Test Equipment Anonymous (TEA) group therapy thread

[Terry01]

Old stuff... lots of old stuff.
Was cruising around the web and ran into a Supreme tube tester from 1934. Got me hooked. Back then test equipment design was as much an art form as it was function.


Years later the radio collection has fallen by the wayside and the piles of antique and vintage test gear have totally taken over.


Here's just the Supreme portion...
http://www.supremeinstruments.org

and my wife thought I had too many radios... 

That's some beautiful stuff buddy! Even though I know nothing about any of it, it really does look something else.

Thanks for sharing... 

[xrunner]

I got the bench in today before the next wave of rain hits for a week.

Installed the drawers and am very pleased with the strength of the design - can stack many inches of gear on top. Now to figure out the layout ...

 

[mnementh]

In Other News...

I have progressed far through the sea of deductions to have some idea how much farther I have to go... my earlier allusions to Odysseus were actually quite apt.  I shall continue to slog...

In Other OTHER News...

The HP DV6-2150US has successfully completed a 24 hour burn-in... but it did not like the cheap Chinese battery. That failed testing after like 2 iterations.

We'll see if it serves during normal usage, and for how long. Like I don't already have enough headaches...

mnem
*Zombie-dwagon*

[bitseeker]

@bitseeker have your fuses arrived yet so you apply some gentle power to yours so we can see if its working without blowing those blasted rifas? 

Yep, got fuses. Installed one and first checked between the Live and Neutral IEC pins with power switch off and on like mnem did, below.

Fuse tests good; Infinity across the mains open circuit, and and 94 Ohms with it turned on.

Unfortunately, I get open circuit with the switch in either position. So, started tracing around the primary side of the power supply.

Start on the live side:

1. Continuity from Live pin to L1? Check. So, fuse and holder are good.
2. Continuity from L1 to L2 when power switch on? Check. So, live side of power switch is good.
3. Continuity from L2 to L3? Check.
4. Continuity from L3 to pin 8 (120V, which the jumper is set to) of transformer? Check. Voltage selection jumper wire is good.

Next, the neutral side:

5. Continuity from Neutral pin to N1? Check.
6. Continuity from N1 to N2 when power switch on? Check. So, neutral side of power switch is good.
7. Continuity from N2 to pin 6 of transformer? Check.

Pin 6 of the transformer is the return for all the other pins on the primary side of the transformer (7, 100V; 8, 120V; 9, 220V; and 10, 240V).

8. Continuity from pin 6 to pin 8? Nope. Any resistance value between them? Nope. OL.
9. Continuity from pin 6 to 7, 9, or 10? Nope. Resistance measures OL.
10. Any inductance from pin 6 to 8? Yep, at 1kHz I get 38 H.
11. Any inductance from pin 6 to 7, 9, or 10? Nope. OL.

Blown transformer? It's odd that there's no inductance reading except between 6 and 8, since I'm measuring directly on the transformer pins, not through the voltage selection jumper.

I'll have to open up one of the other 3478A I have for comparison.

[Martin.M]

Fluke 8300a..

Q40 RIP

[Specmaster]

@bitseeker have your fuses arrived yet so you apply some gentle power to yours so we can see if its working without blowing those blasted rifas? 

Yep, got fuses. Installed one and first checked between the Live and Neutral IEC pins with power switch off and on like mnem did, below.

Fuse tests good; Infinity across the mains open circuit, and and 94 Ohms with it turned on.

Unfortunately, I get open circuit with the switch in either position. So, started tracing around the primary side of the power supply.

Start on the live side:

1. Continuity from Live pin to L1? Check. So, fuse and holder are good.
2. Continuity from L1 to L2 when power switch on? Check. So, live side of power switch is good.
3. Continuity from L2 to L3? Check.
4. Continuity from L3 to pin 8 (120V, which the jumper is set to) of transformer? Check. Voltage selection jumper wire is good.

Next, the neutral side:

5. Continuity from Neutral pin to N1? Check.
6. Continuity from N1 to N2 when power switch on? Check. So, neutral side of power switch is good.
7. Continuity from N2 to pin 6 of transformer? Check.

Pin 6 of the transformer is the return for all the other pins on the primary side of the transformer (7, 100V; 8, 120V; 9, 220V; and 10, 240V).

8. Continuity from pin 6 to pin 8? Nope. Any resistance value between them? Nope. OL.
9. Continuity from pin 6 to 7, 9, or 10? Nope. Resistance measures OL.
10. Any inductance from pin 6 to 8? Yep, at 1kHz I get 38 H.
11. Any inductance from pin 6 to 7, 9, or 10? Nope. OL.

Blown transformer? It's odd that there's no inductance reading except between 6 and 8, since I'm measuring directly on the transformer pins, not through the voltage selection jumper.

I'll have to open up one of the other 3478A I have for comparison.

Oh dear sorry to hear that, sounds like someone may have plugged it in on a 240v system and blown the potted  transformer. Are they available or is it down to finding a donor meter?

[Cerebus]

Blown transformer? It's odd that there's no inductance reading except between 6 and 8, since I'm measuring directly on the transformer pins, not through the voltage selection jumper.

Yes, that's odd. A wild theory is that the primary has blown, but in such a way that the break is acting as a little capacitor. That would give you a situation where you could measure AC but not DC phenomena. The only way to test that theory would be to put it on a VNA and see what the whole complex impedance looks like.

[bd139]

On a positive note it should be pretty easy to bring it up on a power supply to test the rest of it. The thing requires usual +/-15v and two 5v rails (isolated).

A couple of cheap toroidal transformers would be a good substitute and there are no weird multi taps or anything to have to emulate.

All the rails have Zener clamps on them so should be fine even if someone stuffed 250v into it.

[bd139]

Found a flaw in teh TF930 counters ... there's a sensitivity dead spot!

I'm using an Si5351A to generate a 100MHz to 200MHz sweep through a filter. Connected to input B. No reading on 3dBm into 50 ohms between 80-115MHz. Grr! Have to stick it in input A. Problem with that is it goes up to about 135MHz and then stops responding.

Also you NEED a TCXO on the Si5351A not a shitty 27MHz crystal for that sort of tat. Drifts like mad

[med6753]

I finally fixed the drift issue with the Fluke 8600A and I posted the results here:

https://www.eevblog.com/forum/testgear/old-fluke-multimeters/msg1890722/#msg1890722

[Ero-Shan]

Now for something completely ... TEA.

When there actually is something on the 'bay, I do contemplate whether it is really necessary to bid on it. But that sanity filter just doesn't work for very cheap things, and so I jumped at a PM3233, a low-end scope sold as defect/for parts (the pictures showed that the knobs for all pushbutton switches were missing, and two switches were gone completely). Seller said that with the wires from the missing switches connected traces could be seen.
As I have 12 Philips scopes I thought the parts might be worth 10 Euro in case they could be used for the others.

Got it for 2.50 € (+6.50 shipping). Exemplarily packed (even Keysight would have acknowledged this  ).

Also missing: Front cover, handle and feet. I'm beginning to suspect that somewhere there is someone with a foot fetish who steals them off all the equipment.



In order to short the wires (switch on both traces) I opened it and did so. Then switched it on.

Now the bad news: It worked quite well. The traces are somewhat dim and not too focused, but I just love the color! Green with a tint of yellow, beautiful.


Very stable display, not the slightest bit sensitive to knocking. A small ripple on the traces with a frequency that hinted at the SMPS.

I decided to look at the caps and found a few losers. I know you hate these blue Philips caps, but most were still good.


This helped with the ripple.

Then one bulb of the graticule illumination was open. Looking at my lamp collection I was astonished to find a whole bunch with the correct rating (28 V/40 mA). But not the right socket! As is my wont, I try to make do with what I have, especially with something that's officially worthless.
Left is the original, in the middle the original replacement, to the right my makeshift solution.


Now what am I supposed to do? I can not be expected to scrap a working oscilloscope, can I?
BTW: The PM3233 has a split-beam picture tube, a point in its favor, I think.

A few more pics (aren't these nice delay lines?).

[med6753]

That Philips scope is definitely worth fixing up. 

[Berni]

The insides look so neat and tidy, all the wires running in such clean sweeping curves.

[mnementh]

Ero-Shan -

Awesome score!

A working dual-beam 'scope for 10 clams is surely a winner; and that color is different. Is it the actual phosphor or just the lens, (which looks terminally yellowed from here) ?

Excellent MacGyver-fyin' on the bulb; I've been guilty of similar modding on numerous occasions. Always nice to be able to turn what you have into what you need; there's a unique elegance in such solutions where the primary ingredient is your own ingenuity. 

(SNIP)
8. Continuity from pin 6 to pin 8? Nope. Any resistance value between them? Nope. OL.
9. Continuity from pin 6 to 7, 9, or 10? Nope. Resistance measures OL.
10. Any inductance from pin 6 to 8? Yep, at 1kHz I get 38 H.
11. Any inductance from pin 6 to 7, 9, or 10? Nope. OL.

Blown transformer? It's odd that there's no inductance reading except between 6 and 8, since I'm measuring directly on the transformer pins, not through the voltage selection jumper.

I'll have to open up one of the other 3478A I have for comparison.

Hmmm... Sounds like you're best off to back-burner this one for now and move on to one of the other ones, both in terms data collection and repair viability. 

First rule of Triage: Never be afraid to say "He's dead, Jim!" and move onto the next patient, especially if you have multiple of the same breed. Triaging the next one often brings knowledge that will help you resurrect the first one later.

Quality XFMR will usually have a thermal fuse in the common tap on the primary side that often saves the windings; but if you have multiple taps on the primary and no continuity between the other taps, prospects are not good. 

mnem
"Coffee break's over; everybody back on your heads!"

[Cerebus]

A couple of cheap toroidal transformers would be a good substitute and there are no weird multi taps or anything to have to emulate.

I think there's an electrostatic shield between the primary and the secondaries to reduce common mode noise injection. It's a normal feature in most HP bench DMMs; the schematics for the 3478 don't make it clear if there's a shield or if the core is just grounded. Not having it wouldn't be a show stopper, but there are obvious drawbacks if it isn't.

[Specmaster]

Found a flaw in teh TF930 counters ... there's a sensitivity dead spot!

I'm using an Si5351A to generate a 100MHz to 200MHz sweep through a filter. Connected to input B. No reading on 3dBm into 50 ohms between 80-115MHz. Grr! Have to stick it in input A. Problem with that is it goes up to about 135MHz and then stops responding.

Also you NEED a TCXO on the Si5351A not a shitty 27MHz crystal for that sort of tat. Drifts like mad

Just tried mine on input B, works flawlessly all the way to 141MHz which is where my sig gen maxes out at.

[Ero-Shan]

Ero-Shan -

Awesome score!

A working dual-beam 'scope for 10 clams is surely a winner; and that color is different. Is it the actual phosphor or just the lens, (which looks terminally yellowed from here) ?

Excellent MacGyver-fyin' on the bulb; I've been guilty of similar modding on numerous occasions. Always nice to be able to turn what you have into what you need; there's a unique elegance in such solutions where the primary ingredient is your own ingenuity. 

Without filter the traces are a whiteish-green.

Do I now have to look for a second PM3233 that is really dead (but has the switch caps)?

It would have been so much easier if it hadn't worked ... 

[Specmaster]

Ero-Shan, good snag with that scope, shame as you say that it works but it is worth saving as they do make some really excellent scopes and I regret selling mine now. As you can see, most things are so easy to get at and it looks so minimal inside and yet packs a punch.

[mnementh]

Ero-Shan -

Awesome score!

A working dual-beam 'scope for 10 clams is surely a winner; and that color is different. Is it the actual phosphor or just the lens, (which looks terminally yellowed from here) ?

Excellent MacGyver-fyin' on the bulb; I've been guilty of similar modding on numerous occasions. Always nice to be able to turn what you have into what you need; there's a unique elegance in such solutions where the primary ingredient is your own ingenuity. 

Without filter the traces are a whiteish-green.

Do I now have to look for a second PM3233 that is really dead (but has the switch caps)?

It would have been so much easier if it hadn't worked ... 

Looks to me like a good excuse to get into 3DP... 

mnem
*Off to Fry's*

[bitseeker]

Oh dear sorry to hear that, sounds like someone may have plugged it in on a 240v system and blown the potted  transformer. Are they available or is it down to finding a donor meter?

I haven't checked, but I'd be very surprised if the transformers were still available from Keysight. They lack parts for much newer gear. However, I have some other 3478A with problems (two have shorts in their power supplies, maybe the RIFAs). So, either one of them can be a donor to this guy or this can become a donor for them.

Blown transformer? It's odd that there's no inductance reading except between 6 and 8, since I'm measuring directly on the transformer pins, not through the voltage selection jumper.

Yes, that's odd. A wild theory is that the primary has blown, but in such a way that the break is acting as a little capacitor. That would give you a situation where you could measure AC but not DC phenomena. The only way to test that theory would be to put it on a VNA and see what the whole complex impedance looks like.

Yeah, I was able to measure capacitance on it, too.

On a positive note it should be pretty easy to bring it up on a power supply to test the rest of it. The thing requires usual +/-15v and two 5v rails (isolated).

A couple of cheap toroidal transformers would be a good substitute and there are no weird multi taps or anything to have to emulate.

All the rails have Zener clamps on them so should be fine even if someone stuffed 250v into it.

Exactly. It's a pretty simple supply arrangement. Direct injection to the rails is next on the list to verify that the rest of the meter is still working.

[bitseeker]

Hmmm... Sounds like you're best off to back-burner this one for now and move on to one of the other ones, both in terms data collection and repair viability. 

First rule of Triage: Never be afraid to say "He's dead, Jim!" and move onto the next patient, especially if you have multiple of the same breed. Triaging the next one often brings knowledge that will help you resurrect the first one later.

Quality XFMR will usually have a thermal fuse in the common tap on the primary side that often saves the windings; but if you have multiple taps on the primary and no continuity between the other taps, prospects are not good. 

I'll try injecting power before I write it off. It may only be "mostly dead." Since the power supply in these is really simple, a replacement could be made pretty easily, if needed.

[tggzzz]

I'll try injecting power before I write it off. It may only be "mostly dead." Since the power supply in these is really simple, a replacement could be made pretty easily, if needed.

That's what I ended up doing with one of my Tek 1502s. Basically I replaced the batteries with a modern AC-12Vdc brick.

Now it can only work when attached to mains supply (and definitely not underwater!), but it is still useful and usable.

[Ero-Shan]

Looks to me like a good excuse to get into 3DP... 

Someone just had to lure me into that rabbit hole!

If it was anywhere mature like 'normal' printing, I might fall for it.
Where would I get the (whatsitcalled?) model for the cap? Do it myself? Ha ha.
Well, a friend of mine just bought a 3D printer, and once I visit him, he's likely to push me towards that very same hole. 

[Specmaster]

Meantime in other news:- TEA related I have just secured myself yet another Fluke 25, in a carry case complete with manual and a set of leads for the huge sum of £15 plus P&P, looks like a winner to me 

In other news, still remotely related since it involves using some of my TEA items  I recently on Ebay snagged a TEAC CR-H250 CD receiver with DAB which had a few problems, all of which are now firmly fixed but it had a fecked DAB module. Searching around on the Bay revealed anther similar unit but this time it was TEAC CR-H240 which is supposed to be the same model but lower output with its own share of problems CD not working and a duff sound channel but research showed that it was a good source of a replacement DAB module, for which I duly struck a deal. Upon receipt I tore it down to reveal 100% identical pcb's even down to the part numbers  have TEAC been lying to us about the power output, it certainly looks like it.

Anyway I get the DAB module out and remove the screening cover to see its been sat in a shed or similar and the DAB module had been sitting in a bath of condensation and was covered in rust inside the screened box and all over the circuitry, it was horrible. Popped it into my el cheapo ultrasonic cleaner bath and a little while later it was cleaned, dried and fitted into the H250 and wonders of wonders it works perfectly so thats the H-250 finished.

Turned my attention the H-240 and worked my way through it and found one 470uF cap that was bulging, took it out and checked it, read as 19pF  , replaced it and both channels are now functioning ok. Removed the CD deck and stripped it down, cleaning all the gear wheels, reassembled and put back in and it too now works perfectly apart from the DAB module.

Went back onto google and discovered a number of units that used the same DAB module and located on Ebay a faulty tuner that will not switch ON but has the correct modul for the DAB within it and I managed to do a deal on that as well so now I'm waiting my latest 2 toys to arrive.

So while its true that Ebay has not been very good lately for TEA items it has been good to me in other directions and provided some valid reasons for playing with my TEA toys 

So the big question now is, when the tuner arrives and donates its module to the H-240, will I be able get the tuner working again on FM, in which case I'm back at square 1 again, looking for a replacement DAB module 

I'm beginning to feel like I'm getting stuck on a ferris wheel and can't off it 

[Specmaster]

Looks to me like a good excuse to get into 3DP... 

Someone just had to lure me into that rabbit hole!

If it was anywhere mature like 'normal' printing, I might fall for it.
Where would I get the (whatsitcalled?) model for the cap? Do it myself? Ha ha.
Well, a friend of mine just bought a 3D printer, and once I visit him, he's likely to push me towards that very same hole. 

If you can find the part number for the knobs you require and then do some google magic you might just get lucky and find that someone has already produced a file  for the printing of such knobs and then you can find a local printer hub to do them for you. I did that recently for knob for a Tektronix TDS210 and it only cost £4.25 a knob.