Metrix 803B Oscilloscope power supply issue

[smdportugal]

Re: Metrix 803B Oscilloscope power supply issue

Dear sir , i still have one Metrix OM803 that bought at about 25 years ago. It has been all types of faults . The first one when swithc on some relays goes crazy and the osciloscope coulnt start ok , i ´ve found some capacitors in the power supply unit with low capacitance and after replace it works good . After some years starts to not enter in some menus like components tester , It was a fault in a conector inside . After some more years lost the left deflection but as the transistor are smd types and cant see the reference and as i dont have the schematics i give up . I still have it here but with horizontal left deflection fault. Anybody has the Schematics diagram ?

[itsthatidiotagain]

Re: Metrix 803B Oscilloscope power supply issue

Very late reply, but @rbarreiros the short answer is yes. Your PSU issue sounds very similar. Follow through the thread and check/replace the parts I replaced first.
Once you have done this, if it is still not working, check the HT side of things.

[rbarreiros]

Re: Metrix 803B Oscilloscope power supply issue

Any news on the RS232 front ? I'm also curious at controlling the scope through RS232.

Best regards,
Rui

I had 5 minutes to spare today, to check the signals on J18 this is what I have so far.

The colours in the list below are just those of the bit of ribbon cable I used, so they have no particular significance.

 
J18 Pinout - Pin1 at PSU end (same as J19)

Pin- Colour - Signal
1 - Blue1  -  0V slight periodic ripple (Polled output perhaps???) 
2 - Purple1 -  0V slight periodic ripple (Polled output perhaps???) 
3 - Grey1  -  0V slight periodic ripple (Polled output perhaps???) 
4 - White1  -  0V slight periodic ripple (Polled output perhaps???) 
5 - Black   -  0V slight periodic ripple (Polled output perhaps???) 
6 - Brown  -  +12V
7 - Red    -  -12V
8 - Orange  -  10ms +5V pulses (20ms pk to pk square wave)
9 - Yellow  -  0V slight periodic ripple (Polled output perhaps???) 
10 - Green  -  Ground (Confirmed zero ohms to BNC Earth)
11 - Blue2  -  0V but not tied to ground (serial port I/O perhaps???) 
12 - Purple2 -  0V but not tied to ground (serial port I/O perhaps???) 
13 - Grey2  -  +5V slight ripple (serial port I/O perhaps???))
14 - White2 -  +5V slight ripple (serial port I/O perhaps???))

I'll take a closer look at the signals, take a few pictures of the scope traces and probe with the multimeter to see if I can determine which are inputs and outputs when I get more time.

Now that i know the serial port protocol and that it can use 3 wires i.e. no hardware handshake and xon/xoff I can then experiment with a TTL level 9600 baud serial signal fed to which ever I think might be the inputs, so see if I can control the front panel.

The serial port consists of 5 wires and is described thus...

Serial link characteristics

Oscilloscope connector : 25-pin cannon plug
Cable : five wires (two transmission wires, one ground wire, two
control wires)
Protocol : RTS
Data rate :
Data format :9600 bauds
8 bits - no parity - 1 bit stop
Protection : per EIA RS232C standard


.. which may match up with the bottom 5 wires on J19


I haven't found any 3V3 signals so far, so I think everything should be 5V TTL

Pin 8 is interesting, I presume this is an accurate 50Hz pulse, which is the same frequency as the UK mains, and this might be for blanking sync perhaps for the A/D daughter cards. Pure speculation on my part of course.

[rbarreiros]

Re: Metrix 803B Oscilloscope power supply issue

Seems I jumped the gun, the issue I had was this one, which, like it's said in the thread, it's a bad contact in the green cable. Fixed !!

http://www.electro-tech-online.com/t...oscope.146957/

[rbarreiros]

Re: Metrix 803B Oscilloscope power supply issue

I'm sorry to revive this thread, but I do have an oscilloscope like this one, metrix ox 803b, and it's not powering on, but, not completely dead, makes a sound like a relay trying to close circuit, very fast, continuously, some leds in the panel light up, others blink, no display.

Could it be related to the same PSU issue itsthatidiotagain had ?

Cheers,
Rui

[Keeze101]

Re: Metrix 803B Oscilloscope power supply issue

Hi all,

Very interesting thread.. I have got an Philips OP400, which is the Metrix803b. The Metrix is a Philips design, manufactured by Metrix. The unit seems to be working, but the vertical measurement is off by about 20%. When I feed a 5V DC signal the scope shows about 4 volts. I get the same offset when I use the onboard testpoint (2.5v/1kHz)

Does anyone know how to calibrate the vertical axis? Timebase is correct.

Cheers,
Kees

[daverave56]

Re: Metrix 803B Oscilloscope power supply issue

i did some voltage tests today in the switch mode power supply with the UC 3842 chip.

Pin 1 - 0v
Pin 2 - 0v
Pin 3 - 0v
Pin 4 - 0.7v
Pin 5 - ground
Pin 6 - 0v
Pin 7 - 13v
Pin 8 - 2v

changed the two tant capacitors with electrolytics and made no difference scope still dead

[stj]

Re: Metrix 803B Oscilloscope power supply issue

uc3842 datasheets have lots of example circuits - one is probably similar.
and this thread.
https://www.badcaps.net/forum/showthread.php?t=20675

[daverave56]

Re: Metrix 803B Oscilloscope power supply issue

i also have a metrix scope that is dead with switch mode power supply problem which has caused me much frustration cause metrix refuse to supply me with a service manual !!!!!!! my model is a metrix ox 8042 but uses a UC 3842 pwm/oscillator chip rather than the TDA 4605 as used in your scope.

[itsthatidiotagain]

Re: Metrix 803B Oscilloscope power supply issue

For the record, the tube in a large number of these Metrix scoopes is almost certainly..

D14-364GY / 123
CRT Heerlen BV
Made in the Netherlands

https://cdn.badcaps-static.com/pdfs/...0274745688.pdf

Furthermore, the tube in my OX 803B is most probably very similar (the principal difference being the Phosphor coulour).

[itsthatidiotagain]

Re: Metrix 803B Oscilloscope power supply issue

I'm trying to figure out what the purpose of Pin 8 is on the PSU board, my best guess is that this is some sort of crowbar protection, but I thought I'd find out if anybody else has any better ideas based on the previous images and the image below.

[itsthatidiotagain]

Re: Metrix 803B Oscilloscope power supply issue

Quick update on the pinout of the connectors.

Metrix 803B PSU

12 pin power connector

Although the board has no obvious markings, assume pin 1 is the one with the black stripe.

Note: DC ground is tied to main earth, and that for safe operation of the scope it must be earthed.
As with most scopes, all scope input BNC connectors therefore have the Ground side tied to mains earth.

DC Power connector (J1)

Pin 1) -12V Checked on multimeter
Pin 2) -5V Checked on multimeter
Pin 3) +12V Checked on multimeter
Pin 4) +5V 10mS pulses> See Scope trace.
Pin 5) +5V Checked on multimeter
Pin 6) GND
Pin 7) GND
Pin 8) ??? Looks like 0V perhaps feedback power good signal to PSU. Needs confirming
Pin 9) +120V DC Verified (6 x 2 x 10 V) Scoped Measured at 118.0V on multimeter
Pin 10) +180V DC Verified (3.6 x 5 x 10 V) Scoped Measured at 177.7V on multimeter
Pin 11) GND
Pin 12) +5V regulated checked on multimeter-> Option Card (A/D board) - scoped.

Note the +5V on Pin 12 is the same power rail as the +5V on J2 which goes to the option card (Digital (A/D) board in an 8050 etc).

2 pin DC Power connector (J2)

===== <--Locking tab
[. .]

 1 2

Pin 1) GND
Pin 2) +5V

J18 Pinout - Pin 1 at PSU end.

Pin- Colour - Signal
1 - Blue1  -  Floating input??? 
2 - Purple1 -  Floating input???
3 - Grey1  -  Floating input???
4 - White1 -  Floating input???
5 - Black  -  Floating input???
6 - Brown  -  +12V
7 - Red   -  -12V
8 - Orange -  10ms +5V Pulses (20ms pk to pk)
9 - Yellow -  Floating input???
10 - Green  -  Ground (Confirmed zero ohms to BNC Earth)
11 - Blue2  -  Floating input???
12 - Purple2 -  Floating input???
13 - Grey2  -  +5V (floating input ?)
14 - White2 -  +5V (floating input ?)

[itsthatidiotagain]

Re: Metrix 803B Oscilloscope power supply issue

trace the signals back to the source.
the chip may have a uart, so RX/TX with give you the pinout.

Tracing back to the source would require me to dismantle the front panel, which I might end up doing, but for the time being I'm trying to avoid doing so.

[stj]

Re: Metrix 803B Oscilloscope power supply issue

trace the signals back to the source.
the chip may have a uart, so RX/TX with give you the pinout.

[itsthatidiotagain]

Re: Metrix 803B Oscilloscope power supply issue

I had 5 minutes to spare today, to check the signals on J18 this is what I have so far.

The colours in the list below are just those of the bit of ribbon cable I used, so they have no particular significance.

 
J18 Pinout - Pin1 at PSU end (same as J19)

Pin- Colour - Signal
1 - Blue1  -  0V slight periodic ripple (Polled output perhaps???) 
2 - Purple1 -  0V slight periodic ripple (Polled output perhaps???) 
3 - Grey1  -  0V slight periodic ripple (Polled output perhaps???) 
4 - White1  -  0V slight periodic ripple (Polled output perhaps???) 
5 - Black   -  0V slight periodic ripple (Polled output perhaps???) 
6 - Brown  -  +12V
7 - Red    -  -12V
8 - Orange  -  10ms +5V pulses (20ms pk to pk square wave)
9 - Yellow  -  0V slight periodic ripple (Polled output perhaps???) 
10 - Green  -  Ground (Confirmed zero ohms to BNC Earth)
11 - Blue2  -  0V but not tied to ground (serial port I/O perhaps???) 
12 - Purple2 -  0V but not tied to ground (serial port I/O perhaps???) 
13 - Grey2  -  +5V slight ripple (serial port I/O perhaps???))
14 - White2 -  +5V slight ripple (serial port I/O perhaps???))

I'll take a closer look at the signals, take a few pictures of the scope traces and probe with the multimeter to see if I can determine which are inputs and outputs when I get more time.

Now that i know the serial port protocol and that it can use 3 wires i.e. no hardware handshake and xon/xoff I can then experiment with a TTL level 9600 baud serial signal fed to which ever I think might be the inputs, so see if I can control the front panel.

The serial port consists of 5 wires and is described thus...

Serial link characteristics

Oscilloscope connector : 25-pin cannon plug
Cable : five wires (two transmission wires, one ground wire, two
control wires)
Protocol : RTS
Data rate :
Data format :9600 bauds
8 bits - no parity - 1 bit stop
Protection : per EIA RS232C standard


.. which may match up with the bottom 5 wires on J19


I haven't found any 3V3 signals so far, so I think everything should be 5V TTL

Pin 8 is interesting, I presume this is an accurate 50Hz pulse, which is the same frequency as the UK mains, and this might be for blanking sync perhaps for the A/D daughter cards. Pure speculation on my part of course.

[itsthatidiotagain]

Re: Metrix 803B Oscilloscope power supply issue

I bought the OX863 on ebay with some issues hoping to repair, can't find the schematics.

What is the fault on your OX 836?

[itsthatidiotagain]

Re: Metrix 803B Oscilloscope power supply issue

I also found a programming manual for the OX8040, OX8042, OX8062, OX8050 and OX8100, but I can't remember where I found the original link.

I've attached it in case it proves useful to someone in the future.

Also there is a slight screwup in the previous post's links, but I only spotted it after the 90 minute edit window had closed.

[itsthatidiotagain]

Re: Metrix 803B Oscilloscope power supply issue

the '863 service manual was being sold for about 20Euro by an italian company, i ran across the site a few days ago.

I found a couple of other links to Metrix user manuals.

Another couple of copies of the OX 863 user manual.

https://cdn.badcaps-static.com/pdfs/...3f3f3e5329.pdf
www.ghvtrading.cz/download.php?fileid=1880

(both with the same md5sum, so both are the same manual)


.. and a photocopy of the 8620/8627 manual ..

http://www.ghvtrading.cz/download.php?fileid=1880

.. I also connected up a chunk of ribbon cable to J18 and brought it out through the base of the scope, so I can prod around on that connector without much risk to life and limb. I ran out of time, so I can't yet report on the signals on the pins on that header yet, but I hope to probe it with the office Rigol tomorrow.

I'll also see if I can get some voltage readings from the PSU <-> main board connector to assist others if they need to fix one of these in the future.

Also of interest are J19 (unpopulated, not sure of its function) J301 (unpopulated, may give access to the analog multiplexer to allow the D to A card to overlay its image to the tube), and the front panel key connector I described previously (also unpopulated on the 803B).

One other minor issue with my OX 803B, the component checker seems to have a minor defect, it shows a dot, offset from the zero ceter point, rather than a straight line throug the centre of the screen, although sometimes when you tap the front panel it turns in to a line. Looks like a dry joint or cracked resistor or similar. I'll take a look at that later, it is pretty low priority. Ill prod the area of the associated components with an insulated object of some sort, fire the freezer spay on it, that kind of thing.

[stj]

Re: Metrix 803B Oscilloscope power supply issue

the '863 service manual was being sold for about 20Euro by an italian company, i ran across the site a few days ago.

[itsthatidiotagain]

Re: Metrix 803B Oscilloscope power supply issue

Hi, was looking for the OX863 schematics but could only find this user manual, seen this post, so maybe it will be of some help with the RS232 output connections. I bought the OX863 on ebay with some issues hoping to repair, can't find the schematics.

Thanks for the link to the manual, it seems to confirm what I suspect, namely that the Metrix scopes all use the same serial protocol, and pinouts.

What are the issues on your OX863? Also is there a daughter card mounted on J18. Can you share some pictures of the inside of the OX863.

A fairly complete set of teardown pictures of my OX803B are here.

https://plus.google.com/u/0/photos/1...81872199591361