TDK Lambda Alpha II 650 Power Supply issue

[ramin.azizli]

Hello everyone,

I have Alpha II 650 power supply by TDK Lambda. Here is the link in case you want to have a look:

http://www.tdk-lambda.com/products/sps/ps_alpha/alpha2/indexe.html

Just quick explanation: Alpha II 650 power supply (input: 110VAC, 220VAC) has an AC filter and 375VDC in the output. Output goes directly into a transformer with ferrite. That transformer gives ~18VAC pk2pk (!) at the secondary side which is the input of the DC to DC converters. This is what I get with my oscilloscope (see attachments). Ground was at the center of the screen when I made measurements.
So I have in repair one of these boards and it has a problem with its DC to DC converter (24V). In order to hook that up to the lab power supply I need to know the input voltage (which is obvious). But my multimeters did not measure anything neither in DC nor in AC mode at the input of the converters. Meanwhile as was mentioned before I measure 17.8VAC pk2pk (50Hz sinusoidal) with my oscilloscope (see attachments). So I'm puzzled.
Can you please advise or help to find out that input voltage?
Maybe someone has some experience on this boards and maybe he knows the general problems that faces these type of boards (especially with the DC to DC converters).
I would highly appreciate if you can share your knowledge.

Looking forward for your responses and help.

Thanks in advance to the whole community here...

[marcelo.digital]

Olá.. você continua trabalhando com fontes Alpha TDK 400 e 650? Também sou tecnico e gostaria de trocar informações com você, pois estou me especializando nessas fontes de minilabs. Por favor entre em contato, Abraços

Hello .. are you still working with Alpha TDK 400 and 650 fonts? I am also a technician and would like to exchange information with you, as I am specializing in these sources of minilabs. Please get in touch, Hugs