Changing the PSU caps may be a good idea but it's not going to stop this resistor getting charred.

I stopped my self from saying it.

And yes OP needs to confirm the Fan.

 

And yes OP needs to confirm the Fan.

In order to test the fan I disconnected it and attached it to sequentially placed full AA batteries, first two then three. The 3 batteries gave 4,6v. The fan didn't react.

Regarding Alecs post. As I am not an expert I'm afraid I will break/dismantle/get stuck on elements when preventively replacing parts. Also I would need to understand where I can buy what and what I need. So in my logic I should concentrate on what exactly must be done, then on how to do it and what to buy where. Then actually replacing parts. Tough I still hope for a wonder as I am definitely not confident yet about soldering now caps etc.

I could power up a sec as to measure the voltage running over the smoking resistor. However it could do further damage.

 

Is the R573 smoking with the fan removed ?

And is it possible to measure voltages ?

No, I didn't power up without the fan. I remember from the sound that I drew the conclusion it was running.

For measuring voltage I should power up but then it will start smoking. I can try to achieve the measurement within a second literally.

 

If the fan doesn't run off 4.6V it is faulty and is the only definitely faulty part so far found in that circuit. The fan could cause the resistor to overheat.

The fan motor and its equivalents are obsolete, but I did find this one site which appears to have stock: https://ciiva.com/part/mdn-4rb4mrc-10317372#tab_pricing_avail

 

You can power it up without the fan without a problem.
As long there is nothing playing or sound it will not go into protect.
If the resistor does not smoke without fan ..you need a new fan.

 

Does the fan run nicely on 3V? If not it may be the problem.

If the resistor does not smoke without fan ..you need a new fan.

Guess what guys... It doesn't! The resistor is fine without the fan. So likely I caused all on myself by putting the vacuum cleaner on top of it.

Now will check the link for the replacement part! If this is the solution I'm very very pleased

Thank you all for your feedback and contribution! Surely I couldn't have done without it.

 

You can connect the meter across the fan pins and measure the DC voltage, it will be max4-5V, may be less.
If there is no voltage after power up, then you need to play something, a music and slowly increase the volume. You will see the meter showing voltage, may be as low as 1V.
If there is no other problem you should hear music and when you crank the volume, with in few seconds protection will kick in. It is normal.
Your Amp is fine and all you need is a new fan.

 

Thanks, but...

Your Amp is fine and all you need is a new fan.

Isn't that simple... Searching internet for over an hour but can't find anyone selling it. Only posts from years ago of people running into out of stock issues. The ciiva link was also dead.

I saw this part which is different on the picture but they state its a replacement for the MDN-4RB4MRC
http://alltronic.biz/index.php?main...d=4980&zenid=b5da547cde14ef5c70f0042495b64069

Also I saw a German post where the guy managed to find a similar old one he could use. http://radio-bastler.de/forum/showthread.php?tid=1603

Not very hopeful

 

Don't despair. Any fan that uses a similar amount of power and fits the same space will be fine. Do you have specs? Maybe they are written on it?

 

I got an idea....
Can you dismantle the fan and show the motor picture.
I believe those motor are used in CD player "sled" and tray drive's.

 

Hello,

Yes, indeed we should focus on a similar replacement part (or small chance to find a recent one second hand). The part sticker doesn't say much, just MDN-4RB4MRC and 10 dec 90S4, so it's from the very early nighties ;-). The output voltage is variable depending on the volume, the highest i saw is 5,4V and typically it's around 2.8v. According to Encompass.com the Matshushita MDN-4RB4MRC can be substituted by a Panasonic MDN-4RB4MXA, see also https://www.encompassparts.com/item/414723/Panasonic/MDN-4RB4MRC/Motor.

The motor dimensions are
- motor itself diameter 24 mm, height 18,3 mm. That's 0.95 inch and 0.72 inch respectively
- the rotor axe diameter 2mm, length 8 mm. That's 0.08 and 0.315 inch

From the German post i understood the motors are also often used for spinning the CD's in a CD player.

Thanks for helping me to find substitutes. Please note NA dealers are not the most efficient to source from as i live in Amsterdam.

 

I got an idea....
Can you dismantle the fan and show the motor picture.
I believe those motor are used in CD player "sled" and tray drive's.

I was just typing when your post came in, yes, your thoughts, see pic herewith on the CD are confirmed by the German post.

 

I did not read the links but saw the picture of the motor back and it was familiar to the motors I see in CD decks.
CD deck motors motor normally use ~3v.
I think it is possible.
Get your hands on a CD deck motor wire it up to the amp to test

 

Gimme a minute I am at workshop. I am gonna look around....

 

Further on the German post the guy measured the resistance and voltage of the replacement and original motor. He claimed the resistance of the original motor was 18 ohm and the replacement part he took had 14 ohm, see also graph attached.

 

Found one.
Same size as your except the shat is longer....not a problem.
Gave 3 V and is working....!
One problem..bad bearings or something. I can hear rattle inside...!
Just remembered...I replaced this motor on a faulty spin motor CD drive

 

Yet..I do have plenty of working ones with the same dia. but height is less.
Draws 20mA at 3V.

Can you get ur hands on a Spindle motor ?

 

thanks. according to the german post and the graph i shared the 20mA at 3v should work fine.
Question, the voltage is fluctuating and i measured up to 5,4V... should the replacement be a 3v or 6v? Also should i care about the RPM of the motor?

The Dutch distributor i know offers 17 different models but not sure what to look for in terms of spec, see https://www.conrad.nl/nl/universele-elektromotoren-o1230010.html

 

It is fluctuating because motor is not there or there is not feedback from motor.
Try connecting a 680Ω 0.5W resistor instead of the motor.
This will force the voltage to stabilize before amp shutting down due to no RPM. I think you can measure the voltage before going to protect

 

so i should try to buy a 3V? not a 6v? And for the RPM's they range from 6000 to 18.000

both have not perfect dimensions but i should get it mounted and working

option 1)
3VDC with 9000 rpm
spec https://www.conrad.nl/nl/motraxx-el...-stationair-toerental-9000-omwmin-244430.html
drawing http://www.produktinfo.conrad.com/d...99/244430-da-01-en-IGARASHI_2430_65_Motor.pdf

Option 2)
3vdc 6500 rpm
product https://www.conrad.nl/nl/motraxx-el...-stationair-toerental-6500-omwmin-244422.html
drawing spec http://www.produktinfo.conrad.com/d...422-da-01-ml-Igarashi_2427_30_Motor_de_en.pdf