Re: [HP-Agilent-Keysight-equipment] FS: Two Simpson VOMs!
Some of them have the series number towards the bottom of the meter scale. If you don't see that, look at simpson260.com to help identify the meter by other means.
DaveD
toggle quoted message
Show quoted text
On 3/3/2021 12:23 PM, DaveH52 wrote: I've got a 260 that was my grandfather's, but I don't know how to tell what series it is.
I also haven't looked at it for quite a while. How can I tell the series and manufacture date range?
--
This email has been checked for viruses by Avast antivirus software.
|
|
|
Re: 547 HV Transformer: Bill Schell rewind failed
?Roy, I uploaded pictures to album "?547 HV transformer rewind by Bill Schell". Tell me what you think. Dave Wise Update: Still improving; the intensified part of the trace is now visible at the original intensity setting. ________________________________ From: [email protected] < [email protected]> on behalf of Roy Thistle via groups.io <roy.thistle@...> Sent: Wednesday, March 03, 2021 8:47 AM To: [email protected]Subject: Re: [TekScopes] 547 HV Transformer: Bill Schell rewind failed On Wed, Mar 3, 2021 at 08:06 AM, Dave Wise wrote:
I used to think my Bill Schell transformer was wax-impregnated; now I don't. I
think it's epoxy
Hi Dave: Sorry to hear about your trouble. Perhaps you don't remember... because the last time you handled the transformer was when you installed it... but, how does one mistake wax for epoxy?... or vice versa.
|
Re: 2467B with display anomalies
If Ch3 and Ch4 display the sine wave OK at all vertical positions but Ch1 and Ch2 have similar distortions it could point to a problem with the vertical channel switch hybrid.
There are many others here with wider knowledge than me so you will probably have other suggestions.
It is possible to carefully clean the contacts on the hybrid, replacements tend to be expensive.
Regards,
Roger
|
Re: [HP-Agilent-Keysight-equipment] FS: Two Simpson VOMs!
I've got a 260 that was my grandfather's, but I don't know how to tell what series it is.
I also haven't looked at it for quite a while. How can I tell the series and manufacture date range?
|
Re: TEK465 Horizontal trace
Or Amazon Prime! LOL.
I guess I have a bias against Amazon for such things. Kind of like Radio Shack. But why? I guess as long as I shop carefully and understand I might not be getting the best quality product. Why not?
I see packages of assorted types for cheap. Might be worth having a variety. Thanks for kicking me in a different direction Bob!
Dave
toggle quoted message
Show quoted text
On Wednesday, March 3, 2021, 09:07:18 AM PST, Bob Albert via groups.io <bob91343@...> wrote:
I read somewhere that you get free shipping from DigiKey if you prepay with a check.
Bob
? ? On Wednesday, March 3, 2021, 08:56:35 AM PST, Dave Peterson via groups.io <davidpinsf@...> wrote:
? I have removed Q1226/Q1236 PNPs with no effect. They are not part of the problem. This is also part of why I built the LTspice simulation - to get insight into the current switching going on. I've also tested changing horizontal position, as well as unplugging them entirely at P1200 with no effect.
My finding is that, while yes, the Q1224/Q1234 currents drive the signals through the front end of the amp, it doesn't mean that there aren't corresponding voltage signals. The simulation confirms that an excessive negative bias on the input results in the symptoms observed on the bench. It's not a matter of unobservable currents.
I've been chasing the theory that something is pulling the base of Q1224 down, but sleeping on it allowed me to realize that perhaps the issue isn't a pull down, but a weak pull up. As the PNP Q1098 has a problem, perhaps Q1038 does as well. The node at Q1224 base is a huge common point of a lot of drivers. Q1038/Q1098 are significant contributors. I need to order up some fresh 2N3906's, but it occurred to me that the system is likely designed to have Q1038/Q1098 contributing, even if B-sweep is inactive.
I'm thinking about borrowing Q1226 and Q1236 for Q1038/Q1098. I'm hesitant to take them from my working 465 lest I damage them and kill a second scope. I need to accumulate some components to order so I can mitigate the shipping charges from Mouser. Even 100 2N3906's are less than the $8.00 shipping.
Dave
? ? On Wednesday, March 3, 2021, 02:47:36 AM PST, G?ran Krusell <mc1648pp@...> wrote:
Hi Dave, if you remove Q1038 and Q1098, set POSITION pots to center position, sweep through the TIME/DIV positions, no X AXIS signal, what do you have at Q1224 base?
Measure and calculate the current through R1223, 806 ohm. Calculate the various currents going to/from Q1224 base. Does anything make sense?
G?ran
|
Re: TEK465 Horizontal trace
I read somewhere that you get free shipping from DigiKey if you prepay with a check.
Bob
toggle quoted message
Show quoted text
On Wednesday, March 3, 2021, 08:56:35 AM PST, Dave Peterson via groups.io <davidpinsf@...> wrote:
I have removed Q1226/Q1236 PNPs with no effect. They are not part of the problem. This is also part of why I built the LTspice simulation - to get insight into the current switching going on. I've also tested changing horizontal position, as well as unplugging them entirely at P1200 with no effect.
My finding is that, while yes, the Q1224/Q1234 currents drive the signals through the front end of the amp, it doesn't mean that there aren't corresponding voltage signals. The simulation confirms that an excessive negative bias on the input results in the symptoms observed on the bench. It's not a matter of unobservable currents.
I've been chasing the theory that something is pulling the base of Q1224 down, but sleeping on it allowed me to realize that perhaps the issue isn't a pull down, but a weak pull up. As the PNP Q1098 has a problem, perhaps Q1038 does as well. The node at Q1224 base is a huge common point of a lot of drivers. Q1038/Q1098 are significant contributors. I need to order up some fresh 2N3906's, but it occurred to me that the system is likely designed to have Q1038/Q1098 contributing, even if B-sweep is inactive.
I'm thinking about borrowing Q1226 and Q1236 for Q1038/Q1098. I'm hesitant to take them from my working 465 lest I damage them and kill a second scope. I need to accumulate some components to order so I can mitigate the shipping charges from Mouser. Even 100 2N3906's are less than the $8.00 shipping.
Dave
? ? On Wednesday, March 3, 2021, 02:47:36 AM PST, G?ran Krusell <mc1648pp@...> wrote:
Hi Dave, if you remove Q1038 and Q1098, set POSITION pots to center position, sweep through the TIME/DIV positions, no X AXIS signal, what do you have at Q1224 base?
Measure and calculate the current through R1223, 806 ohm. Calculate the various currents going to/from Q1224 base. Does anything make sense?
G?ran
|
Re: TEK465 Horizontal trace
I have removed Q1226/Q1236 PNPs with no effect. They are not part of the problem. This is also part of why I built the LTspice simulation - to get insight into the current switching going on. I've also tested changing horizontal position, as well as unplugging them entirely at P1200 with no effect.
My finding is that, while yes, the Q1224/Q1234 currents drive the signals through the front end of the amp, it doesn't mean that there aren't corresponding voltage signals. The simulation confirms that an excessive negative bias on the input results in the symptoms observed on the bench. It's not a matter of unobservable currents.
I've been chasing the theory that something is pulling the base of Q1224 down, but sleeping on it allowed me to realize that perhaps the issue isn't a pull down, but a weak pull up. As the PNP Q1098 has a problem, perhaps Q1038 does as well. The node at Q1224 base is a huge common point of a lot of drivers. Q1038/Q1098 are significant contributors. I need to order up some fresh 2N3906's, but it occurred to me that the system is likely designed to have Q1038/Q1098 contributing, even if B-sweep is inactive.
I'm thinking about borrowing Q1226 and Q1236 for Q1038/Q1098. I'm hesitant to take them from my working 465 lest I damage them and kill a second scope. I need to accumulate some components to order so I can mitigate the shipping charges from Mouser. Even 100 2N3906's are less than the $8.00 shipping.
Dave
toggle quoted message
Show quoted text
On Wednesday, March 3, 2021, 02:47:36 AM PST, G?ran Krusell <mc1648pp@...> wrote:
Hi Dave, if you remove Q1038 and Q1098, set POSITION pots to center position, sweep through the TIME/DIV positions, no X AXIS signal, what do you have at Q1224 base?
Measure and calculate the current through R1223, 806 ohm. Calculate the various currents going to/from Q1224 base. Does anything make sense?
G?ran
|
Re: 547 HV Transformer: Bill Schell rewind failed
On Wed, Mar 3, 2021 at 08:06 AM, Dave Wise wrote:
I used to think my Bill Schell transformer was wax-impregnated; now I don't. I
think it's epoxy
Hi Dave: Sorry to hear about your trouble. Perhaps you don't remember... because the last time you handled the transformer was when you installed it... but, how does one mistake wax for epoxy?... or vice versa.
|
Re: 547 HV Transformer: Bill Schell rewind failed
Talked to Bill Schell a couple of decades ago about taking over and buying his setup from him.Instead, I ended up contributing what I had learned to Chuck Harris' efforts.My recollection is that Bill did NOT use epoxy, but potted in straight beeswax.Chuck and I discussed this at length, considering beeswax vs paraffin.Chuck tested 10 mixtures and found best dimensional stability with a mixture of both.
I suspect incomplete impregnation or less than ideal coil pack resulting from his scatter winding method.Never heard of a Schell rewind failing until now.Bernie Schroder
toggle quoted message
Show quoted text
-----Original Message----- From: Dave Wise <david_wise@...> To: [email protected] < [email protected]> Sent: Wed, Mar 3, 2021 8:06 am Subject: [TekScopes] 547 HV Transformer: Bill Schell rewind failed In 2017, my 547 with Bill Schell HV transformer (installed around 2000) was working.? It has sat unused in a dry basement since then. Today, in March 2021, that transformer exhibits the same thermal runaway symptom as the original Tek part.? (Fades out in ten minutes.) Hours of warming have not restored it.? I don't think it will.? I used to think my Bill Schell transformer was wax-impregnated; now I don't.? I think it's epoxy, and like Tek's, it has gone bad. I hope other Bill Schell customers can check in with their status. I have an ace in the hole.? In my drawer is... a 2010 Chuck Harris rewind.? To ice the cake, it's the one Stan Griffiths was evaluating - he gave it to me after he was done with it.? I'll install it soon. Dave Wise
|
Re: 3T77 tunnel diodes (again)
In hindsight I realize that the waveform at TP121 will also depend on how fast the feedback will react on the new sample.
That's probably why TP121 waveforms for the S-1 and S-2 are shown separately in the calibration section.
Pff.. long ago that I did similar measurement in 3S76 and 3S1.
Albert
toggle quoted message
Show quoted text
On Wed, Mar 3, 2021 at 02:04 PM, Albert Otten wrote:
Hi Charles,
It would be interesting to look at the S-1 (or S-2) output at pin 4.
Accessible at TP121 <1> of your 3S2. This happens to be also TP121 in the
7S11. You don't need a time base in the 561A.
At the first sample after a jump of your input signal the S-1 responds at the
full jump voltage. That is because the feed-back voltage stabilized at the
level before the jump (with input frequency up to 10 kHz or so). At the
following samples the response will be less and less.
The response at TP121 depends only on the behavior of the S-1 and the quality
of the strobe pulses from the 3S2.
I added 2 pictures to your 3S2 album. Note that triggering on the TP121 signal
is not that easy. You will probably see a mixture of of responses with
different amplitudes.
Albert
|
Re: 547 HV Transformer: Bill Schell rewind failed
?Update. I retract my doom and gloom. Further warming seems to be restoring it after all. I simply left the scope running, with the intensity control at a safe position. I don't have a visible trace yet but as time passes I have to advance the control less and less to get one. This data point corroborates the theory of moisture-ingress or other reversible reaction. I will report back later. Dave Wise Note: This 547 has the 6AU5 screen grid voltage limit mod. ________________________________ From: [email protected] < [email protected]> on behalf of Dave Wise via groups.io <david_wise@...> Sent: Wednesday, March 03, 2021 8:06 AM To: [email protected]Subject: [TekScopes] 547 HV Transformer: Bill Schell rewind failed In 2017, my 547 with Bill Schell HV transformer (installed around 2000) was working. It has sat unused in a dry basement since then. Today, in March 2021, that transformer exhibits the same thermal runaway symptom as the original Tek part. (Fades out in ten minutes.) Hours of warming have not restored it. I don't think it will. I used to think my Bill Schell transformer was wax-impregnated; now I don't. I think it's epoxy, and like Tek's, it has gone bad. I hope other Bill Schell customers can check in with their status. I have an ace in the hole. In my drawer is... a 2010 Chuck Harris rewind. To ice the cake, it's the one Stan Griffiths was evaluating - he gave it to me after he was done with it. I'll install it soon. Dave Wise
|
2467B with display anomalies
My 2467B has developed several problems with the display; I'm not sure if they're related or not but they started about the same time.
The first is if I put a sine wave on the screen and center it, it shows considerable distortion. If I move it well above or just below the center line it displays clean.
Secondly, as soon as a signal is applied the upper and lower readout will oscillate like a sine wave is passing through them. Still readable but definitely not proper.
It's my favorite scope; I'd be grateful for any suggestions on where to start looking.
John
|
Re: [Tek 485] No intensity control
On Wed, Mar 3, 2021 at 07:00 AM, Ozan wrote: Are you still seeing ~ -61mV as before at collector of Q1548 with no dot on
the screen? With no dot on the screen base of Q1544 should be closer to 6V. If
base is still at ~1V please check R1536 for drift to >2.2M, CR1539 for leaky
diode, Q1544 for low hFE. I see ~42mV at collector of Q1548, no dot on screen in XY Mode. Base of Q1544 is at ~1V, HFE measured with a TC1 tester : 214 CR1539 is ok : ~.6V and 0L R1536 measured in circuit gives : 300kohm and 100kohm (when inverting the test leads of DMM).
|
Re: TDS3064B "ripple" on calibrator signal
David,
In my limited experience, I have seen this behavior before, but it's always been due to probe issues. Usually with a long ground lead. Readjusting the probe and ground for better connections at both ends has solved it for me. Hopefully that's all it is in your case. And sorry I don't have a better answer.
Dave
toggle quoted message
Show quoted text
On Wednesday, March 3, 2021, 05:57:33 AM PST, David C. Partridge <david.partridge@...> wrote:
Running an up-hacked TDS3014B, and am seeing small amount of what I'll call
"ripple" on the top of the calibrator signal (i.e. the 5V part of the signal
- the 0V end is relatively stable by comparison).? By "ripple" I mean it's
dancing up and down quite slowly (2Hz?) by about 1/2 a trace width, and the
Ch1 Max value switches between 5.16V and 5.20V.
Has anyone here seen this sort of behaviour before?
Thanks
David
|
547 HV Transformer: Bill Schell rewind failed
In 2017, my 547 with Bill Schell HV transformer (installed around 2000) was working. It has sat unused in a dry basement since then.
Today, in March 2021, that transformer exhibits the same thermal runaway symptom as the original Tek part. (Fades out in ten minutes.)
Hours of warming have not restored it. I don't think it will. I used to think my Bill Schell transformer was wax-impregnated; now I don't. I think it's epoxy, and like Tek's, it has gone bad.
I hope other Bill Schell customers can check in with their status.
I have an ace in the hole. In my drawer is... a 2010 Chuck Harris rewind. To ice the cake, it's the one Stan Griffiths was evaluating - he gave it to me after he was done with it. I'll install it soon.
Dave Wise
|
Re: International Orders for Peter Keller's book were MAILED TODAY
I'm a newbie who joined this group recently and discovered the overwhelming
interest in Peter Keller's book. I'm curious about what appears to be the
"bible" of CRTs, but I missed the boat on ordering.
So I logged on to my local public library branch and was able to request a
copy from the UC San Diego Library. I suggest that if others would like to
"try before you buy" you might consider heading to your local library to see
if they can find a copy for you.
Paul Humel
|
Re: [Tek 485] No intensity control
I used - as someone (Mark ?) suggested - 1N4937.
Looks OK. I will let DC restorer experts to chime in. Are you still seeing ~ -61mV as before at collector of Q1548 with no dot on
the screen? With no dot on the screen base of Q1544 should be closer to 6V. If
base is still at ~1V please check R1536 for drift to >2.2M, CR1539 for leaky
diode, Q1544 for low hFE. Will check later on this afternoon and keep you posted. I guess it makes no
sense to check R1536 in circuit ?
Jose
This check is only needed if you are seeing ~1V instead of ~6V at the base of Q1544 with no beam. You need to lift one leg of R1536 to measure, 2.2M will be swamped out with any other connection. With no beam R1536 should be able to pull base of Q1544 but it only supplies few uA so a small leakage at base node is all it takes to turn off the beam. It could be any of the components at base node of Q1544 (even Q1544 itself). Outside XY or slow timebase modes R1534 is providing extra current. Ozan
|
Re: [Tek 485] No intensity control
On Wed, Mar 3, 2021 at 07:00 AM, Ozan wrote: On DC RESTORER side : I changed all the diodes that are in the High Voltage Please see Tom's message for another DC restorer issue, these diodes need to
have fast reverse recovery time in case you used a different diode than the
original.
I used - as someone (Mark ?) suggested - 1N4937. for Time Div <20ms. For 50ms, .5s, .2s and .1s as well as the X-Y mode I do
not even get a trace ! (and that's new). Is it new meaning it happened last few days, or new meaning that new for this
scope from the beginning?
It happened a few days ago. I do not see any dot when in X-Y mode or in lowest Time/div positions => This
seems to point out something wrong elsewhere. Are you still seeing ~ -61mV as before at collector of Q1548 with no dot on
the screen? With no dot on the screen base of Q1544 should be closer to 6V. If
base is still at ~1V please check R1536 for drift to >2.2M, CR1539 for leaky
diode, Q1544 for low hFE.
Will check later on this afternoon and keep you posted. I guess it makes no sense to check R1536 in circuit ? Jose
|
Re: [Tek 485] No intensity control
On DC RESTORER side : I changed all the diodes that are in the High Voltage Please see Tom's message for another DC restorer issue, these diodes need to have fast reverse recovery time in case you used a different diode than the original. for Time Div <20ms. For 50ms, .5s, .2s and .1s as well as the X-Y mode I do
not even get a trace ! (and that's new). Is it new meaning it happened last few days, or new meaning that new for this scope from the beginning? I do not see any dot when in X-Y mode or in lowest Time/div positions => This
seems to point out something wrong elsewhere. Are you still seeing ~ -61mV as before at collector of Q1548 with no dot on the screen? With no dot on the screen base of Q1544 should be closer to 6V. If base is still at ~1V please check R1536 for drift to >2.2M, CR1539 for leaky diode, Q1544 for low hFE. Ozan
|
DaveH52
Dave Peterson