Hameg 1005 Scope not triggering

[Colin1256]

Dear all,

I've purchased an old Hameg 1005 (100 MHz Scope) because it reminds me of my days at university.

It's fairly beaten up, but I'm trying to restore it to working order.

It is generally working fine; I have already been into it to replace some broken caps on the Channel 3 input, so that is taken care of. Next, I'd like to get it to trigger again. I am unable to get either timebase to trigger on anything but line. If leave it on Auto-Trigger, it won't lock in at all, if I try to set the trigger level manually, it won't lock in.

Any ideas?

Thanks a lot in advance!


Colin

[singapol]

See service manual for relevant info. If you have no electronics experience please asked someone who can repair as there are high voltages in scope that can kill. 

Check pcb for cold solder joints as in:Related topic:

https://www.eevblog.com/forum/testgear/hm1005-repair-12v-rail-unstable/

Oscilloscope troushooting :

www.sphere.bc.ca/test/tek-parts/troubleshooting-scopes.pdf

Hameg 1005 user/service manual:

https://cdn.rohde-schwarz.com/hameg-archive/HM1005_englisch.pdf

[oldway]

First, welcome on the forum.

You must check the following:

- Check voltages and ripples of the power supplies. (check also the -5V !)

- Check for cold solder joints, particularly the mass solders (very common problem)

- Clean the switches with contact cleaner: I recommend KF F2 special contacts.

Another common problem: an interrupted diode of the rectifier bridges. The ripple before stabilization is then 50Hz instead of 100 Hz.

After this, check if you can trigger your scope with external trigger.

[Colin1256]

Guys, thank you!

I did already check the supply rails (though just with a DVM, not with a scope). The voltages were certainly there and pretty much spot-on. Obviously, I didn't check for ripple though.

I will let you know what I find.

Thanks!


Cheers,


Colin

[oldway]

... Obviously, I didn't check for ripple though....

Why not ? You can measure ripple with your multimeter on AC scale, you don't need another oscilloscope to do that. (but to repair a trigger fault of your HM1005, you will !)

[Colin1256]

Quite honestly, I just didn't think of it.

I checked that the voltage rails were there, and my 5 1/2 Digit Multimeter showed them to be within spec and also, they didn't move at all... so it didn't occur to me to look for any ripple on the rails.

I'll have a look this Sunday.

Cheers,


Colin