Solartron7061

[Dek]

My repair project arrived today.

The good bit :- the meter powers up.
The notso good bits :- baaaaaad corrosion around the battery and GLUG DEATH

First thing to do is to deal with the corrosion and any damage, fit a new battery.......

Dek

[Gyro]

At least it's separate from the analogue board. 

[Dek]

Had a go at the 7061.
Pulled the PCB from the meter, took the battery out and gave the affected area a good clean with dilute distilled vinegar and DI water. Rinsed with IPA and installed new battery.
Powered the meter and the "Death of Glug" still hangs over the lab :-(
Checked PSU rails look OK.

Checked the + and - Glugs at TP202,203,204 and 206 - look OK

Read the manual a bit more and carried out Glug Death check 5.3.
This indicated problem with IC 315 or IC313

Checking the cascading 74HC174 flip flops, OP 5 was found to be stuck and a likely culprit.
I'll exchange this IC and see if that clears the dark cloud of Glug Death overshadowing the lab.

Dek

[grizewald]

Good luck with your repair!

This is the first one I have seen with the memory expansion option fitted. What does surprise me is the lack of ventilation holes in the cover over the oscillator and high frequency counter/divider section of the digital board.

Here's what mine looks like:

[Dek]

Good luck with your repair!

This is the first one I have seen with the memory expansion option fitted. What does surprise me is the lack of ventilation holes in the cover over the oscillator and high frequency counter/divider section of the digital board.
Here's what mine looks like:

I'll be able to play a good game of spot the difference :-)

Mine's still not working.
I'm trying to work out what the Glug Dead signal  from IC315  should look like - This goes to the HD63B21PIA (could be that bit on the port might be 'doo-dared')
The FIRQ and OSPCLK outputs from IC312b are working (1.5khz pulses) From the manual these stop when Glug is dead, indication a problem with the HD63B21PIA

The Glug drives and Glug signals all look OK.
Integrator on TP201 looks exactly like the example in the manual -the manual doesn't state the PK-PK voltage, mine is 3v. As the Glugs are working OK I'm assuming this signal is OK.

So I'm still looking around the area of IC315 and IC314. I might build up these ICs on a bread board so I can see exactly what should be going on.....
I'm a bit stuck at the moment so cup of tea and some thinking before wielding the hot air light sabre destroyer.

Dek

[Kleinstein]

3 V pp sounds reasonable for the integrator and doubt there is something simple to change the amplitude except a wrong reference voltage.

I one suspects the 68D21 IO chip, it could also be the socket - maybe move the chip a little out and back in.

The counter 6821 part is relatively close to the battery -  so maybe some hidden corrosion ?

[grizewald]

I'll be able to play a good game of spot the difference :-)

The other difference I spotted was that your meter appears to be one of the very early ones which has PCBs 3 and 5 instead of 13 and 15.

For your glug death problem, are you seeing regular activity on pin 1 of IC315? Those pulses should arrive on a regular basis and prevent the output at pin 10 from changing state and signalling "glug death" to the CPU.

[grizewald]

Looking closer at the logic around IC315, the GLUGDEAD signal is active high, so it should always stay low.

The flip-flops in IC315 are arranged input to output, with the first input on pin 3 being tied to +5V, the first input is always  high. Then the clock which should be arriving on pin 9 clocks that 1 through each flip-flop in turn. So, the 1 will arrive at the output on pin 10 four clock periods later, unless the flip-flops are reset by an incoming CLR (active low) on pin 1.
 

[grizewald]

If you want me to get the 'scope on my 7061 to capture you some comparative traces, just shout!

[Dek]

Hi Grizewald,

Thanks for the help, I'm going to need it
Yes, I think they are the earlier PCBs.
Pin 1 of IC315 is seeing a 1.5khz pulse train - going low for about 50ns so 315 should be getting reset.
Also I only see Q1 (pin 2 and 4)  go high and pin10 never goes high.

Pin 15 (Glug dead signal of the HH63B21) is low.
So that possibly leaves a problem with the Glug Dead input bit (pin 15) on the PIA being faulty?

AHHHHHH !
Just before sending this post, I was checking that all the buttons on the front panel worked....which they do.
Did  reset and it says self test passed, 7061 Initialised with no Glug Death displayed

Turning the meter off and back on again shows Glug Death but clears with a front keyboard reset.

Quick check and :-
DC V are working at least up to 20v
Ohms - a 10k resistor on the 10000 range reads 9.903 KOhm
           the same 10k resistor on the 1000 range reads 0.003,6 KOhm so something looks a bit screwy there.
Possibly someone has mucked about with the calibration???

So at least 2 steps forward.
 
edit: RTFM ! Need 4 wires connected for ohms measurement.
Which results in some sensible readings :-)

Looking much better.
Now if I could work out what's causing the Glug Death  on startup?

[grizewald]

Hi Grizewald,

Thanks for the help, I'm going to need it
Yes, I think they are the earlier PCBs.
Pin 1 of IC315 is seeing a 1.5khz pulse train - going low for about 50ns so 315 should be getting reset.
Also I only see Q1 (pin 2 and 4)  go high and pin10 never goes high.

Pin 15 (Glug dead signal of the HH63B21) is low.

Excellent. That shows that your glugs are being generated and that the watchdog isn't causing the problem.

So that possibly leaves a problem with the Glug Dead input bit (pin 15) on the PIA being faulty?

AHHHHHH !
Just before sending this post, I was checking that all the buttons on the front panel worked....which they do.
Did  reset and it says self test passed, 7061 Initialised with no Glug Death displayed

Turning the meter off and back on again shows Glug Death but clears with a front keyboard reset.

That is encouraging, but very strange!

It almost sounds like a problem with how things are enabled during the start up sequence at power on. You might like to look at the GLUGDEAD signal at power up with respect to pin 23 on the PIA to see what state it is in when the PIA gets enabled.

Quick check and :-
DC V are working at least up to 20v
Ohms - a 10k resistor on the 10000 range reads 9.903 KOhm
           the same 10k resistor on the 1000 range reads 0.003,6 KOhm so something looks a bit screwy there.
Possibly someone has mucked about with the calibration???

So at least 2 steps forward.

I don't know if the calibration constants have a checksum so that the CPU can detect any corruption, so it's possible, but I'd say unlikely. If you go into calibration mode, you should be able to check the calibration date to see what it was last calibrated.

What kind of readings do you get on the various voltage and resistance ranges with the inputs shorted?
Have you checked all the power rails on the two boards for correct voltage levels and if there is any unacceptable ripple on any of the rails? It's a very old meter and the smoothing capacitors could be tired. If there's loads of ripple, the meter will do all kinds of unpredictable things.

[grizewald]

When you check the rails, pay attention to the correct test points in the service manual. As the analogue board is floating, you don't want to try using the digital ground when looking at anything on the analogue board and vice versa!

[Dek]

Hi Grizewald,

I edited my previous post.
I didn't realise for ohms measurement I needed 4 wires even when making a 2 wire measurement.
So with the meter connected correctly I get good readings on a 1 10k and 39k resistors.
With the meter ip shorted, all zeros on all DCV and Ohm ranges
Volts read OK on  all ranges ( max ip 20v DC)

I switched off the meter, powered back up. Glug Death flashes up but the meter functions OK without doing the reset.
There is a section in the manual about adopted settings on power up and reset - I wonder if something is set incorrectly...Off to RTFM again :-)

I'll also check the  GLUGDEAD signal at power up with respect to pin 23 on the PIA as you suggested.

[grizewald]

I have the original cables that Solartron supplied with the meter. The cable that just has positive and negative connections for voltage measurements has all four wires in use. The Hi and Lo sense wires are connected to the red and black leads just before they terminate in the banana plugs.

If your glug problem now seems to be fixing itself, maybe something has a temperature fault. It could be as simple as a poor connection to the PIA or one of the other socketed chips.

Do you know much about the meter's past? If it's been stored in a cold garage for some time, you might just have some moisture in there which will cook out if you leave the meter powered on for a couple of days. However, I wouldn't trust the meter to leave it unattended with power on right away. The Schaffner mains filter in the power inlet has a nasty habit of shorting out and boiling the pitch that the filter capacitors are potted in. When they fail, there's lots of smoke and a terrible smell that is very hard to get rid of!

[Dek]

If your glug problem now seems to be fixing itself, maybe something has a temperature fault. It could be as simple as a poor connection to the PIA or one of the other socketed chips.

Do you know much about the meter's past? If it's been stored in a cold garage for some time, you might just have some moisture in there which will cook out if you leave the meter powered on for a couple of days.

You might be right about a temperature fault.
The 20v is now reading 18v.
I switched off the meter for 10 mins to cool - (the lid was getting quite warm above the transformer and oscillator section), now it's cooled a little, it's reading 20v again.
I'll check the PSU rails tomorrow as well at the glug / PIA reset.
The display still shows Glug Death on startup, but I'll leave that one for now.
No idea about the meters past - the seller said it had been in a cupboard and was working before, but now shows glug death...yeah right, but at least I knew I was taking on a project :-)
Roger on the  Schaffner mains filter.

Dek.

[Dek]

Bit more work today

Checked Glug dead sinal in respect to PIA CS and indeed the glug dead is high for about 0.8 seconds during start up.
So this explains the Glug Death message on start up, but not why watchdog IC315 doesn't get the CLR pulses... OK perhaps, put that to the back of the que for a moment.


Checking the supply rails, not all is good.
TP         Voltage       Actual
TP 901 +36v         32.5 with 1.4v ripple
TP 902  +15         +15. 100mv noise
TP 903  0v
TP 904 -15           -15   100mv noise
TP 905 -36v          -35.5 150mv p-p noise
TP 907 0v
=========================
TP510  9V unreg       9.3v + 1v ripple
TP509  5v                5.1v   ripple + noise
TP501  5v                4.95v  50mv noise
TP502  5v                5.03 10mv noise
TP503  5v                4.63 (downstream of D501 so OK)
TP504  5v                5.1 v 20mv noise
=========================
TP505 +40v           +40v
TP506 +32 unreg    +28.8 +500mv ripple
TP507 -32 unreg     -30.7 no ripple
TP508 0v

So I think look at changing some caps and see if that fixes the bad +36v and +32V supplies and also 5v supply associated with the processor (IC501 & C517).

[grizewald]

It certainly looks like a recapping might help your glug death problem. Otherwise, you'll need to dig deeper into the clock generation circuits and see what happens at power up. There must be some kind of clock coming from PCB 8, or otherwise the GLUGDEATH signal would not get asserted to start with, so it's kind of confusing that it clears itself after 800ms.

These meters do run fairly toasty. The case is designed to act as a heat sink for the transformer, so it's quite normal that it gets hot in that area.
 

[Dek]

Bit more work..
Changed one of the 5v regulators IC501 and associated cap - improved the noise and ripple significantly on TP509.
No change though to the instrument. :-(

Also changed C508 and C509 on the +- unreg 32v supply - no change in the instrument behavior.

Now looking for the source of the 1.4v ripple (and low volts 34.1v)  on the floating +36v supply on PCB 5. Trying to decide what to attack first ;-)
I have a hunch about the bridge rectifier Q901 but the PSU is a weird configuration (to me) and I'm not sure of the function of the 39ohm resistor in the raw dc supply to the LM340 regulator.

Also in the process of making a connector - now just need to find some pins of correct diameter and will have a half decent input method. 

[grizewald]

That's a very nice bit of turning work there! How I wish I had a lathe sometimes.

Sorry to hear that your fixes so far have had little effect on the meter's problems, but it sounds like you're moving in the right direction at least.

The resistor? I think it's there to ensure that the two regulators start up properly, given that IC901 provides the ground input for IC904 and its 8.2V zener which pushes the ground up to the level needed to produce an output voltage higher than the allowed input voltage.
Your low voltage on the 36V rail could be due to the zener being damaged. It might be a good idea to remove it and test it to check if it still has the correct breakdown voltage. If you search for Application Note 103 by Ti/National, it shows a great variety of power supply configurations based on the LM340 series.

[tggzzz]

Also in the process of making a connector - now just need to find some pins of correct diameter and will have a half decent input method.

IIRC you need a diameter of 1.3mm. I used the wrong end of some pogo pins, but IIRC many are 1.2mm. I suggest the good old suck it and see method

[grizewald]

Also in the process of making a connector - now just need to find some pins of correct diameter and will have a half decent input method.

IIRC you need a diameter of 1.3mm. I used the wrong end of some pogo pins, but IIRC many are 1.2mm. I suggest the good old suck it and see method

It just occurred to me that I have some genuine leads with the Fischer connectors here, so I took one apart and my micrometer measures them at 1.28mm.

Your memory is still working well!

[Dek]

Also in the process of making a connector - now just need to find some pins of correct diameter and will have a half decent input method.

IIRC you need a diameter of 1.3mm. I used the wrong end of some pogo pins, but IIRC many are 1.2mm. I suggest the good old suck it and see method

It just occurred to me that I have some genuine leads with the Fischer connectors here, so I took one apart and my micrometer measures them at 1.28mm.
Your memory is still working well!

TGGZZZ,
Good tip re: the pogo pins
Grize, thanks for the confirmation on the dia......you have let slip you don't have a  7 1/2 digit micrometer :-)

Thanks,
Dek.

[grizewald]

Grize, thanks for the confirmation on the dia......you have let slip you don't have a  7 1/2 digit micrometer :-)

Thanks,
Dek.

 

That's probably a good thing!

[Dek]

Bit more of a poke about today - measuring the various rails:

39v raw DC to R901 -3.7v drop across R901 = 35.3v into the regulator (-drop out), no wonder why the 36v rail is low.
The 36v rail varies from 32v to about 34v
R901 is running very hot - too hot to touch for more than 1-2 seconds (could be something on the 36v rail failing and drawing too much current?)
So what should the raw DC from the bridge be at the ip of R901?

Volt drop across the zener is 8.35v

Just in case, replacement bridges, diodes should be here tomorrow. (they will come in handy even if I never use them  )

Bit more thinking to do before firing up the hot air light sabre destroyer again.

Dek





 

[Kleinstein]

The large drop on R901 indicates too much current there. It is really 34 V at the input to IC301 ? If yes, this could indicate a problem (near short) with C902 (the one before the 36 V regulator).
The voltage at R901 relative to ground should be more like 40-50 V (2x 20 V from the  +-20 V supply) + some 8-10 V from the lower ~10 V for the 5 V regulator minus some drop for the capacitor.

Diode can usually be checked in circuit. They usually fail with a short or rarely open. Both cases should be visible with the diode test in circuit.