Hitachi HDR505 - no antenna signal

[jarsudsco]

I have an Hitachi HDR505 Freeview+ Recorder. It uses a Vestel 16MB835N-4 T385 041109 PCB.

It powers up ok and can access the existing recordings on the HD, but it reports there is no antenna signal - so re-tuning results in no channels found, and there is no signal at the aerial output socket (JK2) with a known good aerial connected to the input (JK1).

I have tried re-touching the solder on those discrete components obviously in the signal path from JK1 to the tuner IC's (? MXL5007T) and back out to JK2 with no success.

Any suggestions on what to try or test next would be very welcome.

Regards,


- jarsudsco

[tom66]

Re: Hitachi HDR505 - no antenna signal

Check the +35V from the PSU is OK. This is used to tune the tuner.

[jarsudsco]

Re: Hitachi HDR505 - no antenna signal

@tom66 - Thanks for the quick reply. The external PSU is only 12V so I guess the 35V must be generated on the board but I can't even see any capacitors rated greater than 25V - would you happen to know where I could check?

Regards,


- jarsudsco

[tom66]

Re: Hitachi HDR505 - no antenna signal

It might be of a different design. What is the part # of those ICs near the tuner input?

[jarsudsco]

Re: Hitachi HDR505 - no antenna signal

The two smaller chips nearest the jacks are both marked MXL5007T the two larger chips beneath are both marked D61541GB.

[jarsudsco]

Re: Hitachi HDR505 - no antenna signal

Does anyone happen to have or know where I could find a proper datasheet for the chips I mentioned above - MXL5007T? They appear to be made by Maxlinear but everytime I think I've found a datasheet it turns out to be really just a sales brochure. I've found one image sort of showing the pinouts but it's such a poor image I can't actually read the writing.

Cheers,

- jarsudsco

[tom66]

Re: Hitachi HDR505 - no antenna signal

A lot of those parts don't actually have full public datasheets unfortunately, they are considered proprietary. Not much you can do about this except look for training manuals/schematics/etc.