Yaesu FT1000mp with dead controller. What now?

[rjmusto]

I have all connectors unplugged - so we are looking at just this pcb.

Interesting idea David. Not sure if my dmm will do it, but will have a look tomorrow.

[SiriusHardware]

I have all connectors unplugged - so we are looking at just this pcb.

So noted - to be honest it usually helps if we are informed as to what has already been tried / done so that we don't keep suggesting things you have already thought of. I'll assume you are going to give David's voltage tracing idea a try, otherwise you might have to make further track cuts to establish where that current is going.

It may be worth locating all of the supply decoupling capacitors associated with that rail, desoldering one leg of each of them and checking that none of them have gone steady low resistance. That will be less destructive than making track cuts and you might hit lucky. As others have said, if any of them are Tants, go for those first.

[mickm3for]

lots of c's on that board i would check them first only when everything else # lift the ic legs only the revelent pins the 5v goes to lots of places if you can cut print to sections then at least you will not have to look at loads of parts, on the rig i have the main 5v was low res to ground i found a ceramic sm to be short reasembled it still no 5v a further 2 shorted parts one in dds can a tant 4.7uf and on same board decoupling to the vco section it then worked rx2 not rx1 that was a coil in the other dds can because the other tant was 160 ohms to ground so i had 3/4 faults on that main 5v rail 3 on one board, if i had disconected one at a time the short would have still been their because of multy faults, when i contacted Yaesu about the pin diodes i required i said about the multy shorts on sevral boards teck said not uncommon on this rig esp the sm tants. by the way my required bits have upgraded parts and even the upgraded parts are nla along with most other bits , so i used 1n4148 but deaf after tx for 10/15 mins any way poss not only one part failed Mick

[rjmusto]

Thanks Mick for your input. Could be I have a bigger job on my hands here than I first thought.

to be honest it usually helps if we are informed as to what has already been tried / done so that we don't keep suggesting things you have already thought of.

Absolutely. Too easy to get caught up in the process and not think through your writing properly. And with that thought in mind, I’ll add that the rig was handed to me (belongs to a friend) in a ‘cold and dark’ state, so life at all. A dead PSU obviously. So I have been working on it DC powered, thinking to check the main radio first and then come back to the PSU. It does mean though that there may be collateral damage from when the PSU failed involved here.

I’ll try and get some time today to see if David’s idea gives me some clues.

Ralph

[rjmusto]

Have spent a bit of time on it this afternoon and am now somewhat confused....

Using David's idea (great tip thanks), I homed in on Q5001 and found it was indeed getting warm. I also realised at this point that this is where the supply for the main processor comes from.

However, the voltage on the collector of Q5001 is only 2.5v and after the feed inductor L5002, it is down to 1.5v. So no wonder the uP is not running.

There are two pairs of caps on this line, a ceramic and an electrolytic so my first step was to see if they were involved. Disconnecting one leg of the inductor seemed like a good start, to isolate one side. But this resulted in the current jumping up from 250mA to 560mA.

I have been using a TinySA to check for bus activity and in this state a big 12MHz signal appears, so seems to burst into life.

But, makes no sense. This is with the Vcc on the uP disconnected. The voltage on the collector of Q5001 though does go up to 5v in this condition, so the caps are ok.

So disconnecting the uP supply makes a bit difference to what I'm seeing but just can't make sense of it at the moment......

[SiriusHardware]

Again a couple of uncertainties - the current which rises from 250mA to 580mA, is that the current being drawn by the rail normally supplied by Q5002, 78L05, or...?

You also mention the appearance of a 12MHz signal but you don't say where you are looking to see that. (The crystal for the main uP is a 25MHz crystal).

When you disconnect the supply to the uP it places the many I/O lines of that device in a dead, indeterminate state and may be enabling circuit elements which would normally never be enabled together - so I wouldn't fret about that increase in current too much. It is the result of any number of things which shouldn't be happening, happening.

Of more interest is the fact that when L5002 is fitted it not only pulls down the voltage on Q5001 collector, there is also a substantial volts drop across L5002 - 1 Volt is a rather high drop across a series choke, so check the resistance of that part while you have one end of it disconnected.

But anyway: There are only two elements which can cause such a dramatic volts drop on Q5001 collector when L5002 is connected: One is the uP, and the other is the uP's supply decoupling capacitors C5055 and C5070, the latter being an electrolytic, possibly a Tantalum.

You could obviously have a duff uP but I have a saying, always assume it's the easy / cheap thing first. Reinstate L5002 and then lift first C5070 and then C5055 and see if lifting either of those allows the voltage at Q5001 collector to stay up when L5002 is in-circuit.

If C5070 is a surface mount tantalum I usually find I can melt the solder on one end and, while keeping it melted, bend the body of the capacitor away from the PCB just enough to disconnect one end from its pad.

If C5055 is a surface mount ceramic, I always use a pair of soldering irons with fine points to melt the solder on both ends at once and rather than remove the part altgother I tip it upwards like a tombstone leaving one end still soldered to its pad. This (a) stops the part from vanishing the moment you put it down somewhere, and (b) 'holds' the part still for you so you can make measurements on it without having to chase it all over your bench like a tiddlywink.

[Radio Wrangler]

I strongly agree with Sirius' advice.

The microprocessor will use CMOS logic. When logic lines are standing still, they take no current, nor do their drivers. When lines are switching up and down carrying signals, they take current from the power rail to charge them, and dump it into the ground pins when they are discharged, All CMOS inputs look like capacitors (MOSFET Gates)

Microprocessors often have more than one power supply system, running different parts. It may be that there is a short/partial short on one supply, and when you take this overload off, the regulators recover, volts appear in some of the right places and the clock starts up along with some of the microprocessor, so now you have logic lines doing things and this activity takes current in the working areas.

If you're lucky you have a shorted tant or ceramic capacitor. They seem to be significantly less reliable than microprocessors and support chips.

David

[rjmusto]

Hi Guys,
Thanks for sticking with me on this.

I've checked the caps on the far side of the choke and they are both ok.

For now I am running the board with the 78l05 (Q5002) disconnected and supplying the 5v from the bench supply. It is this that shows the jump in current.

The inductor has a resistance of 14ohms, maybe a little high but not crazy. I changed it anyway for a new one that is about 7ohms. With this new inductor the volts on Q5001 collector drops further to around 1.5v - and I have measured 110mA going through it. Dead processor then maybe?

Point taken though that the uP could be in an indeterminant state with Vcc open.

For the SA signal - I found that the clock on the Keyer uP would stop when checking with a scope probe, so have been using the TinySa with a sniffer coil to look for activity. With this supply inductor open and 560mA taken, the SA sees a big signal near the main processor of 12MHz plus harmonics, so 24MHz there also. (not a precise amplitude measurement obviously, so could well be the 24MHz is really the bigger signal, just the Tiny jumps to the 12) Could be 25MHz; I don't like to leave it running with this high current so can't fiddle with the test gear.....

I am right in stating that the 78L05UA has a max of 100mA, right? As well as this board it also feeds out to the Tuner Control board and provdes the Vcc for that uP. So there's a lot running of it.

So after all that, what I have on this 5v supply;
- 56mA going to the Keyer uP
- 110mA going to the main uP - and thats with a supply of less than 2v
- and 80mA or so going somewhere else

The main uP is a Yaesu proprierty item so I have no idea what its supply current should be (I'm an RF man really and not so much experience of processors...) But does it not kind of look like this is the problem?

And yet, the clock signal appears with the Vcc disconnected.

[Cruisin Marine]

I do hope you changed the decoupling caps on the 7805 regulator, or you may be chasing the results of an oscillator running at a 100 kHz or more, and that will drive you round in circles.

[SiriusHardware]

As there are only three components east of L5002 and you have presumably removed two of them from circuit at least temporarily, I'm afraid it is looking bad for the remaining component on that circuit node, the uP.

My next thought was, as David said, sometimes these big uP ICs have more than one Vcc pin and more than one Vss pin which are internally tied together, so what if that was the case and there was a bad decoupling capacitor on one of the other power pins? But, sadly, it only seems to have the one pair of power pins, one for the digital part and one for the 'analogue' part, and they are tied together.

As to the mystery of why the uP seems to come partly to life when deprived of main power the answer may lie in the fact that its Vref pin (next to the power pins) is connected to the general +5V supply via a 10R resistor, so, when you remove the main power from the chip it may be that some sections of it are effectively back-powered by that secondary supply.

For the SA signal - I found that the clock on the Keyer uP would stop when checking with a scope probe, so have been using the TinySa with a sniffer coil to look for activity.

Yes, that's a good trick to use if you suspect an oscillator might stop if you connect something directly to it. I use a handheld wide-coverage HF-to-UHF scanner receiver for the same purpose.

As you are obviously a radio man, maybe you can try listening on 25.0MHz to see if that '12MHz' spike which comes up when the uP has no power really is actually on 25MHz, or really is 12MHz.

[SiriusHardware]

And, since the uP Vref signal is connected to the main 5V rail normally maintained by the 78L05 via a mere 10R resistor (R5007), try looking at the voltage on both ends of that resistor (one end should be +5V, the other, connected to the uP Vref pin, shouldn't be much less than 5V if the Vref pin is OK).

Maybe that's where all that 78L05 current is sinking to - the uP is connected to the supply from Q5001 collector via a low resistance choke, and to the general 5V supply (from Q5002) via a 10R resistor. If the uP has failed low resistance it could potentially overload both of those supplies. There is also a decoupling capacitor on the Vref pin, C5014, which would put a lot of load on the 78L05 (via R5007) if it failed low-resistance.

[rjmusto]

Some thoughts from today:

I've found that if I feed the uP Vcc from a bench supply, so that I can get it up to 5v, then it seems to run. Certainly the 25MHz clock is there, and as long as I also have the peripheral ICs powered, then there is bus activity.

Problem though is it is pulling over 500mA and gets quite hot quite quickly. I can run it for longer at 3.5v and still see it in action, so can spend longer looking in this condition with the slower heat-up.

So kind of makes me wonder if the processor is ok really, but has one one or more outputs s/c? So have been mulling over the schematic to try and identify what are possible culprit outputs. No luck so far, but worth spending a bit more time on before declaring game over perhaps.....

[frsimen]

On power on do you see the reset pulse on the collector of Q5022? It should stay low until after the power rails have established.

Paula

[SiriusHardware]

Did you look at how much current is being drawn by the Vref pin on the uP? Measuring the voltage on both ends of R5007 will give some clue.

A local failure of the Vref 'module' inside the uP could cause the uP to draw more power from its main AVcc and Vcc supply pins without necessarily affecting most of the rest of the device.

The uP could also be trying to output a logic '1' from one of its I/O pins into something which has gone low resistance or short-circuit (which is what I think you are hoping the problem may be).

[rjmusto]

Did you look at how much current is being drawn by the Vref pin on the uP?

Yes, only a few mV across it, so no problem there.

which is what I think you are hoping the problem may be

Exactly. No luck so far though.

Paula; thanks for your input. The simple answer is no. Because the uP is pulling so much current the output of Q5001 never gets above more than a couple of volts, so the processor never starts. So I’ve been running it powered directly to Vcc from a bench supply.

Is the reset function significant here?

Ralph

[frsimen]

It's certainly worth checking that the reset is working. If the controller isn't resetting properly, the ports will be in an undefined state which could cause a much higher current consumption. I had a reset fault on a micro controlled oscilloscope, which caused some very odd behaviour.

Paula

[SiriusHardware]

It certainly is established wisdom that you should check supplies, the clock and the reset circuit as preliminaries when starting to tackle an 'unresponsive microprocessor' fault. Ralph has demonstrated that if he provides the micro with a supply with enough current headroom it will run - but - what does that mean? Does it mean only that the clock starts running, or does it mean that the unit shows other signs of life, on the display for example?

Behaviour of the uP clock during reset varies from one uP family to another, in some cases asserting reset stops all activity including the clock, but in other cases the clock runs whenever correct power is applied, regardless of the state of the reset input.

Therefore, it is worth checking the state of the reset input to the uP even when the uP clock appears to be running.

[rjmusto]

Thanks again for the inputs here.

Tried running the board in the radio this afternoon - powered as I had it on the bench. But no life showing on the radio itself; front panel still all dark.

As far as I can work out from the schematics, all the LEDs on the front are controlled via the processor.

So can anybody confirm I correct with this - all dark with no processor running, not a single lamp on?

I think the next step is going to have to be purchase of a replacement control board, so would have been comforting to know if this is expected behaviour....

[rjmusto]

Had another go at running the control board in the radio today, just in case I hadn't got it configured correctly last time.

And found this time that the main display was alive, with both VFO's running. But no action from any of the buttons, or the ones I tried anyhow.

So my thinking now is that there is a good chance the uP is ok and that it is one of the peripheral ICs that is causing trouble - and maybe the lack of response from the buttons is a clue.

So I am tempted now to try my luck at removing some of these ICs and see if I get to a point where the high current draw stops. I'm not that experienced yet at SM rework, so wish me luck! I guess there's nothing to loose though, as the board needs to be fixed or replaced anyway.

Ralph

[mickm3for]

Hi you could try and disconnect only the VCC pins. Try running a length of enamel hi temp wire under the pin fix at one end apply heat to pin pull wire it will lift only 1 pin the vcc pin test I move on to the next keeping note what is disconnected Mick