@Med, that HV supply rebuild looks really neat, looks as if it has just come out of the factory, brilliant job
Check threads from GK as he’s built a couple.
https://www.eevblog.com/forum/projects/oscilloscope-under-construction/
Pure gold!
@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.
mnem
Well played... well played.
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.
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.
Bless me Father for I have sinned, and it has been some time since my last confession
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
@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.
mnem
Well played... well played.I have not yet begun to torment you. This is torment.
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?
Kwality items
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.
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.
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.
@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
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.QuoteStill 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.
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?
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. 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.
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.
Wonder if this would make a goodcagecoffin for a very small ex parrot 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
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.
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.
Indeed. Just sold my FT818 and listed a whole load of other stuff so I'm looking at more expensive ones now
Indeed. Just sold my FT818 and listed a whole load of other stuff so I'm looking at more expensive ones now