New Capacitors hitting 300F

[CheeseofBorg]

For the past few months I have been trying to fix a speed issue on my Sony TC-666D. After installing a 3d printed 60hz capstan, it still ran a little slow. I did some searching and found this : http://audiokarma.org/forums/index.php?threads/sony-tc-660-r2r-speed-problem.98443/

Where Fred suggested replacing the phasing capacitor. I did so by replacing Capacitor 504 on the schematic (which has been uploaded to HifiEngine by a helpful member) with two 1uf capacitors (rated for 450V) in parallel to match the 2uf capacitor. When I fired the unit up, not only was it still running slow, but the new capacitors reached over 300 degrees Fahrenheit after about a minute at which point I shut it off. I turned it on briefly to check the voltage across the capacitors and it read at 97V if that helps. What should I be looking at as my next step of troubleshooting?

 

[petehall347]

did you use the correct type of capacitors ?

 

[avionic]

(rated for 450V)

AC or DC ?

 

[CheeseofBorg]

AC or DC ?

This is the part I used:
https://www.digikey.com/short/q3md92

 

[petehall347]

there is the problem ..they are polar so only for DC . they dont even look like they belong with motors in that package .
DO NOT apply power to those again .you are lucky they didn't explode .

 

[petehall347]

i would think it should look more like this

 

[petehall347]

not sure if you need motor run or motor start capacitor .. or if there is any difference between them .

 

[CheeseofBorg]

there is the problem ..they are polar so only for DC . they dont even look like they belong with motors in that package .
DO NOT apply power to those again .you are lucky they didn't explode .

Should I replace them with ceramic capacitors? Also, the capacitor I am replacing is an Electrolytic polar capacitor. Possible replacement: https://www.digikey.com/short/q3mdnq Do you think that the replacement capacitors may again be messing up the speed?

 

[avionic]

This is the part I used:
https://www.digikey.com/short/q3md92

Very surprised a fire extinguisher wasn't required.

 

[CheeseofBorg]

Very surprised a fire extinguisher wasn't required.

I had one ready when I noticed that the replacement was an order of magnitude smaller than the original. Anything I should know for the future regarding this? I thought it would be an adequate replacement as the two in paralell were polar electrolytic like the original.

 

[petehall347]

i dont think it would have been polar for one second . do you still have the old one you can take a picture of ?

 

[CheeseofBorg]

i dont think it would have been polar for one second . do you still have the old one you can take a picture of ?

It is really dark inside the unit, but it is a cylindrical capacitor with a metal casing that is listed as electrolytic. This is the polarity shown in the service manual.

 

[petehall347]

i dont think that is polarity mark . more like common ..
just use 2uf bipolar motor capacitor . it does look like it needs to be tight tolerance to get the speed correct .

 

[CheeseofBorg]

i dont think that is polarity mark . more like common ..
just use 2uf bipolar motor capacitor . it does look like it needs to be tight tolerance to get the speed correct .

Can you suggest a part on Digikey or Mouser? I can't find anything that matches that is listed as a motor capacitor.

 

[petehall347]

i would try a 2uf 5 percent and see how it is then

 

[petehall347]

something like this ..http://uk.rs-online.com/web/p/polypropylene-film-capacitors/8432039/

 

[CheeseofBorg]

At this point, I am going to bring it to Fred at Classic Audio Repair. I'll make a new thread under Tape to ask whether it is worth it to dump another hundred bucks into it.

 

[Blue Shadow]

Digikey>>capacitors section search motor run cap and you get a slew of them. This is one: https://www.digikey.com/product-detail/en/kemet/C274AC34200AA0J/399-13833-ND/6558661 Not that this is the one that is recommended but it is an examply of a Motor Run Capacitor, a device the changes the phase of the electricity to make the motor run properly.

I changed the motor run cap in my Crown tape deck with one of a close match in capacitance, it wasn't an exact match but recommended as one that works just fine.

You need to use the correct type of capacitor for this application. If you can't find what you need, these are available at locations that sell equipment with motors like refrigeration, air conditioning companies and other places. I got mine from Grainger.

 

[Blue Shadow]

The service manual states this is an MP type capacitor in a list of caps that are titled Electrolytic.