Wayniac
Active Member
The FT-3's will be used for the input (C1), and interstage coupling, C10 and C11. The Electrocubes will be installed in locations C8 and C9.
Project MC-30s
- Thread starter Wayniac
- Start date
The FT-3's will be used for the input (C1), and interstage coupling, C10 and C11. The Electrocubes will be installed in locations C8 and C9.
invalidbuffa
Super Member
I can't wait to see the finished products. I'm actually having my Macs worked on as I type by someone much more experienced than me. I wouldn't dare service those amps myself 
Wayniac
Active Member
Progress Update
One amp is mostly complete. I still want to add a thermistor in series with the AC input. It sounds nice on the thrift store test speaker. The large aluminum coupling capacitors are russian mil-spec teflon FT3s. All resistors were replaced with 1% metal film parts, except of course the power supply resistors, which are wirewound. The chassis is all original and has some small pitting and rust. It did clean up nicely. The transformer covers are also sporting the original finish. I left an audio repair shop decal on the right transformer.
Bias is running ~ -52 VDC, with B+ at 440. It is a bit high according to what I've read here, but I'll sort it out.
One amp is mostly complete. I still want to add a thermistor in series with the AC input. It sounds nice on the thrift store test speaker. The large aluminum coupling capacitors are russian mil-spec teflon FT3s. All resistors were replaced with 1% metal film parts, except of course the power supply resistors, which are wirewound. The chassis is all original and has some small pitting and rust. It did clean up nicely. The transformer covers are also sporting the original finish. I left an audio repair shop decal on the right transformer.
Bias is running ~ -52 VDC, with B+ at 440. It is a bit high according to what I've read here, but I'll sort it out.
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chuckworkb
Super Member
Looks great!!
Wayniac
Active Member
This is the underside of the second amplifier. Work is progressing, however this one suffered previous catastrophic failures. At some point in the past, the rectifier tube socket had been replaced and extensions soldered on to damaged transformer wiring. Other wires had also been replaced. I too,had to cut back one of the transformer leads as the insulation was cracking. The multisection capacitor had puked it's guts as well. The surfaces inside this amp are coated with a tacky, waxy residue. Denatured alcohol is cutting it well.
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Wayniac
Active Member
Yes they are. Funny you should mention heat. You can see the mounting squares on the left most cap are not aligned as well as I would have liked. I tried removing it to square it up, even using heat to soften things up. It would not come loose. So I figure, I'll check things now and then and move on to plan-B if needed.
drillher
Super Member
Very nice looking amps.The Russian Teflons are working well for me in a Clarinet Preamp.Let us know how the amps sound when you let them ripen for a time.It's great that you were able to retain the original finish.I like the idea of having the original surface that has gone through time.
Dave
Dave
Wayniac
Active Member
The transformer covers on my second amplifier were rusty with small chips flaking off with any contact (see post #1 of this thread). I elected to repaint these covers but I did not want to use a gloss black as I was concerned with the results showing flaws or being just too glossy. I went with a semi-flat krylon and am currently polishing the covers to nice shine. Below is a photo showing the left transformer cover painted semi-flat, the right cover after an hour of hand polishing. The finish of the right cover approaching the original finish of my other amplifier. You may have the same luck...........................
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drillher
Super Member
Nice job on hand polishing the paint.It looks like they have just the right luster to match the original paint on your other amp.It is the fine details that make a proper restoration right.What preamp.,source components and speakers will you be using those beauties with?
Dave
Dave
Wayniac
Active Member
Initially, the source will be a vintage Denon DCD-910 cd player which has a variable output, directly to the amps, driving a vintage pair of JBL L100t speakers. I purchased the speakers new in 1986 at the base exchange at Yokota AB, Japan. I had the woofers re-foamed/tested recently at a JBL repair center.
My next project will be my Teac X2000R, reel to reel. It has been sitting around, unused for years. I also purchased this new, in Japan back in the eighties. I hope to put the Teac in service with the MC30s as it also has a variable output level.
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Wayniac
Active Member
I just posted a thread in the General Audio sub-forum regarding my first impressions.
Click Here for my first impressions.
Click Here for my first impressions.
