Transistor Looking Device with G21 Marking

[comka]

Hi guys  !

can to whom It will be useful, there is a good frame from my scope 
It looks like an earlier printed circuit board assembly,
This can be seen According to the production of components,
as well as on a hybrid assembly of dated 2006 years.
It can also help see what year And what kind of plant
And how the component marking is applied.
This is useful to identify the original components.
Successes in repair.

[bostonman]

Funny enough, that component isn't marked G21, it's marked G2 with a sideways 11.

[bostonman]

I received the replacement components. Unfortunately I've been too busy to solder them, however, tonight I measured them. Although I was quite sure they'd measure similar, I thought double checking wouldn't hurt.

Attached is a comparison of the G21 component, the one with the sideways 32 (either it was blown or someone chose the wrong type because the measurements are different), and the BAR6304. Also, just to show which component I was measuring, I included a picture of the bag.

I'm anxious to get these soldered in, and hopefully will have time Friday or over the weekend.

Edit: I plan to contact Noopy about sending a chip to him to slice. I need to debate whether I should sacrifice a working chip to some degree in order to ruin. It seems reasonable to do in order to gain knowledge about the chip.

[TurboTom]

The replacement diode compares completely fine to the good "G2" of CH4. Differences of the threshold voltage by a few tens of millivolts are normal and the result of slightly different doping processes (different age / fab). Remeber, this diode is supposed to be operating in its "blocking" region during normal operation of the scope. Slight differences in the voltage drop in the conduction region are irrelevant, important is the thickness of the "intrinsic" zone and thus the lifetime of the charge carriers within it. This is what causes the RF conduction of a PIN diode when forward-biased.

[bostonman]

I assumed the differences were perfectly fine, but wanted to post them since many have taken an interest in this component. I was quite pleased with the readings I got, but somewhat expected them to match since the diode configuration made perfect since once light was shed on the device.

I'm anxious to get these installed and test the scope; and nervous too. Obviously I'll post my results once I get the scope running and tested.

Looking at that sideways 32 component and the difference in out of circuit pin measurements, I wonder whether this component is blown (maybe someone replaced it, in turn it damaged the hybrid, a new sideways 32 chip was installed, and the damaged hybrid blew the component) or not blown and just the wrong component.

Unfortunately we'll never know.

Any guess as to how much this would clamp a high input voltage before the hybrid got damaged? As I mentioned, upon buying this scope, I was told that anything over 5V DC while in 50ohm mode will blow the input channel. I find this hard to believe.

[bostonman]

I soldered the BAR6304 components and today ran a self-calibration.

I'm happy to report all four channels passed calibration. Whether the pin diodes will protect over voltage on the input is another story, but I appreciate all the help. As with a few other threads I started, this has been one helpful thread and I'm glad to see such a message board exists to share knowledge.

I'm uncertain whether I should ask this in a new thread, but, when I went to re-seat the RF shields, I noticed one channel has a different series capacitor from the BNC to the circuitry (see attached).

Unfortunately I doubt finding the value will be easy since I don't have smart tweezers, and I'm uncertain if my Fluke will measure such a capacitor (I'm guessing it's in the Pf range). Obviously I need to remove a good capacitor to measure the value, and I'm a bit scared to tinker with what works.

If I can't solve this capacitor issue, I may just leave it as is. The scope seems to work.

[Zero999]

I wouldn't worry about the capacitor being different, but the soldering is dreadful. I'd remove it and resolder it properly.

[bostonman]

I wouldn't worry about the capacitor being different, but the soldering is dreadful.

In all cases where a component was replaced, this was a typical soldering job. I'm not great at soldering surface mount, mainly due to using a bit too much solder, however, I make it a point to center them and make sure they are flat. Not to mention, cleaning so everything looks shiny. I'll assume the person who replaced the components didn't have a good microscope.

The eight-pin op-amp or whatever it was had solder balls. They were big enough and close enough to pins that I'm shocked it didn't short (or maybe it did and blew the hybrids). Thankfully those were easy enough to replace and make them look new again.

Speaking of centering components and making sure the soldering is good, I totally forgot, the footprint for the SOT-323 fit perfectly.

Ideally I'd like to replace the capacitor. I've really cleaned this scope and leaving a wrong capacitor would be a sin at this point, but it will probably be too difficult to figure out the value since caps have a high tolerance. Due to the soldering job, and the person using a G21 with a sideways 32 (which measured differently), one has to wonder how they chose this capacitor value.

For all I know, it could be the wrong value and causing the input signal to lose amplitude due to impedance mismatch.

Edit: does a more accurate way exist to measure the value of the component? I have a Fluke 179, and I believe I have other meters too. I think I'll go for the big prize and remove a good capacitor to measure (and measure physical size).

[bostonman]

I didn't remove a good capacitor to measure its value, but I began by looking at how it's connected. Fortunately it's connected across a V224NS which is a FET relay.

This capacitor is in series with two 1.96k resistors (also in series) which go across pin 4 and 6 (but they also branch out to other circuitry).

I was hoping looking at the datasheet would specify the capacitor to use, especially since this is a CR snubber, however, I didn't see a value.

The cap size is approximately 0.1" x 0.124".

I plan to remove a good one and measure the value.

Does that look like a ceramic capacitor (so I know what type to search for)?

[Zero999]

If it's working, then both capacitors will be good.

I'd leave well alone, unless it's to fix the crappy soldering.

[gamalot]

For MLCC, especially those with relatively large size, I will choose to replace it with a new one or leave it there without touching it. Re-soldering may run the risk of damaging it due to uneven heating.

[bostonman]

For MLCC

I assume Multi Layer Ceramic Capacitor?

I am 90% in favor of leaving this (unless it's to fix the solder). I'm assuming the difference in physical size is due to under voltage value that may short at some point.

[bostonman]

For MLCC, especially those with relatively large size, I will choose to replace it

Out of curiosity, but how did you know this is a multi-layer capacitor? Or maybe the better question: what physical properties does this have that determines it's a MLCC?

[gamalot]

I haven't seriously studied what the precise definition of MLCC is, and my English has restricted me from describing it in detail. My thinking is simple. If it looks like the MLCCs I have seen in the past, then it should be an MLCC. Although their colors will be different because of the use of different materials (X7R, X5R, COG, Y5V, etc.), it is still easy to put them into one category.

[bostonman]

Stating it's a MLCC is a big help because I thought due to it's size, it was just a higher voltage rated capacitor, however, now I know it's a MLCC.

Because it's a snubber circuit, I want to be sure it protects the component(s) it's designed to protect, and not keep the wrong type/size/value in the circuit.

I'm fearing if I remove a good capacitor to measure the value, it may be out of range for my Fluke. Plus, I still need to figure out if it's a X7R, YSV, etc...

It would be nice to return to the days when components were big and had markings.

[bostonman]

You seem to be correct about it being a MLCC because I removed a good capacitor to measure, and got 24pF.

When I start the filtering process on Mouser (and maybe DigiKey), I begin with 24pF and a 1210 body (I measured the capacitor size to be 0.1" x 0.12) since those are the two things I'm fairly sure of and it basically shows me just MLCC.

I'm going to measure the capacitor with another meter to see if I also get 24pF because I'm finding only around 27pF (.027uF) values I think.

Edit:

I was re-reading a few messages back and realized I made an error when I typed:

I just placed another Digikey order, this time for 15 of the BAR64W. Although I don't have any intentions of using these, I also bought 15 of the E version and 10 of the BAT54S.

Obviously I meant BAR63W, however, it's obvious I ordered the correct ones because I included a picture of the bag in a previous post.

[Zero999]

Are you sure it's a snubber circuit? 24pF is a 5% tolerance value, or better, which is quite close for a capacitor. Snubbers generally don't require close tolerance parts, 20% is often adequate. If it really is a snubber, 5% tolerance might be used to simplifiy the BoM: it's easier to use all 24pF 5% capacitors, rather than a few 24pF 5% and a couple 22pF 20%.

[TurboTom]

This cap appears to be the input AC coupling (DC blocking) element since it's basically in parallel to a photomos relay (this black NAIS labeled component). As such, I'ld expect it to have a rather large(ish) capacitance, at least 100nF, maybe 220 or 470. The 1210 form factor makes me assume its voltage rating is at least 250V, maybe even 400V (since that's the rating of the photomos relay, I assume rather the latter is correct, possibly even higher).

The way to appraoch unknown components is to look at the surrounding circuitry, understand what they are supposed to do and then decide if a measured figure makes sense in this environment. 24pF definitely doesn't seem right to me for this cap.

[bostonman]

The assumption of it being a snubber is due to page 7 of that datasheet which mentioned it being a snubber. Obviously I'm uncertain and open to accepting it being used differently.

I fully agree with you on the voltage. I planned to buy the largest voltage rated capacitor I could; unless of course it became so big that it wouldn't fit under the RF shield.

I already supplied the measurements, but tonight I measured the height to be approximately: 0.065" or 1.65mm

Attached is the measurements using different meters. To make sure I got good connections, I soldered fly leads to the capacitor even after I measured it without the leads and got approximately 24nF.

The first meter I used (not shown) was a Fluke 179, and this is where I got 24nF. Initially I used the test leads connected to clip leads, thus making the leads far too long. Unfortunately this was the only way to make a solid connection, but eventually I used just the clip leads and held them inside the meter test lead holes (although I didn't see much difference in capacitance using shorter leads).

After I used another meter, and, to make sure meter lead length wasn't an issue, I held the capacitor directly to copper wire I shoved in the holes due to them not accepting the larger size plugs on my test leads. The clip lead holding the fly lead on the capacitor isn't connected to anything and just used to prevent my body from altering the capacitance measurement by holding it directly.

You'll see in all cases the capacitor measures approximately 23nF, however, I'm still open to the possibility this capacitor should be a higher value.

The replacement capacitor someone shoved in another channel/circuit is a typical 0603 (?), so I assume it's not the correct voltage. Since I didn't see any capacitors in the other channel with poor soldering, I'm confident someone didn't take time to remove a good capacitor and measure it like I did. My point is: it's probably good I'm taking time to replace the small 0603 capacitor.

On a side note, I sent an email to Panasonic about whether a spec exists for that capacitor value in hopes this is a external value called out for their part. So far I got the request on providing my company name, predicted volume, whether it's a new project, etc... After stating that I'm just a hobbyist requesting technical information, it was asked I provide expected voltage, load current, etc...

Since I don't know any of these numbers, I guess I'm out of luck in taking that route.

[TurboTom]

22nF or 27nF may be correct. Before, we talked about picofarads, but as I now see this may just have been the result of an error converting from microfarads...

Check this search page on Arrow for a selection of 27nF 500V 1210 MLCCs that would surely do the job. I decided to rather chose 27nF since MLCCs from experience usually measure below their rated capacitance, so 22nF may be too small. Anyway, this is not the place for a precision component, and some 10~20% too high wouldn't be an issue.

[bostonman]

Before, we talked about picofarads, but as I now see this may just have been the result of an error converting from microfarads...

I'm mad at myself. I re-read my older message and realized I kept typing pF instead of nF.

I made the same mistake in my last post, however, I caught myself just before sending it. Typically I've only dealt with uF and pF only, and I'm not familiar with having to type nF values.

Making these mistakes aggravates me because I waste my time, and the time of others.

[bostonman]

I think this Acquisition Board for the scope is at the completed stage.

The recent findings was a broken ZIF connector and the capacitor in question (although I knew about the ZIF connector sometime ago).

Anyway, I've gone ahead and replaced the ZIF connector and capacitor. As suggested, I should go with a 27nF, 500V. After digging in DigiKey, I found a 630V and a 22nF capacitor 1000V. I ordered both in hopes the 1000V 22nF would be a bit on the high side (closer to 24nF), however, both capacitors measured near their exact value.

Unfortunately the 1000V seemed a bit too tall. Although it looked like the RF shield would have enough clearance, it was very close. It turns out the 630V 22nF looked like the exact height of a good one. This alludes to the comforting feeling that 630V is either the correct voltage rating, or at least 130V above the original (i.e. 500V).

Upon removing the obvious undersized capacitor and measuring it, I believe (I'll need to double check) it was up around 330nF.

At this point I've replaced all the components in question that were different than those in a good channel; including the two bad hybrid chips.

If not for this message thread, I doubt this scope would have been repaired. Thanks for all the help.

The only remaining change is an upgrade on the power supply fan (arriving tomorrow). This will make the scope run quieter.

After the fan and reassembling the scope, it should pass calibration again since it passed before, and also since nothing major has been changed (except the capacitor and the ZIF connector which is for the Probe Board ribbon cable).

Thanks again

Edit: the capacitor I used is 478-12869-1-ND (the 1000V one that was too large and not used is: 399-C1210C223JDGACAUTOCT-ND)