Test Equipment Anonymous (TEA) group therapy thread

[factory]

That's the bit of kit I wanted 

I guess you didn't bid on the 6177C then. Did you remember to bid on the unicorn TE item or is that still active?

David

Unfortunately no. I really need one as well.

Unicorn is still active ending Friday

I used to have the bigger version (6188C), I kind of regret selling it now but didn't have enough space at the time;


David

P.S. good luck on the unicorn, it's not on my watch list (nothing ending Friday).

Oh that's rather nice that 6188C. I don't need a too hefty one - just a nice current source. Currently I'm using a simple BJT current source usually but that's way too much underkill and compliance depends on how buried the 6206 is

The 6188C wasn't that nice, some anus had sprayed the whole thing with varnish or lacquer, the front, sides, meters, terminals, the lot. They didn't bother removing a large label below the current meter, so there is an area without this too, this doesn't show that well on the pictures due to how long ago they were taken & the poor lighting.
It got sold on the radio forum as I didn't have enough space at the time and I had decided two out of three high voltage PSU's I had was enough. Clearly the anti-TE medication was working too well then.

David

[bd139]

@Specmaster

Ok filled myself up with spaghetti bolognaise, garlic bread and chocolate mousse now (such a philistine) so alive again 

The whole current control thing works by comparing the voltage across a portion of the the 0.1R resistor R51 and R52/VR7 (I will call this VSAMP) with the voltage across the current control pot VR5 (VEXPECT). If VEXPECT > VSAMP it'll current limit.

I reckon this is either VR4 (reference range) or VR7 (current trim) are set wrong. Try recalibration as per manual. If that doesn't work, measure across VR5 both ends of the track and post back and I'll do some calculations on what values are supposed to be there for a PL310. This could be the CD4052 clamping it or leaking somehow on the ADC sample input. Those CMOS ICs suffer from problems in those supplies and this should confirm whether or not it's that or something more insidious.

I've sliced up the schematic for the relevant bits for debugging:

[bd139]

Change the CD4052 mux IC(s). These can develop weird faults and inject voltages into the current sensing circuit.

Dang beat me to it 

[BU508A]

They are using strange symbols for the trimpots, eg. VR4, VR7, VR8.     

[bd139]

Standard here. Flat line = trimmer. Pointy arrow = pot.

At least we don't use coloured in resistors for our inductors 

[BU508A]

Standard here. Flat line = trimmer. Pointy arrow = pot.

At least we don't use coloured in resistors for our inductors 

*scratching head*



Somehow, I'm finding these symbols more intuitive. But this could be, because I'm kinda biased here. For the same reason, I'm always struggling with the resistor symbol from the 'mericans. Never get used to it. 

[mnementh]

Please my friends... a little prayer for my sanity...   

mnem

[bd139]

Standard here. Flat line = trimmer. Pointy arrow = pot.

At least we don't use coloured in resistors for our inductors 

*scratching head*



Somehow, I'm finding these symbols more intuitive. But this could be, because I'm kinda biased here. For the same reason, I'm always struggling with the resistor symbol from the 'mericans. Never get used to it. 

Yeah the American ones are stupid. It's very difficult to see the difference between inductors and resistors if the person is scribbling it on the back of an envelope 

[BU508A]

@mnem:

I'm sending you young Aretha to support you. Hope that helps. 

[BU508A]

Standard here. Flat line = trimmer. Pointy arrow = pot.

At least we don't use coloured in resistors for our inductors 

*scratching head*



Somehow, I'm finding these symbols more intuitive. But this could be, because I'm kinda biased here. For the same reason, I'm always struggling with the resistor symbol from the 'mericans. Never get used to it. 

Yeah the American ones are stupid. It's very difficult to see the difference between inductors and resistors if the person is scribbling it on the back of an envelope 

This!
Exactly this! 
Or, if one has to deal with a not so good copy of some schematics.     

Edit: spelling corrected.

[mansaxel]

6206b update:

The voltage range switching works. The supply is overspecified though,  so that it, unloaded, will be able to go pretty far over the limit of the lower range. Fools you.

The meter selector / range switching assembly was luckily screwed together, not riveted. Two screws hold the decks together in expected fashion, and I was able to separate them out enough that the severed press-fit between first aluminium deck and brass bushing could be freed from the assembly and subjected to the arbor press. I located it so it would go together and just two fingers on the press lever was enough to push it together again. Built up a jig with a staircase block from the drill press clamping kit underneath, and a 1/4" socket (IIRC 8mm) as press interfacing bushing on top. That was the most pressing (sic) problem I knew of, because a broken switch of course would require a parts donor.

Anyway, once that was taken care of, I started bolting the chassis together again. Before replacing the lid, I subjected the supply to a series of tests within the capacity of my lab. Mostly, I'm lacking in resistive loads, so had to make do with a lightbulb for load.

This of course means I can't do all tests I want to, but the ones I can do indicate no problems. The meter was zeroed and once that was done, the metering was found to be in calibration. Of course it is non-linear in overvoltage.

Ripple is one order of magnitude below limit in manual.

Meters used for the verification include the MetraHit 25S, the Fluke 8060, and the -hp- 427, 428b and 3438 meters.

Conclusion: Supply is ready for the bench, once I've done a Med style full power burn-in. As soon as I have a suitable load resistor I'll get on with it.

[Neomys Sapiens]

Host Europe / 123-reg data centre looked like that circa 2003. No exaggeration. Had the misfortune of colo’ing in their facility.

So did Heathrow control tower,circa 1970, before ATC moved to West Drayton.

But that was more signal cables between racks than power cables.

Ok, that explains some NATS lore that I've heard.

[Neomys Sapiens]

Ever seen one of these ??   ..... thank you mailman.....

Yes, and I was happy when they weren't around anymore. It did prove that Keithley makes handheld DMMs only as bad examples to sell more of their desk meters.

[Specmaster]

@Specmaster

Ok filled myself up with spaghetti bolognaise, garlic bread and chocolate mousse now (such a philistine) so alive again 

The whole current control thing works by comparing the voltage across a portion of the the 0.1R resistor R51 and R52/VR7 (I will call this VSAMP) with the voltage across the current control pot VR5 (VEXPECT). If VEXPECT > VSAMP it'll current limit.

I reckon this is either VR4 (reference range) or VR7 (current trim) are set wrong. Try recalibration as per manual. If that doesn't work, measure across VR5 both ends of the track and post back and I'll do some calculations on what values are supposed to be there for a PL310. This could be the CD4052 clamping it or leaking somehow on the ADC sample input. Those CMOS ICs suffer from problems in those supplies and this should confirm whether or not it's that or something more insidious.

I've sliced up the schematic for the relevant bits for debugging:

Thanks for this, it is the precise area of the schematic that I'm painstakingly working my way through by lifting a leg and confirming the values against the parts list and so far nothing has leapt out as being out of sync. I think its fairly safe to eliminate IC7, the OP AMP as that has already been swapped out for a new and it is unlikely that both the old and the new have the same issues as nothing changed.

I'll continue working my way through these sections as and when I get the time to fall back onto it and then I'll attempt the calibration before going on to look at the multiplexer.

I'd already checked R52 (shown as 750 ohms) and got quite excited because it was reading 330 ohms, and then I remembered that mine has version 4 boards and that 330 ohms was correct after all 

[tggzzz]

Host Europe / 123-reg data centre looked like that circa 2003. No exaggeration. Had the misfortune of colo’ing in their facility.

So did Heathrow control tower,circa 1970, before ATC moved to West Drayton.

But that was more signal cables between racks than power cables.

Ok, that explains some NATS lore that I've heard.

Do tell; you can't leave us dangling in mid air

In my experience most large systems that have grown over the years will be held together by sticky tape and people that know where the sticky tape isn't sticking well enough.

[Neomys Sapiens]

Never saw this one, listed in a non-TE category. 


The train would be even cheaper if I had a BR rail pass, unfortunately they stopped providing them to new employees decades ago (before I joined the company).

David

Do you have a serial number for the device?
I have one which I can't repair because the available manuals do not cover the modifications adequately. As with some other power supplies from HP of this period, the checkout and calibration procedures contain some dis-connections which are totally a PITA when you can't find the point where it should be done.
Photograph with open lid would be sufficient for identification. Will you get a manual with it?

[Specmaster]

@mnementh I have already replaced the pass transistor (a single 2N3055 on this) and also rechecked and it is good. I also thought it was the comparator in the CC circuit and this too has been replaced. Currently in the process of removing the resistors associated with the shunt and the comparator to check them open circuit rather than in circuit as they are connected to the shunt and back feeding via it so their values are being distorted by it.

This may come as a dumb question: but have you checked the sensing path? Something like a broken trace or a resistor with an increased value?

Btw, I've looked for the schematics of the PL-310 but I only found this (see attachement) and in the schematics I can see four pass transistors in parallel.   

Edit: Source - contains some more useful information.

Yep, thats the correct manual but boy it takes a bit to get your head around it as is far from the best manual I've come across and it is biased towards the bigger dual channel units with the 4 options of how it is configured by the central switch unit and so the writer must have assumed that the reader would not have the single supply, or that the reader would be fully conversant with the single 1 and 2A units 

[mnementh]

Nooooooooooo!

This thing has been for a week... but at least this is a different kind of kicking. Maybe I have some small measure of hope here... LOL

mnem
 

[med6753]

Standard here. Flat line = trimmer. Pointy arrow = pot.

At least we don't use coloured in resistors for our inductors 

*scratching head*



Somehow, I'm finding these symbols more intuitive. But this could be, because I'm kinda biased here. For the same reason, I'm always struggling with the resistor symbol from the 'mericans. Never get used to it. 

Yeah the American ones are stupid. It's very difficult to see the difference between inductors and resistors if the person is scribbling it on the back of an envelope 

Wut?  Bullshit! 

[med6753]

Nooooooooooo!

This thing has been for a week... but at least this is a different kind of kicking. Maybe I have some small measure of hope here... LOL

mnem
 

  What happen? 

[med6753]

Tell me you can't tell the difference between a resistor and inductor when drawn CORRECTLY. 

[BU508A]

Even though it is drawn correctly, those strange wiggly lines, which may represent a resistor, are harder to spot than a nice looking rectangle. Anytime.     

Edit:

This are the schematics of a Grundig black-and-white television set from 1957. It is hard to read, but here one can spot the difference between coils and resistors easily. Try this with similar schematics this hard to read. 

Hint: the image is huge, it takes some time to load and render it. Well, on my lame PC.     

[tautech]

Tell me you can't tell the difference between a resistor and inductor when drawn CORRECTLY. 

Or timmers and pots. 

[tautech]

Even though it is drawn correctly, those strange wiggly lines, which may represent a resistor, are harder to spot than a nice looking rectangle. Anytime.     

Yep, rectangles are the standard today.

[med6753]

Even though it is drawn correctly, those strange wiggly lines, which may represent a resistor, are harder to spot than a nice looking rectangle. Anytime.     

Funny, for me it's just the opposite. Those little rectangles representing resistors look ridiculous to me.  I guess it's all what you are used to.