Post Your Repair Tips And Links!

throbscottle

Well-Known Member

• Apr 28, 2014

• #61

Can't say I've noticed a big difference in that respect, Jim, but it's a long long time since I've done any really "heavy" de-soldering (oh the heady days of my youth, raiding the TV rental repair place skip for junk boards to strip for parts. *sigh*). OTOH, I haven't had a clogged nozzle for a very long time either. I hadn't made the connection, but maybe the spray is helping!

 

G

gmphadte

Member

• Jun 3, 2014

• #62

If you have a solid state discrete amp with dual supply and you get high dc offset at the output, check voltage across the LTP bases. It should be near zero if your power amp is good.

gmphadte

 

fezder

Well-Known Member

• Jun 3, 2014

• #63

gmphadte said:

If you have a solid state discrete amp with dual supply and you get high dc offset at the output, check voltage across the LTP bases. It should be near zero if your power amp is good.

gmphadte

Click to expand...

what is LTP?

 

G

gmphadte

Member

• Jun 3, 2014

• #64

Long Tailed Pair
The two transistors at the input of a power amp where the input signal and the feedback signal from the output(mostly) of the amp is fed.

gmphadte

 

fezder

Well-Known Member

• Jun 3, 2014

• #65

ok, thanks mate!

 

granddad

Well-Known Member

Most Helpful Member

• Sep 27, 2015

• #66

Just sharing my recent grapple with an Asus EN210 SILENT/DI/1GD3/V2(LP) , Graphics adapter , But could apply to any card with a large heatsink arrangement.... Having moved this card to a different PC (due to a PNY card fail), the whole machine became slow ... really slow after trying several asus (Nvida) drivers i gave up and reluctantly placed it in the suspect box ! and ran with on-board graphics.. not 1920 x 1080 i wanted, The chap next door gave me a similar card but one with a fan , nice chap but his card sounded like a tractor ! brain-wave to swap the fan heatsink / no fan heatsink ....bad to not so bad , thought I would have to force the big lump of fan less aluminium off the chip.... not so it just came away ! and this turned out to be my slow PC problem , I think the graphics chip was cycling through overheating / shutdown ? After i replaced the heat pad I was up and away no problems .. gave the chap his tractor card back and told him he was Mr Fix-it !

 

Last edited: Sep 27, 2015

cowboybob

Well-Known Member

Most Helpful Member

• Sep 27, 2015

• #67

Good job, granddad!

One of those unexpected fixes that turn out so satisfying ...

 

K

KeepItSimpleStupid

Well-Known Member

Most Helpful Member

• Sep 28, 2015

• #68

The measurement I pay attention to is the difference between the output transistor bases. That basically should be Vbe*2. 0 is bad and your amp may suffer from cross-over distortion. In my amp (the leach amp), https://www.google.com/search?q=lea...iLi7wAbwM:&usg=__vFDJUeIda-GDjdQNerwF1R88SJI=

The output stage is wierd, but between the C of Q12 and C of Q13 should be about 3.6 V. (3*0.6)*2. Q18 and Q19 don't count.

 

Quantumleap

New Member

• Mar 13, 2016

• #69

APC SUA1500 Ups problem.
This ups was in the junk pile for a high pitch squeal whenever the unit was plugged in. Found a apparent short at one of the caps near the micro-controller. After de-solder of the suspect cap, the short appeared in the pc board where the component was removed. Traced this back to the micro-controller. After removing the micro-controller the short was gone. The micro-controller is a P87C51FB-4A. I was able to read the program code off the damaged micro-controller and burn it to a new P87C51FB-4A. Installed the new micro-controller and re-soldered the cap. Unit now restored to full working order.

 

cowboybob

Well-Known Member

Most Helpful Member

• Mar 13, 2016

• #70

Welcome to ETO, Quantumleap!

Ballsy and remarkable fix ! Just curious, what do you do for a living (I ask because your fix demonstrates a pretty high level of competence in a number of technical arenas)?

Especially just to repair a trashed UPS .

 

fezder

Well-Known Member

• Mar 14, 2016

• #71

cowboybob said:

Especially just to repair a trashed UPS

Click to expand...

Indeed, United parcel service can be pain in the butt sometimes ....

 

Quantumleap

New Member

• Mar 14, 2016

• #72

Thanks for the reply,
I work as a Networking /Electronics Tech. building custom high performance network raid servers for the High End Computer Network (HECN) at Nasa. We use a lot of APC gear in our server racks, but this unit was from a home computer system in my neighbor hood. I put this out here in hopes to help someone else, because APC won't give you the time of day when it comes to repair or trying to buy parts. So I have been repairing myself for some time now.
BTW most problems with older APC ups units are battery related. Can't tell you how many I have brought back to life just by getting good batteries with the right charge in them.

 

throbscottle

Well-Known Member

• Mar 14, 2016

• #73

Those are big hefty beasts - I installed a load of similar ones a couple of years ago (Ah found it, Smart UPS 750). The ones I put in weighed 13Kg apiece. Worth the effort of repairing - well done.