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Old 7th October 2012, 03:21 PM   #41
dtm1962 is offline dtm1962  Canada
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Default Schematic Measurements With Q617 CE Shorted & Without

Here are measurements that are made today as well.

1st Attachment is with Q617 C & E Shorted and
2nd Attachment is with Q617 C & E not shorted

Note: Q619 & Q621 are removed to isolate the outputs from the measurements....

Note the +/- Rail Voltage does dip by ~3VDC when Q617 C & E is shorted.

If you want higher resolution pdf's of the measurements...

please email me dmullins at cogeco dot ca

Let me know what you think

Thanks in advance,
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Old 7th October 2012, 06:17 PM   #42
dtm1962 is offline dtm1962  Canada
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Default Update Revision 1

Quote:
Originally Posted by dtm1962 View Post
Here are measurements that are made today as well.

1st Attachment is with Q617 C & E Shorted and
2nd Attachment is with Q617 C & E not shorted

Note: Q619 & Q621 are removed to isolate the outputs from the measurements....

Note the +/- Rail Voltage does dip by ~3VDC when Q617 C & E is shorted.

If you want higher resolution pdf's of the measurements...

please email me dmullins at cogeco dot ca

Let me know what you think

Thanks in advance,
A few revisions was worth redoing the attachment.

For some reason +/- Rail voltage would vary enough (+/-3Volts) to make some measurements invalid, hence my reissuing the attachment for "the non-shorted Q617 C & E version". The Shorted version is accurate as is.

The 3 updated voltages are "back circled" for reference.

Let me know your thoughts.

Again Higher resolution copy of marked-up schematics are available if you email me at: dmullins at cogeco dot ca

Thanks in advance,
Attached Files
File Type: pdf RB 990 Q617 C E NOT Shorted REV 1 Measurements.pdf (132.9 KB, 36 views)
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Old 7th October 2012, 06:29 PM   #43
Mooly is offline Mooly  United Kingdom
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Its easily done and no problem

I've just amended the circuit to show two your new readings so I'll have look and see if I can make any sense out of them.

If you want to do a new set of readings that's fine and is a good double check.
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Old 7th October 2012, 06:31 PM   #44
Mooly is offline Mooly  United Kingdom
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Lol, I didn't turn the page... I''ll study your results
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Old 7th October 2012, 06:55 PM   #45
Mooly is offline Mooly  United Kingdom
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Heres what I'm thinking so far...

Two of your results show Q613 with 62.6v on the emitter and 60v on the base. Something amiss there. Can you recheck that measurement under the same conditions and also check by measuring across the B-E junction as well. Thats very important. That B-E drop must not exceed around 0.8volts with the emitter more positive than the base. If it does we might have a problem with that device.
The other result shows Q613 with the base positive with respect to the emitter (so Q613 should be off) and yet there is still nearly 60 volts on the collector. So again that reading also points at Q613

Now there may be other problems too but this seems like one identifiable issue that we must correct first.

I would still leave Q617 shorted as it takes all the circuitry associated with it out of the equation.
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Old 7th October 2012, 07:43 PM   #46
dtm1962 is offline dtm1962  Canada
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Default Measurements Update

Quote:
Originally Posted by Mooly View Post
Heres what I'm thinking so far...

Two of your results show Q613 with 62.6v on the emitter and 60v on the base. Something amiss there. Can you recheck that measurement under the same conditions and also check by measuring across the B-E junction as well. Thats very important. That B-E drop must not exceed around 0.8volts with the emitter more positive than the base. If it does we might have a problem with that device.
The other result shows Q613 with the base positive with respect to the emitter (so Q613 should be off) and yet there is still nearly 60 volts on the collector. So again that reading also points at Q613

Now there may be other problems too but this seems like one identifiable issue that we must correct first.

I would still leave Q617 shorted as it takes all the circuitry associated with it out of the equation.
Hi Mooly:

Here are the results:

A) Q617 C & E shorted...

Q613 BE voltage drop = -0.6V drop with Red lead on E & black lead on B
=+0.6V drop with Red lead on B & black lead on E

Q613 voltages ref to ground = E = +56.5V; +57.3V; +56.7V


B) Q617 C & E NOT shorted...

Q613 BE voltage drop = -1.5V drop with Red lead on E & black lead on B
= +1.5V drop with Red lead on B & black lead on E

Q613 voltages ref to ground = E = +60.2V; +58.5V; +58.1V

Note: When Q617 C & E is shorted that the rail voltages goes down....

I hope this helps.

Thanks in advance,
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Old 7th October 2012, 07:50 PM   #47
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Molly the voltage at the R627 one side read -58.8 volts and the other side +59 volts. The plus side should read +1.2 volts. No? Can he check the resistor R627 for open.
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Old 7th October 2012, 08:11 PM   #48
dtm1962 is offline dtm1962  Canada
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[QUOTE=dtm1962;3193047]Hi Mooly:

Q613 voltages ref to ground = E = +56.5V; +57.3V; +56.7V


B) Q617 C & E NOT shorted...

Q613 voltages ref to ground = E = +60.2V; +58.5V; +58.1V

QUOTE]

So it should read as I forgot to identify the last 2 voltages for each...

A) Q617 C & E shorted...

Q613 voltages ref to ground = E = +56.5V; BASE +57.3V; COLLECTOR +56.7V


B) Q617 C & E NOT shorted...

Q613 voltages ref to ground = E = +60.2V; BASE +58.5V; COLLECTOR +58.1V
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Old 7th October 2012, 08:15 PM   #49
dtm1962 is offline dtm1962  Canada
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Originally Posted by tauro0221 View Post
Molly the voltage at the R627 one side read -58.8 volts and the other side +59 volts. The plus side should read +1.2 volts. No? Can he check the resistor R627 for open.
R627 measures correct as it is 1/2W MF Dale versus 1/4W generic MF type as I have changed it out a couple of times. The ones I remove always mesures within 1% as well...
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Old 7th October 2012, 08:30 PM   #50
Mooly is offline Mooly  United Kingdom
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Hi Dan,

I'm on a different PC so haven't all your info to immediate hand... but this might help 'till tomorrow. I'm still not really happy with Q613 readings and I know this all gets confusing too. The devil is in the detail with these numbers

1. With your red lead on E and black on B you measure minus 0.6 volts. That means the base is higher than the emitter and so the device should be OFF. That appears not to be happening as you have plus 60ish on the collector.

2. The 1.5 volts that you seem to be able to get across this junction with Q617 not shorted again should turn this transistor off.

A quick and dirty test... remove Q613 and see if the voltage on Q617 (still shorted) falls to near the minus supply rail.
If it does replace Q613 but leave the BASE unsoldered and floating. Again see if the Q617 volts falls away. If it doesn't then Q613 is faulty (leaky).

I'll be back on usual PC tomorrow... and maybe that will give you something to go on.
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