Hameg HM 205-3 Ocilloscope disorted screen. - UK Vintage Radio Repair and Restoration Discussion Forum

E IsadG · 12th Sep 2014, 2:22 pm

I got an oscilloscope on-line, the seller told me it was bad and the picture said so, but I am trying to repair this thing and anyone know what it could be.
Pls if anyone had this problem and they repaired this
pls leave a comment on what it could be .

Thanks.

SteveCG · 12th Sep 2014, 3:02 pm

Can please you confirm that what you are displaying in the photograph is intended to be the test calbration waveform with the oscilloscope set to a single channel mode.

David G4EBT · 12th Sep 2014, 6:47 pm

Don't know if you have the manual, which might assist you. If not, you can download it free of charge from Hameg's website here:

http://www.hameg.com/manuals.0.html?&no_cache=1&L=0

It's very comprehensive (65 pages, 3.5MB)

At the above link, in the 'PRODUCT' column, scroll down for HM203-5, and in the 'LANGUAGE' column, choose the language that is best for you out of several listed.

Hope that helps.

Good luck with sorting the fault - sorry I can't help further.

cmjones01 · 12th Sep 2014, 9:54 pm

That looks like shipping damage - I'm almost certain its been dropped and something's broken inside the CRT, distorting the electrode structure and thus the trace. The only way to fix it is to replace the CRT, I'm afraid.

Chris

Radio Wrangler · 12th Sep 2014, 10:28 pm

I'm afraid I think Chris is exactly right. You now need to find another of the same model with a different fault to be able to make one good one. Never send good scopes by couriers or mail. They need box within box within box packaging designed to limit peak G. Electrostatic CRTs are much more fragile than their magnetic cousins.

David

McMurdo · 12th Sep 2014, 10:58 pm

I'm sure there's been a similar topic on the forum before with similar symptoms? The consensus there was internal crt damage too

high_vacuum_house · 12th Sep 2014, 11:24 pm

Good evening,
looks like the glass rods that hold the deflection plates in the CRT have snapped.

An easy way to check is to rock and shake the scope powered up and see if the lines move around the screen.
If they do the deflection plates are wobbling around on their lead in wires. The whole gun assembly would normally be held rigidly together with glass rods fused to all of the electrodes.
Christopher Capener

maninashed · 12th Sep 2014, 11:42 pm

I'm afraid that your crt (cathode ray tube) is damaged, and you will need a new tube from a similar scope.
Bill

Nickthedentist · 13th Sep 2014, 9:35 am

Yes, see here: https://www.vintage-radio.net/forum/...d.php?t=106959

E IsadG · 13th Sep 2014, 10:38 am

Well the CRT is bad so this thing will need to go for parts.

If anyone has a old analogue oscilloscope for a good price I would like to buy it because this was to be my first scope.

jimmc101 · 13th Sep 2014, 3:18 pm

Just a thought but is there any chance it could be caused by extreme ripple on the power supply - enough to cause the regulator to drop out?
Caused by a shorted rectifier diode and/or dried out reservoir cap?

Jim

maninashed · 14th Sep 2014, 9:10 pm

No, I don't think so. CRT shock damage.

John_BS · 14th Sep 2014, 10:32 pm

As this is a storage 'scope with more buttons than normal, it's just possible that it might not be the crt. But you'll need another 'scope to diagnose what's wrong and fix this one, assuming of course that it's not the crt.

You could try removing the connections to the Y plates and see if you can get a straight line across the screen. John

trh01uk · 14th Sep 2014, 10:41 pm

And while I agree that CRT internal damage is the most likely problem here, I did wonder if a strong magnetic field might be causing the trace distortion. That does seems very unlikely - since I can't think of any obvious source of such a field.

Richard

woodchips · 19th Sep 2014, 10:08 am

I had a spectrum analyser that had similar symptoms. It had been dropped on its back and the whole electron structure in the CRT had been moved about 5mm backwards, you could see the scrape marks in the glass. A right off I am afraid, I did try banging it back but no luck.

12th Sep 2014, 2:22 pm	#1
E IsadG Retired Dormant Member Join Date: Sep 2014 Location: Shkodër, Albania Posts: 2	Hameg HM 205-3 Ocilloscope disorted screen. I got an oscilloscope on-line, the seller told me it was bad and the picture said so, but I am trying to repair this thing and anyone know what it could be. Pls if anyone had this problem and they repaired this pls leave a comment on what it could be . Thanks. Attached Thumbnails Last edited by AC/HL; 12th Sep 2014 at 2:43 pm. Reason: Readability

12th Sep 2014, 3:02 pm	#2
SteveCG Nonode Join Date: Jun 2009 Location: Herefordshire, UK. Posts: 2,495	Re: Hameg HM 205-3 Ocilloscope disorted screen. Can please you confirm that what you are displaying in the photograph is intended to be the test calbration waveform with the oscilloscope set to a single channel mode.

12th Sep 2014, 6:47 pm	#3
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,766	Re: Hameg HM 205-3 Ocilloscope disorted screen. Don't know if you have the manual, which might assist you. If not, you can download it free of charge from Hameg's website here: http://www.hameg.com/manuals.0.html?&no_cache=1&L=0 It's very comprehensive (65 pages, 3.5MB) At the above link, in the 'PRODUCT' column, scroll down for HM203-5, and in the 'LANGUAGE' column, choose the language that is best for you out of several listed. Hope that helps. Good luck with sorting the fault - sorry I can't help further. __________________ David. BVWS Member. G-QRP Club member 1339.

12th Sep 2014, 9:54 pm	#4
cmjones01 Nonode Join Date: Oct 2008 Location: Warsaw, Poland and Cambridge, UK Posts: 2,681	Re: Hameg HM 205-3 Ocilloscope disorted screen. That looks like shipping damage - I'm almost certain its been dropped and something's broken inside the CRT, distorting the electrode structure and thus the trace. The only way to fix it is to replace the CRT, I'm afraid. Chris __________________ What's going on in the workshop? http://martin-jones.com/

12th Sep 2014, 10:28 pm	#5
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,902	Re: Hameg HM 205-3 Ocilloscope disorted screen. I'm afraid I think Chris is exactly right. You now need to find another of the same model with a different fault to be able to make one good one. Never send good scopes by couriers or mail. They need box within box within box packaging designed to limit peak G. Electrostatic CRTs are much more fragile than their magnetic cousins. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

12th Sep 2014, 10:58 pm	#6
McMurdo Dekatron Join Date: Jun 2009 Location: Staffordshire Moorlands, UK. Posts: 5,274	Re: Hameg HM 205-3 Ocilloscope disorted screen. I'm sure there's been a similar topic on the forum before with similar symptoms? The consensus there was internal crt damage too __________________ Kevin

12th Sep 2014, 11:24 pm	#7
high_vacuum_house Octode Join Date: May 2003 Location: Belper Derbyshire Posts: 1,936	Re: Hameg HM 205-3 Ocilloscope disorted screen. Good evening, looks like the glass rods that hold the deflection plates in the CRT have snapped. An easy way to check is to rock and shake the scope powered up and see if the lines move around the screen. If they do the deflection plates are wobbling around on their lead in wires. The whole gun assembly would normally be held rigidly together with glass rods fused to all of the electrodes. Christopher Capener __________________ Interests in the collection and restoration of Tefifon players and 405 line television

12th Sep 2014, 11:42 pm	#8
maninashed Rest in Peace Join Date: May 2011 Location: Preston, Lancashire UK Posts: 955	Re: Hameg HM 205-3 Ocilloscope disorted screen. I'm afraid that your crt (cathode ray tube) is damaged, and you will need a new tube from a similar scope. Bill

13th Sep 2014, 9:35 am	#9
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,865	Re: Hameg HM 205-3 Ocilloscope disorted screen. Yes, see here: https://www.vintage-radio.net/forum/...d.php?t=106959

13th Sep 2014, 10:38 am	#10
E IsadG Retired Dormant Member Join Date: Sep 2014 Location: Shkodër, Albania Posts: 2	Re: Hameg HM 205-3 Ocilloscope disorted screen. Well the CRT is bad so this thing will need to go for parts. If anyone has a old analogue oscilloscope for a good price I would like to buy it because this was to be my first scope. Last edited by Mike Phelan; 14th Sep 2014 at 11:56 am.

13th Sep 2014, 3:18 pm	#11
jimmc101 Heptode Join Date: Mar 2009 Location: Portsmouth, Hampshire, UK. Posts: 674	Re: Hameg HM 205-3 Ocilloscope disorted screen. Just a thought but is there any chance it could be caused by extreme ripple on the power supply - enough to cause the regulator to drop out? Caused by a shorted rectifier diode and/or dried out reservoir cap? Jim

14th Sep 2014, 9:10 pm	#12
maninashed Rest in Peace Join Date: May 2011 Location: Preston, Lancashire UK Posts: 955	Re: Hameg HM 205-3 Ocilloscope disorted screen. No, I don't think so. CRT shock damage.

14th Sep 2014, 10:32 pm	#13
John_BS Octode Join Date: Dec 2008 Location: Wincanton, Somerset, UK. Posts: 1,784	Re: Hameg HM 205-3 Ocilloscope disorted screen. As this is a storage 'scope with more buttons than normal, it's just possible that it might not be the crt. But you'll need another 'scope to diagnose what's wrong and fix this one, assuming of course that it's not the crt. You could try removing the connections to the Y plates and see if you can get a straight line across the screen. John

14th Sep 2014, 10:41 pm	#14
trh01uk Octode Join Date: Nov 2010 Location: Ross-on-Wye, Herefordshire, UK. Posts: 1,654	Re: Hameg HM 205-3 Ocilloscope disorted screen. And while I agree that CRT internal damage is the most likely problem here, I did wonder if a strong magnetic field might be causing the trace distortion. That does seems very unlikely - since I can't think of any obvious source of such a field. Richard

19th Sep 2014, 10:08 am	#15
woodchips Octode Join Date: May 2010 Location: Grantham, Lincolnshire, UK. Posts: 1,177	Re: Hameg HM 205-3 Ocilloscope disorted screen. I had a spectrum analyser that had similar symptoms. It had been dropped on its back and the whole electron structure in the CRT had been moved about 5mm backwards, you could see the scrape marks in the glass. A right off I am afraid, I did try banging it back but no luck.