mwl168

Happy Birthday!

Happy belated birthday Kerry! Hope you had a great time.

Maybe try to swap the left and right channel boards and see if the hum follows the PCB board?

So EL34 for the CCS tubes and EMS 20B for the output tubes? Any other modifications needed other than accounting for the 20B filament supplies?

Apart from this audiophile scene, this is a great movie. This particular one is the second of a trilogy. The first of this trilogy is what the movie “Departed” is based on.

Did the PSU blow up while in play or at power-on?

Happy Birthday!

Congratulations Aumkar! Quite an innovative accomplishment! Can’t wait to hear more about the INOX and to try it!

I’ll pm you.

Thanks MLA and Kevin for your help. I got the player up and running yesterday first using the variac to slowly ramp-up. Later tested it without the variac and, fingers crossed, it's working fine so far. The device in question is a Marantz SA-1 SACD/CD player which uses linear power supply based on what I can see in the service manual. To expand on a long story made short, it powered up but was unresponsive when I first took it out of the box. After consulting with the service manual I dissembled the unit and found a blown fuse inside. Instead of the factory spec'ed 1A/250V slow-blow fuse, whoever last serviced the unit put in a fast-blow 2A/250V fuse. Which likely explains why it's blown upon turn-on. I replaced it with a proper slow-blow 1A/250V fuse. This is when I posted my question thinking I should play it safe given the age of the unit and suspecting why the last person serviced it put in an out-of-spec fuse. By the way, this thing is beautifully built like a tank and getting to the fuses take some work. A few photos from the web and of the exact unit. It's wonderful sounding especially with the SACD.

Need advice about safely powering up an all-transistor CD player that has not been powered up for many years. . I have a Marantz SACD/CD player that has been sitting in its box for many years. Is it a good idea to use my variac, like the one in the picture below. to gradually power it up? If so, what's the proper process? Thanks in advance.

iPhone photos while I was in Seattle for business...

Madison, Wisconsin

Happy Birthday Chris!

Have you considered picking up a Canon 1DX then?

Assuming all the removed transistors are indeed all good, this leads me to wonder if the original issue was caused by cold-soldering?

Nothing seems out of ordinary to me based on your description. If the offset trim pots are responding but you cannot get the offset to 0V, most likely you just need to trim the value of the resistors in series with the trim pots. I am going by memory without seeing the schematic but this information is in this thread somewhere.

This what I did exactly with my Megatron.

Did you measure the PZTA42 Vce between the two channels before making the mod?

Did you take another measurement after the amp warmed up? Channel 2 PZTA42 Vce don’t look right. It’s also odd that it happens to both PZTA42 and yet the voltage drop across the 20K is correct?

I first came across this group here...

So I did indeed install 150K and 200K chain for the bias resistors of the C2M1000170D when I first built my Carbon. Today I replaced the 200K with a 150K, I had also dialed the bias back to 18mA and disengaged the servo. Then took a few measurements after letting the amp warmed up. Now the PZTA42 Vce is around 13.7V, voltage drop of the 20K R is 25.4V and the Vgs of the C2M1000170D is around 3.3V. And I did not blow up the amp.

Got it. Thanks. I got work to so then.

Thanks MLA. That was what I was thinking too. Then I don't understand why Simmconn was worried about exceeding the C2M1000170D's max Vgs rating? Here is an interesting thing - I went back to my PM's and could not find anything that discussed this mod to the 175K+175K bias resistor chain. However, I came across an early correspondent with Kevin about my plan to use 200K+150K instead (values I had on hand at the time). Now I wonder if the one that looks like a 100K may be in fact a 200K. It's hard to tell visually. I can desolder the resistor in question and measure it. But part of me, the lazy part, is thinking if all is well why not leave it along? Maybe between the +/- 406VDC rails and the 20mA bias current somehow puts the PZTA42 Vce in the desired region?