Instek GOS-6112 - No signal on either channel

[JamieArbor]

PS: Just seen the "say thanks" button, so have thanked you that way as well as in writing!

[Chris56000]

Hi!

Evening Jamie!

Pleased you've got your '6112 up and running!

Make sure all those little white multi–plugs connecting the cable–forms to the PCBs are firmly pushed home, have a look at the front–panel pcb to male sure no plugs, connectors, switches, buttons,, etc., etc., have got dry or yakky joints, going over anything iffy (carefully!) with your iron prior to wrapping the 'scope up and putting into service!

The two testers you've got will serve you well for development and repair purposes by the way!

Please feel free to come back to the Forum any time, that's what we're all here for!

Good luck!

Chris Williams

[Shopy]

Hi
I like to ask for your help.
I have this osciloscope gos 6112
And chanel 2 volt div is not working chanel 1 is ok
When i turn the knod i do not hear the relay only on chanel 2
What can be the problem
Thanks

[Chris56000]

Hi!

I'll have to download and print the drawings again but I'll be back shortly with fault–finding advice!

Chris Williams

[Shopy]

Thank you chris
Waiting for you kind advice

[Shopy]

Hi chris i understand that you dl the drawings .is it posible to get this link so i can dl this drawings to
Thanks

[Chris56000]

Hi!

I posted a link to the circuit diagram on the second or third post of the first page ot this thread – you can get them free from Elektrotanya!

Chris Williams

[Shopy]

hi Chris

thank you for the link but there is only the inputs drawings of the scope is there more somewhere like the other boards of this scope???

can you please help with the problem I have with channel 2?

thanks

[Shopy]

hi chris

Meanwhile, i did some voltage tests on the shift registers

I found that there is a big different betwine them and I attached the results

I do not know why is that buy it shows wיy one channel is working and the other one is not
I try to contact GW INSTEK and ask about this problem but I did not get much help from them.
but they say that the problem is related to the rotary switch sb09 can be faulty .sb09 encoder ic or ch2 attenuation selector ic 406

what you think about that?

[Chris56000]

Hi!

I can assure you all the manual is there, honestly – you should have 21 pages in total!

Did you wait for Elektrotanya's 30 second timeout before the download link appears?

'4094 CMOS series/parallel shift registers are notorious for causing obscure faults, and in this case, where several are used together with U406, I strongly suggest you bin the lot shown on  the appropriate diagram sheet and replace them all with new, also check all round that panel for dry–joints, plugs not pushed fully home into connectors, etc!

The fact you're getting Ch 1 operational with relay clattering when you turn the ch1 gain control suggests the common main relay supply is present and correct!

The Ch 2 Volts/Division Up/Down button SB09 operates lines S5, S6 and S7 which are multiplexed by UB02 ('74HC138/'74LS138) on the front panel PCB – make sure the inputs of UB02 are being operated by SB09, and if you're doubtful, replace SB09 and UB02 together as a pair!

You should be able to obtain replacement tact switches similar to what GW Instek used from fleabay!

Chris Williams

[Shopy]

hi Chris

thanks for the advice

i did some checking on the front panel and the mainboard. tell you the truth im confused. 
the input from SB09 ch2 and SB08ch1 are entering to UB02 decoder so if ch1 is working and ch2 not i assume this chip works or is it possible only half of it works? I'm not sure. then the output of UB02 goes to UB03 microcontroller. maybe this one i defective on ch2 input?
i swap betwine sb09 and sb08 to eliminate this as the problem .so the problem remains .it is not the buttons defective.
i really do not what to trace? i try to trace the signals with a logic probe i have and did not find much.
what i notice is that when i try to put a signal in ch2 ,i can see the signal but it is like sucked in a constant voltage and is not changing.

do you have any suggestions for me what to look for?

thanks

 

[Shopy]

hi chris

can you please help with this?

when I connect the probe to CAL point I do not get 2v p/p I get about 1.67v on screen

I like to change the vertical to fix it.

what will be the right pot number to do so?

see attached

thanks