Kenwood HM-250 info and manuals?

Hi.

Got me one of these and I'm wondering if you experts might know anything about it or where to find the service manual for it? I found some kind of a users manual at ciari and at one of the sites I found 2 pages from probably the service manual, the pg no's were 146/147 and showed the specs. Google didn't give much more than a few seemingly fake sites without manuals. Maybe the only way is to tear it apart and figure out the bits? But before I do that I will play and do some tests.

I emailed the UK branch of Kenwood but I don't think they are the ones handling measurement equipment. Found that Texio Corp. seems to have taken over Kenwoods instuments. I have searched without succes and now emailed them but they have no references of HM-250(A) on their web. Waiting for their reply.

Replay came informing me that they don't keep documentation on obsolete products :(

An update - I have found that the Kenwood partnumber for the service manual is b51-1092-00.
Another upate. The earlier LEADER LDM-171 seem to look a lot like the HM-250. I believe I will have the meter on Monday to check if the boards are siblings. The LDM-171 service manuals are everywhere and the specs seems to be close enough if not the same.

The Leaders is quite different inside so the partlists must differ a lot - no help. I'll put in some pic's of the HM-250 for your amusement ;)

[IMGDEAD]http://i66.tinypic.com/5xmx79.jpg[/IMGDEAD]

Quite clean...

[IMGDEAD]http://i67.tinypic.com/5mgj5.jpg[/IMGDEAD]

Right side of PCB...

[IMGDEAD]http://i66.tinypic.com/1z5j31z.jpg[/IMGDEAD]

Left side...

[IMGDEAD]http://i66.tinypic.com/2irngwn.jpg[/IMGDEAD]

Bottom/trace side

If I can get this down to -100dB and find a way to stop the notch from drifting I would be glad. It's a nice little meter...

BTW, do you know what this is and maybe give a link to the data sheet :)...


[IMGDEAD]http://i66.tinypic.com/257py6q.png[/IMGDEAD]

Thanks!
Regards
 
Thanks PChi. Found one ref so far with the datasheet for mcd-521 but it doesn't mention the 5221. For now I have no clue of what tolerantes or boundaries these parts works with. I still have to find time for tracing the circuit and measure it to find a part that might suit. Odd that there is so little info about this part on the net. Maybe I interpret the text wrongly and it actually says something else?

Regards

Some good news :). The notch filter doesn't drift at the previous pace. The solution was to jog the various connectors a few times :D. The BOM is almost done by now regarding the main board and given it's an dual side PCB the tracing is doable.

The parts puzzling me besides the optocouplers are C37 and C51 in the preamp and meter amp circuits. I can't find what the color bands stands for...
Regards