Test Equipment Anonymous (TEA) group therapy thread

[tautech]

Jason of Siglent NA received my email and is sending me a new probe. So, I'm impressed with customer service. 

Jason is a top dude and does all the NA Siglent videos.
We chat about things often as he visited NZ a few years back before we got to know one another.

[factory]

While I don't participate in this thread anymore on a regular basis I still want to share TE information and encourage an exchange of knowledge and discussion. I still follow this thread on an intermittent basis but I exclusively post on another forum. But to bring everyone up to date here is what I've been working on. Summary format but I posted links if you want more detail.

Next a Sony/Tek 314 from Ebay. Also needed some minor work. A PSU recap is pending.

Welcome back and thanks for the update, glad you use external picture hosting as yours are the few I can actually see.
I've always thought those 314 scopes looked a bit odd with the volts/div controls and wondered if bits were missing, but that's how they are, much prefer the look of the Tek 323.

Update to a Tek Type 310A Fan Mount.

Fan noise still doesn't bother me, rather be able to hear it and know it's running, more so now I have tinnitus from that noisy lathe at work. Should go measure it one day, need something to check the sound level meters I have in the long repair queue.

David

[med6753]

I have two of these 547 which I will eventually get round to working on one day... I am crossing fingers not to have a dodgy tranny.... will be reading your adventures to improve my chances of success, or at least save myself from wasting money and/or time doing this or that.

If at anytime they were stored in a damp environment 100% the HV Transformer has been compromised. But even without that condition the transformer still seems to suffer from leakage issues. The jury is still out if my bake out method will give long term results. Later this month I will pull out and power up the Type 547 that has been sitting idle for approx 3 months to see if there was any degradation. The Type 547 currently on bench 2 gets regular power and so far there has been no degradation. 

[factory]

Hernia producer overload in the US, half a dozen 524 series counters, yes half a dozen, now common as muck. 



https://www.ebay.com/itm/295457171371
https://www.ebay.com/itm/295456989452
https://www.ebay.com/itm/255911678562
https://www.ebay.com/itm/295455653793
https://www.ebay.com/itm/295455281824
https://www.ebay.com/itm/295453756982



David

[factory]

...snip...

Got the last piece of this puzzle reverse engineered, the HP 1820-0413 divider IC, ended up using a 74LS90, with two 74LS14 inverter gates, one 74LS02 NOR gate and a random used HP 1854-0071 trannystor providing the open-collector gated output.



Will do a KiCad layout one evening, sometime in the new year, this is not a urgent project, just wanted to test all the functions, including those not used on the A14 board.

First go at trying to make the above mess fit in too small a space, needs a bit more work, want to add a decoupling cap, note small one/two gate ICs are not available in LS versions.



Edit: Part numbers of the pictures are incorrect.
David

[xrunner]

Jason of Siglent NA received my email and is sending me a new probe. So, I'm impressed with customer service. 

Jason is a top dude and does all the NA Siglent videos.
We chat about things often as he visited NZ a few years back before we got to know one another.

Holy bandwidth Batman - I measured the -3 dB bandwidth as 300 MHz. I checked my work three times.

I couldn't find anyone else who has checked the bandwidth on this one but I probably missed it. That's a pretty good deal for an advertised 200 MHz scope. 

[tautech]

Jason of Siglent NA received my email and is sending me a new probe. So, I'm impressed with customer service. 

Jason is a top dude and does all the NA Siglent videos.
We chat about things often as he visited NZ a few years back before we got to know one another.

Holy bandwidth Batman - I measured the -3 dB bandwidth as 300 MHz. I checked my work three times.

I couldn't find anyone else who has checked the bandwidth on this one but I probably missed it. That's a pretty good deal for an advertised 200 MHz scope. 

You are a bit high @ 300 whereas 250 MHz is more like it:
https://www.eevblog.com/forum/testgear/siglent-sds2000x-e/msg2144110/#msg2144110

Still, you can enable 350 mode and take it to ~400. 

[xrunner]

You are a bit high @ 300 whereas 250 MHz is more like it:
https://www.eevblog.com/forum/testgear/siglent-sds2000x-e/msg2144110/#msg2144110

Still, you can enable 350 mode and take it to ~400. 

Here's my setup, just checked it again. I measured ~330 MHz using an hp 8648A set to 1 VPP 

Are you sure it hasn't been improved since those last measurements in that other post?

[tautech]

Are you sure it hasn't been improved since those last measurements in that other post?

Maybe they have IDK.
You could wake yours to the 350 model and see if it beats the 405 that I got with a RF gen and a genuine SDS2352X-E.
Do you have the 50 input termination engaged ?
Be sure to keep well within the 5V max.

[xrunner]

Maybe they have IDK.
You could wake yours to the 350 model and see if it beats the 405 that I got with a RF gen and a genuine SDS2352X-E.
Do you have the 50 input termination engaged ?
Be sure to keep well within the 5V max.

I'll check my test equipment but I doubt I'll find anything wrong.

I just checked the frequency accuracy of the Agilent 8648A with an hp freq. counter locked to GPSDO - it's spot-on 328.000000 MHz.

I'll check some other things but it sure looks like it's got a BW of over 300 MHz. That's good! 

[m k]

The jury is still out if my bake out method will give long term results.

Other direction is low pressure and boiling water from there but both are still missing any extraction force for that steam.
And obviously if there is an upwards loop where the water is boiling it's never coming out.
Maybe a gyro like rotator is a bit extreme.

[BU508A]

Maybe it is a god idea to bury the HV unit in 2kg silica gel and let it cook in the oven for a couple of hours at 65°C or so.

https://www.ebay.com/itm/224638171346


NAWTS

[TERRA Operative]

That's a trick to use on carbon composite resistors too.
Bake them at 60 degrees in silica gel then seal with enamel or lacquer etc. helps reduce the drift and lessens noise too apparently.

Although I usually just replace them with metal film, better all round except where high frequency is a consideration.

[Robert763]

Maybe it is a god idea to bury the HV unit in 2kg silica gel and let it cook in the oven for a couple of hours at 65°C or so.

https://www.ebay.com/itm/224638171346


NAWTS

Don't bake stuff in silica gel. All that does is drive any residual water out of the silica gel and increase the humidity around the part. Either just bake it or put it into a airtight heated enclosure cinnected by a tube to a container of sillica gel at room temperaure.

Robert G8RPI.
 

[m k]

If small oven is slowly ventilated with freezed dry air, any idea what kind of times are needed?
When HVAC is sucked dry it takes quite a bit for sort of straight tubes.
Would it be better if that dry air is stuffed in with dry silica gel and a part to somewhere small and airtight.

My intuition says that effective room temperature drying is more effective but truth of it is completely unknown.
Potato flower is obviously very dry but its surface area can be finally quite small.
Silica is widely used but is it because it's commercially viable instead of being overly effective.

[duckduck]

Oh, I do love a good round of opinions. I'd just bake it in an electric oven at > 100*C and expect evaporation and convection to remove the moisture from the part. Look at how they store SMAW welding rods to keep them free of moisture: in an oven.

Reminder that silica gel is sold by the 10+ kg container as "crystal kitty litter" at your local supermarket.

[TERRA Operative]

I just calibrated my Tek 2235 scope, after I ripped out the last few carbon composite resistors and stuff from the front-end and main PCB.

It calibrated perfectly and is working beautifully and looks like it's useable up to almost 130MHz according to the -3db point with a quick and dirty test on the SG5030 levelled sinewave generator.
Will have to see what the Leo Bodnar pulse gen looks like on it tomorrow too.



I do like this scope, I think I'll keep it.

[BU508A]

Maybe it is a god idea to bury the HV unit in 2kg silica gel and let it cook in the oven for a couple of hours at 65°C or so.

https://www.ebay.com/itm/224638171346


NAWTS

Don't bake stuff in silica gel. All that does is drive any residual water out of the silica gel and increase the humidity around the part. Either just bake it or put it into a airtight heated enclosure cinnected by a tube to a container of sillica gel at room temperaure.

Robert G8RPI.

Well, then bake the silica gel first and then bake it with the buried HV unit.

[BU508A]

This video just popped up in my suggestions queue:

[Robert763]

Silica gell absorbs best below 25 deg C (77F). Hence putting it in a separate chamber to a warmed item in a sealed system. Warming the item drives moisture out of it. The silica traps the moisture keeping the humidity low which helps diffusion of vapour out of the system. Alternative, possibly better for some applications, is a heated vacuum chamber. Pump ses more energy though.
https://www.sorbentsystems.com/desiccants_charts.html

Used to have this trouble with Ohmite Carbon composition resistors. New stock, with certification, direct from Ohmite would fail resitance checks out of the box. Ohmite's response "bake them for 24 hours". Very frustrating. We were repairing older aircraft engine instruments. In most other industries you would just replace the composition ones with carbon film (nothing higher than audio frequency so no inductance issues) but the design authority for the instruments (who had bought out the company who bought out the company that designed the instruments 30 years before) where not interested in support and would not authorise alternative parts. They would sell you a $400,000 flat screen integrated replacement mod for all the engine instruments. No conflict of interest there.

Robert G8RPI

[Robert763]

This video just popped up in my suggestions queue:

 

[factory]

Some interesting pricing on JCBPCB, with no panellizing selected;
Five boards approx 11.5mm square $2.00
Ten boards $5.00
15/20 boards $4.20
25/30 boards $4.30

So if you want ten tiny boards, it's cheaper to order 15 to 30 boards.

Nearly done, just got to check pin sizing and board size against the space available, decoupling cap will be through hole part.



David

[Vince]

Strange indeed..... 

[themadhippy]

Some interesting pricing on JCBPCB

If you've used em before do check your account for "coupons",my last order  cost  42p for the boards,down from around  6 quid.

[m k]

Anybody knows any even mildly reliable thickness of visually recognizable thin single side breadboard sets China is selling?
Found one that is stating item height as 0.8mm but it's pretty equal to others that are said to be 1.2mm.

I'm interested in putting to boards back to back, if they are thin enough and have a tall enough edge connection of .15" spacing.
Double sided board would obviously be much better but all seems to have .1" or .156" spaced edge connections.

Other possibility is solid double side FR4 plate and Dremel but that's so much of analog control, total would be around couple hundreds of stripes.