Modding the Technics ST-Z400 Tuner
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Garbz

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Ok so I finally got a radio again
Picked it up for $20AU on ebay, Cost $26AU shipping though


Anyway so it works fine, and being the fiddler I am cracked it open about 10 seconds after I tested it. Here's some internal pictures:



Now from these images you can see the black cable running to the back is the audio output, My guess is thoes two orange electrolytics as coupling in the signal. Now my main amp has an input impednace of 330k so would it be safe to replce these with some type of film cap? Maybe 0.2uf or something along that order or would I still get bass rolloff? (assuming that there's nothing directly after it, i haven't had a look in detail yet).



Now this one is a worry, there's a pretty nasty sized super cap in there. Looks like 2.3v 3.3F caps there and one of them has shat itself. The tuner seems to work but this probably isn't helping performance wise. I don't know what it powers yet but the only replacement i can get is 33F not 3.3F at this point I can even ask if this is a safe replcement :S My guess is it probably runs the memory of the station preset.

Further mods i'll consider in the future is a regulated PSU. Currently the tuner doesn't appear to have regulation, not switching no nothing. So i'll probably rip the bridge and filter caps out and make a separate psu to inject power into there.

Nuff said, any answers on the caps?
 
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mteitsch

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Hi Garbz,
saw your post and am in the process of repairing an ST-Z400 also.
I have the same problem with the two blown 3.3F 2.3v caps as well.
I am replacing the caps and found the exact replacements at Digi-key if you are interested. The digi-key P/N is P11347-ND and they are about 3 bucks each.
I'm not sure what problems if any you were having with your unit, but mine seems to have lousy reception on FM stations below 92Mhz. I thought it was an antenna/ antenna interconnect issue but I think I have ruled that out now.
The antenna connection on the back of the unit is rather unconventional - it is a 75ohm post and a ground clamp that leads me to suppose one is to strip a 75ohm coax back and connect the inner to the post, the braid to the clamp. A little weird though, maybe the way they did it before just introducing an F connector in the back of the unit??
Any ideas??
mteitsch
 
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