Skip to main content


Showing posts from 2017

photo interrupter , lichtsluisje HBM BF30 toerenteller

I got a second hand (but barely used) BF30 clone milling machine.
The rpm meter was not working correctly (not showing high RPM, nonsense numbers)
I investigated and found the photo interrupter on the spindle axle.
It was covered in grease (sticky brown Chinese transport grease).
After taking it apart I noticed all holes were over-sized (and slotted).
Mounting the thing back and getting the perfect alignment would be a gamble (I like more precise work, but it appears all holes in this machine are too large or slotted, every edge is sharp and needs deburring).

I made a little tool to check the workings, it is impossible to adjust once the motor is mounted so it has to be correct before I put the motor back on the machine.

Here is the setup :

The ring has 16 holes, so the rpm is more accurately (or quickly) determined.
How this works : the system counts number of pulses in one second and from that displays the number of rpm ( NL: toerental in omwentelingen per minuut)  (rounds per minut…

Denon DHT T100 DESIGNED TO FAIL : bad caps (ceramic caps this time)

A friend gave me a Denon DHT-T100 to look at.
Do not spend much time on it.. ok.

It had a problem, it started clicking and ticking after power on, and after some time.
(a so called intermittent problem)

Sometimes it did not tick or click, but it was basically not usable.
The clicking had a sharp click in one channel and repeated after about a second, then sound recovered and it would click and drop out again.

He told me, do not spend any time on it, yeah, right. ;-) like I would give up after 15 minutes.
I wanted to know what was going on with this thing, I found some schematic online and started measuring the usual things.

The power supply, 24V did it drop down when a tick occurred ? Difficult to find out because sometimes the thing would play for hours without a glitch.

I eventually found out the 24 V PSU, the step down SMPS on board and the LDO's were all ok, all power rails remained within spec, but it still glitched sometimes. (while power was ok)

I investigated methodically,…