Multimeter repair brymen 786

[redwire]

Re: Multimeter repair brymen 786

I find it's all Brymen fanboys over there, any complaint everyone ignores and goes on how great they are and how Fluke needs to run and hide lol. Dave and others are in a conflict of interest selling them for profit.
I'm unimpressed by Brymens and think they're disposable- black-topped IC's, no schematics, no North American parts source for them etc.

This DC power switch, P-ch mosfet Q18 and NPN BJT Q19 with MCU turning on Q19. You can force (override) it on with a say 10k (to +3V) touching Q19 base, see if it powers up. The start-up pulse, not sure what makes that pulse.

In early builds, the rotary switch was defective. No idea what was changed or was fixed by Brymen. Power would cut out. Like in the video I linked to.

[CapLeaker]

Re: Multimeter repair brymen 786

He's already got a repair thread on eevblog with no help. See

https://www.eevblog.com/forum/repair/repair-brymen-786/

Oh! That sux… I would have thought it would generate some interest.

[stj]

Re: Multimeter repair brymen 786

does the mcu have a crystal or resonator?

[ss45]

Re: Multimeter repair brymen 786

Yeah... It was really surprising that I received no reply at all in eevblog.....

Badcaps forum rocks !

[ss45]

Re: Multimeter repair brymen 786

I find it's all Brymen fanboys over there, any complaint everyone ignores and goes on how great they are and how Fluke needs to run and hide lol. Dave and others are in a conflict of interest selling them for profit.
I'm unimpressed by Brymens and think they're disposable- black-topped IC's, no schematics, no North American parts source for them etc.

This DC power switch, P-ch mosfet Q18 and NPN BJT Q19 with MCU turning on Q19. You can force (override) it on with a say 10k (to +3V) touching Q19 base, see if it powers up. The start-up pulse, not sure what makes that pulse.

In early builds, the rotary switch was defective. No idea what was changed or was fixed by Brymen. Power would cut out. Like in the video I linked to.

Thanks for the suggestion
I have tried that. Blank screen

[ss45]

Re: Multimeter repair brymen 786

does the mcu have a crystal or resonator?

There is crystal on the front side of board,
Opposite of side where what assumed to be main mcu is soldered on

[redwire]

Re: Multimeter repair brymen 786

With Q19 forced on, I would check if the MCU has power (at 0R R150 pin 3?) and power appearing across big C86 and C59 (other side of board) 33uF 16V tantalum. Next to look at is the clock.
The DMM IC (BTC M200 034K-0000) has a 4.9152MHz crystal, but I don't see one for the MCU. The crystal region has not so great PC board design, make sure it's clean and no bad connections to it because it's hand-soldered along with the big film cap. The buzzer is also in the way.

I don't see how the MCU gets it's clock, could be RC or it has a feed from the DMM IC to MCU pin 1 or 2, tricky pcb layout.

[ss45]

Re: Multimeter repair brymen 786

Could be... I don't have any interest to pursue it down the rabbit hole.
So I decided to chuck it into junk box.
Not going to touch it anymore.
Thanks for all the suggestions and inputs

[q2q3]

Re: Multimeter repair brymen 786

Hello, you can post the contents of the 24cs04 microcircuit here. It is on a board with buttons.