PM3394 philips fluke repair help - Page 1
Forum section: electronics / repair

author: alolkema
author_rank: Newbie
timestamp: January 02, 2018, 11:11:26 pm
content: Hi everyone, here a first post from me, after searching and reading all i could about a scope i aquired, a Philips / Fluke PM3394, with an issue.The controls for focus, level and position for all channels are not responding. The text displays are responding, but the actual trace is just outside the picture.I think it must be the DAC on the processor board, a OQ0244T.But there is nothing to find on the web, no data, nothing.Cannot buy one also..I checked the clock (nice sinus), the enable and pwr are high, there is some data comingFrom the 4 lines from the processor,But all outputs stay 2.5v (which is also the ref. Voltage)Anyone has such a DAC, or a complete board for me to buy?The next thing i could do is rip the dac ftom the A1 board, which has 1 for each channel, to test if it is really this chip that is faulty...I do have a working PM3084, but it is my favorite scope and hate to destroy it by swapping cards..Help is much appreciatedGreetings from Holland

author: EHT
author_rank: Frequent Contributor
timestamp: January 04, 2018, 10:39:29 pm
content: I see what you mean.. I looked at the service manual. Can't find anything via Google on the part #. Maybe Phillips rebadged another part. Is it worth a guess from looking at other DAC chips of similar vintage. Knowing the function of each pin from the schematic could help compare with other DAC chips. I can't imagine this would be a special Phillips part would it?

author: SaabFAN
author_rank: Frequent Contributor
timestamp: January 05, 2018, 03:08:29 am
content: It is most likely a Chip Philips made. They had a good DAC-Department that supplied their consumer electronics-devices.It's probably compatible with something Analog Devices made or is still making.I've found chips in a signal gen from the late 70s that were still listed as "Active" by AD.

author: oldway
author_rank: Super Contributor
timestamp: January 05, 2018, 06:47:25 am
content: Perhaps a TDA1541A??

author: guido
author_rank: Regular Contributor
timestamp: January 05, 2018, 07:25:49 pm
content: Close:OQ0244: 5962-01-421-9579: Microcircuit Linear: 0LUA3: Avl: RFQ:TDA1541A/N2: 5962-01-431-8648: Microcircuit ...But not really, it's a 16 channel dac vs 2. I don't get any further info, looks like there is only one supplier for this NSN number (philips).Enable and PWR go to clock and start on the DAC. Cannot imagine clock should be high all the time.Compare with the other two.mental note: page 221

author: grumpydoc
author_rank: Super Contributor
timestamp: January 05, 2018, 11:40:57 pm
content: I'm pretty certain that's a Phillips specific part - if it is dead then the only source will be another 3394 CPU card.Does the front panel work otherwise - do you get the audible clicks when adjusting the position controls, for instance.You can drive the DAC using the "repair tools"/DAC option.

author: SaabFAN
author_rank: Frequent Contributor
timestamp: January 06, 2018, 11:10:08 am
content: I'm pretty sure the DAC uses i2c as interface. With a good logic analyzer that can capture unlimited amounts of data and exercising the DAC enough, you should be able to find all the commands and then program an AVR to translate the commands to a new 16-Channel DAC.Is the chip through hole, or SMD? If it's through hole, you can just build an adaptor, if it is SMD, you'll have to connect to the pads with small wires.Or you get another CPU-Card of course

author: oldway
author_rank: Super Contributor
timestamp: January 06, 2018, 11:31:04 am
content: Although it is not very fair to advise to ask the question on another forum, I know that Dave will not hold me for doing this because the success of this forum is such that it has no competitor.There is a Dutch e-forum and since Philips is a Dutch firm whose measurement instruments branch was located in Eindhoven (Holland), many participants either worked at Philips or still have spare parts.Try to ask for the DAC spare part on:https://www.circuitsonline.net/

author: grumpydoc
author_rank: Super Contributor
timestamp: January 06, 2018, 01:55:44 pm
content: Quote from: SaabFAN on January 06, 2018, 11:10:08 amIt's not I2C, it's a 4-bit parallel interface, with an enable and write strobe.To alolkema:Seeing data on pins 1-4 is not enough, this is the CPU multiplexed address/data bus and will have activity on it continuously. You need to check that the enable and write signals are active - DACPEN-LT and DACPWR-LT. These are both "active low" logic lines and I note you mentioned "enable and pwr are high". If this is true for DACPEN-LT and DACPWR-LT (no low pulses at all) then I would check out D1016 which is a 74LS138 used as an address decoder.Finally did you really mean there was a sine wave on the clock - it should be a 6MHz square wave.QuoteProbably the easiest

author: QQE06-40
author_rank: Newbie
timestamp: January 07, 2018, 10:01:49 am
content: Hi alolkema,i do have most of the boards from a Fluke PM3380B. As far as i know, it is identical with the PM3394 with the exception of the number of channels. I have the CPU board lying in front of me and i see the DAC OQO244T (SMD) just below the big processor. I´m pretty sure the board is fully functional but cannot guarantee. I think i remember i had this board in my other PM3380B for test purposes and it worked o.K.. If You are interested i could leave it to You.B.T.W.: Ik woon in Kleef, dat is in de buurt van Nijmegen / Arnhem.Regards / Groeten,WolfQQE06-40

author: alolkema
author_rank: Newbie
timestamp: January 07, 2018, 05:05:19 pm
content: Thank you all for your thoughts! Helped me further, but i am not sure.As suggested by grumpydoc, i looked at the DACPEN-LT and DACPWR-LT, and they never go low.I did the same measurements on an identical DAC on the A8 board, and this shows a very different pattern:- On the Datalines on the A8, there are bursts visible when i turn the knobs.- On the A3 chip, there are no bursts visible at all, only some sort of carrier wave.-On the START pin of the A8 chip (is EN on the A3 dac), the LOW signals are visible also- On the A3 chip, the signal is Always HIGH.All the inputs for the 74LS138 contain data, but i dont have a logic analiser to determine if the outputs are set low or notI took the multiplexing chip 74LS138 off the board, and put it on a breadboard.Then i checked all outputs and inputs, and checked it against the truth table in the specsheet.All outputs checked out, except that output Y2 ( the one going to the DAC, DACPEN-LT) does not drop to 0.12V, as all others, but dropped to 1.23VTo be sure, i will order a new 74LS138, and in the mean time i asked QQE06-40 for the board. That would be very helpful indeed.Nice to have some extra brains

author: alolkema
author_rank: Newbie
timestamp: January 20, 2018, 04:31:06 pm
content: Hi All,I have replaced the 74LS138, and that fixed the issue. Very happy!I have tested most functions, and everyting seems to work fine,However, when i do a autocalibration, at the end it comes up with the message that it did not finish the job.When i look in the maintainance menu, it shows ‘Calibration error 177’I browsed a few hours, but could not find the error list, to point me in the right direction...I did found someone mentioning that the chips on the A8 board needs to be cooled extra, and overheating could lead to calibration errors. I did so, but still the same message.Does anybody know what this means? Does anybode has a movie of the calibration routine for a 3394 (around 3 min 37 the beep- pace gets slower, and its stops. This is after it does all the jumping with the lines)Next step i guess is to follow the manual’s performance checks, however i do not have all the right equipment for it. But it might reveal the error.To be continued..

author: alolkema
author_rank: Newbie
timestamp: January 30, 2018, 03:56:19 pm
content: I tried to test everything I could, and all functions appear to be working fine.Hopefully I will find a list somehow in the future for the Autocal errors...I will be using the scope normally, and see what happens..

author: grumpydoc
author_rank: Super Contributor
timestamp: January 30, 2018, 04:07:08 pm
content: Quote from: alolkema on January 30, 2018, 03:56:19 pmNot sure what 177 off the top of my head, I wonder if I have seen it before when the screen cal is out (need to find some old posts, will look later).A list exists but I have never seen it - apparently it is rather closely guarded by the individual who possesses itGo through the steps for the screen calibration (no special equipment is needed - you are just lining things up against the graticule) and dark level as set out in the manual, then re-run the autocal.

author: alolkema
author_rank: Newbie
timestamp: January 30, 2018, 05:24:24 pm
content: Hi Grumpydoc!Yes, i have gone through all manual calibration steps described in the service manual.Including the screen cals.(done it more than 20 times now, because every time i take the A8 card out, all is gone...)Also afraid to save the settings, because it can be done only 10 times ?? Dont understand that. I dont think you can retreive the older cals... Why not overwrite them.Any idea how to clear that memory?

author: grumpydoc
author_rank: Super Contributor
timestamp: January 30, 2018, 05:43:03 pm
content: Quote from: alolkema on January 30, 2018, 05:24:24 pmNo but as long as the battery is in it will remember the settings and the cal in RAM so it's not a show stopper.

author: HighVoltage
author_rank: Super Contributor
timestamp: January 31, 2018, 08:34:47 pm
content: Are all 4 lines of all 4 channels visible and round the "-" sign of where they are suppose to be when nothing is connected to the channel inputs?

author: alolkema
author_rank: Newbie
timestamp: January 31, 2018, 08:50:09 pm
content: Yes, they are all 4 spot on. In analog mode and in DSO mode as well.

author: HighVoltage
author_rank: Super Contributor
timestamp: January 31, 2018, 10:00:36 pm
content: Quote from: alolkema on January 31, 2018, 08:50:09 pmok,And AUTO CAL is still not completing alright ?

author: alolkema
author_rank: Newbie
timestamp: February 03, 2018, 11:36:46 am
content: Nope. It will do most of its calibrations, until 3 minutes and 37 seconds. I would guess it fails when doing the timebase cals.

author: HighVoltage
author_rank: Super Contributor
timestamp: February 03, 2018, 11:40:02 am
content: How far off is the timebase?What measurements do you get, when you measure a 10 kHz or 10 MHz sine wave input frequency on each channel in DSO mode?

author: alolkema
author_rank: Newbie
timestamp: February 03, 2018, 12:23:51 pm
content: Just checked.The measurements are spot on.Also when i check with cursors in analog mode.The only thing i see is that the waveform has a shift of 1/2 graticule to the left when i switch from DSO to analog, on all 4 channels