Help needed with a Hameg HM203-6 scope - UK Vintage Radio Repair and Restoration Discussion Forum

barrywebb · 9th Feb 2021, 7:41 pm

I have just got hold of a Hamig HM203-6 scope that has a problem the scope powers up but only a power light and green dot on the screen.
I have opened it up and found two 6R8 resistors blown on the same board the XY board resistor positions are at R924 and R799 the R924 is the worst burnt.
I am working on it with a friends help but just wonder if any one has any ideas why or experienced any thing like it i have ordered some new resistors as the ones fitted are 1/4 w and i only have 1/2 w so might be a little large.
Any help on this would be very helpful.
Barry.

trsomian · 9th Feb 2021, 8:09 pm

I have a 203-5, which came with its circuit diagram. I have no idea what the differences between a -5 and -6 are, but they may be quite minor. I can scan the diagram if you think it may be useful

frsimen · 9th Feb 2021, 8:19 pm

Hello Barry,

Something that those resistors are feeding has gone short circuit by the sound of it. Top suspects would be the decoupling capacitors, particularly the electrolytic or tantalum types. For R799, check C723 and C724. For R924 check C747 and C746.

Before replacing the resistors do check that the +12V and –12V supplies are correct.

Paula

David G4EBT · 9th Feb 2021, 9:43 pm

Do you have the manual Barry?

In addition to the 31-page English Manual, for the circuit board layouts you also need the 44-page Spanish manual.

I don't know why, but for some reason, the English manuals don't have the circuit board layout.

If you don't have them, I can email them to you if you send me a PM with your email address.

Good luck in sorting it.

Goldie99 · 10th Feb 2021, 4:27 pm

If you get stuck for any of the manual / schematics / board layouts, I also have a full set for the HM203-6 thanks to some problems I had with one a couple of years back.

In the mean time, I can strongly recommend & endorse Paula's advice - it's thanks to her help & support, that I have a fully functional HM203-6.

Alan

9th Feb 2021, 7:41 pm	#1
barrywebb Tetrode Join Date: Nov 2013 Location: Redruth, Cornwall, UK. Posts: 85	Help needed with a Hameg HM203-6 scope I have just got hold of a Hamig HM203-6 scope that has a problem the scope powers up but only a power light and green dot on the screen. I have opened it up and found two 6R8 resistors blown on the same board the XY board resistor positions are at R924 and R799 the R924 is the worst burnt. I am working on it with a friends help but just wonder if any one has any ideas why or experienced any thing like it i have ordered some new resistors as the ones fitted are 1/4 w and i only have 1/2 w so might be a little large. Any help on this would be very helpful. Barry.

9th Feb 2021, 8:09 pm	#2
trsomian Hexode Join Date: Oct 2010 Location: Box End, Beds. UK. Posts: 271	Re: Help needed with a Hameg HM203-6 scope I have a 203-5, which came with its circuit diagram. I have no idea what the differences between a -5 and -6 are, but they may be quite minor. I can scan the diagram if you think it may be useful

9th Feb 2021, 8:19 pm	#3
frsimen Heptode Join Date: Jan 2011 Location: Croydon, London, UK. Posts: 773	Re: Help needed with a Hameg HM203-6 scope Hello Barry, Something that those resistors are feeding has gone short circuit by the sound of it. Top suspects would be the decoupling capacitors, particularly the electrolytic or tantalum types. For R799, check C723 and C724. For R924 check C747 and C746. Before replacing the resistors do check that the +12V and –12V supplies are correct. Paula

9th Feb 2021, 9:43 pm	#4
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,761	Re: Help needed with a Hameg HM203-6 scope Do you have the manual Barry? In addition to the 31-page English Manual, for the circuit board layouts you also need the 44-page Spanish manual. I don't know why, but for some reason, the English manuals don't have the circuit board layout. If you don't have them, I can email them to you if you send me a PM with your email address. Good luck in sorting it. __________________ David. BVWS Member. G-QRP Club member 1339.

10th Feb 2021, 4:27 pm	#5
Goldie99 Heptode Join Date: Jul 2014 Location: Boston, Lincolnshire, UK. Posts: 995	Re: Help needed with a Hameg HM203-6 scope If you get stuck for any of the manual / schematics / board layouts, I also have a full set for the HM203-6 thanks to some problems I had with one a couple of years back. In the mean time, I can strongly recommend & endorse Paula's advice - it's thanks to her help & support, that I have a fully functional HM203-6. Alan