Test Equipment Anonymous (TEA) group therapy thread

[bitseeker]

As suggested by Specmaster. And a damn good suggestion it was. And here's the results. A folding side table on the scope cart (trolley). I was somewhat limited in how large I could make it but it does accommodate a typical manual. But a little problematic if it has fold-outs. 

That folding side table is mighty hefty. Awesome!

[factory]

David

P.S. How long will it be before your looking for one of these to check that gauge against?

No, the bigger question is how long before he blows himself up? 

One of these instead then.   

[bitseeker]

Perfect!

[mnementh]

And Now For Something Completely... ON-TOPIC!!!



mnem
It had to happen sooner or later.

So which came first, the Sprague Yellow Jacket capacitors or the company that makes those gauges?   

David
P.S. How long will it be before your looking for one of these to check that gauge against?

Company website sez they've been around 60 years.    This is like the third time I've used the thing since I quit working for Ding & Dent Appliances in 2005. Confidence is pretty high that... no.

No, the bigger question is how long before he blows himself up? 

One of these instead then.   

What... Again? Why you gotta jinx me like that, beeyotch?!?    *quietly snurches pic for later deviltry*
mnem
It's not as bad as you might think. Once you get over the constant smell of grilled hot dogs (which turns to smell of wet dog) and not being able to scratch under the cast... 

[tautech]

David

P.S. How long will it be before your looking for one of these to check that gauge against?

No, the bigger question is how long before he blows himself up? 

Nah, memn's just an aging dwagon that needs a bit of help with his huff and puff.

[mnementh]

mnem
 

[Specmaster]

As suggested by Specmaster. And a damn good suggestion it was. And here's the results. A folding side table on the scope cart (trolley). I was somewhat limited in how large I could make it but it does accommodate a typical manual. But a little problematic if it has fold-outs. 

Nice job, glad I suggested that now, of course it can be used for other things if need be [emoji106]

Sent from my POT-LX1 using Tapatalk

[bitseeker]

As suggested by Specmaster. And a damn good suggestion it was. And here's the results. A folding side table on the scope cart (trolley). I was somewhat limited in how large I could make it but it does accommodate a typical manual. But a little problematic if it has fold-outs. 

Nice job, glad I suggested that now, of course it can be used for other things if need be [emoji106]

Yeah, like lunch and your favorite beverage while tinkering.

[mnementh]

Or the oscilloscope you're using to fix your oscilloscope...

mnem
again. 

[bitseeker]

Good thing he made it hefty.

[Specmaster]

Has to be hefty in order to carry the weight of his coffee bucket

[bd139]

That is a pretty impressive shelf. And it will always have the service manual on it 

Think I managed to source a spare PM3217. Unfortunately the damn thing is in Carlisle, way too far to drive, and the dude is not convinced it'll survive shipping (even though I don't care if it doesn't as long as the front panel is good!) 

[BU508A]

No.

mnem
 

 

I'm convinced, Carole King has ment you with this song:



 

[med6753]

As suggested by Specmaster. And a damn good suggestion it was. And here's the results. A folding side table on the scope cart (trolley). I was somewhat limited in how large I could make it but it does accommodate a typical manual. But a little problematic if it has fold-outs. 

Nice job, glad I suggested that now, of course it can be used for other things if need be [emoji106]

Yeah, like lunch and your favorite beverage while tinkering.

Or the oscilloscope you're using to fix your oscilloscope...

mnem
again. 

Has to be hefty in order to carry the weight of his coffee bucket

That is a pretty impressive shelf. And it will always have the service manual on it 

Bunch of comedians. 

[Specmaster]

Guilty as charged M'Lord 

[Brumby]

Four pages of catch up...  That's what I get for being busy elsewhere, but there were some gems - and I'm not including the monkeys.

[Brumby]

Those images look great. I checked out some videos, too. Very clear, unlike the scopes from just a few years earlier. The ADSM302 is this year's model with twice the working distance (up to 22cm), but the 301 seems just fine (up to 12 cm), considering the lower cost, the same resolution, and the same frame rate.

Help me! It looks like I'm getting one, now. Order submitted.

I can't help you now it's too late. 

The base is solid aluminum but it's not great for laying a board on because it's too slippery-slidey. Just need to put on a material to help a board stay put. Looking at some options like a piece of ESD mat. I did some soldering with it yesterday and was very pleased with how it went.

Took another pic for you at full magnification.

Nice.

Now I officially hate you.    (Now, where's that link....?)

[mnementh]

Has to be hefty in order to carry the weight of his coffee bucket

Hey... I strongly resemble that remark...

No.

mnem
 

    I'm convinced, Carole King has meant you with this song:



 

Thanks for noticing! "Heroes may save the world, but the funny thing is what makes it worth saving." ~my mom

Four pages of catch up...  That's what I get for being busy elsewhere, but there were some gems - and I'm not including the monkeys.

mnem

[med6753]

Has to be hefty in order to carry the weight of his coffee bucket

Hey... I strongly resemble that remark...



mnem
(Attachment Link)

Amen. 

[BU508A]

Those images look great. I checked out some videos, too. Very clear, unlike the scopes from just a few years earlier. The ADSM302 is this year's model with twice the working distance (up to 22cm), but the 301 seems just fine (up to 12 cm), considering the lower cost, the same resolution, and the same frame rate.

Help me! It looks like I'm getting one, now. Order submitted.

I can't help you now it's too late. 

The base is solid aluminum but it's not great for laying a board on because it's too slippery-slidey. Just need to put on a material to help a board stay put. Looking at some options like a piece of ESD mat. I did some soldering with it yesterday and was very pleased with how it went.

Took another pic for you at full magnification.

Nice.

Now I officially hate you.    (Now, where's that link....?)

Here, especially for Down Under:
https://www.ebay.com.au/itm/183855334498

 

[bd139]

Here, especially for Down Under:
https://www.ebay.com.au/itm/183855334498

I think this is the Australian market version

[BU508A]

LMAO!   

[tggzzz]

Tggzzz, if you get a chance to open up your 485 this week these are the parameters you should set up on yours to match my readings. This set up should result in a trace but trigger light OFF. My trigger light is on.

Scope set up:

Channel 1: 1v/div, GND. No signal.
Int Trig set to channel 1
Time/div set to 1mS
Horiz Display to A
Sweep Mode to Auto Trig
Slope to +
Level to slightly negative
A Trig Coupling to AC
A Trig Source to INT

DC voltages on U780:
<copied below>

I've highlighted the differences I suspect are significant.

          med             tgg
Pin 1  +0.495V      -27mV 
Pin 2   +0.0789V   71.4mV
Pin 3   +0.3027V   -284mV
Pin 4   +4.981V     4.97V
Pin 5   -4.961V      -5.01V
Pin 6   +0.0291V   5.44V
Pin 7   +0.4347V   5.55V
Pin 8   +0.6746V   604mV
Pin 9   0                 0
Pin 10  0                unstable

Pin 11  +5.518V    5.55V
Pin 12  +0.0108V  5.5mV
Pin 13   0               0
Pin 14  +4.945V    4.91V
Pin 15  +0.8714V  891mV
Pin 16   0               1.2mV
Pin 17   -0.4684V  -505mV
Pin 18   0               0
Pin 19   0               0
Pin 20  +4.980V    4.98V

The scope traces for pin 17, J816, Q816 base are very similar.

The positive going pulse on pin 16 is around 100ns wide and 2.5V high, the low duty cycle makes it very dim on an analogue scope.

Using the conditions on diagram 6, most of my U780 voltages are similar to the diagram - but not pin 2 which is 77mV instead of 9mV (surprising since it looks like a bias setting from a voltage divider). Pin 3 is very similar which implies it is an output, not (as I guessed) a bias input. A scope trace of pin 1 shows an ~400mV output which falls to 0mV at the sweep interval.

My approach would be to

• check decent waveforms at the input to the tunnel diode section, i.e. u740.9 and u740.5 TP
• check values of R791, R792, since they are the load to u780.3
• check decent waveforms coming out of the tunnel diodes, especially u780.1
• fettle with the tunnel diode pots "between" u740 and u780 to try to get good waveforms hitting u780

[bd139]

There's an HP 6207B on ebay for a reasonable amount of cash. 0-160V 200mA. Considering it but can't think of a use for it. If anyone can come up with any let me know 

Edit: so far:

1. Very low voltage HT supply for tubes
2. Avalanche pulse generator driver
3. Wire it to the letterbox and electrocute the junk mailers.

[med6753]

Tggzzz, if you get a chance to open up your 485 this week these are the parameters you should set up on yours to match my readings. This set up should result in a trace but trigger light OFF. My trigger light is on.

Scope set up:

Channel 1: 1v/div, GND. No signal.
Int Trig set to channel 1
Time/div set to 1mS
Horiz Display to A
Sweep Mode to Auto Trig
Slope to +
Level to slightly negative
A Trig Coupling to AC
A Trig Source to INT

DC voltages on U780:
<copied below>

I've highlighted the differences I suspect are significant.

          med             tgg
Pin 1  +0.495V      -27mV 
Pin 2   +0.0789V   71.4mV
Pin 3   +0.3027V   -284mV
Pin 4   +4.981V     4.97V
Pin 5   -4.961V      -5.01V
Pin 6   +0.0291V   5.44V
Pin 7   +0.4347V   5.55V
Pin 8   +0.6746V   604mV
Pin 9   0                 0
Pin 10  0                unstable

Pin 11  +5.518V    5.55V
Pin 12  +0.0108V  5.5mV
Pin 13   0               0
Pin 14  +4.945V    4.91V
Pin 15  +0.8714V  891mV
Pin 16   0               1.2mV
Pin 17   -0.4684V  -505mV
Pin 18   0               0
Pin 19   0               0
Pin 20  +4.980V    4.98V

The scope traces for pin 17, J816, Q816 base are very similar.

The positive going pulse on pin 16 is around 100ns wide and 2.5V high, the low duty cycle makes it very dim on an analogue scope.

Using the conditions on diagram 6, most of my U780 voltages are similar to the diagram - but not pin 2 which is 77mV instead of 9mV (surprising since it looks like a bias setting from a voltage divider). Pin 3 is very similar which implies it is an output, not (as I guessed) a bias input. A scope trace of pin 1 shows an ~400mV output which falls to 0mV at the sweep interval.

My approach would be to

• check decent waveforms at the input to the tunnel diode section, i.e. u740.9 and u740.5 TP
• check values of R791, R792, since they are the load to u780.3
• check decent waveforms coming out of the tunnel diodes, especially u780.1
• fettle with the tunnel diode pots "between" u740 and u780 to try to get good waveforms hitting u780

Great...thanks.  I'll pull this back up on the bench tomorrow and check those areas.