AnsweredAssumed Answered

HP 54600b Vertical shift not working

Question asked by SimonSpiers on Sep 2, 2011
Latest reply on Aug 9, 2012 by danish

Like • Show 0 Likes0
Comment • 17

Hi, I have saved a scrap HP 54600B scope from work that works perfectly other than no control over vertical trace position on either channels. As I can't find a replacement board, I was looking for any hints ore maybe a schematic of the control board with the position knobs and v/Div switches.
I have run the control test program this to shops both controls unresponsive.
Any help would be received gratefully.

No one else has this question

Outcomes

17 Replies

ksmith Sep 2, 2011 8:46 AM
Mark Correct
Correct Answer
here is a link to the CLIP for the 54600;

http://www.home.agilent.com/agilent/edi ... id=1517718

This is the CLIP, Component Level Information Package, for the 54600A and 54601A oscilloscopes. It includes parts list, part locator, schematics, and block level theory. It does not include power supply schematics.

These pages are scans from a large page format, so you must print the pages and assemble them in order.

Parts may no longer be available from Agilent.

These schematics can also be used to get close to root cause failure on the similar 54600B, 54601B, and 54602B oscilloscopes.
Like • Show 0 Likes0
Actions
SimonSpiers Sep 3, 2011 11:59 PM
Mark Correct
Correct Answer
Thanks Keith, I can't find the circuit for the correct board. What is the description given to the vertical shift controls in the list of components?
Like • Show 0 Likes0
Actions
philippeannet Sep 5, 2011 1:03 AM
Mark Correct
Correct Answer
Have you checked the signal at the encoder level, on the keyboard PCB ? You should see some typical rotary encoder signal (wiki...), these encoders typically have 3 connections to the pcb.
I've got bouncing problems (values are 'unstable' while rotating the knobs) with some knobs on a 54622D, and although the PCB is still orderable, I'm looking to fix it 'the old way'...

Regards
Philippe
Like • Show 0 Likes0
Actions
SimonSpiers Sep 5, 2011 5:57 AM
Mark Correct
Correct Answer
Thanks Philippe, I will take a look. I suspect it's a missing supply to the encoders as both channels are effected and measuring with a DVM shows the encoders going Hi/Lo on rotation unpowered. The only components I can see on the display board are a few SMD transistors. Still trying to find the correct circuit for that board, any idea what the designation is for the encoder on the schematic?
Than you for you assistance.
Simon
Like • Show 0 Likes0
Actions
philippeannet Sep 5, 2011 8:03 AM
Mark Correct
Correct Answer
Hi,

on my 54622D, I'd the chance to have 2 of them, so swapping the front faces (with the keyboard PCB) solved the problem, so I knew where the problem was (OK, now I've got to fix it on the other one, obviously...)
Again, on my model, there are several hex buffers (HC595) on the keyboard PCB, probably 'assembling' the bits from the encoder signal before sending them to the system board. Buffers can typically fail, too... hence my previous question: how does the signal look before (i.e. at the encoder level) and after the hex buffer (this will obviously require an MSO) ?
Are there other knobs behaving incorrectly, are they located in the same PCB area ? etc...

A picture of the PCB could maybe also help clarify the discussion (with the failing knob(s) marked)...

Cheers
Philippe
Like • Show 0 Likes0
Actions
SimonSpiers Sep 5, 2011 11:00 AM
Mark Correct
Correct Answer
Philippe, I will have to borrow A CRO from work, I am close to being out of my depth but determination keeps me going.
I have posted a few pictures, just to confirm the controls.
https://picasaweb.google.com/srspiers/DropBox?authkey=Gv1sRgCKaoiJHU4_3ZXw#5648935688344479346

https://picasaweb.google.com/srspiers/DropBox?authkey=Gv1sRgCKaoiJHU4_3ZXw#5648935688792763234
Like • Show 0 Likes0
Actions
philippeannet Sep 5, 2011 3:36 PM
Mark Correct
Correct Answer
Hi,

I just checked the service manual, it seems that the keyboard PCB has much fewer components than my 54622D (I don't see any buffers, ...), and I couldn't find any mention of the keyboard PCB in the 54600A CLIP neither...

Now... if you want to be realistic, the other option is to check

http://www.etestparts.com/Search.aspx?Mfg=H-P&Page=109

Tucker electronics seem to have one 54600-66502 (the keyboard PCB for your model) in stock for 25 USD, if they really do, this is without any doubt the simplest option...

Regards
Philippe
Like • Show 0 Likes0
Actions
SimonSpiers Sep 6, 2011 12:24 AM
Mark Correct
Correct Answer
I tried to order it, but when I get to the checkout it says they have nil stock
When I looked again the item has been removed from the list, seems strange?
I will email them to find out if they do have it, thanks for spotting it in the first place.
Failing that i'm running out of options I think
Like • Show 0 Likes0
Actions
SimonSpiers Sep 6, 2011 11:24 AM
Mark Correct
Correct Answer
Some good news.
Tucker Electronics contacted me this afternoon saying they had a board with a suspect holdoff control but other than that working. They will post it to me for $10 so a total of $35 is well worth the risk.
I am hoping an encoder swap from my board to the replacement may well fix the holdoff function, although I will never need to use it anyway.
I will let you know the outcome, thanks again for all the time and effort you have spent.
Simon.
Like • Show 0 Likes0
Actions
philippeannet Sep 6, 2011 12:28 PM
Mark Correct
Correct Answer
Good news, indeed. Keep us posted on the outcome. I hope I'll be able to fix my 54622D 'bouncy' knobs as well (PCB is orderable, but costs 350-400$...).

Cheers
Philippe
Like • Show 0 Likes0
Actions
SimonSpiers Sep 6, 2011 1:14 PM
Mark Correct
Correct Answer
If mine are the same I could send you a few?
Like • Show 0 Likes0
Actions
philippeannet Sep 10, 2011 3:31 AM
Mark Correct
Correct Answer
Hi,

let me first check if the problem really lies inside the knobs/encoders (which I don't believe, as at least 4-5 of them behave that way...).
But thanks a lot for the proposal, anyway.

Keep us posted.
Like • Show 0 Likes0
Actions
SimonSpiers Sep 13, 2011 6:19 AM
Mark Correct
Correct Answer
Well the new board arrived today but it is cracked around the Holdoff circutry. I only noticed this after trying it and found along with no Holdoff control one of the two vertical shift controls was not working.
So I desired to have a very close look at the original board. I noticed that the two controls had a common connection that tracks under the flexi that goes to the softkeys under the screen. I simple continuity test showed an open connection to the main ribbon connection. Although I have not tried the board again yet, i'm highly confident that this was the problem as it indeed effected both channels. I have linked the connection and will try again.
The board has clearly suffered a fracture by someone clumping the front panel resulting in a fracture around the torx securings. It might be worth a close look with a good magnifier and buzzer for these hard to spot cracks?
I will let you know the outcome tonight with luck.
Attachments
- repair.jpg108.1 KB
Like • Show 0 Likes0
Actions
SimonSpiers Sep 13, 2011 10:13 AM
Mark Correct
Correct Answer

It works!
Once again thank you Philippe for your help.
If you need any parts I have left please let me know.
All the best.
Simon
Like • Show 0 Likes0
Actions
philippeannet Sep 14, 2011 8:32 AM
Mark Correct
Correct Answer
Hello Simon,

glad to hear you fixed it... I didn't (yet)... That looks really curious, why the heck would an encoder signal be connected to the ribbon going to the screen buttons ????

But indeed, if you don't need one of the keyboard PCBs and/or parts of it anymore (I believe the encoders are the same as on mine), I'd like to buy them from you.
Please contact me at philippe.annet 'at' hotmail.com , I don't think this is the right place for trading...

Regards
Philippe
Like • Show 0 Likes0
Actions
MCDM Feb 20, 2012 1:03 AM
Mark Correct
Correct Answer
Hi, I have found that the digital encoder pots on these digital scopes are just like potentiometers in that the have a wiping contact which goes round 360 deg, like pots they get dirty. I have used an electronics switch cleaner aerosole to spray inside the pots and this cured the problem. Spray into the opening on the pots and turn the pot round half a dozen times, wait a few minutes until the cleaner dries off then turn the scope on and check the operation. I usually removed the front panel to do this operation. I worked at the University of Canterbury in Christchurch New Zealand for 42 years, I ran the undergrad electronics teaching laboratory in the dept of Electronics and Computer Engineering. I had 33 HP 54600A Oscilloscopes in the lab to look after. Don't use an aerosole switch cleaner that has a lubricant in it this will attract dust and dirt to stick to the contacts.
Like • Show 0 Likes0
Actions
danish Aug 9, 2012 5:13 PM
Mark Correct
Correct Answer
I am having a similar issue with both of my 54616C oscilloscopes. The knobs for time and voltage (both channels) on both oscilloscopes generate unstable values when turning the knobs. Two clicks in the same direction may produce one step up followed by one step down. This is really annoying in an otherwise nice piece of equipment. Clearly the rotary encoders are producing unstable values. They are either worn or dirty.

Is it possible to get schematics of the scope?

Is it possible to get manufacturer and part no. information on these rotary encoders?

Thanks
Michael
Like • Show 0 Likes0
Actions

HP 54600b Vertical shift not working

Outcomes

Attachments

Related Content

Recommended Content