[aphexii]

Wow, I must be half asleep today. My bad.
 
This is the one that still isn't in stock: MKS2-1.0/63/5
And this is what i was thinking to replace it with: 

MKT1817510064

 

[sachu]

lol and here i thought i was having insomnia..still can't seem to go to sleep..
yeah..that should work as a sub for the wima.

 

[aphexii]

haha, thanks!

lol

 

[stringgz301]

Ok all you CTH guru's.  I need some troubleshooting help.  My CTH has been on the shelf for a few months and I'd pirated a few parts from it for other projects.  After reinstalling Q4P, C4L/R, and R18L/R and installing a new pot, it powered up fine, e12 went green, and all test voltages are as per the CTH setup page.  However, when I plug in phones I get constant fairly strong white noise (I can hear music playing but not very strong).  The white noise is there with and without a source connected, and doesn't change with the pot volume.  It is independent of the tube (tried 3 different ones) and the phones (although all my phones are low Z or iems).
 
Any ideas where the white noise could be coming from?  It was working fine a few months ago with no noise.
 
Thanks.

 

[cfcubed]

While thinking you're reaping what you sown, my bet would be the C4 connections. The only time I've had everything green/good & got relatively constant noise in the output was after rolling C4 caps w/o solid connections for them.  Do that enough and the pads/traces may go bye-bye & you have to solder cap leads to more sturdy places (e.g. one side directly to tube socket pins). 
 
Quote:

 I'd pirated a few parts from it for other projects.  After reinstalling Q4P, C4L/R, and R18L/R and installing a new pot, it powered up fine, e12 went green, and all test voltages are as per the CTH setup page.  However, when I plug in phones I get constant fairly strong white noise (I can hear music playing but not very strong).

 

[aphexii]

Everything arrived! Started populating the board tonight, hoping to make good progress this weekend.
 
Noticed something when I came to R13L/R13R  - the BOM calls for the following;
 

[size=small]R13L, R13R[/size]

[size=small]2[/size]

[size=small]1/2W 1% Metal Film Resistor 1.5kΩ[/size]

[size=small]Mouser[/size]

[size=small]71-CCF55-1.5K[/size]

 
However, the part number listed is for a 1/4W resistor -   http://www.mouser.com/Search/Refine.aspx?Keyword=71-CCF55-1.5K
 
Is this ok? 

 

[Forte]

 
They are fine. The description reads "Rated to 1/2watt"

 

[aphexii]

Ahhh, sorry about that, didn't even see it, Thanks!!

I'm actually a little worried how bad my reading comprehension is lately.

 

[stringgz301]

Quote:

While thinking you're reaping what you sown, my bet would be the C4 connections. The only time I've had everything green/good & got relatively constant noise in the output was after rolling C4 caps w/o solid connections for them.  Do that enough and the pads/traces may go bye-bye & you have to solder cap leads to more sturdy places (e.g. one side directly to tube socket pins). 
 

That's what it was.  Bad C4 connection.
 
Thanks!

 

[cfcubed]

@stringgz301 - Great to hear its fixed.
 
@aphexii & any other builders - Obvious but perhaps more important in the CTH case, double- (or triple-) check component values, position/placement and soldering. 
Extra time spent upfront could really pay off compared to trying to trouble-shoot such a compact design.  And be very careful with probes when making any measurements. I used pins masking taped to mine.
http://cavalliaudio.com/cth/main.php?page=instructions/assembly
http://cavalliaudio.com/cth/main.php?page=setup

 

[jezz]

I've been fiddling and fiddling and finally got the darn thing working perfectly. Oh wait, let's just rewire it so it looks nicer. --pop-- goes the fuse.
 
I'm pretty sure that the LED leads were shorted to ground (it worked until the epsilon22 went green, and had been working fine prior to me playing with it). Now, when I power on the amp, the red LED never lights and the green one is dimly lit, followed by the green LED lighting up properly. Out of curiosity and fear I desoldered the red LED and unfortunately pulled the lead out of the LED, which didn't fix anything.
 
The voltages involved are: 1.8V -> 2.1V across green and 24V -> 0V across red with no red LED connected . My hunch is that I blew Q4E and maybe Q5E. The base of Q4E goes from 23.5V (triggered) to 23.9V (safe). I think Q3E is still fine because the relay still triggers correctly.
 
Unfortunately, I just moved and am still unpacking my electronics supplies; I think I have spare BC560's somewhere, but before I go digging (or put my mouser order for a second bicolor LED), I'd appreciate someone letting me know if it sounds like I blew Q4E, or if I destroyed the amp entirely or something. Does this sound right? Or am I being really dumb right now (barring rewiring when it wasn't strictly necessary)?

 

[runeight]

Try replacing Q4E and Q5E. You may have damaged other components, but I don't think so.

 

[jezz]

Thanks runeight; doubly so, once for corroborating my mistake and another time for an amazing feat of engineering. You put an outrageous number of through-whole components in a very small space.
 
I'll post here when I get it fixed. It might be a while; I have a few other projects that I planned on ordering parts for and I'll probably to batch the replacement LED and them into one purchase.
 
EDIT: I should add that the amp actually does work fine right now, and the state of the LED and Q4E+Q5E makes it such that it looks basically like it used to, except no red LED while starting. The green LED isn't bright enough while it starts to shine through the tube.

 

[aphexii]

Quote:

replacement parts
 
505-FKP22200/100/5

Is it ok that the replacement is rated at 100v when the BOM calls for a 35v part?
 
EDIT: Ahh, thats what it's rated UP to, so I should be fine I see. Learning as I go

 

[sachu]

yeah..its rated for a higher voltage..so am sure it'll do ok at a lower voltage. I was mainly looking for lead spacing and capcitor type when searching for a replacement.