I think we need to see whats happening across the electro cap to see if the 5v is collapsing
Just a quick update...
The 5vdc to the pic is not dropping off and on.
Also - going to sound weird and i'll do my best to type it in - is the motor pulses. So please bear with me.
vrum, derr , vrum, derr ---- vrrrrumm, derr , vrummm derr , vrum derr, vrum derr, --- vrrrummm, derr
So short time rev pickups and then a long ones... Like a hunting internal combustion engine.
hinekadon (23-02-19)
is there any heating on the transistor thats driving the triac this sounds like the triac is dropping off in volts/speed then picking up again , at a guess that sounds like a faulty pic driver ?
GT250 (24-02-19)
My mistake on the 240v.
I didn't measure it properly (I cant' recall how I did before), but with the neg dmm on the earth connection on the mixer there is 240VAC around the places and the PIC as before.
I also found that with the neg probe on earth and the pos probe on pin 4 (MCLR/VPP), the motor runs fine..!
hinekadon (23-02-19)
thats interesting ???? where are you nomeat and skepto ?????
Needs a bit of thinking here... as it's somewhat risky introducing any earth reference in that circuit which is floating at 'Active' potential.
MCLR (pin4 of the PIC) is the reset input and is pulled high to Vdd by R103 (10k) and there's no means of pulling it down to Vss which would reset the PIC. Attaching an earth referenced voltmeter probe to MCLR would be pulling it up even harder than the R103 due to the earth and neutral being connected together in your switchboard. Pulling MCLR down to Vss would prevent the PIC starting up so there should be no TRIAC drive at all in that condition.
So:
if voltmeter can be safely (securely) connected to MCLR and ground - does the speed control actually work with smoother running?
(the end of R103 closest to the centre of the PCB is connected to MCLR so could could use a small alligator clip on it)
If speed control appears to be normal in this test then check soldering of R103 and JP106 (next to the green 'PASS QC' sticker)
Reducing the value of R103 to, say, 4.7k might make a difference but the existing 10k should be more than adequate
This is extremely hazardous as touching any part of the circuit and ground simultaneously puts you directly across the mains!
Last edited by Skepticist; 23-02-19 at 09:13 PM.
serious case of needing for a isolating transformer puting a meter lead will only introduce megohms to the circuit ????
GT250 (24-02-19)
That's the strange thing about the symptoms observed but it depends on the meter used and the selected range - they vary quite a bit.Originally Posted by hinekadon
An isolating transformer won't stop you getting across the mains between active and neutral with the added disadvantage that an RCD wouldn't be protecting you when the earth is isolated (any A-N fault will not create an imbalance in that case so short circuit protection is about all you'll have)
I also wonder about C104 (the SMD cap across Vdd & Vss on the copper side of the PCB) - it should be the last line of defence against motor and switching noise upsetting the PIC if that's what's happening here. Could be replaced or just bridged with one of those tiny monolithic 100nF caps to be sure.
Last edited by Skepticist; 23-02-19 at 10:41 PM.
Yes sounds like the PIC is resetting and there is no pull up at all. Check that 10k resistor or just replace it if you have one lying around. Check the continuity to the MCLR pin4 and Vdd and carefully refresh the soldering on the resistor and the wire bridge to Vdd.
Update: A deletion of features that work well and ain't broke but are deemed outdated in order to add things that are up to date and broken.
Compatibility: A word soon to be deleted from our dictionaries as it is outdated.
Humans: Entities that are not only outdated but broken... AI-self-learning-update-error...terminate...terminate...
GT250 (24-02-19),hinekadon (24-02-19),Skepticist (23-02-19)
Going by the photo, the solder joints on R103 look like they need a touch up. One of them in particular.
Also the solder side of the board is filthy, you should go over it with a toothbrush and metho to be sure it's clear of tiny foreign objects that could cause a short .
Last edited by loopyloo; 24-02-19 at 12:10 PM.
Hi people,
Have work today, Sunday
So I'll absorb your replies when I get back.
hinekadon (24-02-19)
Just got back in..
Ok. Got to get this done people:
Hinekadon: Post #101. Which 'electro cap' are you talking about?
With the 240vac running around on everything, is this normal for this type of device?
When I tested the 240vac, the DMM is turned OFF and I just put the neg probe on Earth and then put the pos 'wherever'.
Skepticist: You were obviously correct in deducing that the 0.33uF was faulty - kudos!
#106 I'll refresh the soldering on R103 and some others - JP106 - as I'm around that area, but they all do look pretty ok from the other side.
#108 I can get a 100nF mono cap soon if need be.
nomeat #109 "Check the continuity to the MCLR pin4 and Vdd". So that means I use the DMM on Ω and get a reading? Meaning they are connected (with the power slider on, motor moving)?
loopyloo, I'll clean the board tomorrow
Just a Question guys: So a DMM is always 'Short Circuited' even when turned off?
So when testing anything, the micro gizmos inside the DMM take all the 'information' and display the results, pending what option [VDC, VAC, Ω], and so on..?
Skepticist (24-02-19)
Turning a DMM 'OFF' is generally only guaranteed to turn off the electronics and display especially if it's the type with a separate ON/OFF switch so it can still be OFF but the range selector is still switching in various voltage dividers across the probes. A habit I developed in my early days was to always 'park' the multimeter on the highest voltage range (mainly to protect the meter itself due to highest input impedance)
Never ever probe around a powered circuit on the 'ohms' ranges - surest way to blow a fuse in the DMM or far worse. De-energise and Discharge all capacitors first .
The Kenwood design isn't unusual, just economical. Everything is live but well insulated and enclosed in an earthed metal case where no-one can touch it without disassembling the appliance.
R103 is a pullup resistor IE it's connecting MCLR to Vdd via 10k resistance to disable the reset that would occur if MCLR is pulled down to Vss potential (something that can never happen here as there are no other connections to MCLR apart from R103). Simply a momentary connection between MCLR and Vss will restart the PIC.
Last edited by Skepticist; 24-02-19 at 08:01 PM.
gt you have to look at this as two supplies one at 240vac the other at 5vdc but they are tied together on the 240v side the 5vdc is for the operation of the pic device and the 240v for the motor via a triac
The electro dont matter now as you have proved the pic is working but as skepto says " Simply a momentary connection between MCLR and Vss will restart the PIC." this is whats happening as you can see in the video with the" kick" . the pic wont controll the speed on the instant that the motor starts only after its running it would be interesting to see the effect of the speed controll if it was set to mid range with the mains turned off and on . it could be that r103 is a critical valued resistor and any change will have a dymamic effect on the op of the pic !!!! i have never seen a dmm that is "shorted " when turned off???? cheers don
Skepticist (24-02-19)
As MCLR and Vss are adjacent pins (4 and 5) you can force a reset by simply touching a single DMM probe between the 2 pins (carefully).
hinekadon (25-02-19)
sorry to go on about a isolating transformer but it removes the active and neutral from earth so you cant zap yourself its safe for you to touch the active supply and not get a shock unless you happen to have your other finger on the neutral neither has any reference to earth thus making it great for playing with your scope on the circuits and no big BANGS or letting out smoke. The ten x on your scope probe becomes useable . I wouldnt be with out one and proberly dead !!! change r103
NO!! Passive test ONLY with ohm meter. No power connected.
Just test if the 10k resistor actually reads 10k and trace the board's copper and soldering with your ohm meter if it reads 0Ω to Vdd and pin 4 from the resistor respectively.
Solder joints might look OK but can still have a disconnect where the wire of the component goes through the solder blob. I would just re-solder everything in that area, maybe every pin on the PIC.
A DMM has typically 10MΩ in the voltage range, switched off sometimes higher. Of course if you left the plugs in the amp range it will be a very low Ω short.
If you connected the DMM to earth/neutral that is 240V over a voltage divider created by 10MΩ and 10kΩ when the other probe is on the MCLR pin.. That would cause a potential drop of around Vdd - 0.24V on the MCLR pin. This would hardly cause any change if the 10k resistor(and the PIC) is OK. The peak voltage of the AC would be roughly 0.67Vpp, so still far off.
There is also a bit of capacitance to consider, usually roughly 100pF. That would be reactive another 30MΩ , the 10k should still stand up to that.
I can't really imagine any other cause for this behaviour than a missing pull up unless you got something mixed up again when you told us that it works when the DMM is on pin 4 MCLR.
Last edited by Uncle Fester; 25-02-19 at 11:47 AM.
Update: A deletion of features that work well and ain't broke but are deemed outdated in order to add things that are up to date and broken.
Compatibility: A word soon to be deleted from our dictionaries as it is outdated.
Humans: Entities that are not only outdated but broken... AI-self-learning-update-error...terminate...terminate...
hinekadon (25-02-19)
There's a curly sticker on that board that looks like foil. Better get rid of it cos it sits too close to the hold down screw and r107.
Update: It's still starting and stopping.
Have replaced R103 (which read 9.96kΩ).
Replaced C103 - just in case.
Refreshed JP106 and some others around the area.
Cleaned up both the solder sides of the boards, Loopy
hinekadon: #114. I'm not sure of the terminology. My DMM (Fluke 289), was turned off. I just put the neg to earth and the pos to read the 240 volts, so in my mind I'm seeing physical action on a motor by using a 'dead/turned off' DMM probes - so they must be 'connected' inside the DMM somehow...
Skeptist: #115. I'll do that tomorrow and see what happens.
Nomeat: #117. As mentioned, have replaced R103. But will test the Ω to Vdd and pin 4 tomorrow. Nomeat, I really appreciate your time in this.
I'll do a more in depth look at your reply to your post and yes, it's possible that I have mixed things up. Just have lot going on at the moment in my life and sometimes I try and get away by 'fixing up' silly things.
hinekadon (25-02-19)
Best to not reference anything on the PIC board to actual earth. Neutral and earth are connected together at your switch board and the only components getting that 'true' neutral (=earth) are the motor and the Triac when the triac is 'off'. Neutral has been 'fiddled' to create the -5V which is Vss and the common reference (ground) for the electronics but it's not the same as the mains earth which is connected to the metal case and motor housing.
The 'earth' of the case is at a different voltage to Vss (I'm thinking it's at least 5V higher than Vss, probably a lot more than that).
Hope that makes sense - all DC voltages on the PIC board must be referenced to Vss (the yellow wire from the power supply).
Last edited by Skepticist; 25-02-19 at 07:38 PM.
hinekadon (25-02-19)
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