[ctc17]

Im not familiar with that specific set, but I have run accross several bad video detector diodes.
You can NOT use a 1n4004 and it will not test like a 4004.
A 4004, using diode test on a multi meter will read about .500-.600mv, the diode thats in there is Germanium and will read .200-.300mv one direction and open the other direction.
You may be able to use a modern silicon detector diode, the 1n4004 is not even close to high enough frequency to work as a detector.

When they fail they cause a whole bunch of weird problems depending on if they get leaky, short or open. Everything form buzzing and sync issues to poor color performance and ghosting.

I have been using 1N34 or 1N60 as a replacement for these. They are a germanium diode and work just fine.

I just looked on ebay and you can buy these numbers for like 10 for $1