[Forte]

Quote:

This is incredible work!  Can anyone tell me how to mount heatsinks like these?  Are they screw in from the bottom?  Can anyone recommend a source/part number to get a pair of these?  I'm about to build one for a gift.
 
 
 

Check out his thread where you can see some more phtos of this amp including internal shots, this was built very similar to Pete Milletts original point to point method - http://www.head-fi.org/t/422110/casework-share-your-diy-enclosures

 

[tubey1]

Need help!!
 
It has been working great for 4 months but I turned it on today and the right side channel tube was glowing VERY bright like a light bulb and that channel sounded like loud static. I turned it off immediately. All the capacitors(no bulging) and parts look normal with no smoke or any funny smell. I tried another set of 19J6 tubes but got the same thing. I don't understand what is wrong with my amp.
 
I used this schematic.
http://www.diyforums.org/SSMH/schematic/SSMH-origPCB.gif

 

[jacobthellamer]

 
Quote:

Need help!!
 
It has been working great for 4 months but I turned it on today and the right side channel tube was glowing VERY bright like a light bulb and that channel sounded like loud static. I turned it off immediately. All the capacitors(no bulging) and parts look normal with no smoke or any funny smell. I tried another set of 19J6 tubes but got the same thing. I don't understand what is wrong with my amp.
 
I used this schematic.
http://www.diyforums.org/SSMH/schematic/SSMH-origPCB.gif

 
Sounds like either the bias on your mosfet has been tied to the 48V rail (R2+R4) or it has failed causing a drain-source short.
 
Check the voltage on either side of R3 to ground. Let us know.
 
With the circuit powered off check the resistance across R1 and R2 - this should be around 28.7Kohms.

 

[livewire]

I think tubey1 is on to something.
 
I remember the "glows like a light bulb" has been reported before in this thread.
If memory serves me well, it was due to a shorted mosfet in the same channel.
 

 

[jacobthellamer]

Check that R4 is not open circuit and is properly connected to ground - that could also cause the problem.

 

[tubey1]

Yes, R4 is still grounded.
 
Voltage from R3 to ground 46V(yikes). I guess that's the problem. For the R9(left channel) it's 22V. Does everyone get around 22V there or around 19V? Isn't 22V kind of high for 19V heaters?

 

[jacobthellamer]

Check the heater voltage on the heater not the gate as there will be a voltage drop between the gate and source. The IRF510's Gate-Source threashold is between 2V and 4V.

 

[tubey1]

Quote:

Check the heater voltage on the heater not the gate as there will be a voltage drop between the gate and source. The IRF510's Gate-Source threashold is between 2V and 4V.

 
With tubes in sockets, Heater on the (normal) left channel reads 20V while the (malfunctioning) right channel heater reads 46V. Also checked the IRF510 of the channel and all 3 leads are not touching each other. 
 

 

[livewire]

The IRF510 could possibly have an internal short.
Most likely the metal tab (where the mosfet is bolted) is shorting to the heatsink.
(which I am assuming the metal heatsink is also grounded)
 
With the power supply unplugged, do a continuity (ohms) test with your ohmeter between
the heatsink and the mosfet metal tab. If it shows a low resistance, there is your short path to ground.
The mosfet and the insulator pad / washer will need to be replaced.

 

[jacobthellamer]

Second Amp Built -
 
This is hard wired to a grubdac, I have since installed a new heatsink and am waiting for a PSU to arrive.

 

[Ares]

I have just finished building this amplifier, it is the second SSH I have built. The version I built is the 12AU7 modification. It sounds great! Well the left channel does. I haven't had the chance to listen to the right channel yet, but I am working on it. Both tubes light up and both MOSFETs get warm, When I check the heater voltage I get about 13.3V on both left and right heaters. When checking to see if there is audio on pin 2 and 7 of the 12AU7s I find that there is. Switching tubes does not help. I assumed the problem was somewhere between C3 and R6 and output; however, when I crank up the volume enough I can hear the volume of the crosstalk coming through. Likewise, when hooked up to a meter it shows both channels displaying the DC offset 'thump' from 3V to nearly 0V when turning the amp on. making me skeptical that it is one of those and rather a problem with the input. I am hoping to be able to hook it up to a scope to see what is going on, but until then does anyone have any suggestions for debugging it? Additionally, it has been having a nasty habit of burning up IRF510s. I assumed that the output was shorting to ground accidentally but this time I was extra careful in my soldering and as a result I cannot not find the short that killed it this time. I checked the continuity with the heat-sink and with all the other pins before turning it on, everything was alright, turned it on and the one channel worked but after about 20 minutes both tubes turned off and the pins of the MOSFET appear to be conducting between each other. Suggestions? Thank you very much for the help!

 

[jacobthellamer]

What voltage is it at the drain of the fets?

 

[Ares]

It works now! It turns out the problem was, embarrassingly, a broken wire to the output (I think...) that I did not see because of the angle and enclosure. It sounds pretty good, low distortion not much coloration. I was originally using old RCA or another American made clear top 12AU7A that does not sound too good, swapped them out for some British Mullard 12AX7s that I happened to have picked up a few years ago and they sound noticeably better to me. I am pretty pleased with this little thing 

 

[drunkenpoet]

Hey guys,

I'd like to build this for my first DIY amp and would like some advice. I ran into two different part lists which contain different parts...one is HERE at the Pmillett site and the other is HERE at the DIYforums site.

I'm looking to build this as cheaply as possible. Is mouser still the cheapest place to buy most of the parts?

 

[livewire]

 
Quote:

Hey guys,
I'd like to build this for my first DIY amp and would like some advice. I ran into two different part lists which contain different parts...one is HERE at the Pmillett site and the other is HERE at the DIYforums site.
I'm looking to build this as cheaply as possible. Is mouser still the cheapest place to buy most of the parts?

You really need to read back about 396 pages to learn everything. (ha-ha, good luck!)
 
Seriously, the DIYforums BOM is a newer updated version, complete with recommended chassis, hardware and revised components.
The PMillett is the original el cheapo bare-bones BOM. I dont recommend using it, as component values have morphed somewhat.
If you want to go cheap, find some junk laying around to fab your chassis. Rape out an old strereo for knobs, heatsinks, jacks, etc.
That is the original spirit of this build. Good luck finding the 19J6 tubes. They are on ebay, not cheap and may be from dubious sources.
YMMV, buyer beware, rotz-o-ruck.
There are other variants of this amp using other, easier to get (& cheaper) 12AU7 or 12AX7  tubes. Some required component values will change though.
Run a search or do some reading back....really. You will learn a lot.
That is what I did before I fired up the soldering iron, although it took days.

BTW, Mouser is a good source although it may not be the cheapest. Shipping cost is rather high.