Iron Pumpkin(s) and other smaller vegetable animals, Tips 'n' Tricks thread

[Eric]

Don’t you ever sleep?!? Didn’t think there would be a problem with stacking, thanks for confirming!

 

[Zen Mod]

 

[Eric]

Made some more progress. Everything is finished now except for input and output wiring.

Kudos to @Gianluca and the team at Modushop for an awesome chassis and great work on the front plate for me! It really turned out great and I'm very pleased with how it looks.

The rest came together nicely. I chose the 400mm deep chassis in order to keep some space between the power transformers and the circuit board. I probably could have done well with the 300mm deep chassis, oh well...

The knobs on the front are also from Modushop, they look great and have nice locking nuts that hold them firmly to the switch shafts. I drilled out the holes on the back below the volume knob for the LEDs and used a 20k resistor to tame the brightness level.

The back panel turned out OK. The table on my drill press is pretty small, so I wasn't able to set up a fence to keep all of the holes nice and straight. As a result, my stepped bit wandered a little as I drilled some of the holes. Overall, they came out ok. The fuse is 500ma.

Just need a little more time now to wire up the RCA jacks and I'll be back up and running. I have a bunch of 30ga silver wire and teflon tubing left over from making interconnects that I'll use for this job. It's surprising how heavy it is once all of the pieces get put together. Finally, I didn't realize that the Modushop chassis came with feet, so I had already ordered a set of machined aluminum feet from ebay. Oops...

Can't wait to get it into the equipment rack!

 

[Zen Mod]

 

[Eric]

All done! Time to listen (again)!

I neglected to account for the large number of little M3 screws and nuts necessary to hold all of those RCA jacks to the back panel, my stash is now depleted and I need to order more...

 

[Zen Mod]

Is it singing?

 

[Eric]

B-E-A-U-T-I-F-U-L-L-Y! I had some delay in testing the final assembly, I’ve also spent the past week redoing the bathroom ceilings - audio projects are way more fun!

 

[birdbox]

@Eric , what wire did you use there for the RCA connections?

 

[Eric]

It’s DIY: I have a spool of 30ga 0.999 fine silver wire (purchased long ago from Myron Toback) and hand fed it through some 28ga PTFE spaghetti tubing ordered from McMasterCarr. Everything is cut to length and assembled for each use. There is a link on my web page (signature below) for DIY Silver Interconnects that has more detail.

 

[Antealta]

first set pots in CCS portion of JFet buffers to max, confirm with ohmmeter across parallel 39R resistors

then power up, set rails to 12Vdc +/-

then buffer Iq to 20mV across 1R

then output DC offset with pots in signal part of JFet buffers

then you're good with trimpots

edit: NTCs you put there (NTC 101/201) - are they labeled as surge limiters. or you're having plain low current ones?

proper ones for position are of ~6mm Dia, really declared as surge limiting devices


besides - heatsinks orientation is your choice, nothing wrong with them tucked inside

CCS Jfet buffer to max, means max resistance or max clockwise? I get ≈ 22,7R turned max anti clockwise

 

[BrianGasberg]

CCS Jfet buffer to max, means max resistance or max clockwise? I get ≈ 22,7R turned max anti clockwise

"Lower pot" to max resistance -> lowest bias, before adjusting rails.

 

[Antealta]

Thanks

 

[Zen Mod]

ZM Omnidumb

Besides constantly reinventing the Wheel (Babelfishing being sort of same), I'm very familiar with phenomena known as "How couldn't I think of it earlier?"

Now, it's very helpful to do Post Hoc analysis and become aware of everything contextual, train thought amongst other things ........ and I know, in this case, why I didn't thought of it years ago



Watch, and read info bellow video

 

[chromenuts]

I forgot that I don’t have 470uF/35V in my stores for C1-4.

The only thing I have on hand with the correct footprint is some leftover 1200uF/35V from something else I built…maybe ACA?…or F2J 🤷‍♂️

Anyway…is there any problem with using them?

The only other option I have on hand would be to steal the 470uF/35V out of the Iron Pre kit I bought and replace them later.

 

[Eric]

The only other option I have on hand would be to steal the 470uF/35V out of the Iron Pre kit I bought and replace them later.

HA- that's most of the point behind having multiple projects in the works all at once 😉

 

[Zen Mod]

if squeezed in, anything from 220uF upwards will work and you'll not hear the difference
so, 1m2 is OK
though, better 220uF than 1m2

 

[chromenuts]

Stealing from Peter then…at least Paul will be content.

 

[Zen Mod]

heck, even 100uF will work the same

 

[chromenuts]

Looks like I’ll also be stealing heatsinks from the Iron Pre kit…ones I have on hand are all too big.

The sinks are only needed on BD139/140 from what I can tell.

Do I need insulators and gunk between transistors and sinks?…or just gunk maybe for better heat transfer?

 

[Zen Mod]

just gunk
mosfets - if you like them hot, no sinks
if you put them, no harm

size of sinks - see pics I gave you - nothing biggie