Yaesu FT1000mp with dead controller. What now?

[rjmusto]

Hi all,

I have an FT1000mp (not the Mk V) on the bench with a rather unknown history. The main problem I have seems to be a dead controller board. Two issues;
it is drawing around 300mA on the main 5v rail, which is too much for the 78l05 regulator. And there is no life from the processor. No clock signals on the oscillator.

Am I right in thinking the clock should always be running? There’s not some disable line I’m missing?

If so, I guess the only way forward would be a replacement board.

Any other suggestions?

Thanks,
Ralph

[Sinewave]

I'll watch this with interest. I've got an FT1000MP which has started playing up, different issue to yours though (no output on SSB, previously VFO A was being a bit quiet).

[rjmusto]

In your situation, I’d check the 5 and 9 volt regulators on the regulator board have correct outputs. Good place to start anyhow.

[Sinewave]

Thanks, I shall take a look when I get a chance.

[mickm3for]

Hi i have a 1000mp it had 5v reg oc due to short on 5v line this was a tant cap in dds sub unit that sorted rx2, main rx/tx still dead coil in dds pll oc ,reg to the vco' oc , pin diodes tx/rx switch oc ceramic cap on rx board sc , it now receives on both rx1 and 2 tx on 1 and 2 but takes 10-15 mins b4 gain returns to rx after going to tx even with power turned down, if turned off and on again rx is ok . The owner said it went funny after he dropped it and broke the mem select switch ? lots of parts unavailable from Yaesu but the RF board is in stock £200 + Mick

[rjmusto]

I might add that on this unit the front panel is completely dead, nothing lit up at all. I know the processor controls the LEDs, so a dead processor means no action, but still seems odd that nothing at all is lit up.

[SiriusHardware]

it is drawing around 300mA on the main 5v rail, which is too much for the 78l05 regulator.

By which you mean what, that the output from the 78L05 is collapsing to some value significantly less than 5.0V? Digital circuits are notoriously fussy about supply voltages so if the 5.0V supply is anything less than that you can't necessarily expect the digital bits to work.

It's bit premature to be thinking about trying to find a whole replacement PCB, there is a good chance that there is a supply decoupling capacitor, cost, a few pence, which has failed low-resistance. I don't have the circuit diagram handy but look especially for any Tantalum capacitors which are across that supply.

[mickm3for]

Hi with unit ON check voltage at plug j5002 pin 3 this is vcc for micro, the control board is sep, from the display board

[Cruisin Marine]

Look for bad, bad decoupling caps on the 5v rail, especially tant's of course.

[mickm3for]

as well as the 5v reg on the reg panel there is one on the cont board Q5056 78L05 and one on the disp board q5505 also a 7805, the caps DO go short Mick

[rjmusto]

Hi,

The output of the 78l05 gets pulled down to around 2.4v.

I’ve tried running this part of the circuit from a bench supply (connected to the output of the regulator) and it takes 300mA at 5V.

The processor is fed via a 10ohm resistor and this has 75mV across it with 5V on the supply. But no sign of oscillation on the clock.

[mickm3for]

is that q 5056 on cont board

[SiriusHardware]

I think for the moment you need to worry less about the lack of activity than you do about whatever is taking excess current, since they may be effect and cause respectively. If you are running the circuit which normally runs on the output of the regulator from a substitute supply then you really need to disconnect the output of the 78L05 from that rail otherwise your auxiliary supply is trying to back-power the 78L05, which it may not appreciate. One dodge you could try is to remove the 78L05 and (temporarily) wire a heatsinked 7805 onto its pads while you go looking for the fault.

When you are using the auxiliary supply (or 7805), check for anything which is directly across that supply which is running warmer than expected. I don't think your excess current is being drawn by the micro because if it was, that 10R resistor would be burning up and the voltage drop would be a lot greater.

[rjmusto]

The output of Q5056 is good. It is Q5002 that has a problem.

And yes, you're right, I really need to find what is responsible for the high current - and I have looked for something warm, but not found it so far.... Don't see any tantalum caps, just electrolytics. And if one of those was taking DC current, I'd have expected to see it bulge.

The regs on the regulator board are good and on the disp board.

I know I should remove the 78l05 before feeding power in, but it's surface mount and surounded by caps and connectors, so not keen on getting near it with a heat gun. I think, though I could cut the track and try it that way. Will have a go tomorrow.

[SiriusHardware]

Ah, I was thinking that the 78L05 would be a through-hole T092 type. I see your dilemma. Does anyone have a link to an online service manual or circuit diagram?

[rjmusto]

Have attached a zip file with the control board schematic. The unzipped version is a big file, so can't add that.

It is also furstratingly large to view, the original must have been A3 or bigger....

[rjmusto]

Have cut the track and can say the current is 250mA for the part supplied by Q5002.

If the 78l05UA is rated to a max of 100mA, then the correct consumption should be, say 70mA. Which means there is 180mA too much, which at 5V is nearly 1W. So something should be noticably hot surely?

I can say that Q5035 is a bit warm (30deg maybe), which is a uP for the keyer (I think).

Wish I had a thermal camera......

[mickm3for]

This is all i could find https://www.va3cr.net/manuals/1000MPservicemanual.htm

[SiriusHardware]

OK - I notice that the OUT from Q5002 does run all over the PCB but it also leaves the PCB via pin 9 of connector J5010. If that is easy to unplug, try pulling that off and measuring the current being drawn from Q5002 again.

[Radio Wrangler]

With the regulator removed and a current-limited power supply set to the intended rail voltage and a few hundred mA, you next need a high-resolution voltmeter. Using where the supply is connected to your board (either the + or - connection as appropriate) as reference you can measure the voltage rise in the groundplane or tracking arrangement to find the component leg which is most positive and you can measure the voltage drop in the power rail tracking/plane, to find where it is greatest. - likely to be the same component.

This trick needs something like a 5 or 6 -digit voltmeter that can read microvolts, but it works reliably. You can even measure the drop on an IC leg between the solder ring on the PCB pad and where the leg enters the IC package.

If 6 digit DVMs soud all terribly esoteric and awfully difficult, well I bought one dead from a stall at an amateur radio rally for a fiver. Got it home and found a dead 5v reg. The junk box provises one and off it went, agreeing very nicely with my other high res voltmeter.

You don't need this sort of instrument, but if you have one, you can make it perform tricks and it can make life easier. You won't need it very often at all, but for a fiver?

David