B&K Precision 1570A oscilloscope

[coiley]

I have the case of my B&K open.

The lights are on - but no one's home: I have no trace.

Could someone refer me to a systematic troubleshooting proceedure?

Thanks,

-- coiley

 

[davenn]

I noticed in a different forum some one lead you to a site that wanted money for a manual
try Ebaman for manuals its free and they have a huge selection.

whilst you do that you could start by checking the PSU section of the scope, maybe there are voltage testpoints marked. check for those voltages. Any that have a voltage but are reading low, chect for faulty electro caps on those rails they have probably dried out and failed.

Dave

 

[coiley]

I noticed in a different forum some one lead you to a site that wanted money for a manual
try Ebaman for manuals its free and they have a huge selection.

whilst you do that you could start by checking the PSU section of the scope, maybe there are voltage testpoints marked. check for those voltages. Any that have a voltage but are reading low, chect for faulty electro caps on those rails they have probably dried out and failed.

Dave

Dave -

Thank you for your reply.

The PSU is working to the extent that all the panel lights work properly and the scale illumination works fine. The panel button logic and illunination is also intact.

I have examined all components that are visible (that is about 80% - without yet removing the boards that are showing "foil" side) for the characteristic physical signs of failure. I have found one component that shouts failure (two images attached). I think it's a thermistor - the markings are not discernable. It's on what appears to me to be the vertical board: x73-1510-00.

BTW - I don't think the B&K Precision 1570A is really B&K at all. I believe it is entirely Trio-Kenwood. There are stickers inside the case that say "TRIO-KENWOOD". And the PCB numbers (e.g.: x73-1510-00) are all consistent with the board numberings from many other Kenwood test-equipment devices. I have read allegations that the B&K Precision 1570A is nothing but a Trio-Kenwood CS-2070. And images of the two units confirm that they are identical in appearance.

Anyway, I think the visibly failed component is a themistor because the PCB labels it TH1 - and that is how Trio-Kenwood boards label thermistors in other hardware diagrams and parts lists.

If anybody recognizes this component, or has a B&K Precision 1570A or a Kenwood CS-2070 to examine, or has a service manual for either, I would be grateful for a suggestion.

I feel like I am SOOO close to having an oscilloscope.

Any further suggestions?


Thanks Dave,

--coiley

 

[(*steve*)]

That doesn't look pretty.

I'm also a bit concerned about the brown gunk near C25. Is there a nearby board (probably above this in the normal orientation) that has a capacitor leaking electrolyte?

 

[coiley]

That doesn't look pretty.

I'm also a bit concerned about the brown gunk near C25. Is there a nearby board (probably above this in the normal orientation) that has a capacitor leaking electrolyte?

That was my first impression too. But I think C25 is intact - and there is nothing oriented above. And I can read the markings (hiden in pix) on C25.

The shell of component TH1 is cracked open (visible in both pix) and there is a mass of gongealed ooze where the component was originally resting. I lifted TH1 up in order to inspect it for markings. TH1 was originally laying in the mass of leaking substance you refer to. In fact, you can still see some of the brown ooze on the surface of TH1 in the first picture.

If I could know the characteristics ot the alleged thermistor, I could temporarily replace it with a resistor that is within operating range. Maybe I should temporarily replace TH1 with, say, a 50K pot. No?

What would be the purpose of a thermistor in such a location?

-- coiley

 

[(*steve*)]

This may be worth looking at.

I googled the board identifier visible in one of your images.

It seems a remarkable coincidence that another oscilloscope would have boards named the same without there being *some* similarities.

I haven't found a reference to the thermistor yet, but I've only just found the PDF.

edit: The thermistor is close to a power transistor of some sort (I note the connections labelled B and E and C under C25. It is possible that this is an NTC thermistor that prevents switch on surges, or a PTC to limit fault current. I would expect that the resistance is much lower. The above-mentioned PDF refers to TH1 as being an Li2-103-2 and also describes several other thermistors bearing this same part number. You may be able to locate another one and measure the resistance at a couple of temperatures to figure out what it is (or you may be able to read the markings)

 

[coiley]

My previous search results turned up that document as well. That is one of the Kenwood doc's that convinced me the B&K is NOT B&K at all. I could not find a board with the same name in numerous other Kenwood service manuals. And boards with similar numbers prove to be dramatically different. I was hoping for minor differences - rev's. But that is not the case.

--coiley

 

[davenn]

I suggest that brown gunk was where the thermistor was glued to the PCB for thermal reasons

 

[(*steve*)]

I suggest that brown gunk was where the thermistor was glued to the PCB for thermal reasons

That crossed my mind as well. I've never seen a thermistor "vomit".

It also suggests that it is not in the circuit to do either of the things I suggested above.

 

[coiley]

Mid way between Beijing and the the Ronne Ice Shelf (mind your projection) ...and don't call me Sir!

Steve - Do you live near Carnarvon? or are you on a boat between Bermuda and The Virgin Islands. (Goode's Homolosine projection & azimuthal equidistant projection)

--coiley

 

[(*steve*)]

Steve - Do you live near Carnarvon? or are you on a boat between Bermuda and The Virgin Islands.

I don't live on a boat

Goode's Homolosine projection & azimuthal equidistant projection

It is very important to use a projection where straight lines represent the shortest route, and where distances are preserved. The obvious complication is that one of the poles is involved, and very few maps will present an image which allows for an area around the pole to be seen as well as areas beyond the equator.

The best option is actually a map in the form of a 3 dimensional object.

Goode's Homolosine, for example, would rely on you passing near, or through some f the discontinuities, and fairly clearly it is not a route one would actually travel.

The Azimuthal equidistant projection allows for measurement from the centre of the map along straight lines. These maps are also known as great circle maps. An important consideration is where the centre of this projection is. Normally it must be on one of the end points of your journey, however it may also be on a point along the intended route. I would be interested in where you had the projection centred. (The south pole would have been a reasonable option)

I suspect the Carnarvon guess comes from the latter projection. It is incorrect, but it is as close as anyone who has followed my instructions has managed.

It's probably reasonable though because my measurements were done by guestimate, and also it is hard to pick a particular point on the Ronne ice shelf (fixed landmarks are somewhat of a tricky issue).

I suggest that you need to consider making your measurement in the depth of winter

I live in a capital city (and that should give it away)

 

[David Breuer]

Hey everyone,

So I have a BK Precison oscilloscope model 2190D, and BK advertises that one can retrieve a waveform from the scope to be read by a personal computer and used in the future. However, when retrieving the file through a USB thumb drive, all the provided export file types given by the oscilloscope cannot be read by WaveXpress, which was provided by BK Precision for the scope. Anybody have any advice or tips? Any help would be greatly appreciated.

 

[hmonnier]

Recently acquired the B&K 1570 scope. Seems to be in very good condition. Only annoyance is the grid illumination is only effective for the bottom half of the screen, not a killer...... The other one is that when you rotate the range switch on channel 2 clockwise, when you get to the 1/2 o'clock position, you sometimes lose the signal, ie: using the internal sq wave, you just get a flat line. But if you ever so slightly pressure a tiny bit more cw, the signal returns to normal. It does not do this on all settings in that area, just 1 or two. Think some contact cleaner is the route to go??? Iv'e been chicken to try it.....
I do have both the operators manual, and the service manual for the scope.... (in case you have questions and have the same scope).
Thanks.....
Henri