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JD, I have the same problem. I was able to observe that on my A3 board, instead of the CR1070 diode, there is a zero ohm resistor, is this normal?

On Mon, Apr 1, 2024 at 11:27?PM <jking2603@...> wrote:

MORE MEASUREMENTS OF RESISTORS ON A5 BOARD

I agree with Raymond and Tom that you're spinning your wheels by measuring
component values in-circuit.

Right now, in your shoes, I'd be looking at the holdoff voltage from
A1U170. I'm pretty sure it should be more or less directly controlled by
the holdoff control on the FP.
If your holdoff oscillator is stuck, this MIGHT explain all the symptoms
you originally had - save for the weird CH1 signal.
... time passes ...
Actually, looking at the signals that go to the CH1 preamp from the MUX,
they control the VAR gain and the DC balance. If those are bad, this could
inject a phantom signal to the channel.

While you're in there, you might sanity check the rest of the outputs from
U170, same deal as on the A5 board, you want to see that they're DC, can be
controlled from the FP (those that are under any kind of FP control) and
that the S&H op-amps aren't railed.
Refer to the service manual for which signals are controlled by which FP
control - it's pretty self-evident in most cases.

On Mon, Apr 1, 2024 at 10:41?PM <jking2603@...> wrote:

20 B TIM REF, U2427C PIN 8, measures + 5.62VDC, no change in value from
any front panel control

19 A TIM REF U2427 PIN 7, measures + 9.55VDC, no change in value from any

front panel control

This could well be normal now that the calibration has been lost. These
signals would typically fine-tune the sweep speeds.

25 A TRIG LVL R2730,

LEVEL MADE NOW CHANGE

This seems weird, in A trigger mode the trigger level control should change
the A TRIG LVL signal.
Still probably immaterial to your main problem, which is no sweeps.

26 B TRIG LVL R2731,

Likewise here, in B-trigger mode (see manual), the trigger level control
should change this signal.

22 HORIZ POSTION, R2535
mid scale +0.05V DC
CCW 1.37 VDC
CW -1.37 VDC

16 DELAY REF 0, CR2733 CATHODE BAND
DELTA+ REF mid scale +0.01V DC
CCW -1.24 VDC
CW +1.26 VDC

17 DELAY REF 0, CR2742 CATHODE BAND
DELTA T OUT INDEP mid scale +0.01V DC
CCW -1.24 VDC
CW +1.25 VDC

The rest seem OK, the main question was whether these are under software
control, or whether e.g. the op-amp outputs are railed.

On Tue, Apr 2, 2024 at 4:40?AM <jking2603@...> wrote:

Is it normal with SGL Trigger A setup as in the photo for the CRT to go
blank?

Yes this is normal.

Why has the CRT gone blank? Is this blank screen what normally happens?

If you read the manual, you'll see that this is normal behavior. For
photographic purposes, the scope will sweep each enabled trace, before
rendering the OSD once, which will give the user a photograph of the whole
mess, assuming the shutter is open for the duration.

This makes me wonder if as you have said the sweep is stuck in Holdoff
or if the Blanker circuit has come on?

IMHO you might want to verify that the holdoff control voltage is correct -
this doesn't come from the A5 board, as I'd remembered, but rather from
U170 on the A1 board. This is another MUX, which has a bunch of S&H op-amps
behind it.

On Tue, Apr 2, 2024 at 5:06?AM <jking2603@...> wrote:

SO ARE YOU CONFIRMING THAT IN THE FOLLOWING 2 PHOTOS THE TRIGGER MODE LED
IS NOT SHOWN?



Trigger Auto Level



Trigger Auto

The trigger mode LEDs are the LEDs above the trigger mode lever. They are
lit to signify the trigger mode. I see nothing wrong in those photos.

On Mon, Apr 1, 2024 at 09:59 AM, Sigur?ur ?sgeirsson wrote:

In AUTO, yes, have you verified that the OSD displays AUTO trig?

I cannot answer this because I do not know what I am looking to see.

That is why I sent you the pictures. can you see the Display of Auto trig?

Yeah, turns out the sweep mode and the trigger level are displayed on the
OSD, but not the trigger mode. That's indicated by the FP LEDs.

SO ARE YOU CONFIRMING THAT IN THE FOLLOWING 2 PHOTOS THE TRIGGER MODE LED IS NOT SHOWN?


Trigger Auto Level


Trigger Auto

IF THERE IS SUPPOSED TO BE TRIGGER MODE LIGHT ON IN THESE SETUPS THEN THIS THE THE CONDITION I NEED TO MEASURE CIRCUIT VOLTAGES FOR TO TRY AND FIGURE WHAT VOLTAGE VALUES ARE DIFFERENT TO A FUNCTIONING 2465 WHICH IS SHOWING THE TRIGGER READY LED IN AUTO AND /OR AUTO LEVEL

look forward to your reply.

Hi Siggi,
Thanks again for your replies.
As always you get me thinking.

the traces with POS controls about mid-range, then select SINGLE trigger.
Each time you toggle the mode control down, you should get a sweep.

as you see in the photo


Is it normal with SGL Trigger A setup as in the photo for the CRT to go blank?

Why has the CRT gone blank? Is this blank screen what normally happens?


This makes me wonder if as you have said the sweep is stuck in Holdoff
or if the Blanker circuit has come on?

Yours sincerely
Jeff King

Waveform in the schematics look like with a 10x probe based on waveform picture at EXT TRIG IN port.

Manual shows at base of Q309 signal has 10x50mV=500mV peaks as far as I can tell. Scope shot "07 19 38" shows ~200mV peaks and it is not clear if tunnel diode action is happening (could you DC couple for future scope shots?). I think you mentioned sweep works with a sharp edge but not with sine wave. A sharp edge doesn't need tunnel diode action as much as sine wave.

The circuit biases VR304 very close to 10mA (trip point) with no signal. If VR304 is in a socket you can use an ammeter instead of it and measure DC current with no input. Perhaps one of the components shifted or left sides of R300 and R306 are at wrong DC potential and stealing current. It may be as simple as adjusting the blocks prior to R300/R306.

When it is operating, signal coming from trigger amp pushes the tunnel diode VR304 to its high voltage region, and creates a fast spike at bases of Q309 and Q317. Q317 collector produces a pulse, and triggers VR358 through CR319. VR358 waits at the edge of trigger (current through R357+R356) until this time, and Q328 is off. When anode of VR358 jumps to high voltage region (~ 0.5-0.6V? depends on the tunnel diode) sweep is running. Q360 collector signal disables Q526 and sweep starts. When sweep hits ~ 10V Q408/Q409 and the network of devices in hold-off circuit send signal back to CR320/VR322, Q328 turns off and puts VR358 back to low voltage region for next trigger.

If you don't see ~ 0.5-0.6V at anode of VR358 at sweep rate (~10ms in test condition) it could be because it didn't get triggered, or Q328 is pulling it low. If Q328 is in a socket you can remove it to test if something in Q328 path is the problem.

However, most likely issue is wrong DC operating point of VR304 since you already verified VR304 is good and with a large enough signal you can get sweeps.

Does single sweep work?

Ozan

=====

Interleaved:

On 4/1/2024 11:27 PM, jking2603@... wrote:

MORE MEASUREMENTS OF RESISTORS ON A5 BOARD

In addition to previous resistors reported as not measuring to specification in circuit
R2650 measures 8.3K compared to 10K spec. Circuit 1 Reset Control
R2735 measures 3.4K compared to 10K spec. Circuit 2 Delay Ref 0
R2230 measures 0.62K compared to 10K spec. Circuit 2 Front Panel Scanning
R2608
R2610
R2612
R2611

If these resistors are in parallel with any other circuit elements, then the resistance readings you get are not very meaningful.

I now add the following resistors which are off spec.

In addition to in circuit measurements I have read each resistors colour code

R2227
R2228
R2229
R2230
R2734
R2649
R2522
R2525
R2742
R2647 COLOUR CODE RED RED RED DOES NOT MATCH SPEC of 6.8K

That's a 2.2K (2K2), that may be a modification of some sort, valid or not.

R2652
R2646
R2745
R2550
R2020
R2553
R2746

So I ask myself what is going on?

History Summary
2465 was say 5 years ago functioning with all 4 traces.
I turned it on and a RIFA Capacitor started to smoke.
I turned off Power IMMEDIATELY and no explosion occurred.

RIFA capacitors generally don't harm other circuit elements unless they leak.

Surely the RIFA capacitor failure has not caused his damage to control board resistors.

Has this level of damage to resistors taken out a U Chip?

So now I need to take off the A5 Board and lift one end of each resistor
and measure the value of resistor out of circuit.

Or you need to consider what other circuit elements are in parallel with that resistor.

I am certain that some of these resistors are outside specification enough to cause the scope to not trigger.

I know need to look at the circuit for each resistor to see which would not have meaningful measurements in circuit.

In any event any feed back on any resistors that would not need replacing would be useful to know.

I'm not sure that it's just resistors (or if it is indeed, resistors).? I'm far from an expert on this scope, but I'd be sure that the appropriate signals are present in the circuit (hopefully see good quality schematics).

I'd go from there rather than testing all the resistors.

If nothing else, isolate the perceived problem to a specific section and then start to check parts.

Harvey

Yours sincerely
Jeff King

MORE MEASUREMENTS OF RESISTORS ON A5 BOARD

In addition to previous resistors reported as not measuring to specification in circuit
R2650 measures 8.3K compared to 10K spec. Circuit 1 Reset Control
R2735 measures 3.4K compared to 10K spec. Circuit 2 Delay Ref 0
R2230 measures 0.62K compared to 10K spec. Circuit 2 Front Panel Scanning
R2608
R2610
R2612
R2611

I now add the following resistors which are off spec.

In addition to in circuit measurements I have read each resistors colour code

R2227
R2228
R2229
R2230
R2734
R2649
R2522
R2525
R2742
R2647 COLOUR CODE RED RED RED DOES NOT MATCH SPEC of 6.8K
R2652
R2646
R2745
R2550
R2020
R2553
R2746

So I ask myself what is going on?

History Summary
2465 was say 5 years ago functioning with all 4 traces.
I turned it on and a RIFA Capacitor started to smoke.
I turned off Power IMMEDIATELY and no explosion occurred.

Surely the RIFA capacitor failure has not caused his damage to control board resistors.

Has this level of damage to resistors taken out a U Chip?

So now I need to take off the A5 Board and lift one end of each resistor
and measure the value of resistor out of circuit.

I am certain that some of these resistors are outside specification enough to cause the scope to not trigger.

I know need to look at the circuit for each resistor to see which would not have meaningful measurements in circuit.

In any event any feed back on any resistors that would not need replacing would be useful to know.

Yours sincerely
Jeff King

OK Noted.
But first read the message about A5 RESISTORS

Have you tried playing with the FP while
measuring the MUX outputs?

MEASUREMENTS NOW TAKEN

20 B TIM REF, U2427C PIN 8, measures + 5.62VDC, no change in value from any front panel control

19 A TIM REF U2427 PIN 7, measures + 9.55VDC, no change in value from any front panel control

25 A TRIG LVL R2730,
START POINT DEFAULT SETTINGS
MODE AUTO SOURCE
COUPLING
-0.93 VDC

MODE LEVEL -1.19 VDC
MODE NORM -0.99 VDC
MODE SGL +0.93 VDC

SOURCE CH2 -0.93 VDC
SOURCE CH3 -0.89 VDC
SOURCE CH4 -0.89 VDC
SOURCE LINE 0.0 VDC

COUPLING DC -0.93 VDC
COUPLING HF -0.93 VDC
COUPLING LF -0.93 VDC
COUPLING AC -0.93 VDC

SLOPE MADE NO CHANGE
LEVEL MADE NOW CHANGE

26 B TRIG LVL R2731,
CH1 VOLTS / DIV
0.11 AT 50MV
0.0 AT 5V
0.01 AT 1V
0.94 AT 2MV

22 HORIZ POSTION, R2535
mid scale +0.05V DC
CCW 1.37 VDC
CW -1.37 VDC

16 DELAY REF 0, CR2733 CATHODE BAND
DELTA+ REF mid scale +0.01V DC
CCW -1.24 VDC
CW +1.26 VDC

17 DELAY REF 0, CR2742 CATHODE BAND
DELTA T OUT INDEP mid scale +0.01V DC
CCW -1.24 VDC
CW +1.25 VDC

YS
JK

On Tue, Apr 2, 2024 at 12:57 AM, <jking2603@...> wrote:

So if there is still suspicion about the effect of the Options,
Then line junction plugs can be put in place on Circuit 5 to eliminate all
signals out to
the Options. This will allow operating the 2465DMS as a 2465.

The only other conclusions I have is that whatever is faulty on the 2465 is
preventing an activity that allows feedback from
the Option 1 DMM to be displayed on the CRT.

I was suggesting that maybe a fault in an option would inhibit the trace. As you say, take the options (01 and 09) out of the path and see if the 'scope will operate as a regular 2465 first.

Raymond

So if there is still suspicion about the effect of the Options,
Then line junction plugs can be put in place on Circuit 5 to eliminate all signals out to
the Options. This will allow operating the 2465DMS as a 2465.

The only other conclusions I have is that whatever is faulty on the 2465 is preventing an activity that allows feedback from
the Option 1 DMM to be displayed on the CRT.

YS
JK

Hi Siggi and Raymond.

NO I do not see anything on the CRT screen form option 01 the DMM.
I also really wondered about this and if it was the causes of the lack of horizontal scanning problem.

Here is what I found.

On page 108, circuit 21 you will see all the inputs from A1 to A20 the Partial Buffer Board.


Here you can see the places that plugs can be put in place to eliminate connections to the A20 Options Buffer Board.


Yours sincerely
Jeff King

Hi Tom,

Really nice to get your message.
Know doubt you will remember me and the confusion I caused about a Varactor being on the on the Control Board on the Power Supply of the HP 8591E.
As it turns out I miss-read the Code for the Diode.

I thank you for your message because I completely agree that the probability of so many resistors (3) changing value is very unlikely.
Normally I would never undertake uncontrolled behavior or measuring very many resistors in circuit.
But I explained how this came about. There are a huge number of 10K resistors in this circuit and most of them measure 10K +-5%
Once 20 years ago I would have done this and by a process of elimination it did help find the fault.
But say 9 times out of 10 (I do no know what the real probability is) once the component was lifted out of circuit it turned out to to have its specified value which was quite different to the in circuit measured value. Hence the in circuit measurement was a useless waste of time.

However if you look at the circuit following the measurement and if the resistor measured has a simple termination this in circuit can help find a faulty complement.
Same as the diode test which usually give 0.5 0.7 volts in one direction and an extremely variable higher value voltage in the other direction.

Any way I have found even more more resistors (measured in circuit) that have very low values and are on input circuit to input pins 2,4,5 to U2408 and so likely do effect the MUX channels #5, 6, 7 values.

Later today I will carefully write up what I have found.
I will process the findings by marking up circuits and putting these online. That way the others reading here will be able to focus on contributing from their significant knowledge their significant observations.
Yours sincerely
Jeff King

On Mon, Apr 1, 2024 at 08:05 PM, JD wrote:

Do you have any specific recommendations for where to begin debugging this
problem?

Did you follow up on Satbeginner's post (#203616)?

Raymond

Do you have any specific recommendations for where to begin debugging this problem?
I've read through that forum post and don't know where to start.
I've already checked components for shorts and haven't found any so far.

My main question involves how I can follow the "Inverter Troubleshooting Procedure" from the service manual.
I believe this is the problem.
From what I understand, I'm supposed to test the PSU outside of the oscilloscope with the dummy load.
Is this correct?
And if so, this means I'm supposed to attach the PSU to mains voltage too?

On Mon, Apr 1, 2024 at 1:26?PM Raymond Domp Frank <hewpatek@...>
wrote:

On Mon, Apr 1, 2024 at 07:09 PM, Raymond Domp Frank wrote:

Maybe the option has an interaction with the triggering.

Answering my own question: Of course there's at least one interaction, and
with the sequencer; the -01 (DVM) displays on-screen, so interleaving!
Do any of the -01's displays work?

I've never seen a 2465DVM, but according to Jeff it has the CTT, which
does route triggers through the option.

On Mon, Apr 1, 2024 at 07:09 PM, Raymond Domp Frank wrote:

Maybe the option has an interaction with the triggering.

Answering my own question: Of course there's at least one interaction, and with the sequencer; the -01 (DVM) displays on-screen, so interleaving!
Do any of the -01's displays work?

Raymond