# Can i do this?

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#### electrotechnewbie

##### New Member
hello i buy things and sell them. somehtimes the electronics i sell are broken. i would like to fix them if all it takes is soldering back on a resistor that broke off or something like that. Can i do this? or do i need schematics. are schematics available for retail products?

thanks

#### dknguyen

##### Well-Known Member
Schematics tend not to be available for retail products. You have to know what you are looking at in order to fix it.

#### unclejed613

##### Well-Known Member
generally, schematics for new consumer electronics are only available to warranty service techs. after a piece of equipment has been discontinued, some (but not all) manufacturers may make their service manuals available to the general public. some may have them online for free (like Hafler), and some may have them for sale. other manufacturers don't make them publicly available at all, as they prefer to have their own certified service centers continue to repair them. some consumer electronics will not even have parts available for warranty service, since some items are made so cheaply, it's cheaper for the manufacturer to exchange them rather than repair them.

also most failures aren't mechanical damage, such as parts getting broken off the circuit board. most are electrical failures, either something shorted or open (sometimes with components burned up, but often no visible damage exists) or components drift out of spec, so the unit no longer functions correctly. often, it's a combination of both.

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#### tcmtech

##### Banned
I personally do a fair amount of buying broken and selling fixed. Sadly they are right on about the lack of available schematics out there.

I worked as the head service tech for a big welding supply chain and Even then the manufactures would not give out schematics that were of any real use.
Their stand point was, If we give you a schematic for a circuit board you will fix the $2 component on it and get$40 shop labor for it. The manufacturer will not get anything.
If you dont have schematic you will have to replace the whole $1000 board (That has about$50 in actual manufacturing parts and cost into it) but you will still get the $40 shop time for it. Or perhaps you then can talk the customer into buying the latest and greatest engineering failure they came out with! Win Win for the dealer and the manufacturer! But not the customer. Sorry he does not actually count in business financial equations now! (he always wants more and better for less. And thats highly counter productive to actual profit!) If you start doing the buy broken and sell fixed, expect about 60% return to service on the stuff you buy. That is, 6 out of 10 items will likely need only a small repair and 4 out of the 10 will not be practical or cost effective to repair. But they do then become great parts donors! And above all do your market research on the actual resale value of the item you are planning to buy and fix. I pick up industrial equipment every chance I get. When it dont work its worth around 5 to 10% of new. Repaired its typically worth 20 - 50% of new. Down side is spending$500 in a machine of some sort and hoping you will get the 20 - 50% ($2000 -$5000) of new return on it within a year or two.
And not just have $500 yard ornament with a$1000 in new parts sitting there doing nothing!

I got me a few of those!
Anyone want to buy a few 600 amp three phase welders? Or some 10 hp circulating pumps? How about 500 high efficiency solid state light ballasts that run on 277 volt, for the standard 4 ft fluorescent bulbs?
I'll give you a super deal!

#### unclejed613

about 15 years ago i was working on a repar of an RS-232 terminal. it was manufactured by what was then one of the most well known and respected mainframe computer manufacturers. the terminal was a year out of warranty, and a clint was asking if it could be repaired. it used some of the latest surface mount technology, and it had a simple problem on the logic board. the problem was, however that the logic board was a 4 layer board with dense SOIC circuitry. my client had called the manufacturer and had a simple choice, buy a new one for $1000.00, or have it fixed for$900.00. i had it on my bench, and determined that an RS-232 driver chip was bad. the problem was that i had traced it halfway across the board (alternating a couple of times between the top layer and bottom layer of the board)and lost it where it went under a large SOIC chip. to find where it went after that, i needed a service manual with an etch map of the board. i called the manufacturer and asked about buying a service manual. they asked me for my employee ID number (assuming that if i was asking for a service manual, i MUST be one of their own field techs). when i told them i was a tech for a 3rd party wanting to repair an item that was 1)out of warranty, and 2) not covered under one of their field service contracts, they told me they could sell me a service manual....... for $800.00. not too long after that incident, either IBM ot NCR bought that company out, and they had been around since about 1960 making large, expensive mainframe computer systems #### electrotechnewbie ##### New Member thanks they were extremely helpful. #### Mr RB ##### Well-Known Member .... I got me a few of those! Anyone want to buy a few 600 amp three phase welders? Or some 10 hp circulating pumps? How about 500 high efficiency solid state light ballasts that run on 277 volt, for the standard 4 ft fluorescent bulbs? I'll give you a super deal! Will those fluoro ballasts run from 240vac?? Any more details? ie do they run the start filaments or are HV start (4 wires to tube or 2). The mains here is generally 252vac. I may be interested. #### tcmtech ##### Banned Most Helpful Member the majority of them are Magnetec Triad series model B240R277 They are for the four pin type bulbs F40T12-34 or F40T10-40 Rapid start.$1 each plus shipping!
Ive never tried running them on a lower voltage.
Given most electronic ballasts do have a +10 % - 15% input voltage range I would think they would have no problem at 250 volts.

The local college got an energy efficiency improvement grant and switched out the ballasts on one of the buildings. They were told the new ballasts they were having installed are double the energy efficiency of the old ones.
These are rated at around 90% PF the new ones they got are rated at 94% PF. (Their actual running efficiencies power wise were identical!)
If they would have just programed the automated lighting system to shut the lights of a few minutes earlier every day they could have saved far more than what the ballast change out cost!

I Purchased the takeouts on the information that they were all the old magnetic ballast style. The representative one was in fact a magnetic 120 volt unit.
I bid for the whole lot assuming that I just picked up a load of copper and iron salvage for cheap.
Solid state ballasts have zero recycle value. Plus being 277 volt they also have near zero public resale market locally.

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