Hameg 203-6 scope u/s

[ssjenkins]

Hi All .

One of the members on another forum recommended this sub-forum so I'm hoping you can help.

I left my 203-6 on yesterday for an hour or so to warm up. When I returned I was greeted with a blank screen. On further investigation I've found that I seem to have lost the Time/Horizontal deflection. Here's some more details.

Power indicator lights up OK. All switches up, all controls at centre, except the calibrates. Nothing on screen. With probe connected to the 2V test signal and the "X-Y" button depressed I have a 2V vertical line indication on the screen. If I depress the "component tester" I have the expected horizonal indication on screen. There does seem to be a smell of a burnt component coming from it, although I haven't opened it up yet to have a look.

I have been offered a 303-6 for £180, but I'm not keen on throwing things out if they can be repaired at a reasonable price. Hameg in Barcelona have quoted me around £170 to fix mine??

Anywa , I'd appreciate any help and/or advice.

Sammy.

[maninashed]

Hi, you haven't given us a lot to go on here. Are you familiar with the working of a scope, and do you have a manual/circuit diagram? The manual is important when trying to repair a complex piece of test equiptment like a scope. So if you don't have a manual, I suggest you obtain one.
I'm not particularly familiar with the Hameg range of scopes, but from what you describe, eht is present, and you do have a trace, but no horizontal deflection.
This suggests a fault in the timebase/ x amp circuitry, but you will need to check voltages in this area and this is why you need the manual.
Bill

[ssjenkins]

Hi Bill .

No , I've never had to fix a scope before so this will be a first . Saying that , I am reasonably competent and I do repair other electronic items . CB radios etc. I did repair a TV once , but it was with advice from another forum . I do have the standard manual for the scope which has the schematics in it . I will have a look around and see if I can find the dedicated service manual for it .

Just to clarify . You are correct in what you say . EHT and a vertical trace present , just no horizontal deflection .

Regards

[kernowcam]

I found my Hameg Manual at their website. I needed to download the English one in full and the back end of the German one to get the diagrams.

I did call Hameg uk who did not help but put me through to Germany support who told me the scope was old, produced by Hameg and they are now Another company so the trail went cold.
I had an erratic trace on ch 1. Stripped the unit - which involved removing the case and the front panel, then kept digging till the modular board came out. Well made, switched well sealed up but managed to switch clean the required ones. All well since.
I was mindful of the 2000v in there and being a bit of a numpty tried to be careful.

Hope about a good visual and sniff test first?

Also check all the switched are out. That threw me when I reassembled mine.

[maninashed]

Sammy, primarily be careful re the high voltages present in scopes.
First, check all power supply rails are all present on the secondary of the psu, there will be several levels of voltage, some regulated. Some will be + and - rails (ie +12v and -12v). Make sure all are present and correct.
Second, check that the correct power supplies are present to the timebase circuit and X amplifier. The X amp is connected to the X deflection plates in the CRT.
Thirdly, using the circuit diagram, check that the correct voltages are present in the X amp. If you have access to another scope, this will be useful for fault finding further.
Bill

[ssjenkins]

Hi All .

Well , a quick visual inspection has shown R541 melted on the Time Base board . It's got something to do with the 12V line . I've uploaded a few photos and the diagram .

Regards

Sammy

[Vicboduk]

Hi Sammy, I don’t know how familiar you are with the triggering facilities of your scope but before you go any further do make sure that the trigger mode is set to “Auto” and not “Norm”.
This is a common pitfall for the uninitiated. If the trigger is in “Norm” mode a scope will only display a trace if it has something to trigger on and the level control is set correctly, otherwise it will display nothing.

Vic

Edit; I've just found a picture of your scope - I believe that the trigger mode button (AT/NORM.) needs to be out to select auto mode.

Edit,Edit; It looks like you definately have a hardware fault - It appears that you uploaded your pictures as I was composing my reply...

[maninashed]

Well, you have a good clue there!. There is probably a transistor gone s/c associated with it. Unfortunately the resolution of the circuit diagram is not good enough for me to make out the component numbers and values. I will send you a personal message with an email address, and you can send me a scan of the circuit, and hopefully we can get this sorted.
Bill

[ssjenkins]

Hi . Thanks to all . I appreciate the help . The diagrams are on their way Bill .

Cheers !

Sammy

[maninashed]

Thanks for the circuit diagrams.
Ive had a quick look and cant find R541 on the diagram, but there are 2 x R540's so Im assuming that's a typo and the R540 on the right hand side is the resistor that's burnt up. If that's correct, check C529 for short circuit, T512,T513 and T514, one or more may be short circuit. Let us know the results.
Bill

[ssjenkins]

Hi Bill . There's a delay every time I reply to a thread as a moderator has to approve each post . I've emailed you as R541 is in the first diagram . Regards

[maninashed]

Ok, I've found it now. Check T509,510,511, and c517 electrolytic, for s/c. It should be one of those.
Bill

[ssjenkins]

Thanks Bill . Will do . I probably won't be able to look at it till Tuesday , but I'll post back with my findings . Thanks again !

Sammy

[Herald1360]

Originally Posted by kernowcam

I did call Hameg uk who did not help but put me through to Germany support who told me the scope was old, produced by Hameg and they are now Another company so the trail went cold.

Not particularly helpful here but just for information- Hameg is now the Rohde & Schwarz presence at the budget end of the market. Disappointed to hear they're not interested in helping with earlier kit, though. If nothing else it's good "potential customer" relations.

[ssjenkins]

Hi All .

Well I had a bit of spare time and I've found the guilty culprit . C519 was short . I've uploaded a photo . I know the value is 0.1uF , but can some kind person tell me what type it is . Is it a polyester ?

Thanks

Sammy

[Herald1360]

Looks like it. M probably means 20% tolerance. Working voltage- you'll have to figure that by inspection of circuit......

[ssjenkins]

Thanks . I think it's a 12V circuit .

[Herald1360]

Yes- the cap is just HF decoupling for that 12v rail. Pretty much any radial lead polyester that will fit should do!

[PJL]

That ones a ceramic and they are particularly good at decoupling. I am sure Maplins will have one (but that's probably not much help when you are in Spain!).

[ssjenkins]

Originally Posted by PJL

That ones a ceramic

Thanks for that PJL . I'll pick one up during the week when I get some time .

Cheers !

Sammy