开云体育

Hello all,

I had a perfectly functioning 2467B scope (1989 vintage). After reading about possible loss of calibration data due to the NVRAM battery dying, I decided to put in a new battery (mine is the older version, below 50000 serial #) which has the battery separate from the NVRAM. The battery had a date code of 2689, so the battery is 35 years old. I did hook up a backup battery before removing the Lithium battery and confirmed that pin 28 of the RAM chip had at least 3 V on it from the backup battery after removal of the original battery. After putting in the new replacement battery, I also changed out the 4 electrolytic capacitors on the A5 board. When I put the scope back together and fired her up, I got the dreaded " Test 04 Fail 13" message indicating corrupted or lost calibration data. Not sure how this happened since I hooked up a backup battery before removing the original battery. So, the very thing I was hoping to prevent happened by my being proactive!

Before doing all this, I had made a copy of the RAM contents by running through the Exercise 02 option, so I have the original calibration data available. My question is: how to write this data to the RAM? (my scope does not have the GPIB option).

I look forward to your suggestions and hope to get this fine scope functioning again!

Replied to both Nick and Rubens about purchase of cables. Hope you got my private messages?

Craig

Thank you Roger.

I'll double check the low voltage supplies. I did check the voltages with a DVM, but did not check for ripple.

I've had the scope for a while, and it did work properly when I acquired it. A few years ago while I was using it the vertical stopped responding. I turned it off, put the scope away and have since been using a 7603. I decided to see if I could get the 7904A working again, and seem to be in over my head!

I'll second Ozan's helpfulness with this sort of thing. He has helped me a few times isolate a problem like that whcih I'm pretty sure I would not have found on my own. Glad you have something going and hope the correct transistors will fix the rest of the issues with this.

Barry - N4BUQ

Hi all,

A little off topic, but I'm getting desperate....
I'm on the hunt for a copy of the Adjustment Program to enable calibration of the HP/Agilent 4263B LCR meter, part number 04263-65005
It's just a BASIC program but Keysight Japan have given me a solid NOPE for any support regarding this instrument.
I've also emailed a few service/cal houses and they all have turned up dry too.

If anyone has this software, I'd greatly appreciate a copy! I want to calibrate my unit and also wouldn't mind having a go at porting it to Python and open-sourcing it to allow for easier use on modern PC's...


Thanks!
Jared

The HV supply is in the right-hand-rear of the scope and the HV line runs from there to the front of the scope around again to the side of the CRT. If that cable is arcing, it might sound like it's coming from the left-hand side.

If you still hear the arcing, you could remove the top covers and power the scope in a dark room. That might help show where it's coming from.

Barry - N4BUQ

Sorry, just noticed the 'no readout' in your post.

If you also have a problem with lack of intensity control then checking all the low voltage supplies moves to the top of the list.

Roger

My beloved 7704A started arcing internally the other day, At least that's what it sounded like. It seems to be coming from the LH front side next to the CRT. Looking at the explosion diagram, this corresponds to the HT section. Also the display has shrunk by 50% in both directions., so e.g. the readouts are at 25%/75% of height instead of 100%/100%.

Being more than reluctant to enter into an HT section untutored, I am wondering if there are any hints as to what specifically I should be looking for. Scope has been working flawlessly for 15 year, and the problem occurs in both A and B/V and H, so it isn't a plugin.

TIA

EJP

Do you get the readout displayed correctly at top and bottom of the display? That would imply the vertical amplifier was basically OK and you might need to look for a fault in the vertical switching.

Is the scope new to you? If so try exercising the mainframe vertical mode switches several times, they may need cleaning and last but not least check that the vertical deflection plates are connected!

Roger

Thanks to Ozan for helping off-list with some additional measurement advice and insight on expected values. I continue to be amazed at what some of you can understand from a schematic.

He suggested replacing Q309/Q317 in the trigger pulse generator with the pair from my working 7B70, and that did the trick: stable waveform with sine/triangle/square, and controls work as expected.

I had previously tried replacing them individually with a 2N3906 (one of the few PNP transistors I have on hand), with no luck. Replacing both Q309 and Q317 with 2N3906s actually shows a waveform instead of a blank screen, but it stutters so I've ordered some 151-0220-00 replacements.

Adam

Hello.

My 7904A has several problems.
With a time base in either horizontal slot, I am getting a horizontally adjustable trace in the middle of the screen. I am getting a good, adjustable sawtooth signal on the front panel sawtooth output. Horizontal seeks to be working fine.
With a known good vertical plug-in in a vertical slot, the trace will not adjust up or down. At first, turning the position control did affect the triggering somewhat, but after a few minutes, the position control had no affect on triggering. I am using a 7A26--regardless whether it is in alt or chop there is only one trace and the position controls have no affect on the trace. Moving the plug-in between the two vertical slots makes no difference.
The trace remains in the middle of the screen with the beamfinder pressed.
The trace focuses, but the intensity controls have no affect on A or B. The intensity controls are at minimum and the trace is normal brightness, but the controls do not change the brightness at all.
There is no read out.

Any thoughts on what may be the cause of no vertical trace movement, and/or which of these issues may be related to one another and how I might be able to tackle them would be greatly appreciated.

Thanks.
Dave

Please let me know if anyone got stock Cheers

Nick,
I have several available some used and new. If you want to contact me online with your needs.
electronixtoolbox@...

Any of these cables still around?. Please let me know if anyone got stock Cheers

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

Raymond

Yes, I followed up on that post to no avail.

On Sun, Mar 31, 2024 at 04:09 AM, Adam R. Maxwell wrote:

With 7A26 on 0.5V/div, EXT trigger displays a stable waveform with a 1.25 Vpp
square wave. INT trigger displays a stable waveform with 2Vpp from the FG502.

With the 7A26 on 1V/div, EXT works with 1.25Vpp, but INT requires 4Vpp to
display the waveform. I do not understand this interaction with the vertical
amplifier, but the INT trigger only gives a stable waveform if the signal is
4x the vertical V/div setting. EXT only requires 1.25 Vpp.

Adam,
In the 7A26 all attenuation is done is by the input attenuators. Hence after that the same signal is sent to the Vertical amp chain and the trigger amp chain. This means that the signal amplitude at the CRT is important for triggering. In both cases you mentioned here the amplitudes at the CRT are the same.

Albert

The plug-ins have been spoken for. Sorry. The following manuals are still available and they are -- as described -- exceedingly clean. Not new, of course, but with bright pages and not dog-eared.

7D13 Digital Multimeter
070-1096-00
$15 plus S&H

7D15 Counter/Timer
070-1433-00
$15 plus S&H

7A26 Dual Trace Amplifier (two copies)
070-1484-00
$15 plus S&H each

7B92 Dual Time Base
070-1751-00
$15 plus S&H
--
William, k6whp
"A friend told me to cheer up, things could be worse.
So I cheered up and, sure enough, things got worse!"

Is the silk-screen of the electrolytic capacitors C2354, C2224 and C2223 on the A5 board of the Tek 2465 oscilloscope correct?

A while ago my 7704A gave up the ghost and ascended heavenward and I am left with a few articles and manuals that I wish to go to a good home. Firstly, the following plug-ins which are priced nominally. They were working when last used but I am pricing them as "for parts or repair" because I need the shelf space:

Tek 7A16A Amplifier.
$10 plus S&H

Tek 7B50 Delaying Time Base.
$20 plus S&H

Tek 7A22 Differential Amplifier
$20 plus S&H

Also I have these manuals which are all clean and in good shape for their age. Pages are bright and very very, very minimally dog-eared:

7704A Service Manual
070-1260-00
7704A Operator Manual
070-1402-00
$25 plus S&H for both

7A22 Differential Amplifier
070-0931-00
$15 plus S&H for both

7D13 Digital Multimeter
070-1096-00
$15 plus S&H for both

7D15 Counter/Timer
070-1433-00
$15 plus S&H for both

7D26 Digital Multimeter x 2
070-1484-00
$15 plus S&H for both

7B92 Dual Time Base
070-1751-00
$15 plus S&H

Conditions and special pricing:

o Shipping CONUS only.

o For anyone who wants all three of the plug-ins, they can be had for $35 plus S&H.

o For anyone who wants all of the manuals, they can be had for $80 including S&H.
Note that the all will fit into a USPS Priority Mail large flat rate box which costs $25 for shipping. So, you send me $80 and I sent you all the manuals

o I will accept your personal check or I prefer a USPS MO. NO PAYPAL!

o Special preference will be given to the first person who wants to by all the manuals. (Hate to break up the set, as it were.) If you want a manual, I will ship via USPS Priority Mail flat rate envelope.

I will be happy to send pictures if I don't get flooded with requests.

..thanks in advance.
--
William, k6whp
"A friend told me to cheer up, things could be worse.
So I cheered up and, sure enough, things got worse!"

I also agree too with Raymond, Tom and Siggi that my logic of trying to change resistors on the A5 was completely faulty, a total waste of time and will not be pursued.

Thank you again for your futher suggestions to trace and track all in puts to U170.

Like you I had earlier on come to the conclusion that changing all inputs to HRR to Sequencer was the next sensible course of action to eliminating a region of the circuit that was more likely to hold the fault.

Will now more slowly work through this.

YS
Jeff King

Excuse me, what I considered the replacement for the CR1070 is actually the W1060. In any case, the CR1070 diode is not present.