Author Topic: Test Equipment Anonymous (TEA) group therapy thread  (Read 1725267 times)

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Online med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32850 on: June 09, 2019, 12:35:04 am »
And the results. Not as good as I had hoped. The trace is only marginally brighter but acceptable. The focus is good. But the gain both vertical and horizontal still changes with the intensity. So we have a somewhat tired CRT. I'm not going to pursue a replacement as long as it doesn't get worse in the short term. When I calibrate the vertical the assumption will be full intensity.

What CRT is that?

Quote
Left to do: Replace the caps on the vertical and horizontal boards. Then calibrate and check compensation. Will do that tomorrow. After that this project is a wrap.   :-+ :-+

I have no experience in repairing these, but I have a NOS El-Menco 5DEP1 and a used Toshiba 130BHB31, around which, if I do not procrastinate any more, I intend to design and build an old-school scope. For the time being I've been studying circuits and analog scope technology.

Could it be something related to the caps you haven't replaced yet? The circuits I've analyzed up to now show the HV supply to be independent from the amp supply, but in some scopes current flows from the amp supply to the HV supply via the astig plate and the cathode. I was wondering if changing the intensity places a heavier load to the amp supply making it to sag.

The only part number I have for the CRT is the RCA stock number in the manual who is totally useless. I would have to pull the CRT to see what number is stamped on it. It's a 7 inch CRT so it would be something like 7XXX.

The HV supply is essentially independent of the balance of the supply except for a common power transformer. I'm seeing an INCREASE in CRT gain as the intensity is turned up. If the turning up the intensity placed a greater load on the overall circuit I would see the opposite effect. So clearly the gain within the CRT itself increases with greater intensity. It's not a lot but you can see it. And it's probably a characteristic of the design so I'm going to leave it. 
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Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32851 on: June 09, 2019, 12:37:40 am »
@Med, that HV supply rebuild looks really neat, looks as if it has just come out of the factory, brilliant job  :-+

Yes, and don't think I didn't notice that poor, tortured soldering iron cord he made SURE was JUST onscreen JUST to torment me.  :-DD

mnem
Well played... well played.  :clap:
« Last Edit: July 07, 2019, 03:23:10 am by mnementh »
 

Offline tautech

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32852 on: June 09, 2019, 12:43:09 am »
Check threads from GK as he’s built a couple.
https://www.eevblog.com/forum/projects/oscilloscope-under-construction/

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Glen does some really neat shit, spend some time hunting out his threads.  ;)
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Online med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32853 on: June 09, 2019, 12:57:32 am »
@Med, that HV supply rebuild looks really neat, looks as if it has just come out of the factory, brilliant job  :-+

Yes, and don't think I didn't notice that poor, tortured soldering iron cord he made SURE was JUST onscreen JUST to torment me.  :-DD

mnem
Well played... well played.  :clap:

I have not yet begun to torment you. This is torment.  >:D >:D :-DD :-DD




For the record. It is an Ungar Imperial and it's been my go to soldering iron for nearly 40 years. Even has the original tip which unfortunately is welded on and won't come off. So if the tip gives out I'll have to scrap the entire iron. Wouldn't THAT make you happy?  :P :P :P :-DD
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Online beanflying

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32854 on: June 09, 2019, 01:10:30 am »
Kwality items  :-DD

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Offline Housedad

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32855 on: June 09, 2019, 01:33:15 am »
My $22 ebay TDR 1502 showed up today. As expected, it won't power up.  Unexpected: other than a small stress crack in one side of the case,

Methylene chloride will sort that out: it "melts" the plastic and has superb creep. But it is a carcinogen, so be careful.


It probably is, but you will go slowly mad trying to understand it. It woks iff there is a functional battery (or simulation thereof).

Stuff 12V up the battery compartment, and look at the C6341/C6246 spewing acid over the PCB tracks, then go from there.




Somehow, I knew someone would have the answers here.  ;D

Thanks!  The only challenge is fitting my big hand in the relatively small compartment normally inhabited by the battery. On the 1503, I opened the case, so getting 12VDC to the posts was easy. I am going to put the NiCad pack on my bench supply and see if they'll take a charge. If I can get them up to 10V, that will give me enough time to see if the CRT lights up.

And, of course, encourage some of those bastard tantalum caps to erupt.   :-DD
Whoa, wait a minute.  Before you Throw the bath water out, cycle the batteries to see if it is just a memory problem.  Nicads develop a "memory" if they are discharged to the same voltage over and over.  The memory is they begin to act as if the repeated discharge before recharge voltage is the new ground and they stop giving power.

The trick is to completely discharged them through a resistor to zero and then charge them completely, then wash and recycle. It takes several to many cycles of this to erase the memory in a nicad bank.  Sure, they could be toast from use or age, but it won't hurt to try first.  Read more about cycling nicad batteries in various radio control forums or solar panel forums.

Edit:  here is a decent link https://batteryuniversity.com/learn/article/how_to_restore_nickel_based_batteries
« Last Edit: June 09, 2019, 01:54:33 am by Housedad »
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Online beanflying

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32856 on: June 09, 2019, 01:51:50 am »
And sometimes NiCads are just dead. If they won't hold 'any' charge/voltage they are going to be dead and cycling won't help. The memory issue is a capacity thing and not a voltage thing, generally NiCads would still come up to voltage when charged but the discharge curve and capacity was rubbish. Find your local heavy metal recycling bin and place them in it.

Replace with NiMh and at worst tweak the internal charge circuit depending on how it was being done.
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Offline bitseeker

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32857 on: June 09, 2019, 02:02:45 am »
Bless me Father for I have sinned, and it has been some time since my last confession  ;D

After getting an ESR meter adapter PCB from EEVBlog user Jay_Diddy_B I find that it has a 27 mV offset on the output. This is designed to be zeroed out using the 'relative' function on a multimeter but neither my handheld or bench multimeter have this function. Tonight I placed an order for two new meters, one for the bench and one for my toolkit so I can use the ESR adapter properly  :-[

Math vs. TEA — TEA wins. :-DD
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Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32858 on: June 09, 2019, 04:48:01 am »
@Med, that HV supply rebuild looks really neat, looks as if it has just come out of the factory, brilliant job  :-+

Yes, and don't think I didn't notice that poor, tortured soldering iron cord he made SURE was JUST onscreen JUST to torment me.  :-DD

mnem
Well played... well played.  :clap:
      I have not yet begun to torment you. This is torment.  >:D >:D :-DD :-DD

For the record. It is an Ungar Imperial and it's been my go to soldering iron for nearly 40 years. Even has the original tip which unfortunately is welded on and won't come off. So if the tip gives out I'll have to scrap the entire iron. Wouldn't THAT make you happy?  :P :P :P :-DD

*CRINGE*   

Oh yeah?!? Well... take THAT!!!
      And THAT!!!    Duck that crusty flux residue; it can stay there till hell freezes over! :-DD


Just doing something productive and fix-ily for a change.  ;)        

The car battery "overnight" trickle charger I knocked together out of an old "bump-in-a-wire" power pack a decade or so ago finally died so I couldn't resurrect it; the shell broke from brittleness and the innermost filament from the primary got broken off flush with the surface of the winding. Fortunately, I've been keeping this one in the bottom of the power pack bin for just this day; here I'm "de-filtering" the rectifier section because the pulsing DC charges lead-acid batteries better. There's some argument over whether half-wave or full-wave rectification is better; at these charge rates I've never seen a noticeable different between half-wave 60Hz vs 120Hz for full-wave. 

This one's a little hot; it produces approx 12.05V with a 2A load before the filter is removed and 16.2V P-P no-load after. I usually prefer more like 12V@1.5A & 15.5-15.8V P-P for a trickle charge, but that just means I can't plug it in and forget it for days; I have a smart float charger for that anyways.

It's nice to use my workbench for something other than sorting & triage for a change.  ;D

mnem
*toddles off to ded*
« Last Edit: June 09, 2019, 04:53:04 am by mnementh »
 

Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32859 on: June 09, 2019, 05:01:42 am »
Kwality items  :-DD


Don't make me fling a cow at you, barista!!!  :-DD

mnem
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« Last Edit: June 09, 2019, 05:03:26 am by mnementh »
 

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32860 on: June 09, 2019, 05:13:55 am »
Wonder if this would make a good cage coffin for a very small ex parrot  >:D Glued up, coating of Orange oil for finish just need to add some felt lining now.

Have to run, I have some TEA both cooling down and some warming up to play with  :-+
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Offline bitseeker

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32861 on: June 09, 2019, 06:56:00 am »
This evening I started getting set up to take some logs of the USA Cal Club voltage and resistance references. It's a new setup, so a little slow going getting familiar with all the bits.

The bg7tbl noise source arrived. I'll explore that after I get the vrefs set up and logging.

Nice parrot coffin, bean. John Cleese would be proud.
« Last Edit: June 09, 2019, 06:57:54 am by bitseeker »
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Offline tggzzz

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32862 on: June 09, 2019, 07:52:18 am »
Do I have a snowball's chance in hell of getting these batteries to charge?

Not sure. You can stuff 0.1C current into them indefinitely, but I would start much lower. A current limited power supply is sufficient; say 15V/40mA.

Oh yes, I forgot.

RTFM is required. In this case the clause that states they must be recharged once a month. Why? Because even when switched off there is a current drain of 1mA plus another 1mA for a chart recorder, and that slowly discharges the cells and then reverse charges the weakest cell.

Personally I just store the battery pack out of the case, so even if the weakest cell completely self discharges itself, the others won't reverse charge it.

You can use NiMH, but divide the stated capacity by two, and only trickle charge at 0.01C.
« Last Edit: June 09, 2019, 07:59:36 am by tggzzz »
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Offline tggzzz

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32863 on: June 09, 2019, 07:59:02 am »
Whoa, wait a minute.  Before you Throw the bath water out, cycle the batteries to see if it is just a memory problem.  Nicads develop a "memory" if they are discharged to the same voltage over and over.  The memory is they begin to act as if the repeated discharge before recharge voltage is the new ground and they stop giving power.

The trick is to completely discharged them through a resistor to zero and then charge them completely, then wash and recycle. It takes several to many cycles of this to erase the memory in a nicad bank.  Sure, they could be toast from use or age, but it won't hurt to try first.  Read more about cycling nicad batteries in various radio control forums or solar panel forums.

Many people claim the memory effect only occurs in special circumstances, since it requires repeated discharging to the same depth.

OTOH, while discharging NiCd (and other) cells with a resistor is reasonable, with batteries it is suspect. The problem is that fully discharging a battery implies that the weakest cell or cells will be reverse charged, which will harm them.

I conjecture, without evidence, that effect is mistaken for a memory effect.
There are lies, damned lies, statistics - and ADC/DAC specs.
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Online PA0PBZ

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32864 on: June 09, 2019, 08:15:33 am »
The HV supply is essentially independent of the balance of the supply except for a common power transformer. I'm seeing an INCREASE in CRT gain as the intensity is turned up. If the turning up the intensity placed a greater load on the overall circuit I would see the opposite effect. So clearly the gain within the CRT itself increases with greater intensity. It's not a lot but you can see it. And it's probably a characteristic of the design so I'm going to leave it.

If I remember correctly the gain (or maybe better said the deflection) of a CRT increases when the HV decreases, so did you measure the HV while changing the intensity?
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Online bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32865 on: June 09, 2019, 08:32:54 am »
@tggzzz: I keep nearly pulling the trigger on an SA from HP from that era. I would like to thank you for putting me off and saving me a lot of money  :-DD

Before writing off that class of SA, look at how well it is still working. I'm looking for problems; it would be surprising if I didn't find them.

Quote
Still considering building my own. I have build the first LO already. I have no way to evaluate if it's a piece of shit or not though because you need a spectrum analyser!

It will be a POS. Once you've lifted a "portable" real SA, or looked inside a "real" SA, you will begin to understand why.

I think the thing for me is that the HP SA’s are pretty good until they go wonky at which point they are murder.

Yes I had that 7L12 don’t forget which I had to excavate here: https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg1849262/#msg1849262

I think a simplistic homebrew SA, while not suitable as a precision measurement device will allow useful things to be done. Such as filter sweeps, looking at TX harmonics, mixer products etc. Even if it only has 70-80dB of dynamic range and a 100Mhz span that’s good enough for stuff at HF.

I can build a 200Hz filter easily with crystals so RBW at 2nd IF can be quite tight too. Better than those thurlby SA boxes.
 

Online med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32866 on: June 09, 2019, 09:46:09 am »
The HV supply is essentially independent of the balance of the supply except for a common power transformer. I'm seeing an INCREASE in CRT gain as the intensity is turned up. If the turning up the intensity placed a greater load on the overall circuit I would see the opposite effect. So clearly the gain within the CRT itself increases with greater intensity. It's not a lot but you can see it. And it's probably a characteristic of the design so I'm going to leave it.

If I remember correctly the gain (or maybe better said the deflection) of a CRT increases when the HV decreases, so did you measure the HV while changing the intensity?

No, I didn't. Later today when I recap the boards if I think of it I'll get out the HV probe again and measure the HV while varying the intensity. But even if it does change there isn't going to be anything I can do about it because all components, except the power transformer and CRT, are new.

In other news. Tried to make coffee without any water in the drip maker. That ain't gonna work.  :-// Perhaps I should consider that a bad omen and go back to bed.  :-DD
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Offline VK5RC

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32867 on: June 09, 2019, 11:36:15 am »
@med - it means that you really NEED coffee - and lots of it!  Hehe
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Offline GreyWoolfe

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32868 on: June 09, 2019, 12:41:10 pm »
Neat little noise maker, bd! I like all these "quick, I built some test gear" projects you do. :-+

Regarding internet service, the only choices around here are cable or DSL. I'm too far to get more than 6 Mbps down from DSL. Fiber is limited to businesses or specific neighborhoods that were built along with the fiber installation. So, really, there's no choice. For more than 6 Mbps, I have to get cable.

Cost for "up to" 60 Mbps down and whatever the cable company happens to have this hour for up (i.e., unpublished spec) is currently about $70/mo. on a one-year contract with basic TV service (~30 channels). It would be even higher for internet alone. :palm: Despite opting for a one-year contract, they're still able to raise prices during the term by stuffing increases into various fees. So, technically, your contract price hasn't changed, but they still squeeze more from you. What a sham.

From the 60/?? rating, I effectively get 45/5.

Both the cable and phone companies love their monopolies and successfully blocked Google Fiber from entering the market to provide competition. Hopeless.

The good news is that I've only had two major outages over the past ~10 years. So, at least the service is stable despite being residential (no SLA) and not business.

I can't get DSL here, too far from the CO.  My choices are cable or satellite and I am not doing the satellite thing.  We have slowly eliminated the "bundle" thing with the cable company.  We switched over to Roku and Playstation Vue, which saved us about $55 a month.  We got rid of the home phone in January and the price of the internet service didn't change which I was surprised and quite happy about.  We will see what happens after a year.  The internet was more expensive when we had the tv/internet/phone bundle.  When we ditched the tv, the price of the internet and phone both dropped overall.  The neat thing for me is I can get service 7 days a week.  Outages haven't been a really big deal.  Not counting hurricanes, only 1 major outage in the past 15 years.  A really bad storm damaged a lot of cable company infrastructure and we were down for 2.5 days.  A few hours here and there aren't a big thing, I don't count that as major as I can tether my company laptop to my company phone and keep working.
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Online med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32869 on: June 09, 2019, 01:19:57 pm »
The HV supply is essentially independent of the balance of the supply except for a common power transformer. I'm seeing an INCREASE in CRT gain as the intensity is turned up. If the turning up the intensity placed a greater load on the overall circuit I would see the opposite effect. So clearly the gain within the CRT itself increases with greater intensity. It's not a lot but you can see it. And it's probably a characteristic of the design so I'm going to leave it.

If I remember correctly the gain (or maybe better said the deflection) of a CRT increases when the HV decreases, so did you measure the HV while changing the intensity?

No, I didn't. Later today when I recap the boards if I think of it I'll get out the HV probe again and measure the HV while varying the intensity. But even if it does change there isn't going to be anything I can do about it because all components, except the power transformer and CRT, are new.

In other news. Tried to make coffee without any water in the drip maker. That ain't gonna work.  :-// Perhaps I should consider that a bad omen and go back to bed.  :-DD

OK, this has gotten very interesting and in short......PA0PBZ, you are 100% correct.

First, the recap of the vertical and horizontal boards is complete. Going to let the scope burn in for a while before final calibration.

The CRT "gain" issue. I went through and checked all the fixed resistors in the focus, intensity, and astig circuits and they are all in spec. So no issues there. I checked the HV at various intensity settings and got some very interesting results and at the same time a solution/fix. With the intensity off the HV is -1399V. Intensity mid-point, trace just barely visible is -1392V. Full intensity is -1131V. So the HV is sagging and the trace "grows". If I go 3/4 on the Intensity the trace is just as bright as full, is sharper, and there is no increase in "gain". And the HV is -1343V. That is the "sweet" spot. Bright trace, sharp focus, and accurate calibration. I'm going to put a mark on the bezel to align with the pointer on the knob.  :-+

   
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Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32870 on: June 09, 2019, 01:43:57 pm »
Heh gotta love it; the oldest of all calibration methods... empirical analysis resolved to a pencil mark on the dashboard. Decades from now someone will wonder what that mark meant, (if your pet doesn't wind up straight in the tip the day after as you go tits-up) and if they have any sense at all, they'll leave it there until they learn enough to grok it's purpose.  :-+

   Wonder if this would make a good cage coffin for a very small ex parrot  >:D Glued up, coating of Orange oil for finish just need to add some felt lining now.

Have to run, I have some TEA both cooling down and some warming up to play with  :-+

Actually, when I first saw it I thought to myself *That is a dandy little cricket cage; perfect for walkies...* It actually is quite in keeping with a number of traditional styles over the centuries.

For those who don't know, keeping crickets as pets for their song or for luck has been a thing for thousands of years.  :-+

Whoa, wait a minute.  Before you Throw the bath water out, cycle the batteries to see if it is just a memory problem.  Nicads develop a "memory" if they are discharged to the same voltage over and over.  The memory is they begin to act as if the repeated discharge before recharge voltage is the new ground and they stop giving power.

The trick is to completely discharged them through a resistor to zero and then charge them completely, then wash and recycle. It takes several to many cycles of this to erase the memory in a nicad bank.  Sure, they could be toast from use or age, but it won't hurt to try first.  Read more about cycling nicad batteries in various radio control forums or solar panel forums.
Many people claim the memory effect only occurs in special circumstances, since it requires repeated discharging to the same depth.

OTOH, while discharging NiCd (and other) cells with a resistor is reasonable, with batteries it is suspect. The problem is that fully discharging a battery implies that the weakest cell or cells will be reverse charged, which will harm them.

I conjecture, without evidence, that effect is mistaken for a memory effect.

That is a much more concise explanation than the one I was just about to draft up; thank you for saving me a lot of time.  ;) 

As Ni-xx cells age, through time or abuse, the chemistry and therefore the IR of individual cells changes. While trickle and/or shock-charging/desulfating techniques can in some cases rejuvenate a few individual cells such that they have useful capacity again, it is very rare that they ever recover full capacity once they've gotten to this stage, and almost NEVER do you recover an entire battery PACK to full capacity, or even a 25-50% level of useful capacity. As Ni-xx packs are not commonly balance-charged, that makes the likelihood of repeating the death scenario you describe above pretty much inevitable; therefore your least assache solution really is to just rebuild with new cells of same brand/part# so that capacity and IR all match reasonably closely.

Batteries (no matter the chemistry) are livestock; the worst abuse you can do to them is to not use them as a storage medium. Load them down, discharge them, recharge them regularly per manufacturer's recommendation and they will love you long time.  :-+

It will be a POS. Once you've lifted a "portable" real SA, or looked inside a "real" SA, you will begin to understand why.

I think the thing for me is that the HP SA’s are pretty good until they go wonky at which point they are murder.

Yes I had that 7L12 don’t forget which I had to excavate here: https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg1849262/#msg1849262

I think a simplistic homebrew SA, while not suitable as a precision measurement device will allow useful things to be done. Such as filter sweeps, looking at TX harmonics, mixer products etc. Even if it only has 70-80dB of dynamic range and a 100Mhz span that’s good enough for stuff at HF.

I can build a 200Hz filter easily with crystals so RBW at 2nd IF can be quite tight too. Better than those Thurlby SA boxes.

   My very first experience with a SA was in my Tech School daze; the WaveTek reps brought a SAM 450 and demonstrated it's SA output connected to one of the bench scopes. While in principle I agree with tggzzz; anything you make will likely be poop on a PCB, the SA function of the SAM was at least usable as a basic diag tool.

Since they regularly eBay in the $25-45 range, and there are multiple generations as well (though the digital tuning of later models may introduce noise that is problematic to the SA function) to choose from and mod for other purposes, might be worth a few shekels to acquire one of them for your your tinkery time abuse.  :-//

Would probably save you a lot of assache and give you a much better starting point than reinventing the wheel from scratch.
  ;)

mnem
I have too much blood in my caffeine circulatory system right now.
« Last Edit: June 09, 2019, 01:50:08 pm by mnementh »
 

Online bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32871 on: June 09, 2019, 02:09:21 pm »
Indeed. Just sold my FT818 and listed a whole load of other stuff so I'm looking at more expensive ones now  :-DD
 

Offline No.Mad

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32872 on: June 09, 2019, 02:58:29 pm »
Indeed. Just sold my FT818 and listed a whole load of other stuff so I'm looking at more expensive ones now  :-DD

Link maybe? :D
 

Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32873 on: June 09, 2019, 05:15:13 pm »
Indeed. Just sold my FT818 and listed a whole load of other stuff so I'm looking at more expensive ones now  :-DD

And you are agreeing with which of the MANY points in the post(s) above this one?  :-//

mnem
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Online bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #32874 on: June 09, 2019, 05:45:30 pm »
The poop on a PCB comment :D

Although that might be a challenge.
 


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