2. amps-preamps
  3. 123537-8471

CAT SL-1 Reference repair

I recently bought a CAT SL-1 Reference preamp. The line stage is great. But the phono stage doesn't work properly. I crank up the max volume but it doesn't give reasonable listening level and it became too noisy. The sound is dry and week.  It doesn't balance well either.  I replace all the tubes in phono stage but without luck. Anybody has a schematic of this preamp? I didn't find anything on internet. Any suggestion is appreciated. Thank you.
cygnus_859

Showing 3 responses by czarivey

czarivey
5,740 posts
 
 if you're onto DIY,
first, check if tubes light up on you phonostage.
2nd do visual on phono-board by checking any signs of burning or caps leak with magnifying glass
3rd if tube(s) light up, you have to measure bias current or voltage accross bias resistor of each tube. bias resistor can be found in grid circuit and the grid pins can be identified via internet just by querrying your tube ID.
4th, if you're local enough to raleigh nc, i can accept your unit and make it work and if not, unfortunately i don't do shipping turnarround. 

czarivey
5,740 posts
 
Yep check values of bias resistors by removing them from circuit and if one found out of spec, replace resistor and tube. Usually bias resistors goes bad when tube does. Replacing DC caps in the chain of grid bias supply  would also not hurt preventative.
Also would retouch existing solder in case if I spot cold joints. With tube electronics it's very common and often done before any troubleshooting begins.



czarivey
5,740 posts
 
plate voltage in 6dj8 must be 90V.
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