EEVblog Electronics Community Forum

Electronics => Repair => Topic started by: PureZX on September 13, 2017, 11:26:20 pm

Title: If you've got a Mastech MS8050....
Post by: PureZX on September 13, 2017, 11:26:20 pm
...then hello,
Could you please open it up and tell me what value the fried resistor is in the attached photo....

I got this meter off eBay. It was sold as working but wasn't, obviously. Didn't pay a lot for it and I'm not sure if I want to return it for a refund or keep it and repair it.

Thanks
Title: Re: If you've got a Mastech MS8050....
Post by: ModemHead on September 14, 2017, 02:43:46 am
Quite a dilemma.  Help someone in need, or never admit in public that I have one of these things.  Oh well.  It did take 15 minutes just to recover it from underneath the rubble.

In this unit, the smaller ones are all 470 ohms, the two larger ones are both 18K.
Title: Re: If you've got a Mastech MS8050....
Post by: PureZX on September 14, 2017, 03:06:11 am
Thank you.

There can be no shame in helping others but let me distract the masses by letting everyone know that I also have a Maplin function generator. I can't resist a cheapie. If the price is low enough, I'll have it. I may not use it, but I'll have it.
Title: Re: If you've got a Mastech MS8050....
Post by: ModemHead on September 14, 2017, 03:29:38 am
Sorry, no offense intended to you for having one.  :D   I just never liked mine, it was too "drifty", never the same reading twice.  Then I grew to dislike Mastech products in general. 
Title: Re: If you've got a Mastech MS8050....
Post by: retiredcaps on September 14, 2017, 03:58:23 am
Does RF silk screened onto pcb imply Resistor Fusible?
Title: Re: If you've got a Mastech MS8050....
Post by: ModemHead on September 14, 2017, 01:40:50 pm
Does RF silk screened onto pcb imply Resistor Fusible?

They all look like plain old 1% metal-film resistors to me, although their position in front of the spark gaps seems like a good location for fail-safe parts.  The meter is labeled CAT II 1000V.  The blown-up resistor is in series with a 0.047 cap, so it might be some sort of frequency compensation.  The specs say 20kHz bandwidth.  Maybe it was subjected to some high-powered RF signal for the fireworks.
Title: Re: If you've got a Mastech MS8050....
Post by: coromonadalix on August 13, 2020, 11:25:24 pm
Reviving this thread ...

Just found this

It's a rebranded PeakTech 4000 meter    and  a service manual is available

you'll be / should be able to repair the input resistors when they blow ??
Title: Re: If you've got a Mastech MS8050....
Post by: coromonadalix on August 14, 2020, 11:18:00 am
Calibration manual   PeakTech 4000  same as the Mastech Ms8050

Not sure  if all meter based on the FS970X  chipset can be calibrated the same way ??

will be pushed to Ko4bb website