tds 460 power supply problems

[ght_marius]

Hi

I recently bought this scope TDS 460 with a power supply faulty but can not find the schematic diagram. If anyone have the schematic diagram or any idea on how to fix this power supply.

any help much appreciate it.

thanks Marius

[T3sl4co1l]

Probably bad capacitors.

They didn't release any schematic level service information, it's only "replace board X".

The supply doesn't look unusual so it should be easy to follow along with its operation.

Have you checked if it powers up when disconnected from the main board?  Shorted capacitors elsewhere is a possibility (the primary fault is SMT electrolytics leaking).

Tim

[Daxxin]

Not sure but if its PS-1690 its almost the same of LeCroy model that cannot remember exactly what model
difference is only output voltages , can find schematic of lecroy at ko4bb web site.

[ght_marius]

Hi

Looks like it`s not the capacitors, no change in behaviour, and in the end the main transistor end up shorted and it took with it a few more components with it:

1n4148
MJF16006A
1N5234B
CUSTOM RECTIFIER
and possible the teckronix custom chip 100004

First I have managed to open the custom rectifier , and I have found a diode and possible a triac mac228a8 that`s faulty , maybe you can help me to identify the diode and the use of it. I  also found this web site in Italian and he managed to remove the green compound of the custom chip 100004 of this web site http://digilander.libero.it/chopin.i/varie/riparazioni.html
I have managed to make a schematic of the custom rectifier but if you think it`s wrong I will try to do it again, some components the make and model got lost when I was removing the compound. The 1n4148 might be wrong and 1n4006 rectifier module.

[ght_marius]

now the pictures

[T3sl4co1l]

You depotted a potted assembly?

Tim

[tec5c]

Yeah that baby's broke!

Is that really from a 460? If so, that thing must have been through hell.

With reference to the pictures, I'm sure you have a strong idea about what needs replacing. Start with those then test surrounding components...

[hegar93]

Hi,

I got myself a TDS 420 with a faulty PSU some time ago and got it working again, here is the thread on the Tektronix Forum:http://www1.tek.com/forum/viewtopic.php?f=5&t=6283&st=0&sk=t&sd=a&hilit=tds+420&start=10
Main problem was the optocoupler and the LM339 for overcurrent shutdown. Maybe you can get some usefull hints in there.

The potted assembly seems to be a voltage doubler for 120V (and maybe a crowbar), but the one in my scope looked a bit funny, so disconnected it and it still works a treat.
At least for 230V it is not needed for normal operation. "mikeohm" writes a bit more about that in the last posts...

You can get the schematic of a very similar PSU in this manual for a LeCroy scope:
http://www.ko4bb.com/manuals/index.php?dir=LeCroy
Get the one for LeCroy_9354A-M-L and go to page 425/426 for the supply.

hegar

[ght_marius]

Hi

This is the custom chip 100004 picture and I have found a few components faulty like the transistor Q1,ZD3,U1,D4,Q4.Q4 I can not find the type and model , when I removed the green stuff I removed the type and model ass well , if anyone knows the components please share with me . I managed to do the schematic of the ceramic board with components in Altium Designer .Anyone who need the files please give a shout.

thanks marius

[ght_marius]

The capacitors of this custom chip are not all updated on the schematic diagram , only some of them, but when I get some free time I will do it.

[scopeman]

Hi

This is the custom chip 100004 picture and I have found a few components faulty like the transistor Q1,ZD3,U1,D4,Q4.Q4 I can not find the type and model , when I removed the green stuff I removed the type and model ass well , if anyone knows the components please share with me . I managed to do the schematic of the ceramic board with components in Altium Designer .Anyone who need the files please give a shout.

thanks marius

Marius,

Do you have a PDF of that schematic you worked out for this module? The same part is used in LeCroy scopes and we are trying to nail down the schematic and parts.

Thanks,

Sam
W3OHM

[maxxim]

Hi, what is the value of the tantalum capacitor on the underside PS-1690 power supply pcb (hybrid pin 13-19).
Thanks

[elbass7]

I tried downloading the PrjPCB file to open it, but Altium says there's not document inside.  Do you have the printed circuit board design for thei A1 100004 green potted custom board for the Tektronix TDS-420 power supply?

Thanks,