[hellomoto]

Hello,
 
I just rebuilt my unfinished MSSH that was on its shelf for too long, but I can't get it to work... I've powered it up but there happened to be sparkles at the power jack... Do you have any idea of the problem? I'm wonderg of its not a problem with the power jack itself since I bought the one featured on Pete millet's bom but I looked at the spec sheet and it doesn't look like its suited for 48v (the one of diyforums is), I'm wondering if it can be the problem but still, I assume the original bom is correct !
 
 
Rthanks for your help!
 
Antoine
 

 

[ictin]

Hi,
Because i wanted a tube amp, i started to build a starving student. I used the 12AU7 version by the_equalizer with the mods by Dsavitsk. I added also the meyer crossfeed and a hiss buster, and i tried also to put the protection diodes. I made also a stripboard design
 
 

My current problem with this build is that one channel is mixed in both of the headphones, and the other one if very faint, so if i removed the input RCA jack from one channel, i hear music pretty loud in both cans, if i remove the other one i hear only a faint sound in only in one can. Also the pot don't seams to work properly. At 0 a hear a faint sound. If i turn it a few degrees, the sound gets louder, and after that it remains at the same level. Also at the output jack, there is very low resistance between the 2 channels. And i wanted to know where and what to measure to identify the problem, and what should be the normal resistance between the 2 channels at the output.
 
Now for the other problems encounter that lead to this, maybe it will give you a hint.
 
For the case i used the standard hammond case that was used in most of the builds. Yesterday i finished soldering all the components. I fired it up, did some measurements and when all seamed ok i tried a pair of cheap headphones. At first everything seamed good and i tried to put everything in the case. After i put everything in the case the problems started. First one tube didn't light and his channel was humming. Turn out that the tube was not properly inserted into his socket (i use some sockets from an old TV). The sockets are attached to the case and the pins of the sockets are are soldered to the strip board by wires. I tried to push the lamp harder in the socket, and i think that the sockets pins have touched the soldered parts of the strip board. After that i started to hear a very loud buzz in both channels without any source and even with the volume at 0. Also the music was distorted. I tried to investigate, and after touching the pins from one socket the loud buzz was gone, and now i had another problem. If i used only one input channel as i heard good sound in both cans, if i used both input channel i heard a scrambled and somehow metallic sound in both of the cans.By messing further with the pins of the socket the scrambling problem was also gone, but i remained with the final problem(with the mixed channels). It can be a problem from the sockets, being old?
 
During the debugging i removed also the 50K resistors from the pot because at maximum volume the sound wasn't loud enough, and the diodes because i thought that the mixing is because of them. Also i removed the crossfeed completely for a while  to discard it as a source of this extreme channel mixing.

 

[ictin]

Ok, i was able to fix most of the problems (there where some loose connections, i think), but now when i have no input source, i get a loud buzz when a source is connected, even if is on silent, nu buzz or hum is present.
This being my first amp that i build, there are still some thing that i don't understand. The main problem that i had, was that one channel was louder, and the other one, almost at one third as the first one. The thing was that one of the inputs was loose, and if only one channel input was connected, it leaked to the other one, but if both of them are properly connected there is no leak between channels (if i mute one channel, i hear only the other one, and vice-versa).
 
Anyhow, i decided to order a new pot (an ALPS this time) to replace the old one (is not working properly,when i turn it i hear loud hum and some times one of channels get interrupted), and together with the pot i wanted to buy 4 Mundorf caps at 0.22, but they had only 2 on stock. In this situation what caps is better to replace C2&C4 or C3a&C5a? (currently i have some DNA caps - never heard of them, but my father had some spares in his old stash of electronic components).
 

 

[capernicus]

Been busy getting this ready for my build - going to try something a little different - purple heart and maple.  
 
So far I've laminated and rough cut the block as well as hogged out the inside.  Still had a lot of woodwork to do...
 
This one will be a 12AU7 build - wish me luck!
 

 

[takili]

Hi all, I have been lurking for a while after first discovering the amp then making it. This is the 12AU7 version with changes to bias:-
 

 
Well, it looks very nice, I think anyway, but no ways does it want to work! The tubes don't glow or warm up at all, Neither will the mosfets show any sign of warming, (the heatsinks are different but specs are close to the original). When I check voltage, my PSU shows just below 48V at the socket before switch on. After the switch on the voltage drops and appears to rise and fall at various test points, initially falling further but after a while falling less then settling down to a consistent difference between max and min, say 12v, 8v from 12v, zero initial. After a while, three or four minutes, I noticed that C1 was getting warm. I changed it then from a 680uf bipolar to a 1000uf polarised but this made no difference. 
   I have checked the wiring pin to pin, (photoes below), checked the orientation of the valve pins and Mosfet pins and the continuity of all my solder joints plus reflowing a couple that were dodgy.
   My own opinion is that because I am seeing this rising and falling of voltage, the Cisco PSU, rated at 0.38A is somehow seeing too much current demand and cycling on and off, (this could maybe be the cause of C1 getting warm as it passes this varying supply to ground but I am guessing here).
   If anyone has some thoughts I would be grateful as this is my first build after a long absence from DIY electronics and I am trying to find my feet again.

 

 

 

 

[takili]

After much scratching of head my problem amp, (above post), is now working. Yipee! The cause: yep, human error. I somehow managed to get C1/C6 mixed up with C7/C8. All seems to be working ok despite one 220uf cap rated for 16v being subjeced to 48v potential. (I may do a replacement for new caps anyway for C1/C6 just in-case any damage was suffered).
   So, lesson learned, not only check wiring but also check correct component values.

 

[Llama16]

Hey all,
 
It's been a long time and I've been enjoying my SSMH for years now
Sadly faith has struk and I dropped my SSMH. Luckily no tubes are broken and I don't think anything else broke, but the pot did.
 
This is the pot (I made the kit from tomb): http://nl.mouser.com/ProductDetail/Alpha-Taiwan/RV122F-20-15F-A50K/?qs=NDtHcshGFph1R5NpjYPgdw%3d%3d.
 
Now I need something to fit, but here's the catch: I can only order from RS components and Farnell. Yet I can't seem to find the alpha brand, nor anything that would fit.
 
Maybe I looked over it,
Someone care to lend me a hand :S
 
Thanks
Dries

 

[tomb]

Quote:

Hey all,
 
It's been a long time and I've been enjoying my SSMH for years now
Sadly faith has struk and I dropped my SSMH. Luckily no tubes are broken and I don't think anything else broke, but the pot did.
 
This is the pot (I made the kit from tomb): http://nl.mouser.com/ProductDetail/Alpha-Taiwan/RV122F-20-15F-A50K/?qs=NDtHcshGFph1R5NpjYPgdw%3d%3d.
 
Now I need something to fit, but here's the catch: I can only order from RS components and Farnell. Yet I can't seem to find the alpha brand, nor anything that would fit.
 
Maybe I looked over it,
Someone care to lend me a hand :S
 
Thanks
Dries

Shoot me a PM with your address - I think I have some extras I could send you.
 
 

 

[vixr]

Quote:

Shoot me a PM with your address - I think I have some extras I could send you.
 
 

The most awesome guy on these forums.
 

 

[proid]

Can i  use 50V capacitors instead of 63V capacitor? I can't get the  63V here.

 

[tomb]

Quote:

Can i  use 50V capacitors instead of 63V capacitor? I can't get the  63V here.

If you use the Cisco power supply (48VDC), I wouldn't recommend it.  2V is not enough of a safety margin.  There may be many circumstances where the 48V might be exceeded slightly.  There's some overage in the 50V rating of most caps, but it would still be risky.
 
If you can't get 63V, there's nothing wrong with going even higher - 100V.
 
 
EDIT: Thanks for that very kind comment, vixr!!
 
 

 

[Llama16]

Thanks tomb, PM sent

 

[proid]

Are those caps good enough for the MSSH?
Philips BC 470uF/63V 
Nichicon FW 220uF/50V
Rubycon ZL 820uF/63V instead of 680uf

 

[tomb]

Quote:

Are those caps good enough for the MSSH?
Philips BC 470uF/63V 
Nichicon FW 220uF/50V
Rubycon ZL 820uF/63V instead of 680uf

If you use the Nichicon FW 220uf/50V as the cathode bypass - those are an exception.  For instance, the standard cathode bypass cap (C7 and C8) that we supplied in the old SSMH kits was the Nichicon Muse ES 220uf 16V.  The voltage around the cathode bypass is very low and the 16V rating was never an issue.
 
The other caps are fine.  There's no reason you can't go higher on the uf, either.  You didn't specify, but the 820uf would be good in the power positions - C1 and C6.  Also, the 470uf's are fine for output caps - C3 and C5.  However, if you use low impedance phones (32 ohms or lower), you would actually benefit a bit by using 1000uf at C3 and C5.  There's really no limit on C1 and C6, but if you get outrageously high in uf, you may trip the power supply on the startup current surge.

  I would keep all other caps except C7 and C8 at that 63V voltage rating or higher.
 
 

 

[capernicus]

 
Ok y'all, I need a little troubleshooting assistance!!!
 
Left channel works gerat, right channel seems to only get some kind of cross talk - signal comes through but you have to crank it way up - the left channel is ear bleeding just to get audible sound out of right channel.  I don't have any noise to speak of which is nice for a change.
 
I have indicated the voltages I have measured in red, there are some real differences between L and R.  Notably, Pin 1/6 on the tubes - 47.4V (R) vs 26.8V (L)
 
I did measure to see if there is a short between the heatsink and the MOSFET but wasn't able to measure anything.  The heatsinks mounts to wood anyway with the heatsinks floating - not attached to ground as of yet.
 
I suspect I have a blown MOSET but am unsure.  The real kicker is the voltage readings at Pin 1 of the MOSFET - Left (good) side is around 46V while the Right (bad) is not measurable.  The strange thing here is that where R2, R3 and R4 (Right) and R8, R9 and R10 (Left) all meet up I measure 15.4 volts on each side.
 
Something isn't making sense...
 
Please help!!!