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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
atmasphere's avatar
atmasphere
7,068 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 OP
451 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
7,068 posts
 
Yes- it needs the multiplex section to be aligned. The shop will need a stereo multiplex generator to do the service.
goofyfoot OP
451 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.
goofyfoot OP
451 posts
 
OK, so here is the scoop straight from the technician concerning the 350 A; 'we can't find anything wrong with it so we want to give you back your bench fee and you can pick up your tuner also.'
The tech tested the tubes and caps and said they were fine but mentioned that there was significant corrosion in the outputs. He mentioned that 1 capacitor tested low by 10% but that he didn't want to replace it. I asked if he would clean off the corrosion and then have it ready for me today so I'm planning to retrieve my tuner this afternoon. The technician did agree however to come by and listen to the tuner in my home if I were to continue experiencing the issue with the multiplex stereo option.
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