Author Topic: CMU200 repair attempt - shipping damage (oh those post monkeys...) (Read 5408 times)

PA0PBZ · « **Reply #25 on:** October 09, 2020, 11:47:39 am »

Quote from: Yansi on October 09, 2020, 10:08:44 am

I bought this unit very cheaply, almost for scrap price (shipping was more expensive than the unit itself). Wanted it especially for two things: It may have a functional computer and also importantly it has the 50W rated input module! I hope I can salvage it as a downgrade for my unit (as the 50W is the base configuration and my more recent unit has the 2W input option).

Is there any argument why the 2W option is better, than the 50W? Is the 2W option better in anything? I could not find out.

As far as I know the 2W comes with the CMU-B96 additional RF generator option.

Yansi · « **Reply #26 on:** October 09, 2020, 02:20:20 pm »

How does B96 module look like? I do not think there is any module added. Couldn't find any photo of the module on the web.

Above the input assembly, which normally has the huge heatsink, there is a small module, marked as 1100.2600.02 - which acording to quick google search is some kind of "reference board". Not sure what it does, but the unit is fitted with an OCXO. Maybe something to do with it? Part of the OCXO option?

Yansi · « **Reply #27 on:** October 09, 2020, 02:29:15 pm »

@Bicurico: All I bought originally was a fully working unit. But received bashed junk instead, so just trying to repair it now. RX/TX module should be fine in that one. But I now know that these modules tend to fail, due to components drifting out of spec, so some of the selftests may not pass by a few tenths of a dB. (Or so I read somewhere).

Selling on ebay - no, not worth the hassle. Selling locally? Likely impossible to find a buyer. Worst case, unit/s (hopefully one at most) will be gutted for parts. Already heard from a few people interested in buying some parts.

But don't try to change my mind please, I am still optimistic... so far.

PA0PBZ · « **Reply #28 on:** October 09, 2020, 05:16:33 pm »

Quote from: Yansi on October 09, 2020, 02:20:20 pm

How does B96 module look like? I do not think there is any module added. Couldn't find any photo of the module on the web.

Above the input assembly, which normally has the huge heatsink, there is a small module, marked as 1100.2600.02 - which acording to quick google search is some kind of "reference board". Not sure what it does, but the unit is fitted with an OCXO. Maybe something to do with it? Part of the OCXO option?

I'm not sure how the B96 looks like, but the CMU200 is very good at modules in modules in modules, so a good chance that it's hiding somewhere.

About the reference board, let me quote the service manual:

Quote

The REFERENCE BOARD provides all required clock signals (NETCLK1/2) and reference frequencies
(110.8 MHz) as well as the +5 VDC reference voltage for the CMU. The REFERENCE BOARD is a
plug-in module in HVC design.

Yansi · « **Reply #29 on:** October 09, 2020, 06:18:07 pm »

OOokay so that board definitely does not have anything to do with the B96. So how can I tell whether the "2W input only" CMU has the second generator fitted, without actually turning it on (I am not able to, yet)?

Meanwhile I'll try to move home the second boat anchor to be able to better diagnose the power-up issue.

PA0PBZ · « **Reply #30 on:** October 09, 2020, 06:27:12 pm »

I just checked my CMU200 that also has the 2W limit and it has the B95 option which is also an additional RF generator (no idea what the differences are).

PA0PBZ · « **Reply #31 on:** October 09, 2020, 06:37:19 pm »

A bit more info here: https://www.eevblog.com/forum/testgear/rohde-schwarz-cmu200-cmu-b95-additional-rf-generator-removal/

Yansi · « **Reply #32 on:** October 12, 2020, 07:42:28 pm »

Hello,

so another update. I have brought home the other unit, described as "does not turn on". Turns out, it turns on pretty damn well. But the LCD has a failed backlight and it is failing with some error.

After disassembling the unit, to my big surprise, I have found an audio analyzer (B41) installed! Yaaaay! Definitely a keeper.

To not make a mess in this thread to not to mix repairs of two units together, I have created another separate thread for the other unit. I hope you will understand, why splitting the thread may be a good idea.

Link to repair thread of the other unit: will be edited in here in a moment.

Yansi · « **Reply #33 on:** October 22, 2020, 07:59:58 pm »

Update: Back at my home lab, with two great packages!

Many thanks to users Ice-Tea and eb4eqa for kindly providing me these needed spare parts!

Hopefully I will now be able to make this unit work back again.

Yansi · « **Reply #34 on:** October 22, 2020, 10:05:08 pm »

As I couldn't help myself, I needed to try the new computer NOW. So I have assembled the computer chassis with the FMR6+T5 from Ice-Tea. Replaced fan with a good one from the computer assembly from eb4eqa and plugged the whole into the unit, flipped the switch on the back and...

... the unit started, ran for about 3 seconds, then turned off. So I pressed the front soft power button and voila, it's booting! Then halfway through the boot, screen went black. Guess what, the CFL inverter just decided to die on me!

Unit otherwise seems to boot up properly, I got to the spectrum analyzer screen successfully, while holding a strong flashlight against the LCD screen to see at least something in there.

So it seems a lot of work for tomorrow:
- Likely replace the encoder wheel. The one in the unit seems not responding well. It seems to skip pulses.
- Look what happened with the CFL inverter. Again, the stupid SMD fuse? (Interestingly enough, this inverter has a 3A fuse placed, the one I have repaired in the other unit got a 2A fuse, also blown).
- Maybe replace the LCD with the one from eb4eq, as that one was modified with a LED backlight (need to ask how to wire it)
- Source suitable replacement electrolytics for the computer board (at least one is an obvious toast)
- Dismantle the unit down to bare chassis and then pound it back to shape with a hammer

- Mount everything back, while praying it'll still work
- Try installing the B17 option board into it
- Make some haccs to the firmware

Again - many thanks Ice-Tea and eb4eqa for the parts.

Yansi · « **Reply #35 on:** October 23, 2020, 05:17:22 pm »

So, today's update: I have stripped the chassis completely and hammered in into its original shape. Then put everything back and tested, all working again. Great!

Now on to the upgrade task: I have a CRTU-B7 module, that as far as I can tell is identical as CMU-B17 module, the IQ/IF interface. What I am struggling with now, is how to wire it all correctly. I have a hard time understanding the drawing on the cover of the cards.

I have already tried to wire it, but I don't think I have it correctly connected. There are wires left I don't know where to plug.

First, let me photograph the cover drawing in detail - see attachments. I have had some option boards already installed, just need to add the B17. The drawing is also available in the service manual, http://gotroot.ca/cmu200/CMU_Service.pdf page 199. I hope these drawings are the same.

I have added the required 4 BNCs to the back of the unit and connected them to the respective connectors X514, X515, X520, X521. Easy.

Then I have unplugged W33 from the "A7" board (unplugged X703) and plugged it in the B17 module, into X501.
A jumper link was then used to join X502 from B17 back to X703 on A7 board. That also seems quite clear.

But where the hell should X37, X38 and X39 from the RxTx board go?
How to wire the "A7 slot board" back with the B17 in between and what to do with the other option boards I have there?

I find it quite confusing and the lack of any detailed signal diagrams of the modules does not make it any easier.

But how to wire the rest, remains a mystery :-O

Yansi · « **Reply #36 on:** October 23, 2020, 05:19:08 pm »

Okay, I may start to understand what is what. But I may have some cables missing then! O_o I came up with this:

The RxTx module should be connected as following:
X37 to X522
X38 - no connection
X39 to X513

From the B17 module to the "A7" card then:
X518 to X708
X516 to X706

The A7 card also needs likely some reference frequency, originaly port X703, now loops through the B17 module goes into X501 then loops back from X502 to A7-X703.

This way, it seems the instrument is working. Both basic Tx and Rx.

What I am still missing are the connections from X923, X924, X925 of the B68 module.

Looking and thinking more in detail, if the option B68 is installed, the signal should go from A5-X518 to A9-X923, then loop through and back from A9-X924 to A7-X708.

Now I have it wired directly A5-X518 to A7-X708. Which works, but without the B68 option. Huh.

To reduce confusion and make things clear, I made an image. Image is worth thousand words.

This is how it is wired now. Rest of the connections are in their original state, as they were before.

CMU200 repair attempt - shipping damage (oh those post monkeys...)

Wiring may be finished, or it seems now I seem to understand what should go where. .. apart from those 4 BNCs I have added on the back - the wires to them are too short for some of the connections, will need to fix that.

Now I have a few questions I would like to get help with; if anybode knows, please leave a comment below!

1) What type of connector are those small ones on the modules? Seems like MCX, but smaller? I would like to make some custom cables to tidy up the mess in there, currently hacked from random lengths of jumpers.
2) How to access any settings related to the B17 module? Do I need to put in just the right license keys to enable it, or do I need a whole software install madness?
3) Is it normal, that the auxiliary generator (B95) is capable of only up to -60dBm and only through ports RF1 and RF2?

//EDIT: those small connectors seem to be MMCX?

_Wim_ · « **Reply #37 on:** October 23, 2020, 05:45:46 pm »

Here is the "Module and Cable Exchange manual", with has some basic interconnection circuit diagrams. Maybe this can help (never really had a close look at this manual, but archived it for when I would need it...)

_Wim_ · « **Reply #38 on:** October 23, 2020, 05:56:52 pm »

Page 121 of this CRTU service manual also has some instructions on replacing a B7 module

_Wim_ · « **Reply #39 on:** October 23, 2020, 06:05:14 pm »

I forgot my CMU200 also has a B17 option

Here is a picture I took when a received the unit. I can have a closer look maybe this weekend and open my unit up, but maybe this can help already.

PA0PBZ · « **Reply #40 on:** October 23, 2020, 06:05:25 pm »

It's covered in great detail here: https://www.mikrocontroller.net/topic/433164?page=single

I hope your German is sufficient, and it's a long thread so searching for B7 could help.

Yansi · « **Reply #41 on:** October 23, 2020, 06:41:17 pm »

Quote from: _Wim_ on October 23, 2020, 06:05:14 pm

I forgot my CMU200 also has a B17 option

Here is a picture I took when a received the unit. I can have a closer look maybe this weekend and open my unit up, but maybe this can help already.

Thank you for the photo. It seems I have it wired the same way, even though I loop the RX and TX paths through yet another option module. I have there a huge double-width module "B68+B21+B54+B56"

I have already run the "firmware update after board change". That has run successfully. I meant more like where is the control menu to access the setting of the IF/IQ paths, that the B17 module does.

_Wim_ · « **Reply #42 on:** October 23, 2020, 06:51:32 pm »

Quote from: Yansi on October 23, 2020, 06:41:17 pm

I have already run the "firmware update after board change". That has run successfully. I meant more like where is the control menu to access the setting of the IF/IQ paths, that the B17 module does.

I am not in the lab right now, but if I remember correctly, it is in the same screen where you select the input and output channels, but on the 2nd page (so you need to switch pages with the button bottom right)

_Wim_ · « **Reply #43 on:** October 23, 2020, 06:56:36 pm »

Quote from: Yansi on October 23, 2020, 06:41:17 pm

I meant more like where is the control menu to access the setting of the IF/IQ paths, that the B17 module does.

This manual describes the operation (from page 191). Zipped to 3 parts because is was to big to attach here

_Wim_ · « **Reply #44 on:** October 23, 2020, 06:58:29 pm »

Quote from: _Wim_ on October 23, 2020, 06:56:36 pm

Zipped to 3 parts because is was to big to attach here

part 2 (rename to *.z01)

_Wim_ · « **Reply #45 on:** October 23, 2020, 06:59:32 pm »

Quote from: _Wim_ on October 23, 2020, 06:56:36 pm

Zipped to 3 parts because is was to big to attach here

part 3 (rename to *.z02)

_Wim_ · « **Reply #46 on:** October 23, 2020, 07:01:57 pm »

Quote from: _Wim_ on October 23, 2020, 06:51:32 pm

I am not in the lab right now, but if I remember correctly, it is in the same screen where you select the input and output channels, but on the 2nd page (so you need to switch pages with the button bottom right)

This is how it should look like

Yansi · « **Reply #47 on:** October 23, 2020, 07:17:02 pm »

Aaarrgh!!! There is a second screen. Sure, B17 settings are right there.

But I have hard time understanding the diagram with a dozen of switches. Where do the signals go?

I would like to know what exactly the B17 module does inside. The HW diagram of the interconnection inside the unit looks like this (in my unit). But how to correlate between the menu settings and what happens in reality?

I was mostly interested in the B17 module, because I understood it can provide the I and Q baseband signals both for TX and/or RX. That would mean I could, possibly, utilize the CMU200 as a universal transmitter/receiver, with IQ interface I could use for truckload of interesting things.

//By the way, the LCD backlight is repeatedly crapping out on me, but the fault is not in the CFL inverter board, but somewhere on the LCD breakout board, where the big ribbon cable is terminated to. Taping the board fixes the backlight. But it does not seem to be a problem with the ribbon cable connector itself. Power supply is randomly missing for the CFL inverter. Shouldn't the CMU be able to drive an external VGA monitor? //

Yansi · « **Reply #48 on:** October 23, 2020, 07:25:02 pm »

Now looking at it the second time, isn't this it?

It would make sense. But the I/Q ports are not available then anywhere outside the unit. Just the IF signals.

(will download the manual, just a moment pls)

//EDIT: Guessed correctly. See picture from manual. But that also means there are no IQ signals available. The option B17 provides only the four IF3 TX/RX IN/OUT BNC connectors and not really any I/Q signals.

_Wim_ · « **Reply #49 on:** October 23, 2020, 07:36:43 pm »

I never really used that option in mine, so I cant really help with that, but will be reading along if you figure it out


EEVblog Main Site	EEVblog on Youtube	EEVblog on Twitter	EEVblog on Facebook	EEVblog on Odysee

Author Topic: CMU200 repair attempt - shipping damage (oh those post monkeys...) (Read 5408 times)

Share me