2. tech-talk
  3. 1413952026

The HH Scott 350 A MultiplexCircuitry

I've been listening some to my 350 Scott but only in mono. However my belief is that it's all stock so I'm hoping that replacing the tubes in the multiplex will clear up the noise and microphonic echo from the 6BL8. Yes, I'm getting loads of grumble and interference from the stereo selection.
An additional multiplex concern however is that the multiplex circuitry in the 350 was a compromise to the refined circuitry of the 310 E. I have procured (thanks to good Audiogon friends) the repair manuals of both the 310 E and the 350 as well as both schematics and I'm hoping/wondering if my local technician will be able to improve upon the 350 multiplex circuitry by comparing it with that of the 310 E? I was told by a friend that this is possible if I were to provide the technician with the repair manuals and schematics for both tuners but I'm still somewhat doubtful.
If anyone ( Al ? ) would shed some light on this and lend a suggestion/s for me to pass along to the technician, then I'd be very grateful. By the way, I have a Telefunken E80CF (6BL8) , A balanced pair of Telefunken 12AU7's and a Telefunken 12AT7, all Amplitrex tested on hold for payment. These I'll take with the tuner and hope that he orders the best capacitors. I want to go full force with this project to the best of my abilities.
Thanks To All!
goofyfoot
goofyfoot's avatar
goofyfoot OP
1,453 posts
 
I concur Atmasphere, I'm just waiting to have the tubes before I take it to the technician. I'm replacing the multiplex tubes including the audio output with Telefunken's, so I need to be with the tuner before I pay out the bench fee.
Any idea's about the capacitors, what type I'll need and where to find them?
Thanks!
atmasphere's avatar
atmasphere
12,164 posts
 
I would try with Antique Radio Supply in Arizona- they have a pretty wide range of can-style multi-section filter caps.

I assume you are talking about rebuilding the power supply.

Otherwise replacement of other caps is not going to win you much unless they have drifted in value or have some obvious defect.
goofyfoot's avatar
goofyfoot OP
1,453 posts
 
Well a bit frustrating so far. I replaced all four multiplex tubes with Telefunken's, Amplitrex tested. The 6BL8 and the 12AT7 are military grade. The balanced pair of 12AU7's tested high. I did notice an improvement and everything sounded fine as the radio announcer spoke but once a cello came in, the music sounded 'garbled' or 'aggregate like' once again.
I'm at the point where I now plan to take the tuner into the shop tomorrow afternoon and will pay the bench fee to have it fixed.
atmasphere's avatar
atmasphere
12,164 posts
 
Yes- it needs the multiplex section to be aligned. The shop will need a stereo multiplex generator to do the service.
goofyfoot's avatar
goofyfoot OP
1,453 posts
 
Thanks Atmasphere,
Yes, I think it will work out. I dropped of the unit today and the technician said that they'll call me after they look at it. There's about a two week turnaround but that seems reasonable. Once I get word I'll post it here.
More to discover