Date   
Re: Sooty cabling

Chuck Harris
 

One other source of black soot is radon.

Radon exists in the atmosphere everywhere, and
is often concentrated in the lower floors of
houses and businesses... particularly well
sealed houses and businesses.

Radon-222 is a pretty short lived product of
uranium decay, with a half life of 3.8 days.
Which means that if you have a bunch of radon-
222 atoms, after 3.8 days, you will only have
half as much as you started with.

When radon decays, it transmutes into a chain of
rather short lived isotopes, settling for a while
on lead-210.

Lead-210 has a half life of 22 years, so it hangs
around quite a long while as a blackish gray
slightly radioactive, beta emitting dust.

The end of the line for radon-222 decay is
lead-206, which is stable.

Radon daughters, which is what these progeny of
radon decay are commonly called, tend to carry a
positive, or negative electrostatic charge born of
losing the beta or alpha particle, and like to
stick to dust particles. Being charged, they are
especially well attracted to high voltage wires,
such as CRT anode leads.

It can be quite illuminating to take a Geiger-Mueller
counter with a beta (mica) window to these residues.

-Chuck Harris


Merchison Burke merchison@... [TekScopes] wrote:

I agree with you Dave. I still use a solid-state TV with a CRT. It
collects black dust on the outside and on the face of the screen. I have
cleaned it many times and it has been working for the past 8 years
without any failures, yet the black dust keeps appearing, so I don't buy
the indication of failures.

Every scope and TV (with CRTs) that I have seen, have black soot or dust
on the inside and on the outside of the TVs. Even the ceiling just above
he TV is blackened with soot (the TV on top of an instrument rack but
the instruments are rarely on).

I would prefer to believe that the black soot is from automotive
exhaust. We all live with open windows. Even in a lab, which is
air-conditioned, the remnants of the automotive exhaust enters on the
clothes and person of the workers, is attracted and collected by the
high voltage potential. This is the way 'electro-static air filters' work.

Re: TR502 A120 Assembly Required.... transistor update

Ed Breya
 

Congrats on progress so far. It looks like you've answered the question of how the ground plane continuity is provided by the conductive rubber layer. I'd guess it's a grayish colored stuff due to being loaded with silver particles. The same is often used as compressible gasketing for lids and such.

Ed

Re: TR502 A120 Assembly Required.... transistor update

NigelP
 

Now confirmed; feedthroughs removed (unscrewed), clamps undone, microstrips severed and substrate removed from the assembly :).

The substrate is compressed by the screws and clamps onto a conductive rubber (?) backing strip which stretches the whole length of the assembly underneath all the substrates to provide the ground plane; measures pretty much zero ohms.

Now to clean up the transistor pad areas and hopefully solder a new device in......... another day I think; too much excitement for one day!

Nigel G8AYM

Re: 575 curve tracer on UK eBay

Richard Solomon
 

I'll see your 585A and raise you a 555 !!

Great in the winter for keeping the basement
warm.

73, Dick, W1KSZ

On Mon, May 8, 2017 at 8:15 AM, aodiversen@... [TekScopes] <
TekScopes@...> wrote:



You must be exaggerating. Standby 200 W. My 585A power consumption is more
than 3 times larger than that.
Albert


---In TekScopes@..., <daveyk021@...> wrote :

I just looked that up. That gigantic thing is only a curve tracer and not
an oscilloscope? Wow, ugh.

I can see the electric meter spinning every time you test a transistor
(does anyone really do that anymore?).

Dave


On Mon, May 8, 2017 at 10:25 Chris Trask christrask@... mailto:christrask@...

[TekScopes] <TekScopes@... mailto:TekScopes@...>
wrote:


http://www.ebay.co.uk/itm/322485484026 http://www.ebay.co.uk/itm/
322485484026

No affiliation

Cheers
Dave
Blimey - that is expensive. I paid £40 for my first one, and £100 for
my second (with mod 122C).
Maybe I'm just a cheapskate ;-)
I paid $20 for mine. Had to carry it quite a distance to my pickup.
That's
when you learn why there are two heavy leather handles on the top.

Chris Trask
N7ZWY / WDX3HLB
http://www.home.earthlink.net/~christrask/
http://www.home.earthlink.net/~christrask/








[Non-text portions of this message have been removed]

Re: 575 curve tracer on UK eBay

Craig Sawyers <c.sawyers@...>
 

I paid $20 for mine. Had to carry it quite a distance to my pickup. That's when you learn why
there
are two heavy leather handles on the top.

Chris Trask
N7ZWY / WDX3HLB
http://www.home.earthlink.net/~christrask/
That was a nice price for a 575!

Craig

Re: 575 curve tracer on UK eBay

Craig Sawyers <c.sawyers@...>
 

I just looked that up. That gigantic thing is only a curve tracer and not an oscilloscope? Wow, ugh.

I can see the electric meter spinning every time you test a transistor (does anyone really do that
anymore?).

Dave
Well they do more than transistors. Diodes, Zeners, Tunnel Diodes. And you are pushed to test a TD
without a curve tracer. And if you want to match transistors - particularly FET's both junction and
MOS - for audio applications they are darned useful. And you can test and optimise component
combinations, like cascode. With modest additions, you can also do tubes (check recent threads about
tube curve tracing on a 576).

I have two 575's, one with the high voltage Mod 122C, and also the high current facility the 175. I
also have a 577 with split storage screen, a 576 and a 7CT1N. Because why wouldn't you?

Craig

Re: 575 curve tracer on UK eBay

Albert Otten
 

You must be exaggerating. Standby 200 W. My 585A power consumption is more than 3 times larger than that.
Albert


---In TekScopes@..., <daveyk021@...> wrote :

I just looked that up. That gigantic thing is only a curve tracer and not
an oscilloscope? Wow, ugh.

I can see the electric meter spinning every time you test a transistor
(does anyone really do that anymore?).

Dave


On Mon, May 8, 2017 at 10:25 Chris Trask christrask@... mailto:christrask@...
[TekScopes] <TekScopes@... mailto:TekScopes@...> wrote:

> >
> >> http://www.ebay.co.uk/itm/322485484026 http://www.ebay.co.uk/itm/322485484026
> >>
> >> No affiliation
> >>
> >> Cheers
> >> Dave
> >
> >Blimey - that is expensive. I paid £40 for my first one, and £100 for
> >my second (with mod 122C).
> >Maybe I'm just a cheapskate ;-)
> >
>
> I paid $20 for mine. Had to carry it quite a distance to my pickup. That's
> when you learn why there are two heavy leather handles on the top.
>
> Chris Trask
> N7ZWY / WDX3HLB
> http://www.home.earthlink.net/~christrask/ http://www.home.earthlink.net/~christrask/
>
>

Re: Sooty cabling

NigelP
 

As a long-term TV design engineer (since 1966) I can indeed confirm that it is very normal to have black gunk attached to anything high voltage!

In the old days TVs had in excess of 28KV on their final anodes but even a few KV will still attract dirty dust in quite a short timeframe, so for 12-15KV in a scope this is normal.

In fact dust immediately attaches itself to anything remotely static... try rubbing a plastic meter "glass" with a cloth and see what happens (apart from the needle wanging over to one side). Only the other day I was trying to clean something and every time I rubbed a cloth over it more dust appeared!

Nigel G8AYM

Re: AWG2020 Power Supply Standby Circuit

Converter
 

Chris, did you manage to find any electrical circuits for AWG2xxx, as well as information on decoding the error messages of the self-test? I still have the error "710" and "641" on the AWG2020 display.
You wrote about the AWG2041 service manual, can you give me a link to this?


Sergey.

Re: 575 curve tracer on UK eBay

David Kuhn
 

I just looked that up. That gigantic thing is only a curve tracer and not
an oscilloscope? Wow, ugh.

I can see the electric meter spinning every time you test a transistor
(does anyone really do that anymore?).

Dave


On Mon, May 8, 2017 at 10:25 Chris Trask christrask@...
[TekScopes] <TekScopes@...> wrote:


http://www.ebay.co.uk/itm/322485484026

No affiliation

Cheers
Dave
Blimey - that is expensive. I paid £40 for my first one, and £100 for
my second (with mod 122C).
Maybe I'm just a cheapskate ;-)
I paid $20 for mine. Had to carry it quite a distance to my pickup. That's
when you learn why there are two heavy leather handles on the top.

Chris Trask
N7ZWY / WDX3HLB
http://www.home.earthlink.net/~christrask/


[Non-text portions of this message have been removed]

Re: 575 curve tracer on UK eBay

Chris Trask - N7ZWY/WDX3HLB
 


http://www.ebay.co.uk/itm/322485484026

No affiliation

Cheers
Dave
Blimey - that is expensive. I paid £40 for my first one, and £100 for
my second (with mod 122C).
Maybe I'm just a cheapskate ;-)
I paid $20 for mine. Had to carry it quite a distance to my pickup. That's when you learn why there are two heavy leather handles on the top.

Chris Trask
N7ZWY / WDX3HLB
http://www.home.earthlink.net/~christrask/

Re: 575 curve tracer on UK eBay

Craig Sawyers <c.sawyers@...>
 

http://www.ebay.co.uk/itm/322485484026

No affiliation

Cheers
Dave
Blimey - that is expensive. I paid �40 for my first one, and �100 for my second (with mod 122C).
Maybe I'm just a cheapskate ;-)

Craig

Re: AWG2020 Power Supply Standby Circuit

Converter
 

Hello,


You probably already saw on the processor board installed 16-pin microcircuit "Microprocessor control controller/Precision voltage controller" MAX695. You can see the datasheet here: https://datasheets.maximintegrated.com/en/ds/MAX690-MAX695.pdf https://docs.google.com/viewer?docex=1&url=https://datasheets.maximintegrated.com/en/ds/MAX690-MAX695.pdf


I recently bought AWG2020 on eBay, and had a problem with the need to hold down the power button on the front panel. It looked almost the same as that of the author of an article on the Internet: http://jvgavila.com/awg2020n.jpg http://jvgavila.com/awg2020n.jpg .
The cause of the problem is usually the corrosion of printed conductors. In my case, just like the author, 2 tracks were damaged, which are sent to the transistors next to the microcircuit. I also repaired one of the tracks on the back of the PCB. Now this problem is fixed.

Check all the conductors and connections in the area around this IC and on the back of the PCB. Check also the integrity of the through-through metallization of the holes. To fully clean the corrosion, I was forced to completely disassemble the chip and some of the SMD elements, after which they were soldered again.

Sergey.

Re: Sooty cabling

Merchison Burke
 

I agree with you Dave. I still use a solid-state TV with a CRT. It collects black dust on the outside and on the face of the screen. I have cleaned it many times and it has been working for the past 8 years without any failures, yet the black dust keeps appearing, so I don't buy the indication of failures.

Every scope and TV (with CRTs) that I have seen, have black soot or dust on the inside and on the outside of the TVs. Even the ceiling just above he TV is blackened with soot (the TV on top of an instrument rack but the instruments are rarely on).

I would prefer to believe that the black soot is from automotive exhaust. We all live with open windows. Even in a lab, which is air-conditioned, the remnants of the automotive exhaust enters on the clothes and person of the workers, is attracted and collected by the high voltage potential. This is the way 'electro-static air filters' work.

On 2017-May-08 8:30 AM, 'David C. Partridge' @perdrix [TekScopes] wrote:
No - it is normal, not any indication of failures.

Dave

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: 08 May 2017 12:10
To: TekScopes@...
Subject: Re: [TekScopes] Sooty cabling

Right, so far as the sooty EHT components are concerned, it would seem that
these can arise from a blown component elsewhere

575 curve tracer on UK eBay

 

S2A Timebase for D83 scope.

James R. Bartlett
 

Hello to the group.
Long time reader and learner on this site, infrequent poster.
I now find myself in need of an S2A timebase for my D83 Telequipment scope.
Does anyone have one that I could purchase. I also need the Perspex ? knob
for the Delayed timebase.
Any help pointers etc would be much appreciated.
Many thanks
Jim
Ei2BB

Re: Type 503 Oscilloscope Issues

Trevor
 

Measurements point towards open or very leaky -100 volt rail filter capacitors C682 and/or C684.  Electrolytics can fail such as to become leaky, or fail such that they have greatly reduced capacitance, many times essentially zero, when they fail open circuit. Disconnect one lead of each of these caps to facilitate leakage measurement with your DVM.
Then, if you lack a capacitance meter, another more crude capacitance test is as follows: Put your DVM in the resistance mode on the 20k scale and probe the two cap terminals, and watch the meter reading. If the capacitor is functioning properly, the reading will start low and increase over the course of a few seconds or so, as the meter charges to cap, and then read "ol" (or whatever indication the meter gives for off scale readings.) You can repeat the test, but will have to first discharge the cap by shorting it.Ideally, the correct polarity should be employed, meaning that the DVM positive lead should connect to the capacitor positive lead. In practice, at the <2 volts applied, polarity should not matter. If you put the meter on the 200k scale, the charging process slows down by a factor of ten, so will be even more easily observed. Going to an even higher scale, 2M, the capacitor's leakage resistance will begin to interfere with this method. You can get a rough idea of the value of the capacitor by comparing the results to another known good capacitor. So if you have an electrolytic cap that is 20 to 80 microfarads, experiment with it.

Before connecting your DVM or a capacitance meter to any capacitors, assure that the cap. is discharged. If the scope has been off for some time, charges tend to decay toward zero. But to be safe. since some types of capacitors can hold charge for weeks, manually shorting capacitors before measurement is a good practice.
My apologies  to Evan and the mentors if this is redundant advice, it's a long thread and I did not thoroughly scour it.
Trevor

On Sunday, May 7, 2017 1:38 PM, "'John Snyder' Kochcal@... [TekScopes]" <TekScopes@...> wrote:


  I look like your making progress, some things you try don't reveal things.

Dave's point of Turning all the front panel adjustments is a good idea to
see if it changes the loading on the -100V, if one has a big change it can
indicate a part of the circuit that is the problem. If the overload is
through one of the tubes the associated adjustment should change the tube
operating point and current that may release the -100V a bit.

But it might not.

I would try other things before changing any other "inside" calibration
adjustments other then R641. The existing calibration can have some value as
it can take time and equipment to restore.

Other things to look at:

I don't recall if you have already measured the resistance of the -100V bus
to ground (be sure to turn power off, wait, ground -100V bus for a while
remove ground, before testing to remove any charge on the capacitor) that
would be a good starting point.

Have you done a AC voltage reading on the -100V to see if the problem is a
low DC or more of a AC wave on top of the DC resulting in a lower average?

The -100V should have a AC voltage that is very low compared to a volt.

And then the same question as to the +500V on C612

The 500V could have 1's to few 10's of volts of AC but much more then it
would be a concern and need some calulating.

I don't recall or missed if you checked the input DC power caps C611 or
C612.

If you have can you re-report the check?

If you have not, one way to help check those would be to clip on a pair of
350V to 450V caps in parallel with each one. Those generally have a very
large range of value like +20%,-80% so it might only take 30uF's or so to
function. And that would be a good way to help eliminate that possibility
that that part of the power supply that is cutting out 120 times per second.

The scope is functioning enough that you might be able to use it self to
probe some circuits.

Do you have any probes and if so can you tell us, there nature, model
numbers or ratings? To see if they can be used for the voltages needed for
some tests you can do to help.

John

For later:

You can see on the schematics that there are typical voltages at nodes for
parts of the circuit. (best made if all the scope knobs are set as stated in
the manual for testing) Measuring those and reporting them, might lead to
clue as to the location of the problem, but with the -100V low most will
readings will be offset in some way, and it will be a bit more challenging
to use them to locate the area of over current. But we might be able to find
something.

I don't recall if you have done any tests to check D682, C682 C684, a leak
there would be generally independent of the tubes being pulled.

If you are running the scope for a while you can check for the temperature
of D682, C682 C684 if it's different from the other diodes, But be sure to
measure all the voltages 250V 100V -100V to be sure they are discharged be
for sticking a finger in there. Not a great test (see scope probe Questions
below)

You still have a visual check of everything connected to the -100V

And measuring the voltage of across each resistor that is connected to the
-100V

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: Saturday, May 06, 2017 10:39 PM
To: TekScopes@...
Subject: [TekScopes] Re: Type 503 Oscilloscope Issues

Yes, from the calibrator, the scope is out of spec (at 420 mV and 4.1 mV),
but the calibrator image is not stable. Here is a link to what I mean:
https://goo.gl/photos/BZzZ41sma3vz5R717
https://goo.gl/photos/BZzZ41sma3vz5R717.

From the images, the square wave's magnitude is ~0.8 cm (compared to the
expected full 1 cm). However, as seen in the video, the issue of the waves
"warping" is even more present here, aside from a general instability of the
trace.


I still have not looked at turning each adjustment knob to see the effect,
but I will try to get that done tomorrow.


- Evan

[Non-text portions of this message have been removed]

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Re: Sooty cabling

 

No - it is normal, not any indication of failures.

Dave

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: 08 May 2017 12:10
To: TekScopes@...
Subject: Re: [TekScopes] Sooty cabling

Right, so far as the sooty EHT components are concerned, it would seem that
these can arise from a blown component elsewhere

Re: TR502 A120 Assembly Required.... transistor update

NigelP
 

Thanks for all the interesting feedback..... I feel a bit better now :).

My comment about the RF ground plane is that there appears to be no RF-ground continuity between substrates other than via the casing. Certainly the decoupling capacitor ground pads do have a via through to the back-side but that doesn't explain how RF ground continuity is achieved module-to-module since there is no visible ground continuity on the top-side. What is the chance that the substrate is glued into the casing with RF-conductive paste to maintain a continuous RF ground plane from one end of the whole assembly to the other??? There is a total of eight substrates in the daisy-chain; four amplifiers, two filters and two I/O micro-strip to SMA-coax launchers.

I referred to the substrate as being "beryllia", by which I could mean alumina etc; it's a shiny white hard material (although one is not shiny, just a matt finish). The substrates are clamped by metal strips with fingers, the screws being set into the main casing, so yes I presume the fingers create the required pressure.

I should be able to unbolt the two lead-through capacitors connecting to the offending substrate to give better access space since one gold connection tape is already severed and I'd have to sever the other in order to remove the substrate.

Nigel G8AYM

Dm64 Focus

John Exley
 

HI all
I have a dm 64 my problem focus or lack of it the lamp is fine and the photo transistreacts to light and the focus control but
only very slightly on the screen also I have a small pc board fixed to the bottom of pc111 I cannot find any trace of it in the
I think it controles the 100v to the HT but as r415 for the 110v to 100v is on it with a bf305And thank you for your quick reply to my joining emal i will try to contribute but I am no where near as smart as some of
the people on this forum
Regards
John