Need help troubleshooting pcb relay

[Delta Prime]

Hit one out of the park with two men on base!

Relay chatter/sparking

Picked up a free wine cooler...diagnosed a bad relay on pcb...I was getting 12vdc on power supply side of coil but only 6vdc on the side driven by the transistor....I was thinking I shouldn't see 6vdc...I'm confused though not sure if when probing ground to coil I should see 12vdc or 0vdc...

forum.allaboutcircuits.com

 

[73's de Edd]

Hey Mack . . . . . .
You still game here ? . . . . . . . or moving on to YET another forum.
I'm still waiting to find out what that collector voltage (now being 6 VDC you say) of Q6 is, when you short out its base to emitter or another same ground point.
With there then being no base voltage and therefore no transistor conduction, the Q6 Collector voltage should shoot up to 12VDC with its shorted out base.
Forthcoming . . . . . . next test, then would be your monitoring the 12VDC at the relay coil power side and see if its holding at a full and stable 12 VDC voltage .
Then whatever you have to do to make it occur, plug in the unit and get it going into that on and off relay clicking and arcing condition.
Run just long enough, so that you will able to see, if that here to before stable 12 VDC supply source, is NOW coincidentally tracking and cyclically pulling down, to an up and down changing, higher to lower DC supply voltage ?
(Methinks that it will now be going up and down ! )
If that is being the case, then we move on to . . . . . .
Ta Daaaaaaaaaaa . . . .

THE DEFINITIVE CASE OF ENCOUNTERING TIME RELATED ESR ONSET AND RESULTANT ATROPHY WITHIN A 9 YEAR OLD SWITCH MODE POWER SUPPLY . . . .

Details to be forwarded . . . . . . but that's ONLY if you come forth with prior answers . . . .

Edd . . . . .

 

[Macknumber9]

Hey Mack . . . . . .
You still game here ? . . . . . . . or moving on to YET another forum.
I'm still waiting to find out what that collector voltage (now being 6 VDC you say) of Q6 is, when you short out its base to emitter or another same ground point.
With there then being no base voltage and therefore no transistor conduction, the Q6 Collector voltage should shoot up to 12VDC with its shorted out base.
Forthcoming . . . . . . next test, then would be your monitoring the 12VDC at the relay coil power side and see if its holding at a full and stable 12 VDC voltage .
Then whatever you have to do to make it occur, plug in the unit and get it going into that on and off relay clicking and arcing condition.
Run just long enough, so that you will able to see, if that here to before stable 12 VDC supply source, is NOW coincidentally tracking and cyclically pulling down, to an up and down changing, higher to lower DC supply voltage ?
(Methinks that it will now be going up and down ! )
If that is being the case, then we move on to . . . . . .
View attachment 59523 Ta Daaaaaaaaaaa . . . . View attachment 59524

THE DEFINITIVE CASE OF ENCOUNTERING TIME RELATED ESR ONSET AND RESULTANT ATROPHY WITHIN A 9 YEAR OLD SWITCH MODE POWER SUPPLY . . . .

Details to be forwarded . . . . . . but that's ONLY if you come forth with prior answers . . . .

Edd . . . . .

Hey Edd...thanks for the information....I will do everything you tell me short of sticking my hand in a live socket at this point....

I never shorted the base because I did not have the ability to short it and still take measurements....if I need to purchase some very small alligator clips to do this then so be it....

I tested power at transistor base and get .5v. I get 2.28 volts everywhere else before that r14 resistor...

I desoldered the transistor and tested it off board and it passed all tests....replaced anyway and still same exact issue...6v reading at the transistor side of coil and only .5v at the base

While transistor was off I did see 12vdc at the collector side of relay...

The only way I can ge this relay to work is by seeing 6vdc at the collector side....because of this poor .5v at the transistor base (in my uneducated opinion) I can monitor this for you while it starts going crazy rattling and sparking....I can see if transistor base drops even lower while the rattling/shaking starts too....I'm sure that transistor base is just going to go down to about .2 or .3v

 

[Macknumber9]

I now realize after reading your post that you want me to monitor the POWER side to see if that's dropping out from 12v when the arcing/rattling is occuring....correct?