Elecom Function Generator GFG 8016D teardown to repair

[gigauser]

(At first I tried this post in Beginners forum but it didn't work with pics attached, and then I posted it on Test equipment forum but got no reaplies, so now I post it on this forum again)

Hi, I am new guy in this forum and newbie in EE I started EE now at my 50 as a hobby and new career. I have self studied several weeks now and bought several tools including fluke175 dmm used at first and then rigol dso 1054z.

Recently I found an old guy(20 or more older than me) selling this generator and Iwatsu analogue scope ss7611+4probes on a local used site. I paid the former EE guy 160k KRW(about 130 USD) and carried them 2hours back home.

Yesterday I checked the scope most fine and today I checked 8016d. Its most basic functions are working but its "-20dB" button and "offset" knob doesn't make change anything. So I did this EEVblog site does and post my first post on it

You can see in my photos the leakage stains on two 1000 uF and one 4700 uF capacitors' place. I desoldered them from PCB.

I am still studying basice EE, so I am not sure whether replacing them with the new ones will repair the issues.
I checked the caps with my fluke175. Two 1000uF read as 1113uF and 1118uF, 4700uF reads as 5092uF. Do these result mean the two 1000uF caps are resuable even though they have stains leaked and 4700uF is not good?

Anyway I am going to buy the new capacitors with the same size and solder them on the PCB to see any difference. Please recommend me better caps and advise me anything to help my repairing this generator.

Thanks.

DH.

[gigauser]

Today I go to part shops remote from my home and try to find the replacement for the leaky 1000uF/35v and 4700uF/16v. I am not sure whether I can find the right ones. I googled and find this substitution guide randomly.
http://www.niccomp.com/help/capsubguide.asp

 If someone can see the schematics, would recommend the substitutions when I cannot find the exact ones?

[mij59]

The capacitors are probably not bad, but replace them anyway.
Use Panasonic, Nichicon, Rubicon, or other good brand capacitors.
Low esr and high temperature rating are not that important, see what's available at a reasonable price.

The stains on the board underneath the capacitors are probably glue, the glue can become conductive, you have to remove it.

Switches, potentiometers   etc will probably need some cleaning, try a contact cleaner e.g. Kontakt 60.

Check the board for bad solder joints.

[saturation]

Its reads like you are on your way to getting it going.  This is a rebadged GoodWill/Instek model analog FG, when they were called just Good Will.   You can make substitutions as your link suggests.

http://www.radiomuseum.org/r/goodwillin_funktionsgenerator_gfg_80.html

[electricspark]

I note you don't have page four of the schematic and wonder if you have obtained a copy since the posting?

If you have, I would really, really appreciate a copy!

[tronde]

I know this topic is old, but since I have the missing schematics I think it's best posted here. I do also have the circuit description, and can scan if needed.

This instrument is from the early era of far-east test equipment, and there is a lot to say about electrical safety.

I do really recommend to check out the mains switch and the lack of insulation between the main PCB and the conductive shielding inside the case. The two brown wires running along the transformer is one phase of the mains, and only one layer of insulation. The mains switch is just a normal switch meant for low voltage.

As you can see form one of my pictures, the switch is about to carbonize. I can measure ~10kohm. This means that when switched off, the transformer is still fed from mains via a 10kohm "resistor". This "resistor" will continue to carbonize and most likely catch fire.

You can also see that the clearance around the PCB tracks for the mains switch is rather small.