrete CMOS logic chips and for no obvious reason suffered repeated failure of the same 4017 IC which was one of several. There was no logical explanation for this and so I added an inverse parallel diode across the supply along with a Zener for transient protection along with a 0.1uF mounted directly across the supply pins of the chip concerned. The failures stopped.

If I had your TT in front of me then I might consider doing something similar as prevention against an 'unknown possible issue'.