Kenwood SM-220 project

[Radio Tech]

LOL, all nice and cherry

Funny what one can do when in need.

Since this is a low current transformer I am using masking tape between the windings. I will use kraft paper that is waxed on one side between the seperate windings. The original transformer only used masking tape through out.

114 turns so far..

 

[2RT307]

LOL, all nice and cherry

Funny what one can do when in need.

Since this is a low current transformer I am using masking tape between the windings. I will use kraft paper that is waxed on one side between the seperate windings. The original transformer only used masking tape through out.

114 turns so far..

I had no idea there was so much work involved. Just thinking outside the box... have you ever seen the motorized automatic spoolers used for fishing reels in any of the Cabella's or Bass Pro Shops, and do you think something like that might work for this application?

73,
Brett

 

[Radio Tech]

I had no idea there was so much work involved. Just thinking outside the box... have you ever seen the motorized automatic spoolers used for fishing reels in any of the Cabella's or Bass Pro Shops, and do you think something like that might work for this application?

73,
Brett

Yep it is a lot of work. I seen those spoolers you mentioned. The problem here is keeping up with the number of turns. So it is a slow task.

 

[Captain Kilowatt]

Yeah those spoolers run pretty fast and would be hard to keep track of the turns count to say nothing of the mess if something went oopsie.

 

[Radio Tech]

Well, after almost 2 years, my monitor has come back to life.
I found the root cause of the problem, corrected that, and replaced the caps and HV diodes.

Root cause:
C140 had previously went south on the owner before I. This is one of the HV caps. The owner replace said cap. And then sold the unit to me.
I noticed that the trace was not as bright as I thought it should be but it was working.
C139 and 140 are 0.1uf @ 1kv caps.
They are what is called PIO caps. That stands for paper in oil. Looks almost identical to a electrolytic cap. But are not. What the guy did was replace a 0.1uf with a 22uf 600 volt Sprague cap. Crude but it did work. And being the wrong type of cap is not what smoked the transformer. He did not cut the legs on the cap. Had it 2 inches above the board standing on its own. After time with weight and vibrations, the solder pad broke from the board and also breaking the circuit trace that attached to the next cap. The end of the cap lead now came in contact with the bottom metal cover. This but a lot of stress on one of the two high pressure diodes. The diode shorted and this put the 500 volt AC line to ground. Being such low amperage this got the transformer hot until it shorted

D112 and D113 are the HV diodes. Part numbers HVT228-3. Fast switching.
You can replace them with NTE 525.
The capacitors are all PIO type. If they ever explode you will have oil and fuzz ever where along with a hazardous chemical. REMOVE THOSE THINGS!!
You can replace those with polyester film caps. Two 0.1uf @1kv and three 0.1uf @2kv.
You can probably use ceramic TV type caps.

So good to have this unit working again.

Note to self. Most of the time when I buy an older piece of gear I take it apart instead of turning it on.
That mistake costed me.

 

[2RT307]

Since I've never done any work like this, I didn't realize the number of turns was important. I just assumed a certain length of wire was required to spool the whole thing. Would have been nice if you could use the motorized line spooler, because they're not THAT expensive.

Of course pics of the now working unit are mandatory. Please?

73,
Brett

 

[Radio Tech]

Since I've never done any work like this, I didn't realize the number of turns was important. I just assumed a certain length of wire was required to spool the whole thing. Would have been nice if you could use the motorized line spooler, because they're not THAT expensive.

Of course pics of the now working unit are mandatory. Please?

73,
Brett

Yep, that would had been nice. And is my next new piece of equipment I want to build. The transformer winding machine.

Here is the pic of the working unit. I have not done an alignment yet and feeding it with my Tek 2235 just for a signal into the vertical input.