HP 54111D dim display

Anyone know if there is a solution to low display brightness on a HP 54111D oscilloscope, like maybe power supply capacitor replacement?

The CRT power supply voltage described in the service manual is puzzlingly-low...only 120 VDC (?!?) The 300V switching supply is described as used for generating the 5V logic supply.

I haven't dug further, but wonder how a color CRT can get by with such a low voltage...or if the CRT module has an integral flyback supply for anode voltage, and repair being module-focused, isn't discussed.

The CRT thought led me to wondering if CRT rejuvenation was an option.

Thanks

Murray

 

[tom]

<murrayatuptowngallery@gmail.com> wrote in message
news:a75540be-6105-45b5-b8b1-cbbc1f723f2b@googlegroups.com...

Anyone know if there is a solution to low display brightness on a HP
54111D oscilloscope, like maybe power supply capacitor replacement?

The CRT power supply voltage described in the service manual is
puzzlingly-low...only 120 VDC (?!?) The 300V switching supply is described
as used for generating the 5V logic supply.

I haven't dug further, but wonder how a color CRT can get by with such a
low voltage...or if the CRT module has an integral flyback supply for
anode voltage, and repair being module-focused, isn't discussed.

The CRT thought led me to wondering if CRT rejuvenation was an option.

Thanks

Murray

Hi Murray,

Do you have the CLIP for the 54111D available? Can you get hold of an ESR
tester? And where abouts are you located - 120 or 240 volt land?

You might go on the HP Yahoo group with the same request.

https://groups.yahoo.com/neo/groups/hp_agilent_equipment/info

It does sound like one of the bulk capacitors has failed if the 300 volts is
that low.

You must get the power supply working first before any other diagnostics are
done.

 

On Tuesday, 2 January 2018 02:18:06 UTC, Murray atuptown wrote:

Anyone know if there is a solution to low display brightness on a HP 54111D oscilloscope, like maybe power supply capacitor replacement?

The CRT power supply voltage described in the service manual is puzzlingly-low...only 120 VDC (?!?) The 300V switching supply is described as used for generating the 5V logic supply.

I haven't dug further, but wonder how a color CRT can get by with such a low voltage...or if the CRT module has an integral flyback supply for anode voltage, and repair being module-focused, isn't discussed.

The CRT thought led me to wondering if CRT rejuvenation was an option.

Thanks

Murray

Never do that. I've seen so many CRTs ruined by rejuving. Increasing heater voltage works better and stays good.

But if your PSU rail is way out of spec, surely it's obvious that CRT emission failure is not likely to be the cause of a dim screen.


NT

 

[Murray atuptown]

Thanks for the replies.

120 v ac

OK on thumbs down to rejuvenation...


I overly simplified the comments on the power supply which was evidently more confusing than accomplishing a summary.

Based on the service manual’s description of how the voltages are produced, I offered two distractions. The overview described the +300 V supply as being used for producing the +5 VDC logic supply and the CRT supply as they name it is only +120 VDC. I didn’t mean to sound like only measures 120 instead of 300.

There was an implied question-how the heck do they run a CRT on 120 VDC? I didn’t (yet) see further explanation of internal functions on the CRT ass’y. I hope it’s an assembly with the ability to produce all support voltages for a CRT.

The diagnosis for CRT problems, as well as other modules, often ends with ‘replace the module’...I get ‘why?’, during the product’s heyday, but that leads to a ‘problem’ period (for wannabe users/restorers) in the future...which is now.

I haven’t measured anything yet...it’s usable, but I’m just snooping around for answers for that day when all the room lights have to be off to see anything. If I’m going to commit space to such a large (and loud!) I’m trying to be proactive.

I’ll read up on what I can measure without service accessories like extender board etc.

Thank you

 

[Murray atuptown]

Tom - not sure CLIP is.
ESR measurements- yes, if I remove parts & take them to someone else (have access).

 

[tom]

"Murray atuptown" <murrayatuptowngallery@gmail.com> wrote in message
news:46113352-8c9e-482c-a5b7-18319465a999@googlegroups.com...

Tom - not sure CLIP is.
ESR measurements- yes, if I remove parts & take them to someone else (have
access).

CLIP is Component Level Information Package. Has all the schematics.

You can buy a copy - pdf - from artekmedia.com

Good quality scans and will not break the bank.

Regards

 

[Murray atuptown]

Tom-
Not sure what CLIP is but I see it discussed on a 54111D thread on Yahoo group-thanks,

I’ll have to lurk...9 years of blocked Yahoo password change access by AT&T and 9 years of grief led me to kill all Yahoo-owned accounts and now AT&T.

Nobody needs to hear that story.

That scope is heavy and obnoxiously loud. Sounds like it’s awaiting clearance for takeoff, but my basement isn’t long enough for a twin-propeller scope to

 

[Murray atuptown]

I think I better restrict my posting to a computer. I’m on my phone now and have no idea where my previous drafts are (I hope not posted...apologies if they are!)

 

On Tuesday, 2 January 2018 18:40:02 UTC, Murray atuptown wrote:

Thanks for the replies.

120 v ac

OK on thumbs down to rejuvenation...


I overly simplified the comments on the power supply which was evidently more confusing than accomplishing a summary.

Based on the service manual’s description of how the voltages are produced, I offered two distractions. The overview described the +300 V supply as being used for producing the +5 VDC logic supply and the CRT supply as they name it is only +120 VDC. I didn’t mean to sound like only measures 120 instead of 300.

There was an implied question-how the heck do they run a CRT on 120 VDC? I didn’t (yet) see further explanation of internal functions on the CRT ass’y. I hope it’s an assembly with the ability to produce all support voltages for a CRT.

The diagnosis for CRT problems, as well as other modules, often ends with ‘replace the module’...I get ‘why?’, during the product’s heyday, but that leads to a ‘problem’ period (for wannabe users/restorers) in the future...which is now.

I haven’t measured anything yet...it’s usable, but I’m just snooping around for answers for that day when all the room lights have to be off to see anything. If I’m going to commit space to such a large (and loud!) I’m trying to be proactive.

I’ll read up on what I can measure without service accessories like extender board etc.

Thank you

There's all manner of reasons why it might be dim, including muck on the screen. Let us know when you've got some facts we can work with.


NT

 

[pfjw@aol.com]

On Monday, January 1, 2018 at 10:24:14 PM UTC-5, tabb...@gmail.com wrote:

> Never do that. I've seen so many CRTs ruined by rejuving. Increasing heater voltage works better and stays good.

Exactly what do you think rejuvenation entails?

Peter Wieck
Melrose Park, PA

 

[Terry Schwartz]

On Thursday, January 4, 2018 at 11:32:37 AM UTC-6, pf...@aol.com wrote:

On Monday, January 1, 2018 at 10:24:14 PM UTC-5, tabb...@gmail.com wrote:

Never do that. I've seen so many CRTs ruined by rejuving. Increasing heater voltage works better and stays good.

Exactly what do you think rejuvenation entails?

Peter Wieck
Melrose Park, PA

Rejuvenation entails *temporarily* running the heater of a tube at a high voltage, the theory being it boils up the thorium from the cathode and exposes fresh surface. It does not entail leaving the filament at a higher voltage in operation.

That was done with so-called CRT "brighteners" which were merely step-up auto-transformers. We've all seen those. They worked, for a while. But they did cause other picture problems, like saturation that made the contrast look eerie. Sometimes you could adjust some of that out.

Any tube tester could be used to "rejuv" a tube or CRT. The process was well known in the shops. The key was always to leave the tube in the tester for some period of time after applying the 2X or 3X heater voltage for a minute or so (hopefully you didn't burn out the heater) and then seeing if the emissions dropped off unacceptably over the next hour. If emissions stayed up, the rejuv "took" and you were good. If not, maybe you sold a new tube.

The problem with CRT rejuvenation was that the excess electron flow eroded the tiny aperture hole in the gun, causing blurry focus, smear, etc, on the face of the CRT. In lots of cases the customer didn't care, he did not want to spring for a new picture tube or new TV.

I often got the job of replacing CRTs after the sets came back in when the rejuvenation didn't hold up, or the customer didn't like the result. I had a knack for doing convergence, which can be one of the most frustrating things to attempt.

 

On Thursday, 4 January 2018 18:55:05 UTC, Terry Schwartz wrote:

On Thursday, January 4, 2018 at 11:32:37 AM UTC-6, pf...@aol.com wrote:
On Monday, January 1, 2018 at 10:24:14 PM UTC-5, tabb...@gmail.com wrote:

Never do that. I've seen so many CRTs ruined by rejuving. Increasing heater voltage works better and stays good.

Exactly what do you think rejuvenation entails?

Peter Wieck
Melrose Park, PA

Rejuvenation entails *temporarily* running the heater of a tube at a high voltage, the theory being it boils up the thorium from the cathode and exposes fresh surface. It does not entail leaving the filament at a higher voltage in operation.

That was done with so-called CRT "brighteners" which were merely step-up auto-transformers. We've all seen those. They worked, for a while. But they did cause other picture problems, like saturation that made the contrast look eerie. Sometimes you could adjust some of that out.

Any tube tester could be used to "rejuv" a tube or CRT. The process was well known in the shops. The key was always to leave the tube in the tester for some period of time after applying the 2X or 3X heater voltage for a minute or so (hopefully you didn't burn out the heater) and then seeing if the emissions dropped off unacceptably over the next hour. If emissions stayed up, the rejuv "took" and you were good. If not, maybe you sold a new tube..

The problem with CRT rejuvenation was that the excess electron flow eroded the tiny aperture hole in the gun, causing blurry focus, smear, etc, on the face of the CRT. In lots of cases the customer didn't care, he did not want to spring for a new picture tube or new TV.

I often got the job of replacing CRTs after the sets came back in when the rejuvenation didn't hold up, or the customer didn't like the result. I had a knack for doing convergence, which can be one of the most frustrating things to attempt.

The rejuve process used in repair shops that I'm familiar with involves a zapping discharge at the same time as applying heater power. Although it fairly often restores emission, it's only a short term result, and as the emission falls again the tube becomes unusable due to severe smearing.

You could say it was a way to ruin customer TVs prompting another purchase while appearing to be helpful.


NT

 

[Terry Schwartz]

The only zapping process I knew of was used when there were shorted elements in the tube. It can't be done with a tube tester -- rather a charged cap. It can restore emissions, depending on what was shorted in the tube. Heater voltage was not required. If it works, the picture is not typically affected. But too often the short cannot be removed. In fact sometimes it welds an intermittent short permanent.

NT: I'm curious as to your understanding of the process you described -- what is the mechanism that would be in play that would increase emissions by zapping it while powered? Emissions are largely a function of the cathode quality (useful remaining life) and unless a zap removes a cathode short, I don't see how it works. Also don't understand how it would contribute to smear, or how the emissions would fall again, unless the cathode was already bad, in which case the emissions would not have recovered at all.

Terry

The rejuve process used in repair shops that I'm familiar with involves a zapping discharge at the same time as applying heater power. Although it fairly often restores emission, it's only a short term result, and as the emission falls again the tube becomes unusable due to severe smearing.

You could say it was a way to ruin customer TVs prompting another purchase while appearing to be helpful.


NT

 

[pfjw@aol.com]

On Friday, January 5, 2018 at 10:01:46 AM UTC-5, Terry Schwartz wrote:

The only zapping process I knew of was used when there were shorted elements in the tube. It can't be done with a tube tester -- rather a charged cap. It can restore emissions, depending on what was shorted in the tube. Heater voltage was not required. If it works, the picture is not typically affected. But too often the short cannot be removed. In fact sometimes it welds an intermittent short permanent.

NT: I'm curious as to your understanding of the process you described -- what is the mechanism that would be in play that would increase emissions by zapping it while powered? Emissions are largely a function of the cathode quality (useful remaining life) and unless a zap removes a cathode short, I don't see how it works. Also don't understand how it would contribute to smear, or how the emissions would fall again, unless the cathode was already bad, in which case the emissions would not have recovered at all.

Terry

Agreed.

I have used charged caps on three occasions (two successful) to restore bad coils in field-coil speakers. I have tried it several times without any success to 'save' open transformer windings.

But, otherwise, 'rejuvenation' for tubes has consisted of over-voltage on the filament for varying periods of time and at varying percentages over what is rated - and not much more. And CRT "Brighteners" increase voltage to the filament in my experience as well. Some by a variable (adjustable) amount as well. Perhaps NT is conflating different processes?

Peter Wieck
Melrose Park, PA

 

[Fox's Mercantile]

On 1/5/18 9:01 AM, Terry Schwartz wrote:

The only zapping process I knew of was used when there were
shorted elements in the tube.

I have a B&K CRT rejuvinator.
I pulled the CRT out of my 1948 Andrea.
It tested just below the Green range.
Hit the zap-o-matic rejuvinator button. It crept up into the
Green range.
The third time it fell all the way down to the bottom of the
Red range.

Well that settles that. Now it's dead instead of very dim.




--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com

 

[Terry Schwartz]

The B&K units and their ilk work exactly that way -- increasing the filament voltage temporarily. They may also change the grid bias during the process - not sure.

Jeff, I suspect your filament is open now.... unfortunate.

 

[Terry Schwartz]

Ok, a quick google search reveals that the CRT specific rejuvenators apply a high potential between the cathode and G1. The resulting arcing exposes some "fresh" cathode surface. I'd have to believe the area would be tiny and therefore the fix very temporary. Seems like it would also be prone to throwing cathode debris at the phosphor surface, aperture mask, or gun aperture. Ugh. But now I understand the ZAP reference.

I was familiar with the older method that used general purpose tube testers with CRT adapters. There was no such capability with those that I was aware of -- only raising the filament voltage to overheat the cathode and boil up the emitting surface. Seems like a better chance of lasting results, if the filament survives the process.

Funny because I owned a B&K 467 for a while, but I don't think I ever tried to use it for rejuvenation.

 

On Friday, 5 January 2018 15:07:39 UTC, pf...@aol.com wrote:

On Friday, January 5, 2018 at 10:01:46 AM UTC-5, Terry Schwartz wrote:

The only zapping process I knew of was used when there were shorted elements in the tube. It can't be done with a tube tester -- rather a charged cap. It can restore emissions, depending on what was shorted in the tube. Heater voltage was not required. If it works, the picture is not typically affected. But too often the short cannot be removed. In fact sometimes it welds an intermittent short permanent.

NT: I'm curious as to your understanding of the process you described -- what is the mechanism that would be in play that would increase emissions by zapping it while powered? Emissions are largely a function of the cathode quality (useful remaining life) and unless a zap removes a cathode short, I don't see how it works. Also don't understand how it would contribute to smear, or how the emissions would fall again, unless the cathode was already bad, in which case the emissions would not have recovered at all.

Terry


Agreed.

I have used charged caps on three occasions (two successful) to restore bad coils in field-coil speakers. I have tried it several times without any success to 'save' open transformer windings.

But, otherwise, 'rejuvenation' for tubes has consisted of over-voltage on the filament for varying periods of time and at varying percentages over what is rated - and not much more. And CRT "Brighteners" increase voltage to the filament in my experience as well. Some by a variable (adjustable) amount as well. Perhaps NT is conflating different processes?

Peter Wieck
Melrose Park, PA

The zapping method was standard in the TV repair industry here while CRTs were in use. It only takes a couple of minutes to do.

http://www.thegleam.com/ke5fx/crt.html
talks about a pulse of grid current much improving emission. How it works is I gather disagreed on, but it does. The problem is the tube declines after not long, giving a smeared picture.


NT

 

On Friday, 5 January 2018 16:31:22 UTC, Terry Schwartz wrote:
> Ok, a quick google search reveals that the CRT specific rejuvenators apply a high potential between the cathode and G1. The resulting arcing exposes some "fresh" cathode surface. I'd have to believe the area would be tiny and therefore the fix very temporary. Seems like it would also be prone to throwing cathode debris at the phosphor surface, aperture mask, or gun aperture. Ugh. But now I understand the ZAP reference.

Temporary, yes. Typically the customer would get a few more months service then it became unusable due to smearing as the emission declined.

Throwing crud about didn't matter unless it created a short, which it could..

Some folk think it cleaned a bit of cathode, some thing it created electrode hotspots that scavenged gas.

I didn't like zapping at all, preferring an extra turn on the loptf heater wind. That gave a much better lasting result and didn't kill tubes.

I was familiar with the older method that used general purpose tube testers with CRT adapters. There was no such capability with those that I was aware of -- only raising the filament voltage to overheat the cathode and boil up the emitting surface. Seems like a better chance of lasting results, if the filament survives the process.

Funny because I owned a B&K 467 for a while, but I don't think I ever tried to use it for rejuvenation.

The worst CRT I ever did had no visible emission at all, and the tube type, sony trinitron, was known for not responding to attempts to improve emission. I gave it a large permanent heater boost after which it had plenty of emission all round. But colour tracking was lousy, although it gave a nice white the intermediate colours didn't match a healthy set at all well. That thing stayed in service many years and kept going. Occasionally it would arc over for a moment, causing green output to go way up for a few minutes then calm down. It was very much an experiment in trying to fix unfixable tubes.


NT

 

[Terry Schwartz]

The Trinitrons were among the hardest CRTs to converge. Those square corners were hell to get right. Some of the Sony chassis had better convergence controls than others. I will say the last CRT Sony I owned, a 35" 220 lb behemoth, had a beautiful picture and spot-on convergence.

The worst CRT I ever did had no visible emission at all, and the tube type, sony trinitron, was known for not responding to attempts to improve emission. I gave it a large permanent heater boost after which it had plenty of emission all round. But colour tracking was lousy, although it gave a nice white the intermediate colours didn't match a healthy set at all well. That thing stayed in service many years and kept going. Occasionally it would arc over for a moment, causing green output to go way up for a few minutes then calm down. It was very much an experiment in trying to fix unfixable tubes.


NT