Hi guys,
My new toy, a MC240 has arrived. It is a relatively good shape, rust and paint peeling, etc but otherwise untouched, and not molested in anyway.
I wanted to get my hands dirty on the MC240 and compare it to my beloved MC225.
So far the comparison is unfair as my MC225 is on top of it's shape after the work I have done on it, and the MC240 is all original. But I have to say, the MC240 raw like that sound damn good. It's muddier than the MC225 but it put that to the coupling caps, power supply etc.. Maybe the tubes also, I don't know yet.
I plan to change:
- all power supply cap with Authenticaps (OTW from Germany)
- Selenium recifier with a UF4007 + 470R
- Silicon rectifier with UF5408-E3/54 diodes.
- All coupling caps C5, C6, C15, C16 with Russian K40s.
- R24, R27, R47, R50 12K 2W with Vishay 1% Metal Oxyde CPF212K000FKE14.
- R57,R58, R59 100k 1W also metal oxyde 261-100K-RC.
- Bias cap C27 with a 22uf 450V Vishay MAL204281229E3, or with a 33uf or 22uf 250V film capacitor if size fits.
Questions for the experts here:
- Do I need to change the other coupling caps C7, C8, C17, C18 0.22uF 600V, and/or C9,C10,C19,C20 0.47uF 200V? Are those failing like the classic bumblebees?
- What about C4 and C14, 0.22uF 400V?
One last thing: This morning I blew the internal fuse when I by mistake switched off the MC240 and back on immediate after (within the same second).
The only explanation I see it when I did power on the amp again, the thermistor was hot so it did not slow start the amp and the inrush current blew the fuse.
Anyway I replaced it with a sloblo 3A and the amp is back online.
Here is a picture of this nice piece of history.
Thank you for reading.
My new toy, a MC240 has arrived. It is a relatively good shape, rust and paint peeling, etc but otherwise untouched, and not molested in anyway.
I wanted to get my hands dirty on the MC240 and compare it to my beloved MC225.
So far the comparison is unfair as my MC225 is on top of it's shape after the work I have done on it, and the MC240 is all original. But I have to say, the MC240 raw like that sound damn good. It's muddier than the MC225 but it put that to the coupling caps, power supply etc.. Maybe the tubes also, I don't know yet.
I plan to change:
- all power supply cap with Authenticaps (OTW from Germany)
- Selenium recifier with a UF4007 + 470R
- Silicon rectifier with UF5408-E3/54 diodes.
- All coupling caps C5, C6, C15, C16 with Russian K40s.
- R24, R27, R47, R50 12K 2W with Vishay 1% Metal Oxyde CPF212K000FKE14.
- R57,R58, R59 100k 1W also metal oxyde 261-100K-RC.
- Bias cap C27 with a 22uf 450V Vishay MAL204281229E3, or with a 33uf or 22uf 250V film capacitor if size fits.
Questions for the experts here:
- Do I need to change the other coupling caps C7, C8, C17, C18 0.22uF 600V, and/or C9,C10,C19,C20 0.47uF 200V? Are those failing like the classic bumblebees?
- What about C4 and C14, 0.22uF 400V?
One last thing: This morning I blew the internal fuse when I by mistake switched off the MC240 and back on immediate after (within the same second).
The only explanation I see it when I did power on the amp again, the thermistor was hot so it did not slow start the amp and the inrush current blew the fuse.
Anyway I replaced it with a sloblo 3A and the amp is back online.
Here is a picture of this nice piece of history.
Thank you for reading.