Transformer Issue?

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#22
litezoner said:
Do you mean the power terminals as they enter the tranny? I am thinking that is where I would measure the primary resistance? I did that and it shows a closed circuit.
Thank you

also going to peal away some layers here and see if I can find this WAX Hive fuse.

Thanks Guys
Click to expand...

If you measured a few ohms there then the fuse is OK and there is no point making a mess of the transformer trying to look at it.
 
#23
I think I got it figured, I get 48-0-48 out of the main side, (why there is 5 wires and only 3 pins I don't know) on the secondary side I get 8.5V on one side and no reading on the other side at all, and on the 3 pin small connector that goes to the standby board there is no reading at all either, I am now trying to take it apart (play) and see if I can find this fuse you all are pissed about being in there.

Thank you all for your help.

C-Dub😎
 
#25
Okay an update, The transformer is in good condition and putting out voltages, Since I have 0 power to the unit not even standby power, I am now looking at the standby power board, at first glance there seems to be a cap on the board that has a dent in the top of it, Do they implode? I checked across the terminals of this cap and it seems it is an open circuit, this particular cap is on the way to feed the main board with low voltage, I did check the 12 volt transformer on the sdby brd, putting out 11.5v on the other side. Here is a picture of the dented cap. what do you guys think I should do, when I fist got this it had a broken power display board, I replaced and shill nothing, dead, no power on or stanby. I then verified the transformer was okay, and now... well what do you think.

thanks again for all your help on this guys, I really appriciate it alot.

Carl
 

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#26
The cap is not dented. This is where it would vent if there were a problem.

There seems to be a loose (or extra) wire in the picture. Check all wiring and solder connections on and to or from the board. Also check the AC cord. I have seen power cords open before.
 
#27
well it seems ac cord is good and I cannot find any looses solder joints anywhere, I get a/c power to the standby board, just not through to the transformer, This being because there is no power to the low voltage side (Power on/off switch) I think that switch which i checked also is a trigger for the voltage to pass through to the transformer via relay, I jumped that relay on the standby board and got power to the transformer through the standby output to tranny terminals, just like if the power button were switched on. and still nothing, low voltage section checked on the stanby board, 12 volt transformer working okay. What to check now? and how to check it?

Thank you
 
#28
I have seen a few transformer "thermal fuses" fail and it was never due to overheating or prolonged high current stress.

These devices seem to have an habit to just fail open as they get old. In my opinion they have proven to be not very reliable.

The same safety regulations that make these fuses mandatory should enforce them to be *replaceable* too.
 
#30
litezoner said:
well it seems ac cord is good and I cannot find any looses solder joints anywhere, I get a/c power to the standby board, just not through to the transformer, This being because there is no power to the low voltage (Power on/off switch) I think that switch which i checked also is a trigger for the voltage to pass through to the transformer via relay, I jumped that relay on the standby board and got power to the transformer through the standby output to tranny terminals, just like if the power button were switched on. and still nothing, low voltage section checked on the stanby board, 12 volt transformer working okay. What to check now? and how to check it?

Thank you
Click to expand...



Check to see if the relay coil is good. Is there a relay driver? Is it getting power? How do the windings on the standby transformer read? You seem to have narrowed it down to this area.
 
#31
The transformer is 115v in coming and 4.5 to 5.0v out on each side, 11.5 total coming out of it, I bypassed the relay on the board and was then getting power to the main transformer through the standby board but still no power on present. Not sure what a relay driver or a relay coil is?

Thank you

Okay, I just learned what a driver is, and there is one on the standby board with 3 legs, How do I check it?
 
#33
Popped the top off of this fine relay, checked the relay coil and there is no open in the windings, I used an alagator clip to manualy close the relay and still no power, although it did open up power into the main Traffo. also while powered on, I dont seem to be getting the 17V reading going to the dcdc Board. Just has to be somthing in the low voltage side of this unit. I did get a service manual, however it is for the DG600 and definatly not quite the same as the one I need STR-DG720

Any ideas folks

Thanks again
 
#34
Be careful while you have the plastic cap off the relay. You now have exposed AC. If you have power to the main transformer when the relay is closed manually then the problem is probably the relay driver. Do you measure DC voltage to the relay coil on one side and of course ground on the other? This voltage could be as low as 5 V DC or as high as 50 votes but given the transformer voltage you've read it would be more likely to be 5 to 10 V.

Steve
 
#37
litezoner said:
Hello, There is 0.63 dc volts going to the relay coil, and no change when the power button is pressed. or click or anything.
Click to expand...


Check the voltages on the relay driver. There should be three pins, one of which should be attached directly to the relay coil measure the voltage on all three pins reference to ground. Also check DC voltage on each end the rectifier diodes. If you don't find DC somewhere the transformer is open on either the primary or the secondary, or possibly there is another small fuse or fuse resistor that is open.

Steve
 
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