Fluke ScopeMeter 199 no Channel A trace. - Page 1
Forum section: electronics / repair

author: DaveMX5mk1
author_rank: Contributor
timestamp: May 02, 2020, 10:57:09 am
content: Hi, I wonder if anyone can help with a problem I have on a Fluke ScopeMeter 199. I think the 192 and 196 are basically the same.The unit powers up fine but there is no trace. The alphanumeric information is displayed. If I turn on channel B the trace comes on and seems to works as it should. The DVM part of the unit also works as normal.There are two identical circuit sections for A channel and B channel so I was able to compare the two.It looks as though both channels are fed an AC supply to a transformer and the output of this is then rectified to give +5, +3 and -3 volt supplies and these seem to be the same on both channels. I checked these supplies to both main chips N1000 and N1200 and they looked the same.Having tried numerous things I rearlised that the AC/DC relay for channel A was not switching when the button was pressed. You can hear it click when channel B is selected. This seemed something pretty basic so I follwed this path.When pressing the AC/DC button with channel B selected I could see pulses on the S clock and S data pins on IC N1200 and a pulse on pin 61 labeled ACDC and the relay clicked. When doing the same on channel A I could see the same pulses on S clock and S data but no pulse on pin 61 so no relay operation.My gut feeling is that the A channel ASIC ( application specific intergrated circuit ) N1000 has failed which means the unit is beyond repair but would welcome any comments or suggestions.As always, many thanks in advance.Dave.

author: asis
author_rank: Frequent Contributor
timestamp: May 02, 2020, 08:32:29 pm
content: Hi,All control is carried out through the optocoupler isolation H1150 (HCPL4534 / 02 0) to the terminals 23-SCLK and 22-SDAT chips N1000 C-ASIC OQ0260 (Channel-A) and, accordingly, N1200 C-ASIC OQ0260 (Channel-B).This data bus (I2C; SMB; UART) is indexed in the diagram as {CONTROL}.Check if there are control pulses by comparing them on both channels. This is best done using a logic analyzer.This part of the circuit has galvanic isolation from the rest of the circuit N2001 (S-ASIC) and D3500 (D-ASIC), so feel confident.Vladimir.

author: DaveMX5mk1
author_rank: Contributor
timestamp: May 03, 2020, 10:18:53 am
content: Thanks for the reply Vladimir. As I said in my original post " with channel B selected I could see pulses on the S clock and S data pins on IC N1200. When doing the same on channel A I could see the same pulses on S clock and S data " These are on pins 22 and 23 of the chips. I only have a scope and not a logic analyzer but the pulses on both channels looked the same as far as I can tell.Dave.

author: asis
author_rank: Frequent Contributor
timestamp: May 03, 2020, 06:09:00 pm
content: Hi,OK Dave.Now let's look at the presented schemes and collect a test scheme for stimulating both channels simultaneously (Pic 3).This is a calibration chart for remote probes.We check sequentially cascade after cascade in accordance with the scheme. What do we see?Let's continue ...Vladimir.

author: DaveMX5mk1
author_rank: Contributor
timestamp: May 04, 2020, 12:08:08 pm
content: Hi Valdimir, I'm not totally sure what you mean but I've been through the probe calibration procedure on both channels and this is what I got:The test signal that is output from the DVM sockets is a 3 volt square wave at about 550 hzs before the calibration starts. On channel B when the cal is started this goes to a steady 3 volts, after a couple of seconds there are two pulses up to 3.8 volts then after 13 seconds the cal completes. Channel A is the same accept that after the two pulses it just remains at 3 volts and never completes the calibration. ( it times out after a few minuits ).During the probe cal settup both SCLK and SDAT look the same for both channels. They sit at +3.6 volts and pulse down to 0. Also whenever the range buttons are pressed there are the same pulses on both channels. I think these pulses are in fact a series of very fast pulses in groups.I tried to look at the HF and LF inputs and outputs to the two ASICs but no joy.These checks have been done with a scope as I don't have a logic analyzer.Any other thoughts?Thanks again.Dave.

author: asis
author_rank: Frequent Contributor
timestamp: May 04, 2020, 05:36:50 pm
content: Hi,DaveOffering to use the internal calibration generator, I had in mind any stimulating signal, from anywhere,even AC. Having fed it to the inputs of both channels A and B at the same time, it will be easier to track according to the circuit where it is lost.First of all, we look at pins 40; 41 and its feedback pins 37; 38 (Keep in mind the frequency of the input signal at inputs A and B should be, if possible, a large HF-Hight Frequence). Next, we look at pins 30; 28 (important) and his feedback through an optocoupler- pins 35; 34 (LF-Low Frequence).By the way, does your scope you are using now have an internal calibration generator?If yes, you can use it.There is little hope that the OQ0260 chip is alive, but you need to fight to the end.You look in the next forum thread - maybe you will find something useful.https://www.eevblog.com/forum/testgear/search: "Fluke xxx" ...Vladimir.

author: DaveMX5mk1
author_rank: Contributor
timestamp: May 04, 2020, 05:55:03 pm
content: Hi again Vladimir, to be honest I don’t think it’s anything to do with the input circuitry. Even with a 50 ohm terminator on the input of channel B there is still a flat line for the B channel.There is no line ( trace ) at all for the A channel. It’s as if the A channel is turned off.Dave

author: asis
author_rank: Frequent Contributor
timestamp: May 05, 2020, 08:47:20 am
content: Hi,DaveWhen you turn on the scop, where do you see the trigger trigger label on channel A or B, do they move up / down from the MOVE buttons of each channel? Keep in mind that with the MOVE button I can move beam A and / or B together with the TRIG mark down, completely out of sight.Can you switch this label with the F1 button from the channel to the channel or to the EXTernal state?How does the TRIG label appear when switching to a Ch-A that has no line at all?And, if Ch-A is disabled, TRIG must display in EXTernal state.Let's deal with button operations first.I have a coordinating proposal here:Measure the voltage between GND Ch-A and GNG Ch-B. Probably there will be noise from the operation of pulse converters of both channels.I am bringing you to temporarily unite the GND of the galvanically isolated A&B channels. If you are confident in your actions, then do it.Further.Make a jumper from the 2-pin optocoupler H1320 (active Ch-B) to the 2-pin optocoupler H1120 (Ch-A).In fact, we use working channel B to check the entire subsequent path of S-ASIC, D-ASIC, and so on to get the line (trace) image of Ch-A. If you are not confident in yourself, do not apply any voltage to the input of the channels, use only the AC background by hand.Vladimir.

author: DaveMX5mk1
author_rank: Contributor
timestamp: May 05, 2020, 10:56:56 am
content: Hi Vladimir, thanks for your reply.When I turn the scope on it returns to the state it was when I turned it off.If I do a factory reset it comes on with channel A on, B off. Trigger on channel A. The A on both sides of the screen indicate that the trace should be in the centre of the screen and the trigger symbol is in the middle two divisions in from the left edge. I can move the position of the A symbol on the left of the screen up/down with the move keys. With the trigger set to manual I can move the trigger symbol up and down with the centre buttons. I can use F1 to select between A, B, and EXT. The trigger symbol changes from a sort of squared off S when channel A selected to ^ when B or external selected.Turning on channel B and selecting channel B trigger source brings on the trace.I am feeding both channels with the calibration waveform from my other scope, a 500 mV square wave.There is no reading when measuring between GND A and GND B.I joined the GND of the two channels and this made no difference.I didn't feel confident to link the two opt couplers at this stage.Just as an aside I measured the temperature of both C-ASICs, channel A is 39 deg C channel B 42 deg C.I keep coming back to the fact that I can't select between AC and DC coupling on channel A.If the C-ASIC can't even switch the AC/DC relay that says to me that something basic is faulty.Cheers and stay safe.Dave.

author: asis
author_rank: Frequent Contributor
timestamp: May 05, 2020, 12:36:54 pm
content: Hi,DaveWell, let's not force events if you are not quite ready for drastic action.Let's go back to the relay.Judging by the relay circuit K1000A (RELAY DPDT TQ2SA-L-1.5V-Z) is polarized, that is, it stably maintains its state from the polarity of the initial pulse arriving at it.https://www.alldatasheet.com/datasheet-pdf/pdf/528204/PANASONIC/TQ2SA-L-1.5V-Z.htmlhttps://pdf1.alldatasheet.com/datasheet-pdf/view/155642/NAIS/TQ2SA-L-1.5V-Z.htmlThe main task is to measure AC or DC (open / close input of the device).First check the state of the p-n junction structure of the V1004 Dual Transistor (BCV65).Perhaps it is broken and shunt the signal from pin 61.Try to control this relay using a DMM or any dial gauge device with an internal battery, changing the polarity of the terminals. It is advisable to measure the state of contacts.Vladimir.

author: DaveMX5mk1
author_rank: Contributor
timestamp: May 06, 2020, 10:42:44 am
content: Hi again. The relay works fine using an external power source.There is no signal coming out of pin 61 ( ACDC ) of the ASIC to drive it.I can see pulses on pins 22 and 23 ( SDAT and SCLK ) when changing from AC to DC using the F2 button.Sadly I think N1000 has diedDave.

author: asis
author_rank: Frequent Contributor
timestamp: May 06, 2020, 11:20:07 am
content: Hi,DaveProbably yes, sadly.It remains to wish you to find a donor on EBAY.It was nice to talk.All the best!Vladimir.

author: michal82
author_rank: Contributor
timestamp: October 30, 2020, 11:35:37 am
content: HelloDo you know where the OQ0260 is available for purchase?I can't find them anywhere.

author: smaultre
author_rank: Regular Contributor
timestamp: November 01, 2020, 04:12:55 pm
content: If you have a 199 (first gen.) and no channel trace the 95% that is condition asic OQ0260 is bad.If you have a 199B,C (2-nd gen.) and no channel trace, the are two way problems may be: 50% the main chip DASIC need to be re-bolledor 50% that is condition asic OQ0260 is bad..

author: michal82
author_rank: Contributor
timestamp: November 01, 2020, 08:49:15 pm
content: I have 199 first gen.I sent an inquiry to many stores that had OQ0260 on offer, but without success

author: adam1273
author_rank: Newbie
timestamp: June 01, 2023, 12:53:52 pm
content: hello I have a question . How independently are channels A and B switched, since the i2c bus of channels A and B is short-circuited as in the diagram Channels A and B have the same OQ0260 chips, so they have the same I2C addressing or am I wrong?https://www.ebay.com/itm/234721501074

author: asis
author_rank: Frequent Contributor
timestamp: June 05, 2023, 11:47:59 am
content: Hi,That is how it is.This ensures complete galvanic isolation for channel control.See the block diagram page 3-2 of the service manual.You can see all this on the diagram in SM.

author: adam1273
author_rank: Newbie
timestamp: June 05, 2023, 03:51:02 pm
content: hello the sdatext and scltext bus controls the multimeter and understands it. but the sdatflt sclkflt bus goes through the D2000 integrated circuit, which is also switched for calibration and controls one bus two channels A and B of the scopometer. Can someone check on a good scopometer if it is possible to set channel A to AC voltage and Channel B to DC voltage and voltage range channel A 1V and channel B 1kV. And measure two channels A and B simultaneously.

author: asis
author_rank: Frequent Contributor
timestamp: June 06, 2023, 03:38:14 am
content: Can....

author: adam1273
author_rank: Newbie
timestamp: June 06, 2023, 01:41:52 pm
content: hello, thank you asis colleague for helping me solve the problem. My opinion is that the SCLKFLT and SDATFLT bus ((see photo with fluke 123 oscillogram )) controls the C ASIC of channel A and B at the same time, but SASIC and DASIC continue to process it alternately once channel A, then channel B, after conversion, sends to the LCD. SCLKEXT and SDATEXT bus only works on middle plug Meter/Extrenal channel. Am I wrong??https://www.datasheetarchive.com/OQ0260-datasheet.html☹️ inaccessible

author: asis
author_rank: Frequent Contributor
timestamp: June 07, 2023, 03:17:03 am
content: Hi,The DMM channel is also used as a calibrator and external trigger, and therefore is controlled by the SCLKEXT and SDATEXT signals.

author: adam1273
author_rank: Newbie
timestamp: June 07, 2023, 08:57:06 am
content: OQ0260 Philips has a factory defect and I'm afraid to buy these scopemeters from this series because it will surely fail. OQO260 NXP is probably ok.

author: coromonadalix
author_rank: Super Contributor
timestamp: June 07, 2023, 01:43:46 pm
content: and what is it ?? if not asking too much

author: justincr83
author_rank: Newbie
timestamp: November 04, 2023, 07:08:12 pm
content: Hey guys,Sorry if I high jack this thread, but i don’t want to open a new thread until i have the unit in hand..A friend of mine sent me this picture with an fluke 199B which works great, except the oscilloscope function.I have no knowledge about this kind of scopes…Here’s a picture of the screen:Thanks!

author: feedback.loop
author_rank: Frequent Contributor
timestamp: November 04, 2023, 07:14:28 pm
content: This is not 199B, but 199. Most probably either one channel ASIC is dead or both. Try enabling one channel at a time to see which one is dead. If both don't show any trace, then both are dead.Quote from: justincr83 on November 04, 2023, 07:08:12 pm

author: justincr83
author_rank: Newbie
timestamp: November 04, 2023, 10:06:54 pm
content: Ok, in case asics are dead, is there any chance to get replacement parts?

author: feedback.loop
author_rank: Frequent Contributor
timestamp: November 05, 2023, 12:01:20 am
content: I don't think so.Quote from: justincr83 on November 04, 2023, 10:06:54 pm

author: justincr83
author_rank: Newbie
timestamp: November 05, 2023, 08:03:00 am
content: “Cool!”Thank you very much for all the info!