CTC177BE Dead. Relay Clicks 3 Times Model F27630

Came in dead with no click. Replaced shorted HOUT but it blew instantly at turn on. Then replaced fly & HOUT but then only got the relay clicking 3 times. Came across a sym/cure about horizontal being out of phase because of a corrupted eprom so I tried jumping C4402 with an identical .015 cap and now the set does turn on with a good picture (except of course for the bending pincushion effect because of the jumped caps). I tried a new eprom but still have the same problem. So the current status is that it powers up when C4402 is jumped but it doesn't power up when not jumped and a new eprom didn't solve the problem. Any suggestions are greatly appreciated. Thanks, Mark

Reply to
MarkC
Loading thread data ...

Think about your problem. If it is not the frequency, then it is the tank. Good chance a capacitor is way off value, bad replacement flyback, or something else like the yoke is throwing the whole center frequency of the tank off.

Troubleshoot from that direction and see what you get.

Reply to
dkuhajda

Nobody in there right mind would jump that .015 cap.. Why don't you do some serious trouble shooting in that section first change the .015 and did you put in exactly the same HOT Trany ? What are the voltages measuring ..??Give some useful information.

Reply to
kip

The .015 was just jumped temporarily to access the service menu to check the horizontal parameters. The HOUT & fly were replaced with identical OEM parts.

"Nobody in there right mind would jump that .015 cap.. Why don't you do some serious trouble shooting in that section first change the .015 and did you put in exactly the same HOT Trany ? What are the voltages measuring ..??Give some useful information."

Reply to
MarkC

Well if you are not going about it the correct Have Fun.

Reply to
kip

Thank you all for your help so far. I'm getting 170V at the collector of the HOUT but still can't find out what's causing this unregulated voltage. I replaced the STK reg U4101 and the caps C4107 & C4105 and diode CR4106 but no help. How often does T4101 go bad? Mark

Reply to
MarkC

Forgot to add that I also replaced C4402 & CR4704

Reply to
MarkC

Check the parts tied to pins 1 & 2 of the regulator.

Leonard

Reply to
Leonard Caillouet

What is the voltage on the collector of the HOT whilst plugged in but NOT turned on.

kip

Reply to
kip

On Fri, 26 Aug 2005 19:53:24 -0500, snipped-for-privacy@webtv.net (MarkC) put finger to keyboard and composed:

Is C4402 the tuning cap, ie is it connected to the collector of the HOT? If so, and if this cap is open or low in value, then the voltage on the collector is probably rising high enough to trigger the set into protection mode. This voltage may also exceed the Vce rating of the HOT.

- Franc Zabkar

--
Please remove one 's' from my address when replying by email.
Reply to
Franc Zabkar

Did some further troubleshooting. Replaced T4101 but no help. I'm now getting 350V at the cathode and collector of HOUT while in the standby mode.

Reply to
MarkC

And which ground are you using as a reference when you measured

350V!!!!!!?
Reply to
dkuhajda

I get 160V at pin 11 of U4101 using isolated ground and aorund 375V B+ at the cathode of CR4106 at cold ground in the standby mode. I remember running into this problem before but forgot what I did to fix it.

"And which ground are you using as a reference when you measured

350V!!!!!!?"
Reply to
MarkC

You can be sure that the filter capacitor on the 140V b+ line is now bad. Either u4101 is bad or it is missing the feedback voltage used for regulation. Do you have the schematic?

Reply to
dkuhajda

Generic ctc177 power supply schematic available at alt.binaries.schematics.electronic

Reply to
dkuhajda

U4101 was replaced so it must be missing the feedback voltage. I do have a Sams for it.

"You can be sure that the filter capacitor on the 140V b+ line is now bad. Either u4101 is bad or it is missing the feedback voltage used for regulation. Do you have the schematic?"

Reply to
MarkC

It could actually be missing the reference voltage as well on the input to the internal comparator. I like the training manual schematic for troubleshooting as it is easy to figure out what is suppose to be going on.

I have never seen the reference voltage circuit go bad, just the feedback line.

Reply to
dkuhajda

This type of SMPS based on STK730-xxx uses one winding on this transformer (hot side only) for regulation feedback.

The STK730 is triggering on bogus feedback (weak voltage) that makes output rocket to the moon. :) Change 10uF 63V cap, and very, very carefully check the feedback circuit for loss of feedback strength.

When you say isolated ground in reference to measuring items, I assume cold side, hence the confusion for all of us including you. Measure always in same side hot ground for hot or cold ground for cold. Not across, this will gave you bogus readings. This is reason to use isolation transformer while messing in any chassis that has no insulated & isolated power. SMPS and hot chassis (like CTC185) is not isolated bec the hot side is still exposed.

Cheers, Wizard

Reply to
Jason D.

Reply to
Kevin

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.