Repair Hameg HM1505

[jm31]

hello,

I've got a problem on my HM1505 oscilloscope and I need to repair it.
The trace of the channel 1 is out of range : I cannot see it on the screen!
So I'm searching schematic or the service manual for this HM1505.
Thank's for your help.

JM.
 

[oldway]

Wellcome on the forum.

This is the schematic of vertical input attenuator and amplifier and external trigger input of the HM1505.

[jm31]

Hello,
Thank you.
If I understand, this schematic is for the first card that is behind the BNC plug'in?
If it is this card, it's not seem easy to access to it for signal measurements: the card is protected by a metal box and I don't know how unmount this.
So I would want to know If you could send me the schematic of the big card:  it will more easy to see the signals.
Furthermore in the big card there's a SOT23 transistor that look like very strange compared at the others ..
Thank's for your help.
Best regards
JM.
 

[oldway]

If the channel B is OK, that's probably the input FET transistor from channel A who is defective. (T2002 MMBF J 309)

That's the more commun failure due to heavy input overload of channel A .....

[Gertjan]

Hi jm31,

I had a similar problem with my Hameg HM1004. (identical input board)
The cause turned out to be a defective DC offset correction op-amp IC2003. (DC servo)

At first the metal shielding box puzzled me too. But it is easy to open with solder iron.

Regards, Gertjan.

[jm31]

Hi Gertjan,

thank you for you help too!  I'm going to see that this next weekend.
For me, the schematic is very complex! I don't understand anything with all this transistors.

Best regards

JM

[jm31]

hello,
I have opened the metal box and now I need the PCB implantation of the components.
because it's not easy to find the name of  components on the PCB: it's too small for me!
could someone send me this PCB implantation??
thank's!

JM.

[oldway]

Only the smd's of the vertical input board....

[jm31]

Hello,

I've seen the components on the board. Some components are present on board like ALD12W (relay) but i've haven't got MCP601 AOP.
There is an OPA131 op amp, so i think the schematic is not good for my HM1505.
During I was testing the card  the offset of channel  is gone out of range but in the positive voltage, and a few seconds later this offset changed to go to the negative voltage. A moment later I have push "autoset" button then the trace appears on the screen!
But I think it's only a big chance because the last week i had tried to push this button a lot of time...
I don't know what to do..

jm.

[oldway]

It is the schematic of HM1505, I am 100% sure of it, I received them from HAMEG directly by e-mail.

[jm31]

hello,

I have another problem that I just see today!!
When I put a positive square signal on Channel 1 and channel 2, and when I push on the DC/AC switch, i can see on the screen the change DC and after AC, but the signal doesn't change!
It stay positive all the time and this for the two channel !  *
Does this function use relays ?

I have another  question... how the potentiometers work? for X pos and  for amplitude ? because they have difficulties to work

thanks.

JM.

[jm31]

the reference of my oscilloscope is HM1505-2.

[oldway]

the reference of my oscilloscope is HM1505-2.

You asked for schematic of HM1505, not of HM1505-2.

Sorry, I have only schematic of HM1505....I can't help you anymore...

But so far I know, there is no or only minor differences between HM1505 and HM1505-2...
HM1505-2 has a switch to gain access to the menu, HM1505 has not.

I really wonder if you have enough electronic's knowledge and experience to repair such a sophisticaded oscilloscope....you speak about "potentiometers" ...no potentiometer at all but encoders...!!!

Better you ask to somebody who knows really the technology of this oscilloscope to repair it, not to try to repair it yourself.