Good Will GPS1810OH Power supply problem

I don't know what the differences would be (other than 10A/20A) between your GPS1810H (that's a zero) and my GPR1820H, but if you can post a pic somewhere I can compare that to the board(s) in mine and maybe that will shed some light. I also have a full schematic of the GPR-M/H series and a somewhat basic componenet overlay of a/the pcb for that GPR series.

Interesting failure mode; just blew the top but didn't seem to scorch the PCB.

I'd guess a jelly bean op amp or comparator. My money would be a comparator for the current limiting input, so odds are it's an op amp. The resistor layout around it may give a clue.

May want to throw the pic up on a web service. Some usenet servers discard binaries in text groups so some folks with insight into it may not see the image. I've used Imageshack for similar posts; it's free and as far as I have seen they've never used the sign-up info for spammage.

okay.. I will post the picture there.. brb

picture can be found at

tell me if this address doesn't work.. K?

worked for me. Unfortunately, that board is totally different to the PR-8509 pcb in my 1820H, so the info I have is basically useless.

The 150 ohm 2W resistor looks to have heated the pcb near the TO-220 device (reg?). Also, is that goo near the large electro (bottom edge area) for mech strength or is it leakage?

Its not fried, it has blasted off the top section, have you had a good hunt for it ? What is the script on IC2, there's too much glare to read ?

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

It is low grade glue that degrades with heat.

I can't help with the IC identification, but the exposed chip could make an interesting conversation piece or paper weight, imbedded in water-clear resin, for example. Geek-types might compulsively ask.. how did you do that?

The brown glue near the electrolytic cap (lower-right) looks like the nasty brown glue that was used in a lot of consumer electronic gear of the 70s and

When you lift the board to replace the IC, it would probably be worthwhile to touch up/reflow with fresh solder, any questionable/flakey looking solder connections.

Searches may be problematic because of the irrelavent GPS in the model number. There were probably several variations of the same power supply made at the time, with different model numbers and brand names. The 723 voltage regulator was a very popular v-r for these types of supplies, and finding a schematic and/or parts list for a similar type of power supply may be helpful, but a long shot. You may receive more help by trying the other sci.electronics newsgroups, and amateur/ham radio groups, as many electronics enthusiasts often have numerous power supplies.

-- Cheers, WB .............

On Sun, 11 Oct 2009 17:42:40 -0500, Samantha put finger to keyboard and composed:

Where is the heatsink for the pass transistor (?) for the uA723C regulator?

Where is the missing relay (top), and if it isn't missing, then why is the PCB populated with its support components?

Can you trace the circuit around IC3?

What is IC2?

- Franc Zabkar

Jeez, you're not kidding about it being fried!

Ic2 seems to be a 741 op amp... I thought that IC3 MIGHT be the same.. and it PROBABLY is.. Just not sure... Havn't taken the board out yet and tried to retrace what is going on.. was just at the research stage where I am trying to find out if there are any drawings or someone that has had one of them open before.

Thanks!!

Its a 741 op amp.. I will post another picture in alt.binaries.schematics.electronic with less glare..

Thanks.

okay, I posted a picture of it in alt.binaries.schematics.electronic

the ic2 appears to be a 741 and that is probably what this one is as well.. But any pics or docs you have on it would be appreciated... thanks!!

you can contact me at snipped-for-privacy@techemail.com

remplace my name with nospam.

samantha

well, hopefully someone will have on their bench.. thanks for looking!!!

S.

You might send an email to the American distributor for the Good Will line and ask for service data.

INSTEK AMERICA CORP.

Cheers! Dave M

On Wed, 14 Oct 2009 14:02:07 -0500, Samantha put finger to keyboard and composed:

If IC3 is also a 741, then this would beg the question, could the designer have used a dual op-amp, and if so, why not?

- Franc Zabkar

Could easily have been a cost issue. Saving a few pennies on several thousand components lowers the bottom line cost for a product. Increases the profit margin, making owners and/or investors happy.

FWIW Franc, my GPR -M/H schematic has two 741's and a 301. Who knows how and why designers make decisions? I don't, and probably many of my design decisions are a mystery to others ;-)