CW80

The only way I see a CW-80 producing anything close to a sine wave is at full power or if the triacs have shorted and they're just feeding the transformer core voltage through.

A test.  See if the accessory output also has a pure sine wave when adjusted to less than full voltage.

I know of no major updates to the electronics of the CW-80, generating a variable voltage pure (or reasonably pure) sine wave from a fixed transformer voltage is a significantly different logic set than using the triac chopper.  The MTH Z-4000 does such a trick, and there's a LOT more electronics involved in making that happen.

Hello GRJ-

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A test.  See if the accessory output also has a pure sine wave when adjusted to less than full voltage.

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The accessory output is also sine; however, and perhaps an indication as to why I'm seeing a sine wave in the first place, I'm not able to alter the output level... ~20vac no matter what.

thank you,

tom

Are you testing under load?

Hi Rob,

If "under load" means anything beyond a 14v lamp and the (I think) 1m ohm of a simpson 260, no.

I should be able to rig whatever is required to build the necessary lab though.

thank you,

tom

perhaps noteworthy, the accessory output on the cw-80 that produces a chop wave varies just fine under these test conditions.

Look on the bottom and check the model number on each. Is there a letter G?

The fact that you have 20V all the time clearly indicates the triac has probably shorted, you're getting the pure transformer output voltage.  That's why I suggested looking at the accessory output.

You can probably repair it by replacing the triac.

Hey guys,

Carl - both are P/N:6-14198

the one with sine output is marked 1205

the one with chop output is marked G0208

these markings are bottom right corner of the stickers.

GRJ-

for the sake of completeness,

the track output is variable 0-20vac

per your test, it was found that the accessory output could not be varied.

hope this helps.

I need to make a/the triangle screwdriver to open it; however, once in, are there explicit measurements that I can do to test the devices?

thank you,

tom

If you vary the pots and the voltage doesn't change, I'd replace them.

You can also take a look here on testing them: How to test a triac.

Somewhere, I can't find the reference, but the posts are reversed, at least on the accessory of the pre-revision G CW-80. ADCX Rob is all over that issue.

Don't know if that is complicating you diagnostics.

EDIT: Posts A & B are Common on the 1205.

I noticed that the U-U terminals are going to the triacs while A-B are commoned to one side of transformer winding.

Is this what was causing problems early on with transformers because experienced operators assumed U-U was common, and A-B were the hot taps like for ZWs?

Yes.

finally ground a triangle screwdriver... both bta24 devices test short.

I'll follow up with replaced results.

thanks,

tom

I think the problem is that U needs to be common to get the whistle and bell polarities right, but when you have an accessory that has a Common tied to the track, such as an 022 switch motor, the Track and Accessory outputs get shorted together.

If you reverse the terminals to avoid the shorting problem, the whistle and bell are reversed, and that causes a problem because the bell has a different duration/timing than the whistle.

The testing under load is satisfied with a simple light bulb across the output.  This discharges the capacitors that are connected across the Triacs so that a high-impedance meter or 'scope will display correctly.

Hello,

I've replaced both devices and the transformer now produces a chop wave output and functions as it should (now able to 'program' fixed voltage output on aux).  I noticed the fan is not operating.. perhaps the cause of the device failure.  Nonetheless, GRJ, you were spot on.

thanks all,

tom

You can replace the fan with a commonly available 12VDC computer fan.  Mine on the test bench is getting noisy when it starts, so I suspect I'll be replacing the fan soon.

John,

Is there a particular model fan you found that works reliably in the CW80? I was trying to get a better fan than the really poor one that's in there. Between myself and our club, I have four of these things that need fans.  I tried two different fans (one a 12V computer fan I had on hand, the other a brand new Sunon fan with higher performance high-rel bearings), and neither will start reliably and/or run at sufficient speed due to the unfiltered DC power.  When I added a filter cap, the voltage shot up to 20+ volts and the fan took off like the proverbial bat out of you know where.  I've been about ready to just stick a cap and 12V regulator in.

Cheers,

Jim

I am unfamiliar with the CW80 mechanical orientation of fan.  I was told by a brushless fan company that if the fan has its blades facing down with motor above, that this stresses, prematurely dries out (squealing), and wears out the bearing(s).  Optimal was slightly inclined backwards from vertical or with motor down and blades up facing.

Old wives tale??

The fan is vertical in the back.  I just dig in my junkbox of computer fans to find one that fits.

I've only replaced one, and the one I found worked fine. 

I work in the computer industry and replace a lot of small 12v fans.   There are wide discrepancies in quality.  The fans that I've pulled from CW80s were all cheap sleeve bearing fans. 

If you are going to replace the fan I recommend a ball bearing fan. Ball bearing fans typically have a longer life, better heat tolerance and are often quieter.

I've been replacing the CW80 fans with EverCool 40mm ball bearing fans. 

I was getting about a year out of the new CW80s before the fans went belly up.  All of the EverCools that I subsequently put in have been in service for several years now and have not needed replacement.

Thanks Andy, the Evercool ball bearing fans are easy enough to get, I'll order those.  I've used those in computers myself.   I was fairly surprised the fans I tried didn't work and just figured I'd see if someone else had a specific model they used successfully rather than keep guessing.

Cheers,

Jim

Jim, you could "adjust" the voltage by choosing a capacitor smaller than what you used.