Help for Building The S.E.X. 2.1,Impedance Switch and C4S

[mcandmar]

The engineer in me is asking "what did you change last?"

If you visibly inspect all the resistors can you see any burnt or discolored?

 

[i luvmusic 2]

The engineer in me is asking "what did you change last?"

If you visibly inspect all the resistors can you see any burnt or discolored?

No discolored but i found the resistor connected to T16 and T20 is touching the 0.1uf cap lead connected to T19.The 0.1 caps are the last two capacitors that i replaced.C4S Board B side LED's are dead. 

 

[mcandmar]

What i think that did was connect the start of the power supply ~420v to the anode of the 1st tube stage, which would have shorted the output side of the C4S board to the B+.  I dont really know how much damage that would do to the C4S board, it may have zapped all of it :-\

 

[i luvmusic 2]

I just double checked the resistance and all are with in spec just to make sure.Is there a way to test the C4S Board if it is functioning properly?

Thanks!

 

[mcandmar]

Not that i know of.  If your multimeter has a diode test function you could check the LED's, you should get no reading in one direction, and with the leads reversed you should get a voltage reading ~1.55v while it lights up.  If you get no reading in either direction they need replaced.

Transistors would probably need removed from the board to test them, and ideally a transistor tester to check them.

 

[i luvmusic 2]

It looks like the easiest solution is to replace the C4S.Before i order the  replacement board maybe i should disconnect the board and put back the resistor where it was to make sure the amp is functioning properly.I don't want anymore surprises.

 

[Paul Birkeland]

Maybe you could post your voltages?

 

[Natural Sound]

[quote author=mcandmar]I used the Mundorf Silver/Oil in mine and found them a very nice improvement over the Solens, specifically better high end and low end extension which were a little rolled off with the stock caps. I chose the Silver/Oil on the basis of many caps roundup reviews i read all pegged them as being the most neutral sounding of the Mundorf range. The fact i haven't changed a thing with the amp since then really speaks to how happy i am with them. 
[/quote]

I'm still building my 2.1 but decided to leave the stock Solen parafeed cap alone and change the .1 interstage cap with a .1uf/630 volt Theta film and foil AudioCap from Parts Express. I took this advice from another Bottlehead, I think it was Cary. I spent the lions share of my "mad money" on pre-ordering a Bottlehead DAC. I might get something more exotic in the future. Or I may absolutely love the Solen/Theta combination. Time will tell I guess.

 

[i luvmusic 2]

Maybe you could post your voltages?

Sorry! for the late reply.
i have checked the RESISTANCE and VOLTAGE they are all good,The C4S board B side is  definitely DEAD/FRIED everything was discolored and smells burnt.I just ordered a new C4S kit from eileen few days ago.The amp is working fine without the C4S but i miss that sound with C4S hopefully i will received my new kit soon I can't wait. 
THANK YOU GUYS for all your HELP!
   

 

[i luvmusic 2]

I need help the LEFT CHANNEL just died,By inserting the Headphone Jack halfway both channel will work if the jack is inserted all the way in only right channel works.
Thanks in advanced!

Here are my Voltage readings.
Terminal
1  220V
2  0
3  0
4  440V
5  220V
6,16  420V / -0.639
7,17  0
8,18  0
9,19  19.5V / -0.435
10,20  440V / 441V
11,21  402V / -0.695
12,22  0
13,23  0
14,24  0
15,25  17.60V / 1.2V
A1,B1  close to zero
A2,B2  396V / -0.702
A3,B3  17.60V / 1.2V
A4,B4  0 / -19
A5,B5  83V / -0.718
A6,B6  2.6V / 0.99
A7,B7  -2.8V / 2.8V
A8,B8  2.9 / 2.9V
C1  -3.26V
C2  3.08V
C3  0
C4  -3.30V
C5  3.30V

 

[Paul Joppa]

The plate choke goes between terminals 20 and 21, and drops about 40 volts when operatiing correctly. It appears that this connection is not happening. As always, check those solder joints first - its the easiest and most often successful test. Then measure the resistance between those two terminals; I forget the exact number but it must be around 1000 ohms.

The above is incorrect - see later post. I apologize!

 

[Paul Birkeland]

I forget the exact number but it must be around 1000 ohms.

IIRC, they are around 930 Ohms.

 

[i luvmusic 2]

Thanks! for the reply.

I reflow the solder T20 and T21 and measure the resistance the reading is 18.45M and dropping.

Thanks!

 

[i luvmusic 2]

While i'am at it i measured the resistor connected to T6 and T10 the reading is 674R and resistor connected to T16 and T20 the reading is 11.79M and going up.I don't know if this help because my electronic knowledge is limited.

Thanks!

 

[Paul Joppa]

Sorry, I mis-remembered the wiring, which is I admit complicated.

Your last measurement was extremely helpful. That resistor from T16 to T20 is blown. It probably happened due to the short circuit of high voltage T20 to the power triode grid T19 - this would cause the triode to conduct very excessive current, blowing the resistor quickly. I don't recall mention of a blown fuse, so the resistor probably went out faster than the fuse could react.

The plate choke I mentioned before goes from T16 to B2. It is probably OK, but measure the resistance to be sure.

The blown resistor means no voltage is supplied to the PC board, hence no LED glow. The board is probably OK - you won't know until the resistor is replaced and power is restored.

The tube is probably OK, the current surge would have been short and the tube is tough. Voltage checks after power is restored will determine whether there's a problem.

 

[i luvmusic 2]

I will check it tomorrow.

THANK YOU!

 

[i luvmusic 2]

Hi,
  So i measured T6 and A2 reading is 840R and 842R for T16 and B2.220R Carbon Comp. Resistor connected to T19 and B1 is cooked,Can i replaced this with Metal Film instead?

Thanks!

 

[Paul Joppa]

While carbon comp is theoretically better, there is evidence that metal film works well, and they are much sturdier. Do not use wirewound though.

 

[i luvmusic 2]

While carbon comp is theoretically better, there is evidence that metal film works well, and they are much sturdier. Do not use wirewound though.

Metal Film is the only type i can access in that value locally.

Thanks!

 

[mcandmar]

You can get them from Mouser -> http://www.mouser.ie/Search/ProductDetail.aspx?R=OD221JEvirtualkey58810000virtualkey588-OD221JE