Replace unknown fuse on function generator - Page 1
Forum section: electronics / projects

author: rstor22
author_rank: Regular Contributor
timestamp: July 06, 2015, 03:26:26 pm
content: I have a function generator (see attached specifications) where I need to replace the inline fuse on the output (see attached). After removing the inline fuse it has no markings and unfortunately the manual doesn't specify.What rating inline fuse should I use for replacement? Should I choose fast blow or slow blow? Does the fuse need to be DC rated or is only an AC rated fuse fine?Thank you

author: Lightages
author_rank: Unknown
timestamp: July 06, 2015, 05:27:20 pm
content: Based on the fact that it can source >10V P-P at 50ohms, it is capable of outputting around 100mA at least. I would put in a 200mA fuse, fast blow. I would also install some kind of inline fuse holder rather than a soldered type. If you find you are blowing 200mA fuses too easily, up it to 250mA.

author: mcinque
author_rank: Unknown
timestamp: July 06, 2015, 06:59:06 pm
content: Why not try the light bulb trick and if ok try to measure the "nominal" current and then calculate the fuse needed?

author: rstor22
author_rank: Regular Contributor
timestamp: July 06, 2015, 10:21:52 pm
content: Quote from: Lightages on July 06, 2015, 05:27:20 pmThank you. I will try a fast blow 200mA fuse with an in line holder. Does it matter if the fuse is only AC rated?Quote from: mcinque on July 06, 2015, 06:59:06 pmI'm not familiar with the light bulb trick, would you be able to provide details please.

author: Lightages
author_rank: Unknown
timestamp: July 07, 2015, 03:44:25 am
content: AC, DC, no real difference for your application.

author: edavid
author_rank: Super Contributor
timestamp: July 07, 2015, 04:06:35 am
content: Quote from: mcinque on July 06, 2015, 06:59:06 pmWe are talking about a function generator output, not line voltage input

author: mcinque
author_rank: Unknown
timestamp: July 07, 2015, 11:08:59 am
content: didn't read that you were talking of an OUTPUT. Nevermind.

author: miguelvp
author_rank: Super Contributor
timestamp: July 07, 2015, 06:12:51 pm
content: According to this:https://www.eevblog.com/forum/repair/semi-open-fuse/It's a standard 200mA fuseThere is another repair thread:https://www.eevblog.com/forum/repair/gw-instek-gfg-8020h-teardown-and-repair-(help)/But doesn't specify the value of the output fuse, and it's hard to find any information of that fuse by searching for a gfg-8020h.So a fast blow 200mA fuse might do the trick as Lightages suggested.

author: SeanB
author_rank: Super Contributor
timestamp: July 07, 2015, 07:01:12 pm
content: Depending on how it is constructed a slow blow fuse will add a lot of inductance to the output, as they often use a spiral wound element. Fast blow is pretty much always just a straight piece of wire. Will not be an issue until you turn up the output frequency over a few kHz.

author: electr_peter
author_rank: Unknown
timestamp: July 07, 2015, 07:14:11 pm
content: Fuse is there to protect FG output from short circuit. Just for reference, many ~10V FGs use 125mA fast type fuse.

author: rstor22
author_rank: Regular Contributor
timestamp: July 07, 2015, 09:37:10 pm
content: The Instek/Goodwill FG-8016G (which is the one I have) appears to have also been branded under the name Elenco.Elenco informed me of the following:"The only info if found lists it as a 100mA. I would use a standard 100mA 250VAC fast blow."So it looks like the recommended fuses in this thread were in this range. Thanks everyone!