Author Topic: Hameg HM1507-3 repair (Read 24037 times)

paraboloid · « **on:** November 18, 2014, 05:57:25 pm »

Hi there

I scored a Hameg HM1507-3 analog/digital scope from the trash bin (see photos of that model here: https://www.flickr.com/photos/eevblog/with/5823872215 ). However, it seems as if it is not working. The screen remains black (more precisely: green), no activity whatsoever.

Following things I noticed:

- User interface seems to work well. All the buttons, the beeper and LEDs react as expected. So the "logic" side of things seems to be ok.
- The filament of the tube does glow

Because I cannot see anything on the screen I suspect that the acceleration voltage of the tube has a problem, at least that's what I would like to check first. My question is: How? How to check the high voltage without damaging the device and, more importantly, without damaging me? Oh and by the way, does someone have the schematics for this model?

Best regards,
para.

oldway · « **Reply #1 on:** November 18, 2014, 06:58:20 pm »

The filament voltage is coming from an apart transformer of the SMPS.
HV voltage (12KV) is coming from an HV transformer/oscillator and a voltage multiplier. (see schematic )
The best way is to measure the -2KV at TP153.
You need an HV probe to measure this voltage.
Have a look first for R1060 (1R2) open, C1054 (100µF 16V) shorted, and T1006/T1007 shorted.
More often, if you don't have the -2KV, that's a faulty HV transformer or a faulty HV multiplier.

paraboloid · « **Reply #2 on:** November 18, 2014, 07:28:31 pm »

Wow, that is so much more than I expected or even asked to get. Thank you a lot! I will update this post with my findings.

paraboloid · « **Reply #3 on:** November 19, 2014, 06:06:05 pm »

Ok, so I checked the things you mentioned and they all look ok. After that I removed the power supply board from the scope for having access to the back of the board. Measuring the -13.5V and +12V voltages on the IC1003B I noticed that they look a bit odd. With a frequency of 1Hz I am seeing a spike to -18V followed by a capacitive discharge curve on the 13.5V net. +12V looks similar (see pictures attached). Do you happen to have also the schematics for the rest of the power supply?

oldway · « **Reply #4 on:** November 19, 2014, 09:12:03 pm »

SMPS is oscillating at low frequency of aprox. 1.1 Hz
First replace C1009 1µF 100V and C1010 220µF 16V
Be very careful !
If you want to measure on circuity on live mains potential, you need to use an isolation transformer for your safety.

Here is the schematic of the SMPS....

paraboloid · « **Reply #5 on:** November 20, 2014, 10:22:25 am »

Thank you for your help. Could it be that you accidentally added the CRT schematic instead of the SMPS?

I am more of an FPGA guy and this is my first attempt on repairing a power supply. Hence my noob questions: Is the SMPS switching frequency of 1Hz and the graphs of the -13.5V and 12V rails the normal case if there is no load?

oldway · « **Reply #6 on:** November 20, 2014, 12:45:42 pm »

Yes, you are right, that's the wrong schematic.

The SMPS switching frequency is for shure above 25Khz but modulated by a 1 Hz low frequency.
This 1Hz oscillation is coming from unstable feedback.

This SMPS is a flyback configuration and can't work with no load condition.
In no load condition, this kind of instability (1 Hz oscillation) is absolutely normal.

paraboloid · « **Reply #7 on:** November 20, 2014, 06:44:27 pm »

Ok, so here is the guilty one: C1061. A little bit bent on the front, was so stuck between other parts that I did not see it. It still has 22 of the 33nF but I guess the ESR is way too high. Thanks a lot oldway, the screen is now working again.

There is still a problem with channel one. If it is not being grounded (via the button), it's voltage goes into the -infinity(?) range for every volt/div setting. Channel two works fine. I will take a look at this tomorrow and update this post.

oldway · « **Reply #8 on:** November 20, 2014, 10:04:57 pm »

Replace T2002 MMBFJ309
VERY VERY sensitive to ESD !

paraboloid · « **Reply #9 on:** November 30, 2014, 05:14:13 pm »

Your hunch was quite close... The (protection?) diode right next to the transistor was faulty. By soldering the diode from the working channel to the faulty one I could revive the bad channel. So I'm quite lucky that the diode is the only part that suffered from that "incident"

I couldn't quite figure out the number of the diode, that's why I've marked it in your last attachment. If you could give me the exact part number I'll order a replacement part and will have (thanks to your help) saved a fine bit of gear from the landfill

oldway · « **Reply #10 on:** December 01, 2014, 01:28:15 pm »

Well done ! The diode is a BAV199.
Remember that you can always send email to Hameg if you need help.
They are very kind and they will help you.
They have still most of replacement parts for older CRT scopes.
Enjoy your new combiscope

paraboloid · « **Reply #11 on:** December 01, 2014, 02:20:02 pm »

I think we were talking about different diodes here. The BAV199 seems to be a double diode in a SOT23 package but the faulty one is just a single one. To make it more clear I've marked the diode on a photo of the PCB. For your orientation: The T2002 you were talking about is below the marked diode.

paraboloid · « **Reply #12 on:** December 01, 2014, 02:49:51 pm »

Whops, here is the photo

oldway · « **Reply #13 on:** December 01, 2014, 02:53:59 pm »

The diode you have marked on the PCB is D2001.
This is indeed a double diode BAV199 in three terminals SOT23 package, marking code: JY*
There is no other diode near by T2002.

My documentation is from an HM1505, not from an HM1507-3.
Front end boards are different, that's why we have problems to identify this diode.
I can't help you, I don't have the documentation of HM1507-3.
If it is not a zener, you could try a 1N4148 minimelf SMD.

paraboloid · « **Reply #14 on:** December 01, 2014, 03:13:13 pm »

Mh, ok, maybe we are talking about different revisions then. I guess I'll just send a mail to Hameg asking them for the type number.

oldway · « **Reply #15 on:** December 01, 2014, 03:17:53 pm »

Try a LL4148.

paraboloid · « **Reply #16 on:** December 04, 2014, 06:45:09 pm »

For completeness: The faulty diode D2001 is of type BAQ34. Hameg was very helpful, they sent me the service manual by Email at no cost containing all the schematics.

A little word on the repairability of this device: I was not really amused. No silk-screen on the boards, lots of inter-board connections with cables soldered to the boards instead of connectors, heavy shieldings that are soldered to the boards and even worse, soldered to the chassis.

But all in all the repair was an exiting exercise!

oldway · « **Reply #17 on:** December 04, 2014, 11:30:40 pm »

As I told you, Hameg after-sales is very helpful and very nice.

They still have all the spare parts.

For this reason, it is often better to buy a HAMEG used cro than an used cro of another brand.

I have worked with a HM1507 for testing and maintenance of no breaks.

I was not satisfied with it because it often crashed in digital mode when doing a load transfer Inverter / mains.

I have an HM1505.
It looks like the HM1507 but analog only. (150 Mhz).

But I prefer the older HAMEG cro's.
The hm605 is very good, maybe the best.
The HM1005 is also very good, but it has no component tester, which is a serious shortcoming.
In my opinion, it would be the best if he had a component tester.

And now, enjoy your HM1507....

NB: The BAQ34 could be replaced by a LL4148 without any problem.

pinyoro · « **Reply #18 on:** December 05, 2014, 08:18:36 am »

I am impressed by your knowledge Oldway.

paraboloid · « **Reply #19 on:** December 07, 2014, 06:51:51 pm »

One (hopefully last) question: After some minutes of use the text on the CRT (top and bottom) moves out of the screen edges and can't be read anymore. Without knowing the t/div and v/div the scope is barely usable. What would be the best way to correct this issue? Messing around with the CRT (if so, where to do so?) or is there a "digital" option where the text is drawn? I fear a bit that when I mess around with the CRT that the time and voltage scaling will be wrong

oldway · « **Reply #20 on:** December 07, 2014, 11:57:32 pm »

I don't have all schematics, only a few ones.
It seems to be a final Y amplifier fault (readout offset) but I don't have this schematic.
Sorry, I can't help you.

Cyberdragon · « **Reply #21 on:** December 08, 2014, 10:28:11 pm »

Check the resistors in the Y amp. May be as simple as something out of tolerance or getting hot.

Janw93 · « **Reply #22 on:** February 02, 2015, 05:23:07 pm »

Hello,
I recently got one of these Hameg 1507-3. I got it for free and I'm not expert in oscilloscopes, I will rarely use it.
But looks like mine doesn't work properly, I don't know if the settings causing this problem or it's something faulty.
The thing is, when I turn on the device, it doesn't show any logo or anything(software, hardware verison). All the LEDs light up perfectly, everything starts up normally but the screen.
I can even use normally i plugged in some switch and tried it running and shows everything perfectly.

But non of the stuff in black boxes doesn't show...

Anyone experienced trouble like this or know the solution?
Sorry for posting here.

Thanks

tautech · « **Reply #23 on:** February 02, 2015, 08:00:09 pm »

Welcome to the forum.
Good score you have.

OK so the digital display is not working it seems, you can live with out it.

CRO's in this class do not have a boot process as they have no CPU.

Operator manual:
http://www.hameg.com/manuals.0.html?&no_cache=1&L=1%2522%2520onfocus%253D%2522

More study for you:
https://www.eevblog.com/forum/beginners/oscilloscope-training-class-(long)/

Janw93 · « **Reply #24 on:** February 02, 2015, 08:33:28 pm »

Yeah, thought so that digital display not working since I tried working one and you can turn off setting, but on a start screen you still get logo...
I want this oscilloscope to work... Any ideas if display can get replaced? and where to get it?
Thanks for your help, appreciate it!


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Author Topic: Hameg HM1507-3 repair (Read 24037 times)

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